SEAPLANE, SKIPLANE,and FLOAT/SKI EQUIPPED

HELICOPTEROPERATIONSHANDBOOK

2004

U.S. DEPARTMENT OF TRANSPORTATIONFEDERAL AVIATION ADMINISTRATION

Flight Standards Service

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PREFACE

This operational handbook introduces the basic skills necessary for piloting seaplanes, skiplanes, and helicoptersequipped with floats or skis. It is developed by the Flight Standards Service, Airman Testing Standards Branch, incooperation with various aviation educators and industry.

This handbook is primarily intended to assist pilots who already hold private or commercial certificates and who arelearning to fly seaplanes, skiplanes, or helicopters equipped for water or ski operations. It is also beneficial to ratedseaplane pilots who wish to improve their proficiency, pilots preparing for flights using ski equipped aircraft, andflight instructors engaged in the instruction of both student and transitioning pilots. It introduces the future seaplaneor skiplane pilot to the realm of water operations and cold weather operations, and provides information on the per-formance of procedures required for the addition of a sea class rating in airplanes. Information on general pilotingskills, aeronautical knowledge, or flying techniques not directly related to water or cold weather operations arebeyond the scope of this book, but are available in other Federal Aviation Administration (FAA) publications.

This handbook conforms to pilot training and certification concepts established by the FAA. There are differentways of teaching, as well as performing specific operating procedures, and many variations in the explanations ofoperating from water, snow, and ice. This handbook is not comprehensive, but provides a basic knowledge thatcan serve as a foundation on which to build further knowledge. The discussion and explanations reflect common-ly used practices and principles. Occasionally the word “must” or similar language is used where the desired actionis deemed critical. The use of such language is not intended to add to, interpret, or relieve a duty imposed by Title14 of the Code of Federal Regulations (14 CFR).

It is essential for persons using this handbook to also become familiar with and apply the pertinent parts of 14 CFRand the Aeronautical Information Manual (AIM). The AIM is available online at http://www.faa.gov/atpubs.Performance standards for demonstrating competence required for the seaplane rating are prescribed in the appropri-ate practical test standard.

The current Flight Standards Service airman training and testing material and subject matter knowledge codes for allairman certificates and ratings can be obtained from the Flight Standards Service web site at http://av-info.faa.gov.

The FAA greatly appreciates the valuable assistance provided by many individuals and organizations throughout theaviation community whose expertise contributed to the preparation of this handbook.

This handbook supercedes Chapters 16 and 17 of FAA-H-8083-3, Airplane Flying Handbook, dated 1999. This hand-book is available for download from the Flight Standards Service Web site at http://av-info.faa.gov. This Web sitealso provides information about availability of printed copies.

This handbook is published by the U.S. Department of Transportation, Federal Aviation Administration, AirmanTesting Standards Branch, AFS-630, P.O. Box 25082, Oklahoma City, OK 73125. Comments regarding this hand-book should be sent in e-mail form to AFS630comments@faa.gov.

AC 00-2, Advisory Circular Checklist, transmits the current status of FAA advisory circulars and other flight information and publications. This checklist is available via the Internet athttp://www.faa.gov/aba/html_policies/ac00_2.html.

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Photo credits:

Cover (Lake amphibian): Lanshe AerospaceCover (Skiplane), Tom Evans PhotographyPage 2-1, bottom right: Wipaire, Inc.Page 7-1, left column: Airglas Engineering

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Downwind Arc. . . . . . . . . . . . . . . . . . 4-14Downwind Takeoffs. . . . . . . . . . . . . . . . 4-14Glassy Water Takeoffs . . . . . . . . . . . . . . 4-15Rough Water Takeoffs . . . . . . . . . . . . . . 4-16Confined Area Takeoffs . . . . . . . . . . . . . 4-16

CHAPTER 5—PerformancePerformance Considerations for Takeoff, Climb, Cruise, and Landing . . . . . . . . . . . . 5-1

Takeoff . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1Climb and Cruise . . . . . . . . . . . . . . . . . . . 5-2Landing . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Flight Characteristics of Seaplanes withHigh Thrust Lines . . . . . . . . . . . . . . . . . . . 5-3

Multiengine Seaplanes . . . . . . . . . . . . . . . . . 5-4

CHAPTER 6—Seaplane Operations –LandingsLanding Area Reconnaissance

and Planning. . . . . . . . . . . . . . . . . . . . . . . . 6-1Landing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2

Normal Landing. . . . . . . . . . . . . . . . . . . . 6-3Crosswind Landing . . . . . . . . . . . . . . . . . 6-3Downwind Landing . . . . . . . . . . . . . . . . . 6-5Glassy Water Landing . . . . . . . . . . . . . . . 6-5Rough Water Landing . . . . . . . . . . . . . . . 6-7Confined Area Landing . . . . . . . . . . . . . . 6-7Go-Around . . . . . . . . . . . . . . . . . . . . . . . . 6-8Emergency Landing. . . . . . . . . . . . . . . . . 6-8

Postflight Procedures . . . . . . . . . . . . . . . . . . 6-8Anchoring . . . . . . . . . . . . . . . . . . . . . . . . 6-9Mooring . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9Docking . . . . . . . . . . . . . . . . . . . . . . . . . 6-10Beaching . . . . . . . . . . . . . . . . . . . . . . . . 6-10Ramping. . . . . . . . . . . . . . . . . . . . . . . . . 6-10Salt Water . . . . . . . . . . . . . . . . . . . . . . . . 6-11

CHAPTER 7—Skiplane OperationsSkiplane Operations . . . . . . . . . . . . . . . . . . . 7-1Construction and Maintenance. . . . . . . . . . . 7-1

Plain Ski Types . . . . . . . . . . . . . . . . . . . . 7-1Combination Ski Types . . . . . . . . . . . . . . 7-1

CHAPTER 1—Rules, Regulations, and Aidsfor NavigationPrivileges and Limitations . . . . . . . . . . . . . .1-1Seaplane Regulations . . . . . . . . . . . . . . . . . . 1-1

14 CFR Part 91, Section 91.115, Right-of-Way Rules: Water Operations . . . . . . 1-2

Rules of the Sea . . . . . . . . . . . . . . . . . . . . 1-2Inland and International Waters. . . . . . 1-2

United States Aids for MarineNavigation. . . . . . . . . . . . . . . . . . . . . . . . 1-2

Seaplane Landing Areas . . . . . . . . . . . 1-2Buoys and Daybeacons . . . . . . . . . . . . 1-2Nighttime Buoy Identification. . . . . . . 1-4

CHAPTER 2—Principles of SeaplanesSeaplane Characteristics. . . . . . . . . . . . . . . . 2-1Seaplane Flight Principles . . . . . . . . . . . . . . 2-4

CHAPTER 3—Water Characteristics andSeaplane Base OperationsCharacteristics of Water . . . . . . . . . . . . . . . . 3-1Determining Sea Conditions . . . . . . . . . . . . 3-1Water Effects on Operations . . . . . . . . . . . . 3-3Seaplane Base Operations . . . . . . . . . . . . . . 3-4

CHAPTER 4—Seaplane Operations –Preflight and TakeoffsPreflight Inspection . . . . . . . . . . . . . . . . . . . 4-1Starting the Engine. . . . . . . . . . . . . . . . . . . . 4-3Taxiing and Sailing . . . . . . . . . . . . . . . . . . . 4-3

Idling Position . . . . . . . . . . . . . . . . . . . . . 4-3Plowing Position . . . . . . . . . . . . . . . . . . . 4-4Planing or Step Position . . . . . . . . . . . . . 4-4Turns . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5Sailing . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8Porpoising . . . . . . . . . . . . . . . . . . . . . . . . 4-9Skipping . . . . . . . . . . . . . . . . . . . . . . . . . 4-10

Takeoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10Normal Takeoffs . . . . . . . . . . . . . . . . . . 4-12Crosswind Takeoffs . . . . . . . . . . . . . . . . 4-12

Controlled Weathervaning . . . . . . . . . 4-13Using Water Rudders . . . . . . . . . . . . . 4-14

CONTENTS

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Operational Considerations . . . . . . . . . . . . . 7-2Types of Snow . . . . . . . . . . . . . . . . . . . . . 7-2Types of Ice . . . . . . . . . . . . . . . . . . . . . . . 7-2Surface Environments . . . . . . . . . . . . . . . 7-3

Preflight . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-4Taxiing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5Takeoffs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5Off-Airport Landing Sites . . . . . . . . . . . . . . 7-6

Glaciers . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6Lakes and Rivers . . . . . . . . . . . . . . . . . . . 7-6Tundra . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6

Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-6Landings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7Parking/Postflight. . . . . . . . . . . . . . . . . . . . . 7-7Emergency Operations . . . . . . . . . . . . . . . . . 7-8

Ski Malfunction . . . . . . . . . . . . . . . . . . . . 7-8Night Emergency Landing. . . . . . . . . . . . 7-8

CHAPTER 8—Emergency Open SeaOperationsOperations in Open Seas . . . . . . . . . . . . . . . 8-1Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1Sea State Evaluation. . . . . . . . . . . . . . . . . . . 8-1Swell System Evaluation . . . . . . . . . . . . . . . 8-3

High Reconnaissance. . . . . . . . . . . . . . . . 8-3Low Reconnaissance . . . . . . . . . . . . . . . . 8-3Select Landing Heading. . . . . . . . . . . . . . 8-3Select Touchdown Area . . . . . . . . . . . . . . 8-4

Landing Parallel to the Swell . . . . . . . 8-4Landing Perpendicular to the Swell . . 8-4Landing with More Than One SwellSystem . . . . . . . . . . . . . . . . . . . . . 8-4

Effect of Chop . . . . . . . . . . . . . . . . . . . 8-5Night Operations . . . . . . . . . . . . . . . . . . . . . 8-5

Sea Evaluation at Night . . . . . . . . . . . . . . 8-6

Night Emergency Landing. . . . . . . . . . . . 8-6Landing by Parachute Flare. . . . . . . . . 8-6Landing by Markers. . . . . . . . . . . . . . . 8-6

Emergency Landing Under Instrument Conditions . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

Escaping a Submerged Seaplane . . . . . . . . . 8-8Orientation . . . . . . . . . . . . . . . . . . . . . . . . 8-8Water Pressure . . . . . . . . . . . . . . . . . . . . . 8-8Flotation Equipment . . . . . . . . . . . . . . . . 8-8Normal and Unusual Exits. . . . . . . . . . . . 8-8

CHAPTER 9—Float and Ski EquippedHelicoptersFloat Equipped Helicopters . . . . . . . . . . . . . 9-1

Construction and Maintenance . . . . . . . . 9-1Operational Considerations . . . . . . . . . . . 9-2Preflight Inspection . . . . . . . . . . . . . . . . . 9-3Starting. . . . . . . . . . . . . . . . . . . . . . . . . . . 9-3Taxiing and Hovering . . . . . . . . . . . . . . . 9-3Takeoff . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4Landing . . . . . . . . . . . . . . . . . . . . . . . . . . 9-4Autorotation . . . . . . . . . . . . . . . . . . . . . . . 9-6Shutdown and Mooring . . . . . . . . . . . . . . 9-6Ground Handling . . . . . . . . . . . . . . . . . . . 9-6

Ski Equipped Helicopters. . . . . . . . . . . . . . . 9-6Construction and Maintenance

Requirements . . . . . . . . . . . . . . . . . . . . . 9-7Operational Characteristics . . . . . . . . . . . 9-7Preflight Requirements . . . . . . . . . . . . . . 9-7Starting. . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7Taxiing and Hovering . . . . . . . . . . . . . . . 9-7Takeoff . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-7Landing . . . . . . . . . . . . . . . . . . . . . . . . . . 9-8Autorotation . . . . . . . . . . . . . . . . . . . . . . . 9-8Ground Handling . . . . . . . . . . . . . . . . . . . 9-8

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . G-1Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-1

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PRIVILEGES AND LIMITATIONSIn general, the privileges and limitations of a seaplanerating are similar to those of the equivalent land rating.The same standards and requirements apply as forcomparable landplane certificates.

While it is possible for a student to use a seaplane toobtain all the flight training necessary to earn a pilotcertificate, and many pilots have done so, this publica-tion is intended primarily for pilots who already holdairman certificates and would like to add seaplanecapabilities. Therefore, this chapter does not addresspilot certificate requirements, regulations, or proce-dures that would also apply to landplane operations.Information on regulations not directly related to wateroperations is available in other Federal AviationAdministration (FAA) publications.

For certification purposes, the term “seaplane” refersto a class of aircraft. A pilot requires additional train-ing when transitioning to a seaplane. Ground and flighttraining must be received and logged, and a pilot mustpass a class rating practical test prior to initial opera-tions as pilot in command. This training requires theuse of an authorized flight instructor to conduct suchtraining and attest to the competency of a pilot prior totaking the practical test. Because the seaplane rating ispart of an existing pilot certificate, the practical test isnot as extensive as for a new pilot certificate, and cov-ers only the procedures unique to seaplane operations.No separate written test is required for pilots who areadding seaplane to an existing pilot certificate.

Adding a seaplane rating does not modify the overalllimitations and privileges of the pilot certificate. Forexample, private pilots with a seaplane rating are notauthorized to engage in seaplane operations that wouldrequire a commercial certificate. Likewise, a pilot witha single-engine seaplane class rating may not fly multi-engine seaplanes without further training. However,no regulatory distinction is made between flying boatsand seaplanes equipped with floats. [Figure 1-1]

SEAPLANE REGULATIONSBecause of the nature of seaplane operations, certainregulations apply. Most of them are set forth in Title 14

Single-Engine Land

Single-Engine Sea

MultiengineLand

MultiengineSea

AirplaneClass

Figure 1-1. Seaplane is a class.

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of the Code of Federal Regulations (14 CFR) parts 1,61, and 91.

Just as land-based pilots must understand airport oper-ations, the pilot certification requirements in 14 CFRpart 61 require seaplane pilots to know and use therules for seaplane base operations.

Specific regulations recognize the unique characteristicsof water operations. For example, 14 CFR part 61, sec-tion 61.31 takes into account that seaplanes seldom haveretractable landing gear as such, so an endorsement toact as pilot in command of a complex seaplane requirestraining in a seaplane with flaps and a controllable pitchpropeller. Likewise, in 14 CFR part 91, section 91.107,there is an exception to the rule that everyone must havea seat and wear a seatbelt during movement on thesurface. The person pushing off or mooring a seaplaneat a dock is authorized to move around while theseaplane is in motion on the surface.

14 CFR PART 91, SECTION 91.115RIGHT-OF-WAY RULES: WATEROPERATIONSThe right-of-way rules for operation on water aresimilar, but not identical, to the rules governing right-of-way between aircraft in flight.

(a) General. Each person operating an aircraft on thewater shall, insofar as possible, keep clear of allvessels and avoid impeding their navigation, andshall give way to any vessel or other aircraft thatis given the right-of-way by any rule of thissection.

(b) Crossing. When aircraft, or an aircraft and a ves-sel, are on crossing courses, the aircraft or vesselto the other’s right has the right-of-way.

(c) Approaching head-on. When aircraft, or an air-craft and a vessel, are approaching head-on, ornearly so, each shall alter its course to the right tokeep well clear.

(d) Overtaking. Each aircraft or vessel that is beingovertaken has the right-of-way, and the one over-taking shall alter course to keep well clear.

(e) Special circumstances. When aircraft, or an air-craft and a vessel, approach so as to involve riskof collision, each aircraft or vessel shall proceedwith careful regard to existing circumstances,including the limitations of the respective craft.

RULES OF THE SEAAccording to United States Coast Guard (USCG)regulations, the definition of a vessel includes virtu-ally anything capable of being used for transportationon water, including seaplanes on the water.Therefore, any time a seaplane is operating on the

water, whether under power or not, it is required tocomply with USCG navigation rules applicable to ves-sels. Simply adhering to 14 CFR part 91, section91.115 should ensure compliance with the USCGrules. Pilots are encouraged to obtain the USCGNavigation Rules, International-Inland, M16672.2D,available from the U.S. Government Printing Office.These rules apply to all public or private vessels navi-gating upon the high seas and certain inland waters.

INLAND AND INTERNATIONAL WATERSInland waters are divided visually from internationalwaters by buoys in areas with frequent ocean traffic.Inland waters are inshore of a line approximately paral-lel with the general trend of the shore, drawn throughthe outermost buoy. The waters outside of the line areinternational waters or the high seas.

Seaplanes operating inshore of the boundary linedividing the high seas from the inland waters mustfollow the established statutory Inland Rules (PilotRules). Seaplanes navigating outside the boundaryline dividing the high seas from inland waters mustfollow the International Rules of the Sea. All sea-planes must carry a current copy of the rules whenoperating in international waters.

UNITED STATES AIDS FOR MARINENAVIGATIONFor safe operations, a pilot must be familiar withseaplane bases, maritime rules, and aids to marinenavigation.

SEAPLANE LANDING AREASThe familiar rotating beacon is used to identify lightedseaplane landing areas at night and during periods ofreduced visibility; however, the colors alternate whiteand yellow for water landing areas. A double whiteflash alternating with yellow identifies a military sea-plane base.

On aeronautical charts, seaplane landing areas aredepicted with symbols similar to land airports, with theaddition of an anchor in the center. As with their landcounterparts, tick marks around the outside of thesymbol denote a seaplane base with fuel and servicesavailable, and a double ring identifies military facili-ties. [Figure 1-2]

BUOYS AND DAYBEACONSBuoys are floating markers held in place with cables orchains to the bottom. Daybeacons are used for similarpurposes in shallower waters, and usually consist of amarker placed on top of a piling or pole driven into thebottom. Locations of buoys within U.S. waters are

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The buoyage system used in the United States employsa simple arrangement of colors, shapes, numbers, andlights. Whenever operating near buoys, keep in mindthat the length of chain holding the buoy in place islikely to be several times the depth of the water, so thebuoy may be some distance from its charted location,as well as from any danger or obstruction it is intendedto mark. Do not come any closer to a buoy thannecessary.

Buoys with a cylindrical shape are called can buoys,while those with a conical shape are known as nunbuoys. The shape often has significance in interpretingthe meaning of the buoy. [Figure 1-3]

Since a buoy’s primary purpose is to guide shipsthrough preferred channels to and from the open sea,the colors, shapes, lights, and placement becomemeaningful in that context. Approaching from sea-ward, the left (port) side of the channel is markedwith black or green can buoys. These buoys use oddnumbers whose values increase as the vessel movestoward the coast. They also mark obstructions thatshould be kept to the vessel’s left when proceedingfrom seaward.

The right side of the channel, or obstructions thatshould be kept to the vessel’s right when headedtoward shore, are marked with red nun buoys. These

shown on nautical charts prepared by the Office ofCoast Survey (OCS), an office within the NationalOceanic and Atmospheric Administration (NOAA).Light lists prepared by the Coast Guard describe light-ships, lighthouses, buoys, and daybeacons maintainedon all navigable waters of the United States.

Seaplane BaseNo Facilities or CompleteInformation is Not Available

Civil Seaplane Basewith Fuel and Services

Military Seaplane Basewith Fuel and Services

Figure 1-2. Seaplane landing areas have distinctive symbolsto distinguish them from land airports.

Keep to Right of Buoy or Piling when Coming from Seaward

Keep to Left of Buoy or Piling when Coming from Seaward

Keep to Rightto FollowPrimary ChannelComing fromSeaward

Keep to Leftto FollowPrimary ChannelComing fromSeaward

Mid-Channel Markers

Figure 1-3. Buoys typically used along waterways.

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buoys use even numbers whose values increase fromseaward. The mnemonic “red, right, returning” helpsmariners and seaplane pilots remember to keep the redbuoys to their right when proceeding toward the shore(“returning” to their home port).

Black and white vertically striped buoys mark the cen-ter of the channel or fairway (the nautical term for thenavigable part of a river, bay, or harbor), and may useletters starting at A from seaward.

Naturally, not all waterways lead straight from ocean toport, so there are also buoys to mark the junctions ofwaterways. Buoys with red and black horizontal bandsmark junctions or places where the waterway forks.They also mark wrecks and obstructions that can bepassed on either side. The color of the top band (red orblack) and the shape of the buoy (nun or can) indicatethe side on which the buoy should be passed by a ves-sel proceeding inbound along the primary channel. Ifthe topmost band is black, the buoy should be kept tothe left of an inbound vessel. If the topmost band is red,keep the buoy to the right when inbound. Buoys withthe black top band will usually be cans, while thosewith the red top band will usually be nuns.

For waterways that run more or less parallel to thecoast, there is no obvious inbound or outbound to givedirection to the waterway, so by convention theinbound direction of such waterways is assumed to be“clockwise” around the contiguous states. This meansthat for waterways running parallel to the east coast,southbound is considered the inbound direction; forwaterways along the Gulf coast, inbound meanswestbound; and for waterways along the west coast,northbound is inbound.

Daybeacons and daymarks serve similar purposes asbuoys and use similar symbology. In the United States,green is replacing black as the preferred color for port-side daymarks. [Figure 1-4]

These are just the most basic features of the most com-mon buoyage system in the United States. There are

other buoyage systems in use, both in the United Statesand in other countries. Sometimes the markings areexactly the opposite of those just described. Goodpilots will obtain a thorough understanding of the mar-itime aids to navigation used in the areas where theyintend to fly.

NIGHTTIME BUOY IDENTIFICATIONUsually only the more important buoys are lighted.Some unlighted buoys may have red, white, or greenreflectors having the same significance as lights of thesame colors. Black or green buoys have green or whitelights; red buoys have red or white lights. Likewise,buoys with a red band at the top carry red lights, whilethose with a black band topmost carry green lights.White lights are used without any color significance.Lights on red or black buoys are always flashing orocculting. (When the light period is shorter than thedark period, the light is flashing. When the light isinterrupted by short dark periods, the light is occulting.)A light flashing a Morse Code letter “A” (dot-dash)indicates a mid-channel buoy.

There is much more to the system of maritime naviga-tion aids than can be presented here. Nautical booksand online resources can be a great help in extendingknowledge and understanding of these important aids.

Daymark Daymark

Pointer Pointer

Port (Left) Markers(When Comingfrom Seaward)

Starboard (Right) Markers(When Comingfrom Seaward)

Figure 1-4.Typical daymarks.

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SEAPLANE CHARACTERISTICSThere are two main types of seaplane: flying boats (oftencalled hull seaplanes) and floatplanes. The bottom of aflying boat’s fuselage is its main landing gear. This isusually supplemented with smaller floats near thewingtips, called wing or tip floats. Some flying boatshave sponsons, which are short, winglike projectionsfrom the sides of the hull near the waterline. Their pur-pose is to stabilize the hull from rolling motion whenthe flying boat is on the water, and they may also pro-vide some aerodynamic lift in flight. Tip floats aresometimes known as sponsons. The hull of a flyingboat holds the crew, passengers, and cargo; it has manyfeatures in common with the hull of a ship or boat. Onthe other hand, floatplanes typically are conventionallandplanes that have been fitted with separate floats(sometimes called pontoons) in place of their

wheels. The fuselage of a floatplane is supportedwell above the water’s surface.

Some flying boats and floatplanes are equipped withretractable wheels for landing on dry land. These aircraftare called amphibians. On amphibious flying boats, themain wheels generally retract into the sides of the hullabove the waterline. The main wheels for amphibiousfloats retract upward into the floats themselves, justbehind the step. Additional training is suggested for any-one transitioning from straight floats to amphibiousaircraft. [Figure 2-1]

There are considerable differences between handlinga floatplane and a flying boat on the water, but simi-lar principles govern the procedures and techniquesfor both. This book primarily deals with floatplane

Figure 2-1. Flying boats, floatplanes, and amphibians.

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operations, but with few exceptions, the explanationsgiven here also apply to flying boats.

A number of amphibious hull seaplanes have theirengines mounted above the fuselage. These seaplaneshave unique handling characteristics both on the waterand in the air. Because the thrust line is well above thecenter of drag, these airplanes tend to nose down whenpower is applied and nose up as power is reduced. Thisresponse is the opposite of what pilots have come toexpect in most other airplanes, and can lead to unex-pected pitch changes and dangerous situations if the pilotis not thoroughly familiar with these characteristics.Pilots transitioning to a seaplane with this configurationshould have additional training.

Many of the terms that describe seaplane hulls andfloats come directly from the nomenclature of boatsand ships. Some of these terms may already befamiliar, but they have specific meanings whenapplied to seaplanes. Figures 2-2 and 2-3 describebasic terms, and the glossary at the end of this bookdefines additional terms.

Other nautical terms are commonly used when operat-ing seaplanes, such as port and starboard for left andright, windward and leeward for the upwind and down-wind sides of objects, and bow and stern for the frontand rear ends of objects.

Research and experience have improved float and hulldesigns over the years. Construction and materials havechanged, always favoring strength and light weight.Floats and hulls are carefully designed to optimizehydrodynamic and aerodynamic performance.

Floats usually have bottoms, sides, and tops. A strongkeel runs the length of the float along the center of thebottom. Besides supporting the seaplane on land, thekeel serves the same purpose as the keel of a boat whenthe seaplane is in the water. It guides the float in astraight line through the water and resists sidewaysmotion. A short, strong extension of the keel directlybehind the step is called the skeg. The chine is the seamwhere the sides of the float are joined to the bottom.The chine helps guide water out and away from thefloat, reducing spray and helping with hydrodynamiclift. Hydrodynamic forces are those that result frommotion in fluids.

On the front portion of the float, midway between thekeel and chine, are the two sister keelsons. These lon-gitudinal members add strength to the structure andfunction as additional keels. The top of the float formsa deck that provides access for entering and leaving thecabin. Bilge pump openings, hand hole covers, andcleats for mooring the seaplane are typically locatedalong the deck. The front of each float has a rubberbumper to cushion minor impacts with docks, etc.Many floats also have spray rails along the inboardforward portions of the chines. Since water spray is sur-prisingly destructive to propellers, especially at highr.p.m., these metal flanges are designed to reduce theamount of spray hitting the propeller.

Floats are rated according to the amount of weight theycan support, which is based on the weight of the actualvolume of fresh water they displace. Fresh water is thestandard because sea water is about 3 percent denserthan fresh water and can therefore support moreweight. If a particular float design displaces 2,500pounds of fresh water when the float is pushed underthe surface, the float can nominally support 2,500

StepChineKeel

Wingtip Float

Bow

Spray Rail

Forebody Length Afterbody Length

Stern

Figure 2-2. Hull components.

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diverting the water and the air downward. The forwardbottom portion of a float or hull is designed very muchlike the bottom of a speedboat. While speedboats areintended to travel at a fairly constant pitch angle, sea-planes need to be able to rotate in pitch to vary thewings’ angle of attack and increase lift for takeoffs andlandings. The underside of a seaplane float has a sud-den break in the longitudinal lines called the step. Thestep provides a means of reducing water drag duringtakeoff and during high-speed taxi.

At very low speeds, the entire length of the floatssupports the weight of the seaplane through buoy-ancy, that is, the floats displace a weight of waterequal to the weight of the seaplane. As speedincreases, aerodynamic lift begins to support a certainamount of the weight, and the rest is supported byhydrodynamic lift, the upward force produced by themotion of the floats through the water. Speed increasesthis hydrodynamic lift, but water drag increases morequickly. To minimize water drag while allowinghydrodynamic lift to do the work of supporting theseaplane on the water, the pilot relaxes elevator backpressure, allowing the seaplane to assume a pitch atti-tude that brings the aft portions of the floats out of thewater. The step makes this possible. When running onthe step, a relatively small portion of the float ahead ofthe step supports the seaplane. Without a step, the flowof water aft along the float would tend to remainattached all the way to the rear of the float, creatingunnecessary drag.

The steps are located slightly behind the airplane’scenter of gravity (CG), approximately at the pointwhere the main wheels are located on a landplane

pounds. A seaplane equipped with two such floatswould seemingly be able to support an airplaneweighing 5,000 pounds, but the floats would both becompletely submerged at that weight. Obviously,such a situation would be impractical, so seaplanesare required to have a buoyancy of 80 percent inexcess of that required to support the maximumweight of the seaplane in fresh water. To determinethe maximum weight allowed for a seaplane equippedwith two floats, divide the total displacement by 180percent, or 1.8. Using the example of two floats thateach displace 2,500 pounds, the total displacement of5,000 pounds divided by 1.8 gives a maximum weightfor the seaplane of 2,778 pounds. Many other consid-erations determine the suitability of a particular set offloats for a specific type of airplane, and floatinstallations are carefully evaluated by the FederalAviation Administration (FAA) prior to certification.

All floats are required to have at least four watertightcompartments. These prevent the entire float from fill-ing with water if it is ruptured at any point. The floatscan support the seaplane with any two compartmentsflooded, which makes the seaplane difficult to sink.

Most floats have openings with watertight covers alongthe deck to provide access to the inside of each com-partment for inspection and maintenance. There arealso smaller holes connected by tubes to the lowestpoint in each compartment, called the bilge. Thesebilge pump openings are used for pumping out thebilge water that leaks into the float. The openings aretypically closed with small rubber balls that pushsnugly into place.

Both the lateral and longitudinal lines of a float or hullare designed to achieve a maximum lifting force by

Step

Skeg

RetractableWater Rudder

MooringCleat

Mooring Cleat

Bumper

Bumper

Internal Bulkheads DividingWatertight Compartments

Deck

Hand Hole Covers

Chine

Chine

Sister Keelson

Sister Keelson

Keel

Keel

Bilge PumpOpenings

Spray Rail

Bow

Stern

Figure 2-3. Float components.

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with tricycle gear. If the steps were located too far aftor forward of this point, it would be difficult, if notimpossible, to rotate the airplane into a nose-up attitudeprior to lifting off. Although steps are necessary, thesharp break along the underside of the float or hullconcentrates structural stress into this area, and thedisruption in airflow produces considerable drag inflight. The keel under the front portion of each float isintended to bear the weight of the seaplane when it ison dry land. The location of the step near the CG wouldmake it very easy to tip the seaplane back onto the rearof the floats, which are not designed for such loads. Theskeg is located behind the step and acts as a sort ofchock when the seaplane is on land, making it moredifficult to tip the seaplane backward.

Most floatplanes are equipped with retractable waterrudders at the rear tip of each float. The water ruddersare connected by cables and springs to the rudderpedals in the cockpit. While they are very useful inmaneuvering on the water surface, they are quitesusceptible to damage. The water rudders should beretracted whenever the seaplane is in shallow water or

where they might hit objects under the water surface.They are also retracted during takeoff and landing,when dynamic water forces could cause damage.

SEAPLANE FLIGHT PRINCIPLESIn the air, seaplanes fly much like landplanes. Theadditional weight and drag of the floats decrease theairplane’s useful load and performance compared tothe same airplane with wheels installed. On many air-planes, directional stability is affected to some extentby the installation of floats. This is caused by thelength of the floats and the location of their verticalsurface area in relation to the airplane’s CG. Becausethe floats present such a large vertical area ahead ofthe CG, they may tend to increase any yaw or sideslip.To help restore directional stability, an auxiliary fin isoften added to the tail. Less aileron pressure is neededto hold the seaplane in a slip. Holding some rudderpressure may be required to maintain coordination inturns, since the cables and springs for the waterrudders may tend to prevent the air rudder fromstreamlining in a turn.

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CHARACTERISTICS OF WATERA competent seaplane pilot is knowledgeable in thecharacteristics of water and how they affect the sea-plane. As a fluid, water seeks its own level, and formsa flat, glassy surface if undisturbed. Winds, currents,or objects traveling along its surface create waves andmovements that change the surface characteristics.

Just as airplanes encounter resistance in the form ofdrag as they move through the air, seaplane hulls andfloats respond to drag forces as they move throughwater. Drag varies proportionately to the square ofspeed. In other words, doubling the seaplane’s speedacross the water results in four times the drag force.

Forces created when operating an airplane on waterare more complex than those created on land. Forlandplanes, friction acts at specific points where thetires meet the ground. Water forces act along theentire length of a seaplane’s floats or hull. Theseforces vary constantly depending on the pitch atti-tude, the changing motion of the float or hull, andaction of the waves. Because floats are mountedrigidly to the structure of the fuselage, they provideno shock absorbing function, unlike the landing gearof landplanes. While water may seem soft and yielding,damaging forces and shocks can be transmitteddirectly through the floats and struts to the basicstructure of the airplane.

Under calm wind conditions, the smooth water surfacepresents a uniform appearance from above, somewhatlike a mirror. This situation eliminates visual refer-ences for the pilot and can be extremely deceptive. Ifwaves are decaying and setting up certain patterns,or if clouds are reflected from the water surface, theresulting distortions can be confusing even forexperienced seaplane pilots.

DETERMINING SEA CONDITIONSThe ability to read the water’s surface is an integralpart of seaplane flying. The interaction of wind andwater determine the surface conditions, while tides andcurrents affect the movement of the water itself.Features along the shore and under the water’s surfacecontribute their effects as well. With a little study, theinterplay between these factors becomes clearer.

A few simple terms describe the anatomy and charac-teristics of waves. The top of a wave is the crest, andthe low valley between waves is a trough. The heightof waves is measured from the bottom of the trough tothe top of the crest. Naturally, the distance between twowave crests is the wavelength. The time intervalbetween the passage of two successive wave crests at afixed point is the period of the wave.

Waves are usually caused by wind moving acrossthe surface of the water. As the air pushes the water,ripples form. These ripples become waves in strong orsustained winds; the higher the speed of the wind, orthe longer the wind acts on them, the larger the waves.Waves can be caused by other factors, such as under-water earthquakes, volcanic eruptions, or tidalmovement, but wind is the primary cause of mostwaves. [Figure 3-1 on next page]

Calm water begins to show wave motion when thewind reaches about two knots. At this windspeed,patches of ripples begin to form. If the wind stops, sur-face tension and gravity quickly damp the waves, andthe surface returns to its flat, glassy condition. If thewind increases to four knots, the ripples become smallwaves, which move in the same direction as the windand persist for some time after the wind stops blowing.

As windspeed increases above four knots, the watersurface becomes covered with a complicated pattern ofwaves. When the wind is increasing, waves becomelarger and travel faster. If the wind remains at a con-stant speed, waves develop into a series of evenlyspaced parallel crests of the same height.

In simple waves, an object floating on the surfaceshows that waves are primarily an up and down motionof the water, rather than the water itself moving down-wind at the speed of the waves. The floating objectdescribes a circle in the vertical plane, moving upwardas the crest approaches, forward and downward as thecrest passes, and backward as the trough passes. Aftereach wave passes, the object is at almost the same placeas before. The wind does cause floating objects to driftslowly downwind.

While the wind is blowing and adding energy to thewater, the resulting waves are commonly referred toas wind waves or sea. (Sea is also occasionally used

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to describe the combined motion of all the factorsdisturbing the surface.) These waves tend to be achaotic mix of heights, periods, and wavelengths.Because the wind causes the height to increase fasterthan the wavelength, they often have relativelysteep, pointed crests and rounded troughs. With awindspeed of 12 knots, the waves begin to break attheir crests and create foam.

The height of waves depends on three factors: wind-speed, length of time the wind blows over the water,and the distance over which the wind acts on the water.As waves move away from the area where they weregenerated (called a fetch), they begin to sort them-selves by height and period, becoming regular andevenly spaced. These waves often continue for thou-sands of miles from where they were generated. Swellis the term describing waves that persist outside thefetch or in the absence of the force that generated them.A swell may be large or small, and does not indicate thedirection of the wind. The wake of a boat or ship is alsoa swell.

Unlike wind and current, waves are not deflected muchby the rotation of the Earth, but move in the direction

in which the generating wind blows. When this windceases, water friction and spreading reduce the waveheight, but the reduction takes place so slowly that aswell persists until the waves encounter an obstruction,such as a shore. Swell systems from many differentdirections, even from different parts of the world, maycross each other and interact. Often two or more swellsystems are visible on the surface, with a sea wave sys-tem developing due to the current wind.

In lakes and sheltered waters, it is often easy to tellwind direction by simply looking at the water’s sur-face. There is usually a strip of calm water along theupwind shore of a lake. Waves are perpendicular to thewind direction. Windspeeds above approximately eightknots leave wind streaks on the water, which are paral-lel to the wind.

Land masses sculpt and channel the air as it moves overthem, changing the wind direction and speed. Winddirection may change dramatically from one part of alake or bay to another, and may even blow in oppositedirections within a surprisingly short distance. Alwayspay attention to the various wind indicators in the area,especially when setting up for takeoff or landing.

Terms Usedby U.S.

Weather Service

Calm

Light Air

LightBreeze

GentleBreeze

ModerateBreeze

FreshBreeze

StrongBreeze

ModerateGale

Velocitym.p.h.

Less than 1

1 - 3

4 - 7

8 - 12

13 - 18

19 - 24

25-31

32-38

Estimating Velocitieson Land

Smoke rises vertically.

Smoke drifts; windvanes unmoved.

Wind felt on face; leavesrustle; ordinary

vane moves by wind.

Leaves and small twigsin constant motion;

wind extends light flag.

Dust and loose paperraised; small branches

are moved.

Small trees begin tosway; crested wavelets

form in inland water.

Large branches in motion;whistling heard in telegraph

wires; umbrellas usedwith difficulty.

Whole trees in motion;inconvenience felt in

walking against the wind.

Sea like a mirror.

Ripples with the appearanceof scales are formed but

without foam crests.

Small wavelets, still shortbut more pronounced; crestshave a glassy appearance

and do not break.

Large wavelets; crests begin tobreak. Foam of glassy appearance.

(Perhaps scattered whitecaps.)

Small waves, becoming longer;fairly frequent whitecaps.

Moderate waves; taking a morepronounced long form; many

whitecaps are formed.(Chance of some spray.)

Large waves begin to form;white foam crests are more

extensive everywhere.(Probably some spray.)

Sea heaps up and white foamfrom breaking waves beginsto be blown in streaks along

the direction of the wind.

Estimating Velocitieson Sea

Check your glassy watertechnique before water flying

under these conditions.

Ideal water flyingcharacteristics inprotected water.

This is considered roughwater for seaplanes and

small amphibians,especially in open water.

This type of water conditionis for emergency only in small

aircraft in inland waters andfor the expert pilot.

Figure 3-1.The size of waves is determined by the speed of the wind.

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can subject the floats to hard pounding as they strikeconsecutive wave crests. Operating on the surface inrough conditions exposes the seaplane to forces thatcan potentially cause damage or, in some cases,overturn the seaplane. When a swell is not alignedwith the wind, the pilot must weigh the dangersposed by the swell against limited crosswindcapability, as well as pilot experience.

On the other hand, calm, glassy water presents a differentset of challenges. Since the wind is calm, taxiing anddocking are somewhat easier, but takeoffs and landingsrequire special techniques. Takeoff distances may belonger because the wings get no extra lifting help fromthe wind. The floats seem to adhere more tenaciously tothe glassy water surface. When landing, the flat,featureless surface makes it far more difficult togauge altitude accurately, and reflections can createconfusing optical illusions. The specific techniquesfor glassy water operations are covered in Chapter4, Seaplane Operations–Preflight and Takeoffs, andChapter 6, Seaplane Operations–Landing.

Tides are cause for concern when the airplane isbeached or moored in shallow water. A rising tide canlift a beached seaplane and allow it to float out to sea ifthe airplane is not properly secured. Depending on theheight of the tide and the topography of the beach, anoutgoing tide could leave a beached seaplane strandedfar from the water. [Figure 3-2]

While waves are simply an up and down undulation ofthe water surface, currents are horizontal movementsof the water itself, such as the flow of water down-stream in a river. Currents also exist in the oceans,where solar heating, the Earth’s rotation, and tidalforces cause the ocean water to circulate.

WATER EFFECTS ON OPERATIONSCompared to operations from typical hard-surfacerunways, taking off from and landing on water pres-ents several added variables for the pilot to consider.Waves and swell not only create a rough or unevensurface, they also move, and their movement must beconsidered in addition to the wind direction.Likewise, currents create a situation in which thesurface itself is actually moving. The pilot maydecide to take off or land with or against the current,depending on the wind, the speed of the current, andthe proximity of riverbanks or other obstructions.

While a landplane pilot can rely on windsocks andindicators adjacent to the runway, a seaplane pilotneeds to be able to read wind direction and speed fromthe water itself. On the other hand, the landplane pilotmay be restricted to operating in a certain directionbecause of the orientation of the runway, while the sea-plane pilot can usually choose a takeoff or landingdirection directly into the wind.

Even relatively small waves and swell can compli-cate seaplane operations. Takeoffs on rough water

Figure 3-2. An outgoing tide can leave a seaplane far from the water. A rising tide can cause a beached seaplane to float away.

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Many of the operational differences between land-planes and seaplanes relate to the fact that seaplaneshave no brakes. From the time a seaplane casts off,it is usually in continuous motion due to the windand current, so the pilot must take deliberate actionto control this movement. Often these forces can beused to the pilot’s advantage to help move the seaplaneas desired. Starting the engine, performing the enginerunup, and completing most pre-takeoff checks are allaccomplished while the seaplane is in motion. Theseaplane continues moving after the engine is shutdown, and this energy, along with the forces of windand current, is typically used to coast the seaplane tothe desired docking point.

As with land airplanes, the wind tends to make theairplane weathervane, or yaw, until the nose pointsinto the wind. This tendency is usually negligible onlandplanes with tricycle landing gear, more pro-nounced on those with conventional (tailwheel) gear,and very evident in seaplanes. The tendency toweathervane can usually be controlled by using thewater rudders while taxiing, but the water rudders aretypically retracted prior to takeoff. Weathervaningcan create challenges in crosswind takeoffs andlandings, as well as in docking or maneuvering inclose quarters.

SEAPLANE BASE OPERATIONSIn the United States, rules governing where seaplanesmay take off and land are generally left to state andlocal governments.

Some states and cities are very liberal in the lawsregarding the operation of seaplanes on their lakesand waterways, while other states and cities mayimpose stringent restrictions. The Seaplane PilotsAssociation publishes the useful Water LandingDirectory with information on seaplane facilities,landing areas, waterway use regulations, and localrestrictions throughout the United States. Before

operating a seaplane on public waters, contact theParks and Wildlife Department of the state, the StateAeronautics Department, or other authorities todetermine the local requirements. In any case, sea-plane pilots should always avoid creating a nuisancein any area, particularly in congested marine areas ornear swimming or boating facilities.

Established seaplane bases are shown on aeronauticalcharts and are listed in the Airport/Facility Directory.The facilities at seaplane bases vary greatly, but mostinclude a hard surface ramp for launching, servicingfacilities, and an area for mooring or hangaring sea-planes. Many marinas designed for boats also provideseaplane facilities.

Seaplanes often operate in areas with extensive recre-ational or commercial water traffic. The movements offaster craft, such as speedboats and jet-skis are unpre-dictable. People towing skiers may be focusing theirattention behind the boat and fail to notice a landingseaplane. Swimmers may be nearly invisible, oftenwith just their heads showing among the waves. Thereis no equivalent of the airport traffic pattern to governboat traffic, and although right-of-way rules exist onthe water, many watercraft operators are unaware ofthe limits of seaplane maneuverability and mayassume that seaplanes will always be able to maneuverto avoid them. Many times, the seaplane itself is anobject of curiosity, drawing water traffic in the form ofinterested onlookers.

When seaplane operations are conducted in bushcountry, regular or emergency facilities are often lim-ited or nonexistent. The terrain and waterways arefrequently hazardous, and any servicing becomes theindividual pilot’s responsibility. Prior to operating inan unfamiliar area away from established seaplanefacilities, obtain the advice of FAA AccidentPrevention Counselors or experienced seaplanepilots who are familiar with the area.

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PREFLIGHT INSPECTIONBegin the preflight inspection with a thorough reviewof the existing local weather, destination weather, andwater conditions. This weather evaluation shouldinclude the direction and speed of the wind to deter-mine their effects on takeoffs, landings, and otherwater operations.

The preflight inspection of a seaplane is somewhat dif-ferent from that of a landplane. Inspecting a seaplaneon the water is complicated by the need to repositionthe seaplane to gain access to all parts of the airframe.On the other hand, preflighting a seaplane on land maycreate certain challenges because the wings and tailsurfaces may be out of reach and difficult to inspectwhen standing on the ground.

The following preflight description omits many itemsthat are identical in landplanes and seaplanes in orderto emphasize the differences between the two proce-dures. The process and the equipment to be checkedvary from airplane to airplane, but the followingdescription provides a general idea of the preflightinspection for a typical high wing, single-engine float-plane. As always, follow the procedures recommendedin the Airplane Flight Manual (AFM) or Pilot’sOperating Handbook (POH).

If the seaplane is in the water during the preflight, takea good look at how it sits on the surface. This can pro-vide vital clues to the presence of water in the floats, aswell as to the position of the center of gravity. Is theseaplane lower in the water than it should be, given itsload? Is one wing lower than the other, or is one floatriding noticeably lower in the water than the other? Arethe sterns of the floats low in the water? If any of thesesigns are present, suspect a flooded float compartmentor an improperly loaded seaplane. At more than 8pounds per gallon, even a relatively small amount ofwater in a float compartment can seriously affect bothuseful load and center of gravity (CG).

In the cockpit, verify that the throttle is closed, themixture control is full lean, and the magnetos andmaster switch are turned off. Lower the water ruddersand check for any stiffness or binding in the action ofthe cables. Check that necessary marine and safetyequipment, such as life vests, lines (ropes), anchors,and paddles are present, in good condition, andstowed correctly. Obtain the bilge pump and fuelsample cup.

Standing on the front of the float, inspect the propeller,forward fuselage, and wing. Check the usual items,working from the nose toward the tail. Water spray dam-age to the propeller looks similar to gravel damage, andmust be corrected by a mechanic. Check the oil and fuellevels and sample the fuel, ensuring that it is the propergrade and free of contaminants. Naturally, the mostlikely contaminant in seaplane fuel tanks is water. Payextra attention to the lubrication of all hinges. Not onlydoes lubrication make movement easier, but a good coat-ing of the proper lubricant keeps water out and preventscorrosion. Look for any blistering or bubbling of thepaint, which may indicate corrosion of the metal under-neath. Check the security of the float struts and theirattachment fittings. Be careful moving along the float,and pay attention to wing struts, mooring lines, and otherobstacles. If the seaplane is on land, do not stand on thefloats aft of the step or the seaplane may tip back.

Next, inspect the float itself. Water forces can createvery high loads and lead to cumulative damage. Lookcarefully for signs of stress, such as distortion or buck-ling of the skin, dents, or loose rivets. The chinesshould form a continuous smooth curve from front toback, and there should be no bends or kinks along theflange. If the floats are made of fiberglass or compositematerials, look carefully for surface cracks, abrasions,or signs of delamination. Check the spreader barsbetween the floats, and look at the bracing wires andtheir fittings. Any sign of movement, loose fasteners,broken welds, or a bracing wire that is noticeablytighter or looser than the others is cause for concern.Check for signs of corrosion, especially if the seaplanehas been operated in salt water. Although corrosion is

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less of an issue with composite floats, be sure to checkmetal fittings and fasteners. [Figure 4-1]

Use the bilge pump to remove any accumulated waterfrom each watertight compartment. The high dynamicwater pressure and the physical stresses of takeoffs andlandings can momentarily open tiny gaps between floatcomponents, allowing small amounts of water to enter.Conversely, sitting idle in the water also results in asmall amount of seepage and condensation. While it isnormal to pump a modest amount of water from eachcompartment, more than a quart or so may indicate aproblem that should be checked by a qualified aircraftmechanic experienced in working on floats. Normal isa relative term, and experience will indicate how muchwater is too much. [Figure 4-2]

If pumping does not remove any water from a compart-ment, the tube running from the bilge pump opening tothe bottom of the compartment may be damaged or

loose. If this is the case, there could be a significantamount of water in the compartment, but the pump isunable to pull it up. [Figure 4-3] Be sure to replace theplugs firmly in each bilge pump opening.

At the stern of the float, check the aft bulkhead, or tran-som. This area is susceptible to damage from the waterrudder moving beyond its normal range of travel.Carefully check the skin for any pinholes or signs ofdamage from contact with the water rudder or hingehardware. Inspect the water rudder retraction and steer-ing mechanism and look over the water rudder for anydamage. Remove any water weeds or other debrislodged in the water rudder assembly. Check the waterrudder cables that run from the float to the fuselage.[Figure 4-4]

Figure 4-1. A preflight inspection with the seaplane on landprovides an opportunity to thoroughly examine the floatsbelow the waterline. Note the spray rail on the inboard chineof the far float in this photo.

Figure 4-2. Bilge pump openings are closed with a soft rub-ber ball.

Figure 4-3. Be suspicious if pumping does not remove asmall amount of water. If the bilge pump tube is damaged,there may be water in the compartment that the pump can-not remove.

Figure 4-4. Inspect the water rudders, cables, springs, andpulleys for proper operation.

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engine. With oil pressure checked, idle r.p.m. set, andthe seaplane taxiing in the desired direction, the pilotthen fastens the seatbelt and shoulder harness, securesthe door, and continues preparing for takeoff.

When a qualified person is available to help launch theseaplane, the pilot can strap in, close the door, and startthe engine while the helper holds the seaplane. In mostsituations, the helper should position the seaplane so itis facing outward, perpendicular to the dock. It is veryimportant that the helper have experience in the properhandling of seaplanes, otherwise an innocent mistakecould cause serious damage to the seaplane or tonearby boats, structures, or other seaplanes.

TAXIING AND SAILINGOne major difference between taxiing a landplane andtaxiing a seaplane is that the seaplane is virtuallyalways in motion, and there are no brakes. Whenidling, a landplane usually remains motionless, andwhen moving, brakes can be used to control its speedor bring it to a stop. But once untied, the seaplanefloats freely along the water surface and constantlymoves due to the forces of wind, water currents,propeller thrust, and inertia. It is important that theseaplane pilot be familiar with the existing wind andwater conditions, plan an effective course of action,and mentally stay ahead of the seaplane.

There are three basic positions or attitudes used inmoving a seaplane on the water, differentiated by theposition of the floats and the speed of the seaplanethrough the water. They are the idling or displacementposition, the plowing position, and the planing or stepposition.

IDLING POSITIONIn the idling position or displacement position, thebuoyancy of the floats supports the entire weight ofthe seaplane and it remains in an attitude similar tobeing at rest on the water. Engine r.p.m. is kept as lowas possible to control speed, to keep the engine fromoverheating, and to minimize spray. In almost all cir-cumstances, the elevator control should be held all theway back to keep the nose as high as possible and min-imize spray damage to the propeller. This alsoimproves maneuverability by keeping more of thewater rudder underwater. The exception is when astrong tailwind component or heavy swells couldallow the wind to lift the tail and possibly flip theseaplane over. In such conditions, hold the elevatorcontrol forward enough to keep the tail down.[Figure 4-5 on next page]

To check the empennage area, untie the seaplane, gen-tly push it away from the dock, and turn it 90° so thetail extends over the dock. Take care not to let the waterrudders contact the dock. In addition to the normalempennage inspection, check the cables that connectthe water rudders to the air rudder. With the air ruddercentered, look at the back of the floats to see that thewater rudders are also centered. (On some systems,retracting the water rudders disengages them from theair rudder.) If the seaplane has a ventral fin to improvedirectional stability, this is the time to check it. Sprayfrequently douses the rear portion of the seaplane, sobe particularly alert for signs of corrosion in this area.

With the empennage inspection complete, continueturning the seaplane to bring the other float against thedock, and tie it to the dock. Inspect the fuselage, wing,and float on this side. If the seaplane has a door on onlyone side, turn the seaplane so the door is adjacent to thedock when the inspection is complete.

When air temperatures drop toward freezing, icebecomes a matter for concern. Inspect the float com-partments and water rudders for ice, and consider thepossibility of airframe icing during takeoff due tofreezing spray. Water expands as it freezes, and thisexpansion can cause serious damage to floats. A largeamount of water expanding inside a float could causeseams to burst, but even a tiny amount of water freez-ing and expanding inside a seam can cause severeleakage problems. Many operators who remove theirfloats for the winter store them upside down with thecompartment covers off to allow thorough drainage.When the time comes to reinstall the floats, it’s a goodidea to look for any bugs or small animals that mighthave made a home in the floats.

STARTING THE ENGINECompared to a landplane, a seaplane’s starting proce-dures are somewhat different. Before starting theengine, the seaplane usually needs to be pushed awayfrom the dock, and quite often, it is the pilot whopushes off. Therefore, the pilot should perform asmany of the items on the starting checklist as possibleprior to shoving off. This includes briefing passengersand seeing that they have fastened their seatbelts. Thepassenger briefing should include procedures for evac-uation, the use of flotation gear, and the location andoperation of regular and emergency exits. All passen-gers are required to be familiar with the operation ofseatbelts and shoulder harnesses (if installed). Whenthe engine is primed and ready to start, the pilot leavesthe cockpit, shoves off, returns to the pilot’s seat,quickly turns on the master switch and magnetos, veri-fies that the propeller area is clear, and starts the

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Use the idling or displacement position for most taxi-ing operations, and keep speeds below 6-7 knots tominimize spray getting to the propeller. It is especiallyimportant to taxi at low speed in congested or confinedareas because inertia forces at higher speeds allow theseaplane to coast farther and serious damage can resultfrom even minor collisions. Cross boat wakes or swellsat a 45° angle, if possible, to minimize pitching orrolling and the possibility of an upset.

PLOWING POSITIONApplying power causes the center of buoyancy to shiftback, due to increased hydrodynamic pressure on thebottoms of the floats. This places more of the sea-plane’s weight behind the step, and because the floatsare narrower toward the rear, the sterns sink fartherinto the water. Holding the elevator full up also helpspush the tail down due to the increased airflow fromthe propeller. The plowing position creates high drag,requiring a relatively large amount of power for amodest gain in speed. Because of the higher r.p.m.,the propeller may pick up spray even though the noseis high. The higher engine power combined with lowcooling airflow creates a danger of heat buildup in theengine. Monitor engine temperature carefully to avoidoverheating. Taxiing in the plowing position is not

recommended. It is usually just the transitional phasebetween idle taxi and planing. [Figure 4-6]

PLANING OR STEP POSITIONIn the planing position, most of the seaplane’s weightis supported by hydrodynamic lift rather than thebuoyancy of the floats. (Because of the wing’s speedthrough the air, aerodynamic lift may also be support-ing some of the weight of the seaplane.)Hydrodynamic lift depends on movement through thewater, like a water ski. As the float moves fasterthrough the water, it becomes possible to change thepitch attitude to raise the rear portions of the floatsclear of the water. This greatly reduces water drag,allowing the seaplane to accelerate to lift-off speed.This position is most often called on the step. [Figure4-7]

There is one pitch attitude that produces the minimumamount of drag when the seaplane is on the step. Anexperienced seaplane pilot can easily find this “sweetspot” or “slick spot” by the feel of the floats on thewater, but the beginning seaplane pilot usually needsto rely on gauging the position of the nose on the hori-zon. If the nose is considerably high, the rear portionsof the floats contact the water, drag increases, and the

Figure 4-5. Idling position.The engine is at idle r.p.m., the seaplane moves slowly, the attitude is nearly level, and buoyancy sup-

ports the seaplane.

Figure 4-6. Plowing position.

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seaplane tends to start settling back into more of aplowing position. If the nose is held only slightlyhigher than the ideal planing attitude, the seaplanemay remain on the step but take much longer to accel-erate to rotation speed. On the other hand, if the noseis too low, more of the front portion of the float con-tacts the water, creating more drag. This condition iscalled dragging, and as the nose pulls down and theseaplane begins to slow, it can sometimes feel similarto applying the brakes in a landplane.

To continue to taxi on the step instead of taking off,reduce the power as the seaplane is eased over onto thestep. More power is required to taxi with a heavy load.However, 65 to 70 percent of maximum power is agood starting point.

Taxiing on the step is a useful technique for coveringlong distances on the water. Carefully reducing poweras the seaplane comes onto the step stops accelerationso that the seaplane maintains a high speed across thewater, but remains well below flying speed. At thesespeeds, the water rudders must be retracted to preventdamage, but there is plenty of airflow for the air rudder.With the seaplane on the step, gentle turns can be madeby using the air rudder and the ailerons, always main-taining a precise planing attitude with elevator. Theailerons are positioned into the turn, except whenaileron into the wind is needed to keep the upwind wingfrom lifting.

Step taxiing should only be attempted in areas where thepilot is confident there is sufficient water depth, no float-ing debris, no hidden obstructions, and no other watertraffic nearby. It can be difficult to spot floating hazardsat high speeds, and an encounter with a floating log orother obstruction could tear open a float. Your seaplaneis not as maneuverable as craft that were designed forthe water, so avoiding other vessels is much more diffi-cult. Besides the obvious danger of collision, otherwater traffic creates dangerous wakes, which are a

much more frequent cause of damage. If you see thatyou are going to cross a wake, reduce power to idleand idle taxi across it, preferably at an angle. Nevertry to step taxi in shallow water. If the floats touchbottom at high speed, the sudden drag is likely to flipthe seaplane.

From either the plowing or the step position, whenpower is reduced to idle, the seaplane decelerates quiterapidly and eventually assumes the displacement oridle position. Be careful to use proper flight controlpressures during the deceleration phase because asweight is transferred toward the front of the floats anddrag increases, some seaplanes have a tendency to noseover. Control this with proper use of the elevator.

TURNSAt low speeds and in light winds, make turns using thewater rudders, which move in conjunction with the airrudder. As with a landplane, the ailerons should bepositioned to minimize the possibility of the wind lift-ing a wing. In most airplanes, left turns are somewhateasier and can be made tighter than right turns becauseof torque. If water rudders have the proper amount ofmovement, most seaplanes can be turned within aradius less than the span of the wing in calm conditionsor a light breeze. Water rudders are usually more effec-tive at slow speeds because they are acting in compar-atively undisturbed water. At higher speeds, the sternof the float churns the adjacent water, causing the waterrudder to become less effective. The dynamic pressureof the water at high speeds may tend to force the waterrudders to swing up or retract, and the pounding cancause damage. For these reasons, water rudders shouldbe retracted whenever the seaplane is moving at highspeed.

The weathervaning tendency is more evident in seaplanes,and the taxiing seaplane pilot must be constantly aware ofthe wind’s effect on the ability to maneuver. In strongerwinds, weathervaning forces may make it difficult to turn

Figure 4-7. On the step. The attitude is nearly level, and the weight of the seaplane is supported mostly by hydrodynamic lift.Behind the step, the floats are essentially clear of the water.

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downwind. Often a short burst of power provides suf-ficient air over the rudder to overcome weathervan-ing. Since the elevator is held all the way up, theairflow also forces the tail down, making the waterrudders more effective. Short bursts of power arepreferable to a longer, continuous power application.With continuous power, the seaplane accelerates,increasing the turn radius. The churning of the waterin the wake of the floats also makes the water ruddersless effective. At the same time, low cooling airflowmay cause the engine to heat up.

During a high speed taxiing turn, centrifugal forcetends to tip the seaplane toward the outside of the turn.When turning from an upwind heading to a downwindheading, the wind force acts in opposition to centrifu-gal force, helping stabilize the seaplane. On the otherhand, when turning from downwind to upwind, thewind force against the fuselage and the underside ofthe wing increases the tendency for the seaplane to leanto the outside of the turn, forcing the downwind floatdeeper into the water. In a tight turn or in strong winds,the combination of these two forces may be sufficientto tip the seaplane to the extent that the downwind floatsubmerges or the outside wing drags in the water, andmay even flip the seaplane onto its back. The further

the seaplane tips, the greater the effect of the cross-wind, as the wing presents more vertical area to thewind force. [Figure 4-8]

When making a turn into the wind from a crosswindcondition, often all that is necessary to complete theturn is to neutralize the air rudder and allow the sea-plane to weathervane into the wind. If taxiing directlydownwind, use the air rudder momentarily to get theturn started, then let the wind complete the turn.Sometimes opposite rudder may be needed to controlthe rate of turn.

Stronger winds may make turns from upwind to down-wind more difficult. The plow turn is one technique forturning downwind when other methods are inadequate,but this maneuver is only effective in certain seaplanes.It takes advantage of the same factor that reduces afloatplane’s yaw stability in flight: the large vertical areaof the floats forward of the center of gravity. In theplowing attitude, the front portion of each float comesout of the water, presenting a large vertical surface forthe wind to act upon. This tends to neutralize the weath-ervaning force, allowing the turn to proceed. At thesame time, the center of buoyancy shifts back. Sincethis is the axis around which the seaplane pivots while

Wind Force

CentrifugalForce

Wind Force

CentrifugalForce

CentrifugalForce

WindForce

CentrifugalForce

WindForce

Figure 4-8. Wind effects in turns. When the wind and centrifugal force act in the same direction, the downwind float can beforced underwater. When the wind is countered by centrifugal force, the seaplane is more stable.

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on the water, more of the fuselage is now forward ofthe axis and less is behind, further decreasing theweathervaning tendency. In some seaplanes, thischange is so pronounced in the plowing attitude thatthey experience reverse weathervaning, and tend toturn downwind rather than into the wind. Experiencedseaplane pilots can sometimes use the throttle as aturning device in high wind conditions by increasingpower to cause a nose-up position when turning down-wind, and decreasing power to allow the seaplane toweathervane into the wind. [Figure 4-9]

To execute a plow turn, begin with a turn to the right,then use the weathervaning force combined with fullleft rudder to turn back to the left. As the seaplanepasses its original upwind heading, add enough powerto place it into the plow position, continuing the turnwith the rudder. As the seaplane comes to the down-wind heading, reduce power and return to an idle taxi.From above, the path of the turn looks like a questionmark. [Figure 4-10]

Plow turns are useful only in very limited situationsbecause they expose the pilot to a number of potentialdangers. They should not be attempted in rough wateror gusty conditions. Floatplanes are least stable whenin the plowing attitude, and are very susceptible tocapsizing. In spite of the nose-high attitude, the highpower setting often results in spray damage to thepropeller. In most windy situations, it is much saferto sail the seaplane backward (as explained in thenext section) rather than attempt a plow turn.

When the seaplane is on the step, turns involve carefulbalancing of several competing forces. As the rate of

turn increases, the floats are being forced to movesomewhat sideways through the water, and they resistthis sideways motion with drag, much like an airplanefuselage in a skidding turn. More power is required toovercome this drag and maintain planing speed. Thisskidding force also tends to roll the seaplane towardthe outside of the turn, driving the outside float deeperinto the water and adding more drag on that side. Toprevent this, use aileron into the turn to keep the out-side wing from dropping. Once full aileron into thestep turn is applied, any further roll to the outside canonly be stopped by reducing the rate of turn, so paycareful attention to the angle of the wings and the feelof the water drag on the floats to catch any indicationthat the outside float is starting to submerge. Whenstopping a step turn, always return to a straight pathbefore reducing power.

At step taxi speeds, the centrifugal force in a turn is fargreater than at idle taxi speed, so the forces involved inturning from downwind to upwind are proportionatelymore dangerous, especially in strong winds. Chancesare, by the time a pilot discovers that the outside floatis going under, the accident is almost inevitable.However, immediate full rudder out of the turn andpower reduction may save the situation by reversing

Engine IdlingWater Rudder DownElevator Full Up

Add Power to AssumePlowing Attitude.Full Right AileronElevator Full Up

Full Right RudderFull Left AileronElevator Full Up

Full Left RudderFull Left AileronElevator Full Up

Reduce Power to IdleRudder as Neededto Maintain Heading

Full Left Rudder, Full Right Aileron,Elevator Full Up

Figure 4-9. In the plowing position, the exposed area at thefront of the floats, combined with the rearward shift of thecenter of buoyancy, can help to counteract the weathervan-ing tendency.

Figure 4-10. Plow turn from upwind to downwind.

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the centrifugal force and allowing the buried float tocome up.

SAILINGLandplane pilots are accustomed to taxiing by pointingthe nose of the airplane in the desired direction androlling forward. In seaplane operations, there are oftenoccasions when it is easier and safer to move the seaplanebackward or to one side because wind, water conditions,or limited space make it impractical to attempt a turn. Ifthere is a significant wind, a seaplane can be guided intoa space that might seem extremely cramped to an inexpe-rienced pilot. Sailing is a method of guiding the seaplaneon the water using the wind as the main motive force. It isa useful technique for maneuvering in situations whereconventional taxiing is undesirable or impossible. Sincethe seaplane automatically aligns itself so the nose pointsinto the wind, sailing in a seaplane usually means movingbackward.

In light wind conditions with the engine idling or off, aseaplane naturally weathervanes into the wind. If thepilot uses the air rudder to swing the tail a few degrees,the seaplane sails backward in the direction the tail ispointed. This is due to the keel effect of the floats,which tends to push the seaplane in the direction thesterns of the floats are pointing. In this situation, lift thewater rudders, since their action is counter to what isdesired. When sailing like this, the sterns of the floatshave become the front, as far as the water is concerned,but the rear portions of the floats are smaller and there-fore not as buoyant. If the wind is strong and speedstarts to build up, the sterns of the floats could start to

submerge and dig into the water. Combined with thelifting force of the wind over the wings, the seaplanecould conceivably flip over backward, so use full for-ward elevator to keep the sterns of the floats up andthe seaplane’s nose down. Adding power can alsohelp keep the floats from submerging.

If enough engine power is used to exactly cancel thebackward motion caused by the wind, the seaplane isnot moving relative to the water, so keel effect disap-pears. However, turning the fuselage a few degrees leftor right provides a surface for the wind to push against,so the wind will drive the seaplane sideways in thedirection the nose is pointed. Combining these tech-niques, a skilled pilot can sail a seaplane around obstaclesand into confined docking spaces. [Figure 4-11]

Figure 4-12 shows how to position the controls for thedesired direction of motion in light or strong winds.With the engine off, lowering the wing flaps and open-ing the cabin doors increases the air resistance andthus adds to the effect of the wind. This increases sail-ing speed but may reduce the effect of the air rudder. Ifsailing with the engine off results in too much motiondownwind, but an idling engine produces too muchthrust, adding carburetor heat or turning off one mag-neto can reduce the engine power slightly. Avoid usingcarburetor heat or running on one magneto forextended periods. Instead, start the engine briefly toslow down.

Where currents are a factor, such as in strong tidalflows or a fast flowing river, sailing techniques must

With Left Rudder and LeftAileron Down, SeaplaneMoves Downwind to the Right

With Rudder and AileronsNeutral, Seaplane MovesStraight Downwind

Engine Thrust toBalance Wind Motion

With Right Rudderand Right AileronDown, SeaplaneMoves Downwindto the Left

WaterRudders Up

Figure 4-11. When the seaplane moves through the water, keel effect drives it in the direction the tail is pointed. With no motionthrough the water, the wind pressure on the fuselage pushes the seaplane toward the side the nose is pointed.

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incorporate the movement of the water along with thewind. The current may be a help or a hindrance, orchange from a help to a hindrance when the pilotattempts to change direction. The keel effect onlyworks when the floats are moving through the water. Ifthe current is moving the seaplane, there may be littleor no motion relative to the water, even though theseaplane is moving relative to the shore. Using wind,current, and thrust to track the desired course requirescareful planning and a thorough understanding of thevarious forces at work.

With the engine shut down, most flying boats sailbackward and toward whichever side the nose ispointed, regardless of wind velocity, because the hulldoes not provide as much keel effect as floats in pro-portion to the side area of the seaplane above thewaterline. To sail directly backward in a flying boat,release the controls and let the wind steer. Sailing isan essential part of seaplane operation. Since eachtype of seaplane has its own peculiarities, practice

sailing until thoroughly familiar with that particulartype. Practice in large bodies of water such as lakesor bays, but sufficiently close to a prominent object inorder to evaluate performance.

Before taxiing into a confined area, carefully evaluatethe effects of the wind and current, otherwise the sea-plane may be driven into obstructions. With a seaplaneof average size and power at idle, a water current of 5knots can offset a wind velocity of 25 knots in theopposite direction. This means that a 5 knot currentwill carry the seaplane against a 25 knot wind.Differential power can be used to aid steering in multi-engine seaplanes.

PORPOISINGPorpoising is a rhythmic pitching motion caused bydynamic instability in forces along the float bottomswhile on the step. An incorrect planing attitude sets offa cyclic oscillation that steadily increases in amplitudeunless the proper pitch attitude is reestablished. [Figure4-13]

A seaplane travels smoothly across the water on thestep only if the floats or hull remain within a moder-ately tolerant range of pitch angles. If the nose is heldtoo low during planing, water pressure in the form of asmall crest or wall builds up under the bows of thefloats. Eventually, the crest becomes large enough thatthe fronts of the floats ride up over the crest, pitchingthe bows upward. As the step passes over the crest, thefloats tip forward abruptly, digging the bows a littledeeper into the water. This builds a new crest in frontof the floats, resulting in another oscillation. Eachoscillation becomes increasingly severe, and if not cor-rected, will cause the seaplane to nose into the water,resulting in extensive damage or possible capsizing. Asecond type of porpoising can occur if the nose is heldtoo high while on the step. Porpoising can also cause apremature lift-off with an extremely high angle ofattack, which can result in a stall and a subsequentnose-down drop into the water. Porpoising occurs dur-ing the takeoff run if the planing angle is not properlycontrolled with elevator pressure just after passingthrough the “hump” speed. The pitching created whenthe seaplane encounters a swell system while on thestep can also initiate porpoising. Usually, porpoisingdoes not start until the seaplane has passed a degree ortwo beyond the acceptable planing angle range, and

RightAileron Up

Left Rudder

Left AileronDown

Direction of Motionwith Engine Idling

Direction of Motionwith Power JustBalancing Wind

Direction of Motionwith Enough Powerto Overcome Wind

Direction of Motionwith Power Off

Figure 4-12. By balancing wind force and engine thrust, it ispossible to sail sideways or diagonally forward. Of course,reversing the control positions from those illustrated per-mits the pilot to sail to the opposite side.

Figure 4-13. Porpoising increases in amplitude if not corrected promptly.

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does not cease until after the seaplane has passed out ofthe critical range by a degree or two.

If porpoising occurs due to a nose-low planing attitude,stop it by applying timely back pressure on the elevatorcontrol to prevent the bows of the floats from digginginto the water. The back pressure must be applied andmaintained until porpoising stops. If porpoising does notstop by the time the second oscillation occurs, reduce thepower to idle and hold the elevator control back firmlyso the seaplane settles onto the water with no furtherinstability. Never try to “chase” the oscillations, as thisusually makes them worse and results in an accident.

Pilots must learn and practice the correct pitch attitudesfor takeoff, planing, and landing for each type of sea-plane until there is no doubt as to the proper angles forthe various maneuvers. The upper and lower limits ofthese pitch angles are established by the design of theseaplane; however, changing the seaplane’s grossweight, wing flap position, or center of gravity locationalso changes these limits. Increased weight increasesthe displacement of the floats or hull and raises thelower limit considerably. Extending the wing flaps fre-quently trims the seaplane to the lower limit at lowerspeeds, and may lower the upper limit at high speeds. Aforward center of gravity increases the possibility ofhigh angle porpoising, especially during landing.

SKIPPINGSkipping is a form of instability that may occur whenlanding at excessive speed with the nose at too high apitch angle. This nose-up attitude places the seaplane atthe upper trim limit of stability and causes the seaplaneto enter a cyclic oscillation when touching the water,which results in the seaplane skipping across the sur-face. This action is similar to skipping flat stones acrossthe water. Skipping can also occur by crossing a boatwake while taxiing on the step or during a takeoff.Sometimes the new seaplane pilot confuses a skip witha porpoise, but the pilot’s body sensations can quicklydistinguish between the two. A skip gives the body ver-tical “G” forces, similar to bouncing a landplane.Porpoising is a rocking chair type forward and aftmotion feeling.

To correct for skipping, first increase back pressure on theelevator control and add sufficient power to prevent thefloats from contacting the water. Then establish the properpitch attitude and reduce the power gradually to allow theseaplane to settle gently onto the water. Skippingoscillations do not tend to increase in amplitude, as inporpoising, but they do subject the floats and airframeto unnecessary pounding and can lead to porpoising.

TAKEOFFSA seaplane takeoff may be divided into four distinctphases: (1) The displacement phase, (2) the hump orplowing phase, (3) the planing or on the step phase, and(4) the lift-off.

The displacement phase should be familiar from thetaxiing discussion. During idle taxi, the displacementof water supports nearly all of the seaplane’s weight.The weight of the seaplane forces the floats down intothe water until a volume that weighs exactly as muchas the seaplane has been displaced. The surface area ofthe float below the waterline is called the wetted area,and it varies depending on the seaplane’s weight. Anempty seaplane has less wetted area than when it isfully loaded. Wetted area is a major factor in the cre-ation of drag as the seaplane moves through the water.

As power is applied, the floats move faster through thewater. The water resists this motion, creating drag. Theforward portion of the float is shaped to transform thehorizontal movement through the water into an upwardlifting force by diverting the water downward.Newton’s Third Law of Motion states that for everyaction, there is an equal and opposite reaction, and inthis case, pushing water downward results in anupward force known as hydrodynamic lift.

In the plowing phase, hydrodynamic lift begins push-ing up the front of the floats, raising the seaplane’s noseand moving the center of buoyancy aft. This, combinedwith the downward pressure on the tail generated byholding the elevator control all the way back, forcesthe rear part of the floats deeper into the water. Thiscreates more wetted area and consequently more drag,and explains why the seaplane accelerates so slowlyduring this part of the takeoff.

This resistance typically reaches its peak just beforethe floats are placed into a planing attitude. Figure 4-14shows a graph of the drag forces at work during a sea-plane takeoff run. The area of greatest resistance isreferred to as the hump because of the shape of thewater drag curve. During the plowing phase, theincreasing water speed generates more and morehydrodynamic lift. With more of the weight supportedby hydrodynamic lift, proportionately less is supportedby displacement and the floats are able to rise in thewater. As they do, there is less wetted area to causedrag, which allows more acceleration, which in turnincreases hydrodynamic lift. There is a limit to how farthis cycle can go, however, because as speed builds, sodoes the amount of drag on the remaining wetted area.Drag increases as the square of speed, and eventuallydrag forces would balance the power output of theengine and the seaplane would continue along the sur-face without further acceleration.

Seaplanes have been built with sufficient power toaccelerate to takeoff speed this way, but fortunately thestep was invented, and it makes further accelerationpossible without additional power. After passing overthe hump, the seaplane is traveling fast enough that itsweight can be supported entirely by hydrodynamic lift.Relaxing the back pressure on the elevator controlallows the float to rock up onto the step, and lifts the

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rear portions of the floats clear of the water. This elim-inates all of the wetted area aft of the step, along withthe associated drag.

As further acceleration takes place, the flight controlsbecome more responsive, just as in a landplane.Elevator deflection is gradually reduced to hold therequired planing attitude. As the seaplane continues toaccelerate, more and more weight is being supportedby the aerodynamic lift of the wings and waterresistance continues to decrease. When all of theweight is transferred to the wings, the seaplanebecomes airborne.

Several factors greatly increase the water drag orresistance, such as heavy loading of the seaplane orglassy water conditions. In extreme cases, the drag mayexceed the available thrust and prevent the seaplanefrom becoming airborne. This is particularly true whenoperating in areas with high density altitudes (high ele-vations/high temperatures) where the engine cannotdevelop full rated power. For this reason the pilot shouldpractice takeoffs using only partial power to simulatethe longer takeoff runs needed when operating wherethe density altitude is high and/or the seaplane is heavilyloaded. This practice should be conducted under thesupervision of an experienced seaplane instructor, and inaccordance with any cautions or limitations in theAFM/POH. Plan for the additional takeoff area required,as well as the flatter angle of climb after takeoff, andallow plenty of room for error.

Use all of the available cues to verify the wind direc-tion. Besides reading the water, pick up clues to thewind’s direction from wind indicators and streamerson the masts of moored boats, flags on flagpoles, orrising smoke. A boat moored to a buoy points into thewind, but be aware that it may have a stern anchor aswell, preventing it from pointing into the wind.

Waterfowl almost always align themselves facing intothe wind.

Naturally, be sure you have enough room for takeoff.The landing distance of a seaplane is much shorter thanthat required for takeoff, and many pilots have landedin areas that have turned out to be too short for takeoff.If you suspect that the available distance may be inad-equate, consider reducing weight by leaving some ofyour load behind or wait for more favorable weatherconditions. A takeoff that would be dangerous on a hot,still afternoon might be accomplished safely on the fol-lowing morning, with cooler temperatures and a briskwind.

In addition to wind, consider the effects of the currentwhen choosing the direction for takeoff. Keep in mindthat when taxiing in the same direction as the current,directional control may be reduced because the seaplaneis not moving as quickly through the water. In rivers ortidal flows, make crosswind or calm wind takeoffs in thesame direction as the current. This reduces the waterforces on the floats. Suppose the seaplane lifts off at 50knots and the current is 3 knots. If winds are calm, theseaplane needs a water speed of 47 knots to take offdownstream, but must accelerate to a water speed of 53knots to become airborne against the current. This dif-ference of 6 knots requires a longer time on the waterand generates more stress on the floats. The situationbecomes more complex when wind is a factor. If thewind is blowing against the current, its speed can helpthe wings develop lift sooner, but will raise higherwaves on the surface. If the wind is in the same directionas the current, at what point does the speed of the windmake it more worthwhile to take off against the current?In the previous example, a wind velocity of 3 knotswould exactly cancel the benefit of the current, since theair and water would be moving at the same speed. Inmost situations, take off into the wind if the speed of thewind is greater than the current.

Unlike landplane operations at airports, many otheractivities are permitted in waters where seaplaneoperations are conducted. Seaplane pilots encounter avariety of objects on the water, some of which arenearly submerged and difficult to see. These includeitems that are stationary, such as pilings and buoys,and those that are mobile, like logs, swimmers, waterskiers, and a variety of watercraft. Before beginningthe takeoff, it is a good practice to taxi along theintended takeoff path to check for any hazardousobjects or obstructions.

Make absolutely sure the takeoff path ahead is freeof boats, swimmers, and other water traffic, and besure it will remain so for the duration of the takeoffrun. Powerboats, wind-surfers, and jet-skis canmove quickly and change direction abruptly. As the

PO

UN

DS

TH

RU

ST

OR

DR

AG

KNOTS 20 40 60 80

"Hump"

WaterDrag

PropellerThrust

Figure 4-14. This graph shows water drag and propellerthrust during a takeoff run.

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seaplane’s nose comes up with the application of fullpower, the view ahead may be completely blocked bythe cowling. Check to the sides and behind the sea-plane as well as straight ahead, since many watercraftmove much faster than the normal taxi speed and maybe passing the seaplane from behind. In addition to thevessels themselves, also scan for their wakes and try toanticipate where the wakes will be during takeoff.Operators of motorboats and other watercraft often donot realize the hazard caused by moving their vesselsacross the takeoff path of a seaplane. It is usually betterto delay takeoff and wait for the swells to pass ratherthan encountering them at high speed. Even smallswells can cause dangerous pitching or rolling for aseaplane, so taxi across them at an angle rather thanhead-on. Remember to check for other air traffic andmake any appropriate radio calls.

Be sure to use the pre-takeoff checklist on every take-off. All checks are performed as the seaplane taxies,including the engine runup. Hold the elevator controlall the way back throughout the runup to minimizespray around the propeller. If there is significant wind,let the seaplane turn into the wind for the runup. Asr.p.m. increases, the nose rises into the plowing posi-tion and the seaplane begins to accelerate. Since this isa relatively unstable position, performing the runupinto the wind minimizes the possibility of crosswinds,rough water, or gusts upsetting the seaplane. Waste notime during the runup checks, but be thorough and pre-cise. Taxi speed will drop as soon as the power isreduced.

Water rudders are normally retracted before applyingtakeoff power. The buffeting and dynamic water pres-sure during a takeoff can cause serious damage if thewater rudders are left down.

As full power is applied during takeoff in most sea-planes, torque and P-factor tend to force the left floatdown into the water. Right rudder pressure helps tomaintain a straight takeoff path. In some cases, leftaileron may also help to counter the tendency to turnleft at low speeds, by increasing drag on the right sideof the seaplane.

Density altitude is particularly important in seaplaneflying. High, hot, and humid conditions reduce enginepower and propeller efficiency, and the seaplane mustalso attain a higher water speed in order to generate thelift required for takeoff. This increase in water speedmeans overcoming additional water drag. All of thesefactors combine to increase takeoff distances anddecrease climb performance. In high density altitudeconditions, consider not only the length of the waterrun, but the room required for a safe climbout as well.

The land area around a body of water is invariablysomewhat higher than the water surface. Tall trees arecommon along shorelines, and in many areas, steep ormountainous terrain rises from the water’s edge. Becertain the departure path allows sufficient room forsafe terrain clearance or for a wide climbing turn backover the water.

There are specific takeoff techniques for differentwind and water situations. Large water areas almostalways allow a takeoff into the wind, but there areoccasionally circumstances where a crosswind ordownwind takeoff may be more appropriate. Over theyears, techniques have evolved for handling roughwater or a glassy smooth surface. Knowing and prac-ticing these techniques not only keep skills polished sothey are available when needed, they also increaseoverall proficiency and add to the enjoyment ofseaplane flying.

NORMAL TAKEOFFSMake normal takeoffs into the wind. Once the winddirection is determined and the takeoff path chosen,configure the seaplane and perform all of the pre-take-off checks while taxiing to the takeoff position. Verifythat the takeoff will not interfere with other traffic,either on the water’s surface or in the air.

Hold the elevator control all the way back and apply fullpower smoothly and quickly, maintaining directionalcontrol with the rudder. When the nose reaches its highestpoint, ease the back pressure to allow the seaplane tocome up on the step. Establish the optimum planing atti-tude and allow the seaplane to accelerate to lift-off speed.In most cases, the seaplane lifts off as it reaches flyingspeed. Occasionally it may be necessary to gently helpthe floats unstick by either using some aileron to lift onefloat out of the water or by adding a small amount of backpressure on the elevator control. Once off the water, theseaplane accelerates more quickly. When a safe airspeedis achieved, establish the pitch attitude for the best rate ofclimb (VY) and complete the climb checklist. Turn asnecessary to avoid overflying noise-sensitive areas, andreduce power as appropriate to minimize noise.

CROSSWIND TAKEOFFSIn restricted or limited areas such as canals or narrowrivers, it is not always possible to take off or landdirectly into the wind. Therefore, acquiring skill incrosswind techniques enhances the safety of seaplaneoperation. Crosswinds present special difficulties forseaplane pilots. The same force that acts to lift theupwind wing also increases weight on the downwindfloat, forcing it deeper into the water and increasingdrag on that side. Keep in mind that the allowablecrosswind component for a floatplane may be signifi-cantly less than for the equivalent landplane.

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A crosswind has the same effect on a seaplane duringtakeoff as on a landplane, that is, it tends to push theseaplane sideways across the takeoff path, whichimposes side loads on the landing gear. In addition,wind pressure on the vertical tail causes the seaplane totry to weathervane into the wind.

At the beginning of the takeoff roll in a landplane, driftand weathervaning tendencies are resisted by the fric-tion of the tires against the runway, usually assisted bynosewheel steering, or in some cases even differentialbraking. The objective in a crosswind takeoff is thesame in landplanes and seaplanes: to counteract driftand minimize the side loads on the landing gear.

The sideways drifting force, acting through the sea-plane’s center of gravity, is opposed by the resistance ofthe water against the side area of the floats. This createsa force that tends to tip the seaplane sideways, pushingthe downwind float deeper into the water and lifting theupwind wing. The partly submerged float has even moreresistance to sideways motion, and the upwind wing dis-plays more vertical surface area to the wind, intensifyingthe problem. Without intervention by the pilot, this tip-ping could continue until the seaplane capsizes.

During a takeoff in stiff crosswinds, weathervaningforces can cause an uncontrolled turn to begin. As theturn develops, the addition of centrifugal force actingoutward from the turn aggravates the problem. The keelsof the floats resist the sideways force, and the upwindwing tends to lift. If strong enough, the combination ofthe wind and centrifugal force may tip the seaplane tothe point where the downwind float submerges and

subsequently the wingtip may strike the water. This isknown as a waterloop, and the dynamics are similar to agroundloop on land. Although some damage occurswhen the wingtip hits the ground during a groundloop,the consequences of plunging a wingtip underwater in aseaplane can be disastrous. In a fully developed water-loop, the seaplane may be severely damaged or maycapsize. Despite these dire possibilities, crosswind take-offs can be accomplished safely by exercising goodjudgment and proper piloting technique.

Since there are no clear reference lines for directionalguidance, such as those on airport runways, it can bedifficult to quickly detect side drift on water. Wavesmay make it appear that the water is moving sideways,but remember that although the wind moves the waves,the water remains nearly stationary. The waves aresimply an up-and-down motion of the water surface—the water itself is not moving sideways. To maintain astraight path through the water, pick a spot on the shoreas an aim point for the takeoff run. On the other hand,some crosswind techniques involve describing acurved path through the water. Experience will helpdetermine which technique is most appropriate for agiven situation.

CONTROLLED WEATHERVANINGIn light winds, it is easy to counteract the weathervan-ing tendency during the early part of the takeoff run bycreating an allowance for it from the beginning. Priorto adding takeoff power, use the water rudders to set upa heading somewhat downwind of the aim point. Theangle will depend on the speed of the wind—the higher

Begin Takeoff byAiming Downwind of the Intended Takeoff Path

AirplaneWeathervanes toIntended PathDuring Takeoff Run

Intended Takeoff Path

Figure 4-15. Anticipate weathervaning by leading the aim point, setting up a somewhat downwind heading prior to starting thetakeoff. Choose an aim point that does not move, such as a buoy or a point on the far shore.

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the wind, the greater the lead angle. Create just enoughof a lead angle so that when the water rudders are raisedand power is applied, the seaplane weathervanes to thedesired heading during the time it gains enough speedto make the air rudder and ailerons effective. As theseaplane transitions to the plowing attitude, the weath-ervaning tendency decreases as the fronts of the floatscome out of the water, adding vertical surface area atthe front of the seaplane. Use full aileron into the windas the takeoff run begins, and maintain enough aileronto keep the upwind wing from lifting as airspeed builds.[Figure 4-15 on previous page]

USING WATER RUDDERSAnother technique for maintaining a straight takeoffpath involves leaving the water rudders down to assistwith steering. Using the water rudders provides addeddirectional control until the aerodynamic controlsbecome effective.

To use this technique, align the seaplane with the aimpoint on the shore, hold full aileron into the wind, andapply takeoff power. As the seaplane accelerates, useenough aileron pressure to keep the upwind wingdown. The downwind float should lift free of the waterfirst. After lift-off, make a coordinated turn to establishthe proper crab angle for the climb, and retract thewater rudders.

This takeoff technique subjects the water rudders tohigh dynamic water pressures and could cause damage.Be sure to comply with the advice of the float manu-facturer. [Figure 4-16]

DOWNWIND ARCThe other crosswind takeoff technique results in acurved path across the water, starting somewhat into thewind and turning gradually downwind during the takeoffrun. This reduces the actual crosswind component at thebeginning of the takeoff, when the seaplane is most sus-ceptible to weathervaning. As the aerodynamic controlsbecome more effective, the pilot balances the side loadsimposed by the wind with the skidding force of an inten-tional turn, as always, holding the upwind wing downwith the ailerons. [Figure 4-17]

The pilot plans a curved path and follows this arc toproduce sufficient centrifugal force so that the seaplanetends to lean outward against the wind force. Duringthe run, the pilot can adjust the rate of turn by varyingrudder pressure, thereby increasing or decreasing thecentrifugal force to compensate for a changing windforce. In practice, it is quite simple to plan sufficientcurvature of the takeoff path to cancel out strongcrosswinds, even on very narrow rivers. Note that the

tightest part of the downwind arc is when the seaplaneis traveling at slower speeds.

The last portion of a crosswind takeoff is somewhatsimilar to a landplane. Use ailerons to lift the down-wind wing, providing a sideways component of lift tocounter the effect of the crosswind. This means that thedownwind float lifts off first. Be careful not to drop theupwind wing so far that it touches the water. Whenusing a straight takeoff path, keep the nose on the aimpoint with opposite rudder and maintain the proper stepattitude until the other float lifts off. Unlike a land-plane, there is usually no advantage in holding the sea-plane on the water past normal lift-off speed, and doingso may expose the floats to unnecessary pounding asthey splash through the waves. Once airborne, make acoordinated turn to the crab angle that results in astraight track toward the aim point, and pitch to obtainthe desired climb airspeed.

Again, experience plays an important part in successfuloperation during crosswinds. It is essential that all sea-plane pilots have thorough knowledge and skill in thesemaneuvers.

DOWNWIND TAKEOFFSDownwind takeoffs in a seaplane present a somewhatdifferent set of concerns. If the winds are light, thewater is smooth, and there is plenty of room, a down-wind takeoff may be more convenient than a longdownwind taxi to a position that would allow a takeoffinto the wind. In any airplane, the wing needs to attaina specific airspeed in order to fly, and that indicatedairspeed is the same regardless of wind direction.

Start Takeoff Run with WaterRudders Down.

Retract Water RuddersAfter Lift-Off.

Continue Takeoff UsingAppropriate Aerodynamic

Controls

Figure 4-16. Remember to retract the water rudders aftertakeoff to avoid damage during the next landing.

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However, when taking off downwind, obtaining theairspeed means accelerating to a proportionately highergroundspeed. Naturally, the takeoff run is longerbecause the wings must first be accelerated to the speedof the wind, then accelerated to the correct airspeed togenerate the lift required for takeoff. So far, this isidentical to what occurs with a landplane during adownwind takeoff. But in addition, a downwind takeoffrun in a seaplane is further lengthened by the factor offloat drag. The speed of the floats in the water correspondsto the higher groundspeed required in a landplane, but thedrag of the floats increases as the square of their speed.This increase in drag is much greater than the increasein rolling resistance of tires and wheel bearings in alandplane. A tailwind may lengthen the seaplane’stakeoff distance much more dramatically than the sametailwind in a landplane.

Nevertheless, there are situations in which a downwindtakeoff may be more favorable than taking off into thewind. If there is a long lake with mountains at theupwind end and a clear departure path at the other, adownwind takeoff might be warranted. Likewise, noiseconsiderations and thoughtfulness might prompt adownwind takeoff away from a populated shore area ifplenty of water area is available. In areas where thecurrent favors a downwind takeoff, the advantagegained from the movement of the water can more thancompensate for the wind penalty. Keep in mind thatovercoming the current creates far more drag thanaccelerating a few extra knots downwind with the cur-rent. In all cases, safety requires a thorough knowledgeof the takeoff performance of the seaplane.

GLASSY WATER TAKEOFFSGlassy water makes takeoff more difficult in twoways. The smoothness of the surface has the effect ofincreasing drag, making acceleration and lift-offmore difficult. This can feel as if there is suctionbetween the water and the floats. A little surfaceroughness actually helps break the contact betweenthe floats and the water by introducing turbulence andair bubbles between water and the float bottoms. Theintermittent contact between floats and water at themoment of lift-off cuts drag and allows the seaplaneto accelerate while still obtaining some hydrody-namic lift, but glassy water maintains a continuousdrag force. Once airborne, the lack of visual cues tothe seaplane’s height above the water can create apotentially dangerous situation unless a positive rateof climb is maintained.

The takeoff technique is identical to a normal takeoffuntil the seaplane is on the step and nearly at flyingspeed. At this point, the water drag may prevent theseaplane from accelerating the last few knots to lift-offspeed. To reduce float drag and break the grip of thewater, the pilot applies enough aileron pressure to liftone float just out of the water and allows the seaplaneto continue to accelerate on the step of the other floatuntil lift-off. By allowing the seaplane to turn slightlyin the direction the aileron is being held rather thanholding opposite rudder to maintain a straight course,considerable aerodynamic drag is eliminated, aidingacceleration and lift-off. When using this technique, becareful not to lift the wing so much that the oppositewing contacts the water. Obviously, this would haveserious consequences. Once the seaplane lifts off,establish a positive rate of climb to prevent inadver-tently flying back into the water.

Another technique that aids glassy water takeoffsentails roughening the surface a little. By taxiingaround in a circle, the wake of the seaplane spreads andreflects from shorelines, creating a slightly roughersurface that can provide some visual depth and helpthe floats break free during takeoff.

Occasionally a pilot may have difficulty getting theseaplane onto the step during a glassy water takeoff,particularly if the seaplane is loaded to its maximumauthorized weight. The floats support additionalweight by displacing more water; they sink deeper intothe water when at rest. Naturally, this wets more sur-face area, which equates to increased water drag whenthe seaplane begins moving, compared to a lightlyloaded situation. Under these conditions the seaplanemay assume a plowing position when full power isapplied, but may not develop sufficient hydrodynamiclift to get on the step due to the additional water drag.The careful seaplane pilot always plans ahead and con-siders the possibility of aborting the takeoff.

Centrifugal Force

Figure 4-17.The downwind arc balances wind force with cen-trifugal force.

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Nonetheless, if these conditions are not too excessive,the takeoff often can be accomplished using thefollowing technique.

After the nose rises to the highest point in the plowingposition with full back elevator pressure, decrease backpressure somewhat. The nose will drop if the seaplanehas attained enough speed to be on the verge of attain-ing the step position. After a few seconds, the nose willrise again. At the instant it starts to rise, reinforce therise by again applying firm back pressure. As soon asthe nose reaches its maximum height, repeat the entireroutine. After several repetitions, the nose attainsgreater height and speed increases. If the elevator controlis then pushed well forward and held there, the seaplanewill slowly flatten out on the step and the controls maythen be eased back to the neutral position. Once on thestep, the remainder of the takeoff run follows the usualglassy water procedure.

ROUGH WATER TAKEOFFSThe objective in a rough water takeoff is similar to thatof a rough or soft field takeoff in a landplane: to transferthe weight of the airplane to the wings as soon as possi-ble, get airborne at a minimum airspeed, accelerate inground effect to a safe climb speed, and climb out.

In most cases an experienced seaplane pilot can safelytake off in rough water, but a beginner should notattempt to take off if the waves are too high. Using theproper procedure during rough water operation lessensthe abuse of the floats, as well as the entire seaplane.

During rough water takeoffs, open the throttle to take-off power just as the floats begin rising on a wave. Thisprevents the float bows from digging into the water andhelps keep the spray away from the propeller. Apply alittle more back elevator pressure than on a smoothwater takeoff. This raises the nose to a higher angleand helps keep the float bows clear of the water.

Once on the step, the seaplane can begin to bouncefrom one wave crest to the next, raising its nose higherwith each bounce, so each successive wave is struckwith increasing severity. To correct this situation andto prevent a stall, smooth elevator pressures should beused to set up a fairly constant pitch attitude that allowsthe seaplane to skim across each successive wave asspeed increases. Maintain control pressure to preventthe float bows from being pushed under the water sur-face, and to keep the seaplane from being thrown intothe air at a high pitch angle and low airspeed.Fortunately, a takeoff in rough water is generallyaccomplished within a short time because if there issufficient wind to make water rough, the wind is alsostrong enough to produce aerodynamic lift earlier andenable the seaplane to become airborne quickly.

The relationship of the spacing of the waves to thelength of the floats is very important. If the wavelength

is less than half the length of the floats, the seaplane isalways supported by at least two waves at a time. Ifthe wavelength is longer than the floats, only one waveat a time supports the seaplane. This creates dangerouspitching motions, and takeoff should not be attemptedin this situation.

With respect to water roughness, consider the effect ofa strong water current flowing against the wind. If thecurrent is moving at 10 knots and the wind is blowingthe opposite direction at 15 knots, the relative velocitybetween the water and the wind is 25 knots, and thewaves will be as high as those produced in still waterby a wind of 25 knots.

The advisability of canceling a proposed flight becauseof rough water depends on the size of the seaplane, wingloading, power loading, and, most importantly, thepilot’s ability. As a general rule, if the height of thewaves from trough to crest is more than half the heightof the floats from keel to deck, takeoffs should not beattempted except by expert seaplane pilots. Chapter 8,Emergency Open Sea Operations, contains moreinformation on rough water operations.

CONFINED AREA TAKEOFFSIf operating from a small body of water, an acceptabletechnique may be to begin the takeoff run whileheaded downwind, and then turning to complete thetakeoff into the wind. This may be done by putting theseaplane on the step while on a downwind heading,then making a step turn into the wind to complete thetakeoff. Exercise caution when using this techniquesince wind and centrifugal force are acting in the samedirection and could result in the seaplane tipping over.The water area must be large enough to permit a widestep turn, and winds should be light.

In some cases, the water area may be adequate butsurrounding high terrain creates a confined area. Theterrain may also block winds, resulting in a glassywater situation as well. Such conditions may lead toa dangerous situation, especially when combined witha high density altitude. Even though landing was notdifficult, careful planning is necessary for the takeoff. Ifthe departure path leads over high terrain, consider cir-cling back over the water after takeoff to gain altitude. Ifair temperatures have increased since landing, make theproper allowance for reduced takeoff performance dueto the change in density altitude. Think about spendingthe night to take advantage of cooler temperatures thenext morning. Although the decision may be difficult,consider leaving some cargo or passengers behind iftakeoff safety is in question. It is far better to make asecond trip to pick them up than to end your takeoff inthe trees along the shore.

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PERFORMANCE CONSIDERATIONSFOR TAKEOFF, CLIMB, CRUISE, ANDLANDINGSince many pilots are accustomed to a certain level ofperformance from a specific make and model of landairplane, the changes in performance when that sameairplane is equipped with floats can lead to trouble fora careless or complacent pilot. Floats weigh somewhatmore than the wheeled landing gear they replace, butfloats are designed to produce aerodynamic lift to off-set some of the weight penalty. Generating liftinevitably creates induced drag, which imposes a smallreduction in overall performance. By far the greatestimpact on performance comes from the parasitic dragof the floats.

TAKEOFFIn a landplane, takeoff distance increases with addi-tional takeoff weight for two reasons: it takes longerfor the engine and propeller to accelerate the greatermass to lift-off speed, and the lift-off speed itself ishigher because the wings must move faster to producethe extra lift required. For seaplanes, there are twomore factors, both due to water drag. As seaplaneweight increases, the floats sink deeper into the water,creating more drag during initial acceleration. As withthe landplane, the seaplane must also accelerate to ahigher airspeed to generate more lift, but the seaplanemust overcome significantly more water drag force asspeed increases. This extra drag reduces the rate ofacceleration and results in a longer takeoff run.

Naturally, the location of the additional weight withinthe seaplane affects center of gravity (CG) location.Because of the way the floats respond to weight, theCG location affects the seaplane’s handling charac-teristics on the water. If the CG is too far aft, it maybe impossible to put the seaplane on the step. If theCG is located to one side of the centerline, one floatwill be pushed deeper into the water, resulting inmore water drag on that side. Be sure to balance thefuel load between left and right wing tanks, and payattention to how baggage or cargo is secured, so thatthe weight is distributed somewhat evenly from sideto side. [Figure 5-1]

The importance to weight and balance of pumping outthe float compartments should be obvious. Waterweighs 8.34 pounds per gallon, or a little over 62pounds per cubic foot. Performance decreases when-ever the wings and engine have to lift and carry uselesswater in a float compartment. Even a relatively smallamount of water in one of the front or rear float com-partments could place the airplane well outside of CGlimits and seriously affect stability and control.Naturally, water also moves around in response tochanges in attitude, and the sloshing of water in thefloats can create substantial CG changes as the sea-plane is brought onto the step or rotated into a climbattitude.

Some pilots use float compartments near the CG tostow iced fish or game from hunting expeditions. It isimperative to adhere to the manufacturer’s weight andbalance limitations and to include the weight andmoment of float compartment contents in weight andbalance calculations.

Density altitude is a very important factor in seaplanetakeoff performance. High altitudes, high tempera-tures, high humidity, and even low barometric pressurecan combine to rob the engine and propeller of thrustand the wings of lift. Seaplane pilots are encouragedto occasionally simulate high density altitude byusing a reduced power setting for takeoff. This exer-cise should only be attempted where there is plentyof water area, as the takeoff run will be much longer.An experienced seaplane instructor can assist withchoosing an appropriate power setting and demon-strating proper technique.

Unbalanced Fuel Load

Figure 5-1. The location of the CG can affect seaplanehandling.

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CLIMB AND CRUISEWhen comparing the performance of an airplane withwheels to the same airplane equipped with floats, thedrag and weight penalty of the floats usually results ina reduced climb rate for any given weight. Likewise,cruise speeds will usually be a little lower for a partic-ular power setting. This in turn means increased fuelconsumption and reduced range. Unless the airplanewas originally configured as a seaplane, the perform-ance and flight planning information for a landplaneconverted to floats will typically be found in theSupplements section rather than the Performance sec-tion of the Airplane Flight Manual (AFM) or Pilot’sOperating Handbook (POH).

In addition to working within the limits of the sea-plane’s range, the pilot planning a cross-country flightmust also consider the relative scarcity of refuelingfacilities for seaplanes. Amphibians have access to landairports, of course, but seaplanes without wheels needto find water landing facilities that also sell aviationfuel. While planning the trip, it is wise to call ahead toverify that the facilities have fuel and will be open atthe intended arrival times. The Seaplane PilotsAssociation publishes a Water Landing Directory thatis very helpful in planning cross-country flights.

In flight, the seaplane handles very much like the cor-responding landplane. On many floatplanes, the floatsdecrease directional stability to some extent. The floatstypically have more vertical surface area ahead of theairplane’s CG than behind it. If the floats remainaligned with the airflow, this causes no problems, but ifthe airplane begins to yaw or skid, this vertical area actssomewhat like a large control surface that tends toincrease the yaw, making the skid worse. [Figure 5-2]Additional vertical surface well behind the CG cancounteract the yaw force created by the front of thefloats, so many floatplanes have an auxiliary finattached to the bottom of the tail, or small vertical sur-faces added to the horizontal stabilizer. [Figure 5-3]

LANDINGLandplane pilots are trained to stay on the lookout forgood places to land in an emergency, and to be able toplan a glide to a safe touchdown should the engine(s)fail. An airplane equipped with floats will usually havea steeper power-off glide than the same airplane withwheels. This means a higher rate of descent and adiminished glide range in the event of an engine fail-ure, so the pilot should keep this in mind when spottingpotential landing areas during cruising flight.

Seaplanes often permit more options in the event of anunplanned landing, since land can be used as well aswater. While a water landing may seem like the onlychoice for a non-amphibious seaplane, a smoothlanding on grass, dirt, or even a hard-surface runwayusually causes very little damage to the floats or hull,and may frequently be the safer alternative.

Figure 5-2. The side area of the floats can decrease direc-tional stability.

Figure 5-3. Vertical surfaces added to the tail help restoredirectional stability.

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The most extreme pitch force logically results from asudden engine failure, when the full thrust of theengine and its associated downward pitching force aresuddenly removed. Forward thrust is replaced by thedrag of a windmilling propeller, which adds a newupward pitching force. Since the seaplane is alreadytrimmed with a considerable elevator force to coun-teract the downward pitch force of the engine, thenose pitches up abruptly. If this scenario occurs justafter takeoff, when the engine has been producingmaximum power, airspeed is low, and there is littlealtitude, the pilot must react instantly to overpowerthe upward pitching forces and push the nose down toavoid a stall.

The reversal of typical pitch forces also comes intoplay if porpoising should begin during a takeoff. Asdiscussed in Chapter 4, Seaplane Operations -Preflight and Takeoffs, porpoising usually occurswhen the planing angle is held too low by the pilot,forcing the front portion of the floats to drag until awave builds up and travels back along the float. Thesame thing can happen with the hull of a flying boat,and the nose-down force of a high thrust line can makeporpoising more likely. Once porpoising develops, thestandard solution is to reduce power and let the air-plane settle back into the water. But if power isreduced too quickly in a seaplane with a high-mountedengine, the sudden upward pitching force can combinewith the porpoising to throw the seaplane into the airwith inadequate airspeed for flight, decreasing thrust,and inadequate altitude for recovery.

Depending on how far the engine is from the airplane’sCG, the mass of the engine can have detrimentaleffects on roll stability. Some seaplanes have theengine mounted within the upper fuselage, while oth-

FLIGHT CHARACTERISTICS OFSEAPLANES WITH HIGH THRUST LINESMany of the most common flying boat designs havethe engine and propeller mounted well above the air-frame’s CG. This results in some unique handlingcharacteristics. The piloting techniques necessary tofly these airplanes safely are not intuitive and must belearned. Any pilot transitioning to such an airplane isstrongly urged to obtain additional training specific tothat model of seaplane.

Designing a seaplane with the engine and propellerhigh above the water offers some important advan-tages. The propeller is out of the spray during takeoffsand landings, and more of the fuselage volume can beused for passengers and cargo. The pilot usually sitswell forward of the wing, and enjoys an excellent viewin almost every direction.

Pilots who fly typical light twins are familiar with whathappens when one engine is producing power and theother is not. The airplane tends to yaw toward the deadengine. This happens because the thrust line is locatedsome distance from the airplane’s CG. In somerespects, this situation is similar to the single-engineseaplane with a high thrust line, except that the sea-plane flies on one engine all the time. When power isapplied, the thrust tends to pitch the nose down, and aspower is reduced, the nose tends to rise. [Figure 5-4]This is exactly the opposite of what most pilots areaccustomed to. In typical airplanes, including mostfloatplanes, applying power raises the nose and initi-ates a climb.

Naturally the magnitude of these pitch forces is pro-portional to how quickly power is applied or reduced.

Figure 5-4. Pitching forces in seaplanes with a high thrust line.

Increasing Thrust

Decreasing Thrust

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ers have engines mounted on a pylon well above themain fuselage. If it is far from the CG, the engine canact like a weight at the end of a lever, and once startedin motion it tends to continue in motion. Imaginebalancing a hammer upright with the handle on thepalm of the hand. [Figure 5-5]

Finally, seaplanes with high-mounted engines mayhave unusual spin characteristics and recovery tech-niques. These factors reinforce the point that pilotsneed to obtain thorough training from a qualified

instructor in order to operate this type of seaplanesafely.

MULTIENGINE SEAPLANESA rating to fly single-engine seaplanes does not entitlea pilot to fly seaplanes with two or more engines. The

addition of a multiengine sea rating to a pilotcertificate requires considerable additional training.Dealing with engine failures and issues of asymmetri-cal thrust are important aspects in the operation ofmultiengine seaplanes.

Figure 5-5. Roll instability with a high-mounted engine.

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LANDING AREA RECONNAISSANCEAND PLANNINGWhen a landplane makes an approach at a towered air-port, the pilot can expect that the runway surface willbe flat and free of obstructions. Wind information andlanding direction are provided by the tower. In wateroperations, the pilot must make a number of judgmentsabout the safety and suitability of the landing area,evaluate the characteristics of the water surface, deter-mine wind direction and speed, and choose a landingdirection. It is rare for active airport runways to beused by other vehicles, but common for seaplane pilotsto share their landing areas with boats, ships, swim-mers, jet-skis, wind-surfers, or barges, as well as otherseaplanes.

It is usually a good practice to circle the area ofintended landing and examine it thoroughly forobstructions such as pilings or floating debris, and tonote the direction of movement of any boats that maybe in or moving toward the intended landing site. Evenif the boats themselves will remain clear of the landingarea, look for wakes that could create hazardous swellsif they move into the touchdown zone. This is also thetime to look for indications of currents in movingwater. Note the position of any buoys marking pre-ferred channels, hidden dangers, or off-limits areassuch as no-wake zones or swimming beaches. Just as itis a good idea in a landplane to get a mental picture ofthe taxiway arrangement at an unfamiliar airport priorto landing, the seaplane pilot should plan a taxi routethat will lead safely and efficiently from the intendedtouchdown area to the dock or mooring spot. This isespecially important if there is a significant wind thatcould make turns difficult while taxiing or necessitatesailing backward or sideways to the dock. If the wateris clear, and there is not much wind, it is possible tosee areas of waterweeds or obstructions lying belowthe surface. Noting their position before landing canprevent fouling the water rudders with weeds whiletaxiing, or puncturing a float on a submerged snag. Inconfined areas, it is essential to verify before landingthat there is sufficient room for a safe takeoff under theconditions that are likely to prevail at the intendeddeparture time. While obstruction heights are regulatedin the vicinity of land airports and tall structures areusually well marked, this is not the case with most

water landing areas. Be alert for towers, cranes, powerlines,and the masts of ships and boats on the approach path.Finally, plan a safe, conservative path for a go-aroundshould the landing need to be aborted.

Most established seaplane bases have a windsock, butif one is not visible, there are many other cues to gaugethe wind direction and speed prior to landing. If thereare no strong tides or water currents, boats lying atanchor weathervane and automatically point into thewind. Be aware that some boats also set a stern anchor,and thus do not move with changes in wind direction.There is usually a glassy band of calm water on theupwind shore of a lake. Sea gulls and other waterfowlusually land into the wind and typically head into thewind while swimming on the surface. Smoke, flags,and the set of sails on sailboats also provide the pilotwith a fair approximation of the wind direction. If thereis an appreciable wind velocity, wind streaks parallel tothe wind form on the water. In light winds, they appearas long, narrow, straight streaks of smooth waterthrough the wavelets. In winds of approximately 10knots or more, foam accents the streaks, forming dis-tinct white lines. Although wind streaks show directionvery accurately, the pilot must still determine whichend of the wind streak is upwind. For example, an east-west wind streak could mean a wind from the east orthe west—it is up to the pilot to determine which.[Figure 6-1]

Figure 6-1. Wind streaks show wind direction accurately, butthe pilot must determine which end of the streak is upwind.

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If there are whitecaps or foam on top of the waves, thefoam appears to move into the wind. This illusion iscaused by the motion of the waves, which move morequickly than the foam. As the waves pass under thefoam, the foam appears to move in the opposite direc-tion. The shape of shorelines and hills influences winddirection, and may cause significant variations fromone area to another. Do not assume that because thewind is from a certain direction on this side of the lakethat it is from the same direction on the other side.

Except for glassy water, it is usually best to plan to landon the smoothest water available. When a swell systemis superimposed on a second swell system, some of thewaves may reinforce each other, resulting in higherwaves, while other waves cancel each other out, leav-ing smoother areas. Often it is possible to avoid thelarger waves and land on the smooth areas.

In seaplanes equipped with retractable landing gear(amphibians), it is extremely important to make certainthat the wheels are retracted when landing on water.Wherever possible, make a visual check of the wheelsthemselves, in addition to checking the landing gearposition indicators. A wheels-down landing on water isalmost certain to capsize the seaplane, and is far moreserious than landing the seaplane on land with thewheels up. Many experienced seaplane pilots make apoint of saying out loud to themselves before everywater landing, “This is a water landing, so the wheelsshould be up.” Then they confirm that each wheel is upusing externally mounted mirrors and other visual indi-cators. Likewise, they verbally confirm that the wheelsare down before every landing on land. The water rud-ders are also retracted for landings.

When planning the landing approach, be aware that theseaplane has a higher sink rate than its landplane coun-terpart at the same airspeed and power setting. Withsome practice, it becomes easy to land accurately on apredetermined spot. Landing near unfamiliar shore-

lines increases the possibility of encountering sub-merged objects and debris.

Besides being safe, it is also very important for sea-plane pilots to make a conscious effort to avoid inflict-ing unnecessary noise on other people in the area.Being considerate of others can often mean the differ-ence between a warm welcome and the banning offuture seaplane activity in a particular location. Theactions of one pilot can result in the closing of a desir-able landing spot to all pilots. People with houses alongthe shore of a lake usually include the quiet as one ofthe reasons they chose to live there. Sometimes highterrain around a lake or the local topography of a shore-line can reflect and amplify sound, so that a seaplanesounds louder than it would otherwise. A good practiceis to cross populated shorelines no lower than 1,000feet AGL whenever feasible. To the extent possibleconsistent with safety, avoid overflying houses duringthe landing approach. If making a go-around, turn backover the water for the climbout, and reduce powerslightly after attaining a safe altitude and airspeed. Areduction of 200 r.p.m. makes a significant differencein the amount of sound that reaches the ground.

LANDINGIn water landings, the major objectives are to touchdown at the lowest speed possible, in the correct pitchattitude, without side drift, and with full controlthroughout the approach, landing, and transition totaxiing.

The correct pitch attitude at touchdown in a landplanevaries between wide limits. For example, wheel land-ings in an airplane with conventional-gear, require anearly flat pitch attitude, with virtually zero angle ofattack, while a full-stall landing on a short field mightcall for a nose-high attitude. The touchdown attitudefor a seaplane typically is very close to the attitude fortaxiing on the step. The nose may be a few degreeshigher. The objective is to touch down on the steps,

Figure 6-2.The touchdown attitude for most seaplanes is almost the same as for taxiing on the step.

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contact the water in a nose-down attitude, driving thefloat bows underwater and capsizing the seaplane.Raising the flaps can help keep the seaplane firmly onthe water. To end the step taxi, close the throttle andgradually apply full up elevator as the seaplane slows.

CROSSWIND LANDINGLanding directly into the wind might not be practicaldue to water traffic in the area, obstructions on orunder the water, or a confined landing area, such as ariver or canal. In landing a seaplane with any degree ofcrosswind component, the objectives are the same aswhen landing a landplane: to minimize sideways driftduring touchdown and maintain directional controlafterward. Because floats have so much more side areathan wheels, even a small amount of drift at touchdowncan create large sideways forces. This is importantbecause enough side force can lead to capsizing. Also,the float hardware is primarily designed to take verticaland fore-and-aft loads rather than side loads.

If the seaplane touches down while drifting sideways,the sudden resistance as the floats contact the watercreates a skidding force that tends to push the down-wind float deeper into the water. The combination ofthe skidding force, wind, and weathervaning as theseaplane slows down can lead to a loss of directionalcontrol and a waterloop. If the downwind float sub-merges and the wingtip contacts the water when theseaplane is moving at a significant speed, the seaplanecould flip over. [Figure 6-3 on next page]

Floatplanes frequently have less crosswind componentcapability than their landplane counterparts.Directional control can be more difficult on waterbecause the surface is more yielding, there is less sur-face friction than on land, and seaplanes lack brakes.These factors increase the seaplane’s tendency toweathervane into the wind.

One technique sometimes used to compensate forcrosswinds during water operations is the same as thatused on land; that is, by lowering the upwind wingwhile holding a straight course with rudder. This cre-ates a slip into the wind to offset the drifting tendency.The apparent movement of the water’s surface duringthe landing approach can be deceiving. Wave motionmay make it appear that the water is moving sideways,but although the wind moves the waves, the wateritself remains virtually stationary. Waves are simplyan up-and-down motion of the water surface—thewater itself is not moving sideways. To detect sidedrift over water and maintain a straight path duringlanding, pick a spot on the shore or a stationary buoyas an aim point. Lower the upwind wing just enoughto stop any drift, and use rudder to maintain a straight

with the sterns of the floats near or touching the waterat the same time. [Figure 6-2] If the nose is muchhigher or lower, the excessive water drag puts unneces-sary stress on the floats and struts, and can cause thenose to pitch down, allowing the bows of the floats todig into the water. Touching down on the step keepswater drag forces to a minimum and allows energy todissipate more gradually.

NORMAL LANDINGMake normal landings directly into the wind.Seaplanes can be landed either power-off or power-on,but power-on landings are generally preferred becausethey give the pilot more positive control of the rate ofsink and the touchdown spot. To touch down at theslowest possible speed, extend the flaps fully. Useflaps, throttle, and pitch to control the glidepath andestablish a stabilized approach at the recommendedapproach airspeed. The techniques for glidepath con-trol are similar to those used in a landplane.

As the seaplane approaches the water’s surface,smoothly raise the nose to the appropriate pitch atti-tude for touchdown. As the floats contact the water,use gentle back pressure on the elevator control tocompensate for any tendency of the nose to drop.When the seaplane is definitely on the water, closethe throttle and maintain the touchdown attitude untilthe seaplane begins to come off the step. Once itbegins to settle into the plowing attitude, apply fullup elevator to keep the nose as high as possible andminimize spray hitting the propeller.

As the seaplane slows to taxi speed, lower the waterrudders to provide better directional control. Raise theflaps and perform the after-landing checklist.

The greater the speed difference between the seaplaneand the water, the greater the drag at touchdown, andthe greater the tendency for the nose to pitch down.This is why the touchdown is made at the lowest possi-ble speed for the conditions. Many landplane pilotstransitioning to seaplanes are surprised at the shortnessof the landing run, in terms of both time and distance.It is not uncommon for the landing run from touch-down to idle taxi to take as little as 5 or 6 seconds.

Sometimes the pilot chooses to remain on the step aftertouchdown. To do so, merely add sufficient power andmaintain the planing attitude immediately after touch-down. It is important to add enough power to preventthe seaplane from coming off the step, but not so muchthat the seaplane is close to flying speed. With too muchtaxi speed, a wave or swell could throw the seaplane intothe air without enough speed to make a controlledlanding. In that situation, the seaplane may stall and

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path. As the seaplane touches down on the upwindfloat, the water drag will quickly slow the seaplane andthe other float will touch down as aerodynamic liftdecreases. Close the throttle, and as the seaplane’sspeed dissipates, increase aileron to hold the upwindwing down. The seaplane is most unstable as it is com-ing off the step and transitioning through the plowingphase. Be ready for the seaplane to weathervane into thewind as the air rudder becomes less effective. Manypilots make a turn to the downwind side after landing tominimize weathervaning until the seaplane has slowedto taxi speed. Since the seaplane will weathervanesooner or later, this technique reduces the centrifugalforce on the seaplane by postponing weathervaning untilspeed has dissipated. Once the seaplane settles into thedisplacement attitude, lower the water rudders for betterdirectional control. [Figure 6-4]

Another technique used to compensate for crosswinds(preferred by many seaplane pilots) is the downwindarc method. Seaplanes need not follow a straight pathduring landing, and by choosing a curved path, the pilotcan create a sideward force (centrifugal force) to offsetthe crosswind force. This is done by steering the sea-plane in a downwind arc as shown in figure 6-5. Duringthe approach, the pilot merely plans a curved landingpath and follows this path to produce sufficient cen-trifugal force to counter the wind force. During thelanding run, the pilot can adjust the amount of centrifu-gal force by varying rudder pressure to increase or

decrease the rate of turn. This technique allows thepilot to compensate for a changing wind force duringthe water run.

Figure 6-5 shows that the tightest curve of the down-wind arc is during the time the seaplane is traveling atlow speed. Faster speeds reduce the crosswind effect,and at very slow speeds the seaplane can weathervaneinto the wind without imposing large side loads orstresses. Again, experience plays an important part insuccessful operation during crosswinds. It is essentialthat all seaplane pilots have thorough knowledge andskill in these maneuvers.

Figure 6-3. Improper technique or excessive crosswind forces can result in an accident.

VerticalComponent

HorizontalComponent

Angle Exaggeratedfor Clarity.

Figure 6-4. Dropping the upwind wing uses a horizontal com-ponent of lift to counter the drift of a crosswind.

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DOWNWIND LANDINGAlthough downwind landings often require signifi-cantly more water area, there are occasions when theyare more convenient or even safer than landing into thewind. Sometimes landing upwind would mean a long,slow taxi back along the landing path to get to the dockor mooring area. If winds are less than 5 knots and thereis ample room, landing downwind could save taxi time.Unless the winds are light, a downwind landing is sel-dom necessary. Before deciding to land downwind, thepilot needs a thorough knowledge of the landing char-acteristics of the seaplane as well as the environmentalfactors in the landing area.

As with a downwind landing in a landplane, the mainconcern for a seaplane is the additional groundspeedadded by the wind to the normal approach speed. Theairspeed, of course, is the same whether landingupwind or downwind, but the wind decreases ground-

speed in upwind landings and increases groundspeedin downwind landings. While a landplane pilot seldomthinks about the additional force placed on the landinggear by a higher groundspeed at touchdown, it is a seri-ous concern for the seaplane pilot. A small increase inwater speed translates into greatly increased water dragas the seaplane touches down, increasing the tendencyof the seaplane to nose over. In light winds, this usuallypresents little problem if the pilot is familiar with howthe seaplane handles when touching down at higherspeeds, and is anticipating the increased drag forces. Inhigher winds, the nose-down force may exceed theability of the pilot or the flight controls to compensate,and the seaplane will flip over at high speed. If thewater’s surface is rough, the higher touchdown speedalso subjects the floats and airframe to additionalpounding.

If there is a strong current, the direction of water flowis a major factor in choosing a landing direction. Thespeed of the current, a confined landing area, or the sur-face state of the water may influence the choice oflanding direction more than the direction of the wind.In calm or light winds, takeoffs usually are made in thesame direction as the flow of the current, but landingsmay be made either with or against the flow of the cur-rent, depending on a variety of factors. For example,on a narrow river with a relatively fast current, thespeed of the current is often more significant than winddirection, and the need to maintain control of the sea-plane at taxi speed after the landing run may presentmore challenges than the landing itself. It is imperativethat even an experienced seaplane pilot obtain detailedinformation about such operations before attemptingthem for the first time. Often the best source of infor-mation is local pilots with comprehensive knowledgeof the techniques that work best in specific locationsand conditions.

GLASSY WATER LANDINGFlat, calm, glassy water certainly looks inviting andmay give the pilot a false sense of safety. By its nature,glassy water indicates no wind, so there are no con-cerns about which direction to land, no crosswind toconsider, no weathervaning, and obviously no roughwater. Unfortunately, both the visual and the physicalcharacteristics of glassy water hold potential hazardsfor complacent pilots. Consequently, this surface con-dition is frequently more dangerous than it appears fora landing seaplane.

The visual aspects of glassy water make it difficult tojudge the seaplane’s height above the water. The lackof surface features can make accurate depth percep-tion very difficult, even for experienced seaplanepilots. Without adequate knowledge of the seaplane’s

CentrifugalForce

SkiddingForce

Figure 6-5. A downwind arc is one way to compensate for acrosswind.

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height above the surface, the pilot may flare too high ortoo low. Either case can lead to an upset. If the seaplaneflares too high and stalls, it will pitch down, very likelyhitting the water with the bows of the floats and flip-ping over. If the pilot flares too late or not at all, theseaplane may fly into the water at relatively high speed,landing on the float bows, driving them underwater andflipping the seaplane. [Figure 6-6]

Besides the lack of surface features, the smooth,reflecting surface can lead to confusing illusions asclouds or shore features are reproduced in stunningdetail and full color. When the water is crystal clear andglassy, the surface itself is invisible, and pilots mayinadvertently judge height by using the bottom of thelake as a reference, rather than the water surface.

The lack of surface texture also presents a physicalcharacteristic that adds slightly to the risk of glassywater landings. A nice smooth touchdown can result infaster deceleration than expected, for the same reasonthat the floats seem to stick to the surface during glassywater takeoffs: there is less turbulence and fewer airbubbles between the float bottoms and the water, whicheffectively increases the wetted surface area of thefloats and causes higher drag forces. Naturally, thissudden extra drag at touchdown tends to pull the nosedown, but if the pilot is expecting it and maintains theplaning attitude with appropriate back pressure, thetendency is easily controlled and presents no problem.

There are some simple ways to overcome the visualillusions and increase safety during glassy water land-ings. Perhaps the simplest is to land near the shoreline,using the features along the shore to gauge altitude. Becertain that the water is sufficiently deep and free ofobstructions by performing a careful inspection from asafe altitude. Another technique is to make the finalapproach over land, crossing the shoreline at the lowestpossible safe altitude so that a reliable height referenceis maintained to within a few feet of the water surface.

When adequate visual references are not available,make glassy water landings by establishing a stable

descent in the landing attitude at a rate that will pro-vide a positive, but not excessive, contact with thewater. Recognize the need for this type of landing inample time to set up the proper final approach. Alwaysperform glassy water landings with power. Perform anormal approach, but prepare as though intending toland at an altitude well above the surface. For exam-ple, in a situation where a current altimeter setting isnot available and there are few visual cues, this alti-tude might be 200 feet above the surface. Landingpreparation includes completion of the landing check-list and extension of flaps as recommended by themanufacturer. The objective is to have the seaplaneready to contact the water soon after it reaches the tar-get altitude, so at approximately 200 feet above thesurface, raise the nose to the attitude normally used fortouchdown, and adjust the power to provide a constantdescent rate of no more than 150 feet per minute(f.p.m.) at an airspeed approximately 10 knots abovestall speed. Maintain this attitude, airspeed, and rate ofdescent until the seaplane contacts the water. Once thelanding attitude and power setting are established, theairspeed and descent rate should remain the samewithout further adjustment, and the pilot shouldclosely monitor the instruments to maintain this stableglide. Power should only be changed if the airspeed orrate of descent deviate from the desired values. Do notflare, but let the seaplane fly onto the water in the land-ing attitude. [Figure 6-7]

Upon touchdown, apply gentle back pressure to theelevator control to maintain the same pitch attitude.Close the throttle only after the seaplane is firmly onthe water. Three cues provide verification throughthree different senses—vision, hearing, and body sen-sation. The pilot sees a slight nose-down pitch attouchdown and perhaps spray thrown to the sides bythe floats, hears the sound of the water against thefloats, and feels the deceleration force. Accidents haveresulted from cutting the power suddenly after the ini-tial touchdown. To the pilot’s surprise, a skip had takenplace and as the throttle closed, the seaplane was 10 to15 feet in the air and not on the water, resulting in astall and substantial damage. Be sure all of the cues

Flare Too Early Stall

Failure to Flare

Figure 6-6.The consequences of misjudging altitude over glassy water can be catastrophic.

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indicate that the seaplane is staying on the waterbefore closing the throttle. After the seaplane settlesinto a displacement taxi, complete the after-landingchecklist and lower the water rudders.

An accurately set altimeter may allow the pilot to setup for the touchdown at an altitude somewhat closerto the surface. If the pilot can be certain that the land-ing configuration and 150 f.p.m. descent will beestablished well above the water’s surface, startingthe final glide nearer the surface shortens the descenttime and overall landing length.

This technique usually produces a safe, comfortablelanding, but the long, shallow glide consumes consid-erable landing distance. Be certain there is sufficientroom for the glide, touchdown, and water run.

ROUGH WATER LANDINGRough is a very subjective and relative term. Waterconditions that cause no difficulty for small boats canbe too rough for a seaplane. Likewise, water that posesno challenge to a large seaplane or an experiencedpilot may be very dangerous for a smaller seaplane ora less experienced pilot.

Describing a typical or ideal rough water landing pro-cedure is impractical because of the many variablesthat affect the water’s surface. Wind direction andspeed must be weighed along with the surface condi-tions of the water. In most instances, though, make theapproach the same as for any other water landing. Itmay be better, however, to level off just above thewater surface and increase the power sufficiently tomaintain a rather flat attitude until conditions appearmore acceptable, and then reduce the power to touchdown. If severe bounces occur, add power and lift offto search for a smoother landing spot.

In general, make the touchdown at a somewhat flatterpitch attitude than usual. This prevents the seaplanefrom being tossed back into the air at a dangerouslylow airspeed, and helps the floats to slice through thetops of the waves rather than slamming hard againstthem. Reduce power as the seaplane settles into thewater, and apply back pressure as it comes off the stepto keep the float bows from digging into a wave face.If a particularly large wave throws the seaplane intothe air before coming off the step, be ready to applyfull power to go around.

Avoid downwind landings on rough water or in strongwinds. Rough water is usually an indication of strongwinds, and vice versa. Although the airspeed for land-ing is the same, wind velocity added to the seaplane’snormal landing speed can result in a much highergroundspeed, imposing excessive stress on the floats,increasing the nose-down tendency at touchdown, andprolonging the water run, since more kinetic energymust be dissipated. As the seaplane slows, the ten-dency to weathervane may combine with the motioncreated by the rough surface to create an unstablesituation. In strong winds, an upwind landing meansa much lower touchdown speed, a shorter water run,and subsequently much less pounding of the floatsand airframe.

Likewise, crosswind landings on rough water or instrong winds can leave the seaplane vulnerable to cap-sizing. The pitching and rolling produced by the watermotion increases the likelihood of the wind lifting awing and flipping the seaplane.

There is additional information on rough water land-ings in Chapter 8, Emergency Open Sea Operations.

CONFINED AREA LANDINGOne of the first concerns when considering a landingin a confined area is whether it is possible to get out

200 Feet

Establish Landing Attitude and150 f.p.m. Descent at 200 Feet

Maintain Landing Attitude, Airspeed, andDescent Rate All the Way to the Water

After Landing, CloseThrottle and MaintainPlaning Attitude

Perform a Normal Approach, but Set Upto Land at 200 Feet Abovethe Water Surface

Figure 6-7. Hold the landing attitude, airspeed, and 150 f.p.m. rate of descent all the way to the surface.

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again. For most seaplanes, the takeoff run is usuallymuch longer than the landing run. Before landing, thepilot should also consider the wind and surface condi-tions expected when it is time to leave. If the seaplanelands into a stiff breeze on water with small waves, itmight be more difficult to leave the next morning whenwinds are calm and the water is glassy. Conversely, ifthe seaplane lands in the morning when the air temper-ature is low, departure in the hot afternoon might meana significant loss in takeoff performance due to thedensity altitude.

It is especially important to carefully inspect thelanding area for shallow areas, obstructions, or otherhazards. After touchdown is not the time to discoverfactors that make a confined landing area evensmaller or less usable than originally supposed.Evaluation of the landing area should includeapproach and departure paths. Terrain that risesfaster than the seaplane can climb is an obvious con-sideration, both for the eventual takeoff as well as incase of a go-around during landing. If climbout overthe terrain is not easily within the seaplane’s capabilities,be certain there is sufficient room to make a gentle turnback over the water for climb.

GO-AROUNDWhenever landing conditions are not satisfactory, exe-cute a go-around. Potential conflicts with other aircraft,surface vessels or swimmers in the landing area, recog-nition of a hazard on the water, wind shear, wake tur-bulence, water surface conditions, mechanical failure,or an unstabilized landing approach are a few of thereasons to discontinue a landing attempt. Climb to asafe altitude while executing the go-around checklist,then evaluate the situation, and make another approachunder more favorable conditions. Remember that it isoften best to make a gentle climbing turn back over thewater to gain altitude, rather than climbing out over ashoreline with rising terrain or noise-sensitive areas.The go-around is a normal maneuver that must be prac-ticed and perfected like any other maneuver.

EMERGENCY LANDINGEmergency situations occurring within gliding distanceof water usually present no landing difficulty. Althoughthere is some leeway in landing attitude, it is importantto select the correct type of landing for the water condi-tions. If the landing was due to an engine failure, ananchor and paddle are useful after the landing is com-pleted.

Should the emergency occur over land, it is usuallypossible to land a floatplane with minimal damage in asmooth field. Snow covered ground is ideal if there areno obstructions. The landing should be at a slightly flat-ter attitude than normal, a bit fast, and directly into thewind. If engine power is available, landing with a small

amount of power helps maintain the flatter attitude.Just before skidding to a stop, the tail will begin to rise,but the long front portions of the floats stop the riseand keep the seaplane from flipping over.

A night water landing should generally be consideredonly in an emergency. They can be extremely danger-ous due to the difficulty of seeing objects in the water,judging surface conditions, and avoiding large wavesor swell. If it becomes necessary to land at night in aseaplane, seriously consider landing at a lighted air-port. An emergency landing can be made on a runwayin seaplanes with little or no damage to the floats orhull. Touchdown is made with the keel of the floats orhull as nearly parallel to the surface as possible. Aftertouchdown, apply full back elevator and additionalpower to lessen the rapid deceleration and nose-overtendency. Do not worry about getting stopped withadditional power applied after touchdown. It will stop!The reason for applying power is to provide additionalairflow over the elevator to help keep the tail down.

In any emergency landing on water, be as prepared aspossible well before the landing. Passengers and crewshould put on their flotation gear and adjust it prop-erly. People sitting near doors should hold the liferaftsor other emergency equipment in their laps, so no onewill need to try to locate or pick it up in the scrambleto exit the seaplane. Unlatch all the doors prior totouchdown, so they do not become jammed due todistortion of the airframe. Brief the passengers thor-oughly on what to do during and after the landing.These instructions should include how to exit theseaplane even if they cannot see, how to get to thesurface, and how to use any rescue aids.

POSTFLIGHT PROCEDURESAfter landing, lower the water rudders and completethe after-landing checklist. The flaps are usually raisedafter landing, both to provide better visibility and toreduce the effects of wind while taxiing. It is a goodpractice to remain at least 50 feet from any other ves-sel during the taxi.

After landing, secure the seaplane to allow safeunloading, as well as to keep winds and currentsfrom moving it around. Knowing a few basic termsmakes the following discussions easier to under-stand. Anchoring uses a heavy hook connected tothe seaplane by a line or cable. This anchor digsinto the bottom due to tension on the line, and keepsthe seaplane from drifting. Mooring means to tiethe seaplane to a fixed structure on the surface. Theseaplane may be moored to a floating buoy, or to apier, or to a floating raft. For this discussion, dock-ing means securing the seaplane to a permanentstructure fixed to the shore. To beach a seaplanemeans to pull it up onto a suitable shore surface, sothat its weight is supported by relatively dry ground

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rather than water. Ramping is defined as using aramp to get the seaplane out of the water and ontothe shore.

ANCHORINGAnchoring is the easiest way to secure a seaplane onthe water surface. The area selected should be out ofthe way of moving vessels, and in water deep enoughthat the seaplane will not be left aground during lowtide. The holding characteristics of the bottom areimportant in selecting an appropriate anchorage. Thelength of the anchor line should be about seven timesthe depth of the water. After dropping the anchor withthe seaplane headed into the wind, allow the seaplaneto drift backward to set the anchor. To be sure theanchor is holding, watch two fixed points somewhereto the side of the seaplane, one farther away than theother, that are aligned with each other, such as a tree onthe shore and a mountain in the distance. If they do notremain aligned, it means that the seaplane is driftingand dragging its anchor along the bottom. The nauticalterm for when two objects appear directly in line, onebehind the other, is “in range” and the two objects arecalled a range.

When choosing a place to anchor, think about what willhappen if the wind shifts. Allow enough room so thatthe seaplane can swing around the anchor without strik-ing nearby obstacles or other anchored vessels. Be cer-tain the water rudders are retracted, as they caninterfere with the seaplane’s ability to respond to windshifts.

If anchoring the seaplane overnight or for longer peri-ods of time, use a heavier anchor and be sure to complywith maritime regulations for showing an anchor lightor daytime visual signals when required. [Figure 6-8]

When leaving the seaplane anchored for any length oftime, it is a good idea to secure the controls with theelevator down and rudder neutral. Since the seaplanecan rotate so that it always faces into the wind, thisforces the nose down and reduces the angle of attack,keeping lift and wind resistance at a minimum.

MOORINGMooring a seaplane eliminates the problem of theanchor dragging. A permanent mooring installationconsists of a heavy weight on the bottom connected bya chain or cable to a floating buoy with provisions forsecuring mooring lines. Approach a mooring at a verylow speed and straight into the wind. To keep fromoverrunning the mooring, shut down the engine earlyand let the seaplane coast to the mooring. If necessary,the engine can be started again for better positioning.

Never straddle a buoy with a twin-float installation.Always approach while keeping the buoy to the out-side of the float to avoid damage to the propeller andunderside of the fuselage. Initial contact with the buoyis usually made with a boat hook or a person standingon the deck of one float.

While approaching the mooring, have the person onthe float secure one end of a short line to the bottom ofa float strut, if one is not there already. Then taxi theseaplane right or left of the mooring so that the float onwhich the person is standing comes directly alongsidethe buoy. The free end of the line can then be securedto the mooring.

Exercise extreme caution whenever a person is assist-ing in securing the seaplane. There have been manyinstances of helpers being struck by the propeller. On

Figure 6-8. Anchoring.

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most floatplanes, the floats extend well in front of thepropeller arc. Eager to do a good job, an inexperiencedhelper might forget the spinning propeller while walk-ing forward along the float.

DOCKINGThe procedure for docking is essentially the same asfor mooring, except that approaching directly into thewind may not be an option. The keys to successfuldocking are proper planning of the approach to thedock, compensating for the existing environmentalconditions, and skill in handling the seaplane in con-gested areas. Bear in mind that a seaplane is fragile andhitting an obstruction can result in extensive damage.

Plan the approach to the dock so as to keep the wind onthe seaplane’s nose as much as possible. While stillwell clear of the dock area, check the responsiveness ofthe water rudders and be sure the seaplane will be ableto maneuver in the existing wind and current. If controlseems marginal, turn away and plan an alternativemethod of reaching the dock. While approaching thedock, the person who will be jumping out to secure theseaplane should take off seatbelts and unlatch the door.When it is clear that the seaplane will just make it tothe dock, shut down the engine and let the seaplanecoast the remaining distance to encounter the dock asgently as possible. The person securing the seaplaneshould step out onto the float, pick up the mooring lineattached to the rear float strut, and step onto the dock asthe seaplane stops. The line should be secured to amooring cleat on the dock. Use additional mooringlines if the seaplane will be left unattended. Be sure tocomplete any remaining items on the checklist, and todouble-check that the mixture, magnetos, and masterswitch are in the off positions.

BEACHINGSuccess in beaching depends primarily on the type andfirmness of the shoreline. Inspect the beach carefullybefore using it. If this is impossible, approach the beachat an oblique angle so the seaplane can be turned outinto deeper water if the beach is unsatisfactory. Thehardest packed sand is usually near the water’s edgeand becomes softer where it is dry, further from thewater’s edge. Rocky shorelines are likely to damagethe floats, especially if significant waves are rolling in.Mud bottoms are usually not desirable for beaching.

To protect them from damage, water rudders should beup before entering the shallow water near a beach. Sandis abrasive and erodes any protective coatings on thebottoms of the floats. If possible, beach the seaplane bysailing backward with the water rudders up. The aftbottoms of the floats do not dig into the sand as deeplyas the forward bottoms, so backing onto a beach is notas hard on the floats as going in nose-first.

Do not leave the seaplane unattended unless at least atail line is fastened to some solid object ashore.Moderate action of the water rapidly washes away thesand under the floats and lets the seaplane drift. Anincoming tide can float a beached seaplane in just a fewminutes. Likewise, a receding tide may leave a sea-plane stranded 30 or 40 feet from the water in a fewhours. Even small waves may alternately pick up anddrop the seaplane, potentially causing serious damage,unless the seaplane is beached well out of their reach.Flying boat pilots should be sure to clear the main gearwells of any sand or debris that may have accumulatedbefore departing.

If the seaplane is beached overnight or higher windsare expected, use portable tiedowns or stakes driveninto firm ground and tie it down like a landplane. Ifsevere winds are expected, the compartments of thefloats can be filled with water. This holds the seaplanein very high winds, but it is a lot of work to pump outthe floats afterward.

RAMPINGFor the purpose of this discussion, a ramp is a slopingplatform extending well under the surface of the water.If the ramp is wood, the seaplane can be slid up ordown it on the keels of the floats, provided the surfaceof the ramp above the water is wet. Concrete boatramps are generally not suitable for seaplanes. Waterrudders should be down for directional control whileapproaching the ramp, but raised after the seaplane hitsthe ramp.

If the wind is blowing directly toward the shore, it ispossible to approach the ramp downwind with enoughspeed to maintain control. Continue this speed until theseaplane actually contacts the ramp and slides up it.Many inexperienced pilots make the mistake of cuttingthe power before reaching the ramp for fear of hitting ittoo hard. This is more likely to result in problems, sincethe seaplane may weathervane and hit the ramp side-ways or backward, or at least need to be taxied out foranother try. When approaching at the right speed, thebow wave of the float cushions the impact with theramp, but if the seaplane is too slow or decelerating,the bow wave moves farther back along the float andthe impact with the ramp may be harder. Many pilotsapply a little power just prior to hitting the ramp, whichraises the fronts of the floats and creates more of acushioning bow wave. Be sure to hold the elevator con-trol all the way back throughout the ramping.[Figure 6-9]

When the seaplane stops moving, shut down the engineand complete the appropriate checklist. Ideally, the sea-plane should be far enough up the ramp that waves orswells will not lift the floats and work the seaplane

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back into the water, but not so far up the ramp thatshoving off is difficult. Ramps are usually quite slip-pery, so pilot and passengers must be very cautious oftheir footing when walking on the ramp.

The most difficult approach is when the wind is blow-ing parallel to the shore, and strong enough to makecontrol marginal. If the approach is made into the wind,it may not be possible to turn the seaplane crosswindtoward the ramp without excessive speed. In mostcases, the best procedure is to taxi directly downwinduntil near the ramp, then close the throttle at the rightpoint to allow weathervaning to place the seaplane onthe ramp in the proper position. Then apply power topull the seaplane up the ramp and clear of the water.This should not be attempted if the winds are high or

the ramp is too slippery, since the seaplane could beblown sideways off the leeward side of the ramp.[Figure 6-10]

Experience and proficiency are necessary for rampingin strong winds. In many instances, the safest proce-dure is to taxi upwind to the ramp and near enough fora helper to attach a line to the floats. The seaplane maythen be left floating, or pushed and pulled into a posi-tion where a vehicle can haul it up the ramp.

SALT WATERAny time the seaplane has been operated in salt water,be sure to flush the entire seaplane with plenty of freshwater to minimize corrosion.

Approach Rampfrom Upwind Side

Allow Wind toWeathervane the Seaplane UntilLined Up with theRamp. Use Powerto Pull the Seaplane Wellonto the Ramp.

Figure 6-9.The bow wave cushions the contact with the ramp.

Figure 6-10. Crosswind approach to a ramp.

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7-1

SKIPLANE OPERATIONSThis chapter introduces pilots to the proceduresrequired in the operation of skiplanes. Since mostskiplane operations and training are conducted insingle-engine airplanes with a conventional gear(tailwheel) configuration, this information is basedon operating skiplanes of this type. [Figure 7-1]

A skiplane configuration affects the overall operationand performance of an airplane in several differentways, including ground handling, takeoff, landing, andflight operations. Some manufacturers provide recom-mended procedures and performance data in theAirplane Flight Manual (AFM) and/or Pilot’sOperating Handbook (POH).

Title 14 of the Code of Federal Regulations (14 CFR)part 61 does not require specific pilot training andauthorization to operate skiplanes; however, it isimportant to train with a qualified skiplane flightinstructor.

Since most skiplanes operate in a wide variety of con-ditions, such as landing on frozen or snow-coveredlakes and sloping glaciers, with varying qualities ofsnow, it is important to know how performance isaffected. Use the performance data provided by themanufacturer.

CONSTRUCTION AND MAINTENANCEModern airplane ski designs are a compromise for thevarious forms and conditions of snow and ice. Forexample, a long, wide ski is best for new fallen, pow-dery, light snow, whereas a sharp, thin blade is bestfor hard-packed snow or smooth ice. Many skidesigns feature a wide, flat ski with aluminum or steelrunners on the bottom. Airplane skis may be madefrom composites, wood, or aluminum, and some havea polyethylene plastic sheathing bonded or riveted tothe bottom surfaces. Ski designs fall into two maincategories: plain and combination. Plain skis can onlybe used on snow and ice, while combination skis alsoallow the wheels to be used to land on runways.

PLAIN SKI TYPES• Wheel Replacement—Wheels are removed and

ski boards are substituted. [Figure 7-2]

• Clamp-On—Skis that attach to the tires andbenefit from the additional shock absorbingqualities of the tires.

• Roll-On or Full Board—Similar to the clamp-ontype except the tires are bypassed and do not carryside or torque loads. Only the tire cushioningeffect is retained with this installation.

COMBINATION SKI TYPES• Retractable Ski—Can be extended into place for

snow operations or retracted for non-snow opera-tions. This is accomplished by either a hydraulicpump or crank.

Figure 7-1. Skiplane.

Figure 7-2. Wheel replacement ski.

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• Penetration Ski—The wheel extends down par-tially below the ski, allowing the skiplane tooperate from both snow and non-snow surfaces.This type of ski gives poor ground clearance onnon-snow surfaces and causes extra drag whenon snow. [Figure 7-3]

The plastic polyethylene sheathing on the bottoms ofthe skis may be punctured by sharp objects, includingice. It also may shatter from impacts in extremely coldtemperatures. Replacing the bonded type sheathing isvery difficult in the field. If the sheathing is riveted,machine screws may be used to secure loose sheathing,but the screw holes must provide for expansion andcontraction. Follow the manufacturer’s recommen-dations for patching limited sheathing damage. Ifdamage is extensive, the entire ski bottom may neednew covering.

Shock cord bungees used in ski rigging deterioraterapidly when left under tension. When parking theskiplane overnight, detach the bungees at the lowerfitting and allow them to hang free. Reattaching thebungees normally requires two or more people.

Hydraulic ski retracting mechanisms usually functionwell in cold environments, but the small, abrupt changeof ski attitude occurring at touchdown imposes a severeload on the external hydraulic lines leading to the skis.These lines are a more prevalent source of trouble thanthe internal parts.

Use low temperature oils and greases to lubricate fric-tion points. For lubrication requirements, see theAFM/POH or the ski manufacturer’s manual.

The condition of the limiting cables and their fasten-ings is important to safety in flight. Be sure there is nofraying, kinking, rusting, or other defective conditionbefore each flight.

OPERATIONAL CONSIDERATIONSIn the air, skiplane flight characteristics are similar tothose of airplanes with standard landing gear, exceptfor a slight reduction in cruising speed and range.Leaving the skis in the extended position in flight pro-duces no adverse effect on trim, but may cause a slightloss of speed. Consult the operator’s manual forskiplane performance data, and weight and center ofgravity considerations.

The AFM/POH skiplane supplement may provide lim-itations including limiting airspeeds for operation withskis in flight and for other wheel/ski configurations.These speeds may be different from the wheel-typelanding gear configuration, depending on the type ofski and the tension of the springs or bungees holdingthe fronts of the skis up.

Understand both the limitations and advantages of theski equipment. Compared to the standard wheelequipped airplane that incorporates individual brakesfor steering, skis are clumsy and the airplane is lessmaneuverable while on the ground. Like a floatplane,a skiplane has a tendency to weathervane with thewind and needs considerable space to maneuver.Maneuvering on the ground and parking require spe-cial techniques which are acquired only throughpractice.

TYPES OF SNOW

• Powder Snow—Dry snow in which the watercontent and ambient temperature are low.

• Wet Snow—Contains high moisture and isassociated with warmer temperatures near thefreezing point.

• Granular Snow—Wet snow that has had atemperature drop causing the snow to ball upand/or crust.

TYPES OF ICE

• Glaze Ice—Snow that has been packed down andfrozen to a solid ice pack, or frozen snow.

• Glare Ice—A smooth sheet of ice that is exceed-ingly slippery with no deformities, cracks, orother irregularities in the surface. This ice lacksany kind of traction, with a coefficient of frictionnear zero.

• Clear Ice—Ice that forms smoothly over a sur-face and has a transparent appearance.

Figure 7-3. Penetration ski.

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attracting attention and signaling for help in bothdaylight and darkness; and treatment of injuries.Obtain appropriate survival training and know howto make effective use of the equipment. Whether thecause is a forced landing or an engine that fails torestart after landing at a remote location, the survivalgear and clothing should keep the pilot and passen-gers alive until help arrives.

When planning for an overnight stay away from an air-port, or if the skiplane is routinely parked outside, otheritems may be added to the equipment carried on theskiplane. These might include portable tiedowns, aflashlight, a shovel, and a broom. Wing and fuselagecovers can prevent the buildup of frost and snow, sim-plifying the preflight. In temperatures below 0° F, anengine cover and a catalytic heater may be necessary topreheat the engine compartment. If the pilot carriesappropriate hand tools and a bucket, the crankcase oilcan be drained from the engine and kept indoors. It mayalso be helpful to remove the battery and keep it in awarmer location. Many pilots carry burlap sacks, plasticgarbage bags, or wooden slats to place under the skis toprevent them from freezing to the surface. Some carry acan of non-stick cooking spray to use on the bottom ofthe ski to avoid sticking or freezing to the surface.Depending on the needs of the skiplane, it may be nec-essary to carry extra engine oil, hydraulic fluid, ordeicer fluid. Markers such as red rags, colored flags, orglow sticks may come in handy, as well as 50 feet ofnylon rope, and an ice pick or ice drill. Select equip-ment according to the situation, and know how to use it.

If a skiplane has been sitting outside overnight, themost important preflight issues are to ensure that theairframe is free of snow, ice, and frost and that the skisare not frozen to the ground. Often, while sitting onthe ground, precipitation may fall and cover theskiplane. Temperatures on the ground may be slightlycolder than in the air from which the precipitationfalls. When liquid precipitation contacts the colder air-craft structure, it can freeze into a coating of clear ice,which must be removed completely before flight.Wing and tail surfaces must be completely frost free.Any frost, ice, or snow destroys lift and also can causeaileron or elevator flutter. Aerodynamic flutter isextremely dangerous and can cause loss of control orstructural failure.

The preflight inspection consists of the standard aircraftinspection and includes additional items associated withthe skis. The AFM or POH contains the appropriatesupplements and additional inspection criteria. Typicalinspection criteria include:

• Skis—Examine the skis for damage, delamina-tion, sheathing security, and overall condition.

SURFACE ENVIRONMENTS• Glaciers—Sloping snow or ice packs.

• Frozen Lakes—Frozen bodies of water with orwithout snow cover.

• Tundra—A large area of grass clumps support-ing snow cover.

PREFLIGHTBefore departing on any trip, it is important to doproper preflight planning. A good preflight shouldinclude a review of the proposed route as well aspossible alternate routes; terrain; local, en route, anddestination weather; fuel requirements; facilitiesavailable at the destination; weight and balance; andtakeoff and landing distance requirements.

Obtain a complete weather briefing for each leg, andfile a flight plan with appropriate remarks. For localflights, always inform someone at home of the area ofoperation and the expected time of return if a flightplan is not filed.

Include good Aeronautical Decision Making (ADM)procedures, such as running a personal minimumschecklist, and think PAVE (Pilot, Aircraft,Environment, and External Pressures) during thepreflight phase.

Cold weather is implicit in flying a skiplane, sopreflight planning must also include preparationsfor possible contingencies unique to cold weatheroperations. This is especially important for flightsin bush country, where facilities are scarce andemergency assistance may be limited or nonexistent.

Evaluate all passengers’ clothing for suitability in theconditions expected. Consider the passenger whenmaking this evaluation. Children and older people needmore protection from the environment than a middle-aged person in good health. Every occupant should bedressed for a long walk, including adequate boots orrubber-bottomed shoes and an arctic parka. Sunglassesare highly recommended, even on cloudy days. Pilotscan be blinded by the brightness of the snow, and glarecan destroy depth perception.

Survival equipment is required by some states andcountries, and many areas require specific items foreven the shortest local flights. The requirements usu-ally vary between winter and summer months. Be sureto check the current requirements for the particularjurisdiction. Beyond the minimum requirements, usegood judgment to select and carry any other equipmentthat could help occupants survive an unplanned stay inthe specific terrain and environmental conditions alongthe route of flight. Always consider means of provid-ing warmth, shelter, water, and food; methods of

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• Hardware—Inspect the condition and securityof the clamping bolts, cotter keys, diaper pins,limiting cables, and bungees. Be sure cables andbungees are adjusted properly.

• Retracting Mechanism—(if equipped)—Checkthe hydraulic fluid level and examine thehydraulic lines for leaks. Inspect all cables forfraying and check cable ends for security. Do notcycle the retracting mechanism while on theground.

• Ski Freedom—Be sure the skis are free to moveand are not frozen to the surface. If the ambienttemperature approaches the melting point, theskis can be freed easily. Gentle swinging of thetail at the rear fuselage, or rocking the airplane atthe struts may free the skis. If this does not work,dig the skis out.

• Tire Pressure—Check the tire pressure whenusing skis that depend on the tires for shockabsorption, as well as for combination skis. Thisis especially important if moving a skiplane froma warm hangar to cold temperatures outdoors, astires typically lose one pound of pressure forevery ten-degree drop in ambient temperature.

• Tailwheel—Check the tailwheel spring and tailski for security, cracks, and signs of failure.Without a tail ski, the entire tailwheel and rudderassembly can be easily damaged.

• Fuel Sump—During fuel sump checks, some-times moisture can freeze a drain valve open,allowing fuel to continue to drain. Ice inside thefuel tank could break loose in flight and blockfuel lines causing fuel starvation. If the manufac-turer recommends the use of anti-icing additivesfor the fuel system during cold weather opera-tions, follow the ratio and mixing instructionsexactly.

• Survival Equipment—Check that all requiredsurvival equipment is on board and in good con-dition.

STARTING Adequately preheat the engine, battery, and the cockpitinstruments before startup and departure. Sometimesengine oil may require heating separately. Check themanufacturer’s recommendation for starting theengine when ambient temperatures are below freezing.

Batteries require special consideration. In cold climatesa strong, fully charged battery is needed. With just a lit-tle cold-soaking, the engine may require three times theusual amperage to crank the engine.

Another consideration is the electrolyte freezing point. Afully charged battery can withstand temperatures of -60to -90° F since the electrolyte’s specific gravity is at a

proper level. Conversely, the electrolyte in a weak ordischarged battery may freeze at temperatures near 32°F. If a fully charged battery is depleted by an unsuccess-ful start, it may freeze as it cools to ambienttemperature. Later, when the engine is started and thebattery is receiving a charge, it could explode.

After start, a proper warmup should be completedprior to a runup and high power settings. Performthe warmup according to the engine manufac-turer’s recommendations. Some manufacturersrecommend a minimum of 1,000 r.p.m. to ensureadequate lubrication.

If the skiplane is parked on heavily crusted snow orglaze ice with the skis frozen to the surface, it may bepossible to start the engine and perform the runup inthe parking area. Be sure the area behind the skiplaneis clear, so as not to cause damage with the propellerwash. If a ski should become unstuck during therunup, reduce power immediately. Then use one of thefollowing procedures to secure the airplane.

Tie down or chock the skiplane prior to engine start,warmup, and runup. Keep all ropes, bags, etc., clear ofthe propeller. After warmup is complete, and if noassistance is available, shut down the engine to untieand unchock the skiplane, then restart as quickly aspossible. If a post, tree, boulder, or other suitableobject is available, tie a rope to an accessible structuralcomponent in the cockpit, take the end around theanchor object, bring it back to the cockpit, and tie it offwith a quick-release knot. When the warmup andrunup are complete, release the knot and pull the ropeinto the cockpit as the skiplane begins to taxi.

If tiedowns or chocks are not available, build smallmounds of snow in front of each ski. The mounds mustbe large enough to prevent the skiplane from taxiingover them during engine start and warmup, but smallenough to allow taxiing when power is applied afterthe warmup is complete. If tiedowns or means to blockthe skis are not available, the runup can be accom-plished while taxiing when clear of obstacles or otherhazards. [Figure 7-4]

Figure 7-4. Engine warmup.

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TAXIINGTaxiing a skiplane on snow and ice presents someunusual challenges. With little or no brakes for stop-ping or turning, and the ability to skid sideways, askiplane normally requires more maneuvering roomand space to turn than an airplane with wheels.

The tailwheel ski provides marginal directional controlon ice and hard packed snow. In such conditions, direc-tional control comes from airflow over the rudder.Adding power and forward elevator control pressurecan often help turn the skiplane. The goal is to lightenthe tail to help the turn without putting the skiplane onits nose.

Taxiing in strong crosswinds can be difficult. Skiplanestend to weathervane into the wind. Drifting sideways inthe direction of the wind is also commonplace. Taxi ina skid or let the skiplane weathervane partly into thewind during crosswind operations to compensate.[Figure 7-5] A short blast of power may be required toturn the skiplane from upwind to downwind. It is nor-mal to drift sideways in turns. Preplan the taxi track soas to remain clear of drifts, ridges, or otherobstructions.

When taxiing in crosswinds on glare ice, get a helper ateach wingtip to help with turns and aligning theskiplane for takeoff.

As a general rule, power settings and taxi speeds shouldbe kept as low as possible on ice or crusted snow. Onloose or powder snow, add enough power to maintainforward motion and keep the skis on top of the snow.The skiplane may even be step-taxied in a manner sim-ilar to a floatplane, staying below takeoff speed. If theskiplane is allowed to sink into soft snow, it may stopmoving and become stuck. When the snow is wet andsticky, work the rudder and elevator to get the skiplanemoving and maintain forward motion to prevent theskis from sticking again. If the skis are freed during

preflight, but stick again before starting the engine andbeginning to taxi, free the skis again and pull theskiplane onto tree branches, leaves, or anything thatwill prevent the skis from sticking. Burlap bags canbe used by tying a line to the bags and pulling theminto the cockpit after the skiplane has taxied forward.Keep all ropes, bags, etc., clear of the propeller. Rapidrudder movement will usually break the skis free ifthey begin to stick during a slow taxi. Use a shortblast of power to create more airflow over the tail. Athin coat of engine oil or non-stick cooking spray alsoprevents sticking if the bottoms of the skis are easilyaccessed.

At some snow-covered airports, airport managers orfixed base operators spray red or purple dye onto taxiroutes and snow banks as visual aids. They may evenimbed pine boughs in the snow at regular intervals tohelp define taxiways and runways or mark hazardousareas. These helpful aids simplify ground operationsand improve safety.

TAKEOFFSSince skiplanes operate from a variety of surfaces, it isimportant to remember that many takeoff areas cancontain unforeseen hazards; therefore, it is important toalways plan for the unexpected.

If the condition of the takeoff path is unknown, walkor taxi the full length of the takeoff area and back tocheck the surface for hazards and help pack the snow.It is better to discover any irregularities beforeattempting a takeoff than to encounter them at highspeeds during takeoff.

Most takeoff distances are greater on snow than forwheel-equipped airplanes on cleared runways andother hard surfaces. On wet or powder snow, two orthree times the normal distance may be required. Besure to remove any frost or crusted snow from the skisbefore takeoff. Such accumulations increase drag andweight, resulting in a greater takeoff distance.

Select a takeoff direction that provides an adequatedistance to lift off and clear any obstructions. Useheadwinds or a downhill slope for takeoff whenpossible to ensure best performance. When turning intothe wind, keep moving and turn in a wide arc. Trying toturn too sharply can cause a ski to dig in, resulting in agroundloop or noseover.

Plan and configure for a soft-field takeoff. Soft-fieldprocedures are recommended because the lack ofcontrast and surface detail or glare off snow or icemay hide possible hazards. Undetected drifts or softsticky spots can cause sudden deceleration and evena possible noseover.

Directionof Movement

Figure 7-5. Crosswind taxi.

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When lining up to depart, have the skiplane configuredproperly and keep moving. Do not stop before addingtakeoff power because the skiplane may settle into softsnow and limit acceleration. If this happens, it may benecessary to taxi the takeoff path again to pack thesnow.

Crosswind takeoffs require the standard procedures andtechniques. Be aware that the skiplane may be slidingin a crab during takeoff acceleration. On glaze ice anincrease in lateral drift may be seen on takeoff.

OFF-AIRPORT LANDING SITESLandings on unprepared areas can be accomplishedsafely if the proper precautions are followed.Evaluating each new landing site thoroughly, obtainingadvice from well-qualified pilots already familiar withthe area, and staying within the limitations of personalskill and experience can all contribute to safety andreduce risks.

GLACIERSThere are a number of factors that must be consid-ered when operating from glaciers. There can bemany hidden hazards.

The first consideration is the condition of the snow andits suitability for landing. To evaluate a new area, flydownhill with the skis on the surface, just touching thesnow, as slowly as possible above stall speed. Thishelps determine the snow condition. If unsure of thequality of the snowpack, look for a gentle slope andland up the slope or hill. This situation will allow theairplane to accelerate easily on a downslope takeoff.

If the slope angle of the landing area is very steep,always evaluate the area for the possibility of an ava-lanche. Avoid landing near the bottom of a valleybecause ice falls may exist and provide rough andunusable terrain.

Glaciers are very deceptive. It is advisable to train withan experienced glacier pilot and become comfortablebefore departing alone. Use extreme caution, as just afew clouds overhead can totally change the picture ofthe intended landing area.

LAKES AND RIVERSSnow-covered frozen lakes and rivers can provide anumber of obstacles. Wind causes snow to form intoripple-shaped wind drifts. Wind also breaks snow intosmaller particles, which bond quickly together to formsolid ridges. These ridges can be so rough that they candamage or destroy the landing gear and skiplane. Thebest plan is to land parallel to ridge rows, even if thereis a slight crosswind. Another option is to find a lee area(protected area), where there are no wind drifts andland in this area.

Other problems that may be encountered are beaverdams, houses, or other hidden obstructions that havebeen covered with snow and have become invisible,especially in flat lighting situations.

A condition known as “overflow” can present prob-lems on landing and takeoff. The overflow is water, ina liquid state, that is cooled below its freezing point.The moment a ski or any other part of the skiplanetouches this supercooled water, it freezes solid. As thewater freezes, it will provide a rapid deceleration.Overflow may exist on frozen lakes and rivers with orwithout snow cover. Thin ice also creates a problembecause it is not always obvious. It may be thickenough to support a layer of snow or other material,but not a skiplane.

It is easier to see obstacles on lakes and rivers that arefrozen without snow cover. Spider holes are portsformed by escaping air from under the ice, forming aweak area or bubble at the surface. These may or maynot support the skiplane. Avoid running over spiderholes.

Clear ice, under certain conditions, can be extremelyslick and will not allow directional control once theaerodynamic controls become ineffective due to theloss of airflow. This becomes critical in crosswindlanding conditions.

Avoid landing near the shoreline where rivers or sewerlines empty into lakes. The ice is likely to be very thinin those areas.

TUNDRATundra is probably the least desirable landing surfacesince most of the above hazards can exist. Tundra istypically composed of small clumps of grass that cansupport snow and make ridge lines invisible. They alsohide obstacles and obscure holes that may be too weakto support skiplanes. Avoid tundra unless the area iswell known. [Figure 7-6]

LIGHTINGPilots routinely encounter three general lightingconditions when flying skiplanes. They are flatlighting, whiteout, and nighttime. The implications

Figure 7-6.Tundra.

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of nighttime are obvious, and in the interest ofsafety, night operations from unlighted airstrips arenot recommended.

Flat lighting is due to an overcast or broken skycondition with intermittent sunlight. Hills, valleys, andsnow mounds take on varying shades of white, and mayappear taller, shorter, or wider than they really are. Thisindirect lighting alters depth perception. The pilot maynot realize that depth perception has been compro-mised, and this can cause serious consequences whenoperating skiplanes near hilly terrain. When flatlighting is encountered, avoid or discontinue flightoperations, especially at an unfamiliar strip.

Whiteout can occur when flying in a valley with bothwalls obscured by snow or fog. Clear sky conditionscan exist, but references cannot be established.Reference to attitude gyro instruments helps when thiscondition is encountered. Climb out of the valley soadditional visual references can be established.

Takeoffs and landings should not be attempted underflat lighting or whiteout conditions.

LANDINGSLanding a skiplane is easy compared to landingwith wheels; however, for off-airport landings,extra precautions are necessary. Be careful inchoosing a landing site. Before landing, evaluatethe site to be sure a safe departure will be possible.

Upon arriving at a prospective landing site, a passshould be made over the landing area to determinelanding direction, and to determine if a safe approachand landing can be completed. A trial landing shouldbe accomplished to determine the best approach, sub-sequent departure path, and the quality of the surface.

To perform the trial landing, plan and configure for asoft-field landing with a stable approach. Then per-form a gentle soft-field touchdown, controlled withpower, while remaining near takeoff speed forapproximately 600 to 800 feet, and then initiating ago-around.

A trial landing is very helpful in determining the depthand consistency of the snow, evaluating surface condi-tions, and looking for possible hazards. Be prepared togo around if at any time the landing does not appearnormal or if a hazard appears. Do not attempt to landif the ski paths from the trial landing turn black. Thisindicates “overflow” water beneath the snow wettingthe tracks.

When landing on a level surface, and the wind can bedetermined, make the landing into the wind. If landingon a slope, an uphill landing is recommended. Toavoid a hard landing, fly the skiplane all the way to the

surface and add some power just before touchdown.Be sure to turn the skiplane crosswise to the slopebefore it stops. Otherwise it may slide backward downthe slope.

When using combination skis to land on solid ice with-out the benefit of snow, it is better to land with thewheels extended through the skis to improve the groundhandling characteristics. Solid or clear ice surfacesrequire a much greater landing distance due to the lackof friction. The skiplane also needs more area for turnswhen taxiing. If the surface has little or no friction, con-sider the possibility of a groundloop, since the center ofgravity is typically behind the main skis and the tail skimay not resist side movement. Keep the skiplanestraight during the runout, and be ready to use a burst ofpower to provide airflow over the rudder to maintaindirectional control.

Under bright sun conditions and without brush or treesfor contrast, glare may restrict vision and make it diffi-cult to identify snowdrifts and hazards. Glare can alsoimpair depth perception, so it is usually best to plan asoft-field landing when landing off airports.

After touchdown on soft snow, use additional power tokeep the skiplane moving while taxiing to a suitableparking area and turning the skiplane around. Taxislowly after landing to allow the skis to cool down priorto stopping. Even though they are moving against coldsurfaces, skis warm up a few degrees from the frictionand pressure against the surface. Warm skis could thawthe snow beneath them when parked, causing the skis tofreeze to the surface when they eventually cool.

PARKING/POSTFLIGHTSkiplanes do not have any parking brakes and willslide on inclines or sloping surfaces. Park perpendicu-lar to the incline and be prepared to block or chock theskis to prevent movement.

When parked directly on ice or snow, skis may freezeto the surface and become very difficult to free. Thishappens when there is liquid water under the skis thatsubsequently freezes. If both the surface and the skisare well below freezing, there will be no problem, butif the skis are warm when the airplane stops, they meltthe surface slightly, then the surface refreezes as theheat flows into the ground. Similarly, the weight ofthe skiplane places pressure on the skis, and pressuregenerates heat. If the ambient temperature goes up tojust below freezing, the heat of pressure can melt thesurface under the skis. Then as the temperature dropsagain, the skis become stuck.

If parking for a considerable amount of time, supportthe skis above the snow to prevent them from stickingor freezing to the surface. Place tree boughs, woodslats, or other materials under the skis to help prevent

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them from becoming frozen to the surface. [Figure 7-7]Some pilots apply a coat of non-stick cooking spray orengine oil to the polypropylene ski surface to preventice or snow from sticking during the next takeoff.

If the skis are the retractable type and the frozen sur-face will support the wheels, place the skis in the UPposition. Next, dig the snow out from around the skisuntil ready to depart. This keeps the skis away fromthe surface. When parking on a hill, pay attention tothe position of the fuel selector valve. Typically, theuphill tank should be selected to prevent fuel fromtransferring to the lower wing and subsequentlyventing overboard.

EMERGENCY OPERATIONSWhen operating a skiplane, carry an adequate survivalkit. A good rule of thumb is to carry what is needed tobe comfortable. Alaska, Canada, and Sweden providelists on the internet of the survival equipment requiredfor flights in northern areas. In addition to communi-cating the current requirements for specificjurisdictions, these lists can help pilots chooseadditional equipment to meet their needs, beyond theminimum required. Also be sure to check for anyrestrictions on the carriage of firearms if they are partof your survival kit.

SKI MALFUNCTIONIf skis are not rigged properly, or when recommendedairspeeds are exceeded, it is possible that a ski will tuckdown and give a momentary downward rotation of thenose of the skiplane. This is generally caused by springor bungee tension not being sufficient to hold ski tipsup. The immediate fix is to reduce power and reducethe speed of the skiplane. When the air loads aredecreased below the tension of the spring or bungee,the ski will pitch back into place and the control prob-lem will go away. Have a maintenance shop correctlyadjust the spring or bungee tension and avoid exceed-ing the speed limits specified for the skis.

A precautionary landing may be necessary for eventssuch as a broken ski cable or broken hydraulic line. If aski cable breaks, the front of the ski will tip down. Thiscreates an asymmetrical drag situation, similar to alarge speed brake on one side of the skiplane. This con-dition is controllable; however, it will take skill tomaintain control. Not only does the tilted ski create alot of drag, it also complicates the landing, since thefront of the ski will dig in as it contacts the surface,causing abrupt deceleration and severe damage to thelanding gear. If efforts to get the ski into a stream-lined position fail, a landing should be made as soonas practical.

To attempt to streamline the ski, slow to maneuveringspeed or less. It may be possible for a passenger to use along rod such as a broom handle to push down on theback end of the ski, aligning it with the airflow and mak-ing possible a relatively normal landing. If the skis areretractable, try to ensure that they are both in the UP posi-tion (for a pavement landing) and land on pavement.

If it is not possible to get the ski to trail correctly, theskiplane must be landed in such a way as to minimizedanger to the occupants. This usually means trying toland so that the hanging ski breaks off quickly ratherthan digging in and possibly destroying the skiplane. Flyto an area where help is available, since damage is virtu-ally inevitable. It is often best to land on a hard surfaceto increase the chances of the ski breaking away.

With a broken hydraulic line, a condition of one ski upand one ski down may develop. Again, the skiplane iscontrollable with proper rudder and braking technique.

NIGHT EMERGENCY LANDINGA night landing should never be attempted at an unfa-miliar location except in an emergency. To increasethe likelihood of a successful landing, perform thechecklist appropriate for the emergency, and unlatchthe doors prior to landing to prevent jamming due toairframe distortion in the event of a hard landing. Iftime permits, make distress calls and activate theemergency locator transmitter (ELT).

When selecting a landing area, frozen lakes and riversare a good choice if the ice is thick enough to supportthe aircraft. If the ice is thin or the thickness unknown,a landing in an open field would be a better option.

After selecting a landing area, perform a reconnais-sance and look for obstructions, field condition, winddirection, and snow conditions if possible. Fly over thelanding area in the intended direction of touchdown anddrop glow sticks 2 seconds apart along the length of thetouchdown zone. Use the glow sticks to aid in depth per-ception during final approach. Make the touchdownwith power, if available, and as slow as possible.

Figure 7-7. Supporting the skis above the surface preventsthem from freezing in place.

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OPERATIONS IN OPEN SEASOpen sea operations are very risky and should beavoided if possible. If an open sea landing cannot beavoided, a thorough reconnaissance and evaluation ofthe conditions must be performed to ensure safety. Thesea usually heaves in a complicated crisscross patternof swells of various magnitudes, overlaid by whateverchop the wind is producing. A relatively smooth spotmay be found where the cross swells are less turbulent.Both a high and a low reconnaissance are necessaryfor accurate evaluation of the swell systems, winds,and surface conditions.

DEFINITIONSWhen performing open sea operations, it is impor-tant to know and understand some basic ocean terms.A thorough knowledge of these definitions allowsthe pilot to receive and understand sea conditionreports from other aircraft, surface vessels, andweather services.

Fetch—An area where wind is generating waves onthe water surface. Also the distance the waves havebeen driven by the wind blowing in a constant direc-tion without obstruction.

Sea—Waves generated by the existing winds in thearea. These wind waves are typically a chaotic mix ofheights, periods, and wavelengths. Sometimes the termrefers to the condition of the surface resulting fromboth wind waves and swells.

Swell—Waves that persist outside the fetch or in theabsence of the force that generated them. The waveshave a uniform and orderly appearance characterizedby smooth, regularly spaced wave crests.

Primary Swell—The swell system having the greatestheight from trough to crest.

Secondary Swells—Swell systems of less height thanthe primary swell.

Swell Direction—The direction from which a swell ismoving. This direction is not necessarily the result ofthe wind present at the scene. The swell encounteredmay be moving into or across the local wind. A swelltends to maintain its original direction for as long as itcontinues in deep water, regardless of changes in winddirection.

Swell Face—The side of the swell toward the observer.The back is the side away from the observer.

Swell Length—The horizontal distance between suc-cessive crests.

Swell Period—The time interval between the passageof two successive crests at the same spot in the water,measured in seconds.

Swell Velocity—The velocity with which the swelladvances in relation to a fixed reference point, meas-ured in knots. (There is little movement of water in thehorizontal direction. Each water particle transmitsenergy to its neighbor, resulting primarily in a verticalmotion, similar to the motion observed when shakingout a carpet.)

Chop—A roughened condition of the water surfacecaused by local winds. It is characterized by its irregu-larity, short distance between crests, and whitecaps.

Downswell—Motion in the same direction the swell ismoving.

Upswell—Motion opposite the direction the swell ismoving. If the swell is moving from north to south, aseaplane going from south to north is moving upswell.

SEA STATE EVALUATIONWind is the primary cause of ocean waves and there isa direct relationship between speed of the wind and thestate of the sea in the immediate vicinity. Windspeedforecasts can help the pilot anticipate sea conditions.Conversely, the condition of the sea can be useful indetermining the speed of the wind. Figure 8-1 on thenext page illustrates the Beaufort wind scale with thecorresponding sea state condition number.

While the height of the waves is important, it is oftenless of a consideration than the wavelength, or the dis-tance between swells. Closely spaced swells can bevery violent, and can destroy a seaplane even thoughthe wave height is relatively small. On the other hand,the same seaplane might be able to handle much higherwaves if the swells are several thousand feet apart. Therelationship between the swell length and the height of

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the waves is the height-to-length ratio [Figure 8-2].This ratio is an indication of the amount of motion aseaplane experiences on the water and the threat to cap-sizing. For example, a body of water with 20-footwaves and a swell length of 400 feet has a height-to-length ratio of 1:20, which may not put the seaplane atrisk of capsizing, depending on the crosswinds.

However, 15-foot waves with a length of 150 feet pro-duce a height-to-length ratio of 1:10, which greatlyincreases the risk of capsizing, especially if the wave isbreaking abeam of the seaplane. As the swell lengthdecreases, swell height becomes increasingly critical tocapsizing. Thus, when a high swell height-to-lengthratio exists, a crosswind takeoff or landing should notbe attempted. Downwind takeoff and landing may bemade downswell in light and moderate wind; however,a downwind landing should never be attempted whenwind velocities are high regardless of swell direction.

When two swell systems are in phase, the swells acttogether and result in higher swells. However, whentwo swell systems are in opposition, the swells tend tocancel each other or “fill in the troughs.” This providesa relatively flat area that appears as a lesser concentra-tion of whitecaps and shadows. This flat area is a goodtouchdown spot for landing. [Figure 8-3]

Sea surface smooth and mirror-like

Scaly ripples, no foam crests

Small wavelets, crests glassy, no breaking

Large wavelets, crests begin to break, scattered whitecaps

Small waves, becoming longer, numerous whitecaps

Moderate waves, taking longer form, many whitecaps, some spray

Larger waves, whitecaps common, more spray

Sea heaps up, white foam streaks off breakers

Moderately high, waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks

High waves, sea begins to roll, dense streaks of foam, spray may reduce visibility

Very high waves, with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility

Exceptionally high waves, foam patches cover sea, visibility more reduced

Air filled with foam, sea completely white with driving spray, visibility greatly reduced

Calm, glassy

0

Calm, rippled0 – 0.3

Smooth, wavelets0.3-1

Slight1-4

Moderate4-8

Rough8-13

Very rough13-20

High20-30

Very high30-45

Phenomenal45 and over

0

1

2

3

4

5

6

7

8

9

0

1

2

3

4

5

6

7

8

9

10

11

12

Less than1

1-3

4-6

7-10

11-16

17-21

22-27

28-33

34-40

41-47

48-55

56-63

64 and over

Beaufort Number

Wind Velocity (Knots)

Calm

Light Air

Light Breeze

Gentle Breeze

ModerateBreeze

Fresh Breeze

Strong Breeze

Near Gale

Gale

Strong Gale

Storm

Violent Storm

Hurricane

Wind Description Sea State Description

Term and Height of

Waves (Feet)

Sea State

ConditionNumber

BEAUFORT WIND SCALE WITH CORRESPONDING SEA STATE CODES

Figure 8-1. Beaufort wind scale.

400 Feet

150 Feet

20 Feet

15 Feet

Height-to-Length Ratio 1: 20

Height-to-Length Ratio 1: 10

Figure 8-2. Height-to-length ratio.

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5. To determine the swell length or distancebetween crests in feet, multiply the square of theswell period by 5. For example, using a 6-secondswell period, 62 multiplied by 5 equals 180 feet.[Figure 8-4]

LOW RECONNAISSANCEPerform the low reconnaissance at 500 feet to confirmthe findings of the high reconnaissance and obtain amore accurate estimate of wind direction and velocity.

If the direction of the swell does not agree with thedirection noted at 2,000 feet, then there are two swellsystems from different directions. The secondary swellsystem is often moving in the same direction as thewind and may be superimposed on the first swell sys-tem. This condition may be indicated by the presenceof periodic groups of larger-than-average swells.

The wind direction and speed can be determined bydropping smoke or observing foam patches, white-caps, and wind streaks. Whitecaps fall forward withthe wind but are overrun by the waves. Thus, the foampatches appear to slide backward into the directionfrom which the wind is blowing. To estimate windvelocity from sea surface indications, see figure 8-1.

SELECT LANDING HEADINGWhen selecting a landing heading, chart all observedvariables and determine the headings that will provethe safest while taking advantage of winds, if possible.Descend to 100 feet and make a final evaluation byflying the various headings and note on which headingthe sea appears most favorable. Use the heading thatlooks smoothest and corresponds with one of the pos-sible headings selected by other criteria.

Consider the position of the sun. A glare on the waterduring final approach might make that heading anunsafe option.

Use caution in making a decision based on the appear-ance of the sea. Often a flightpath directly downswellappears to be the smoothest, but a landing on thisheading could be disastrous.

SWELL SYSTEM EVALUATIONThe purpose of the swell system evaluation is to deter-mine the surface conditions and the best heading andtechnique for landing. Perform a high reconnaissance,a low reconnaissance, and then a final determination oflanding heading and touchdown area.

HIGH RECONNAISSANCEDuring the high reconnaissance, determine the swellperiod, swell velocity, and swell length. Perform thehigh reconnaissance at an altitude of 1,500 to 2,000feet. Fly straight and level while observing the swellsystems. Perform the observation through a complete360º pattern, rolling out approximately every 45º.

Fly parallel to each swell system and note the heading,the direction of movement of the swell, and the direc-tion of the wind.

To determine the time and distance between crests, andtheir velocity, follow these directions:

1. Drop smoke or a float light and observe the windcondition.

2. Time and count the passage of the smoke or floatlight over successive crests. The number ofwaves is the number of crests counted minus one.(A complete wave runs from crest to crest. Sincethe timing starts with a crest and ends with acrest, there is one less wave than crests.) Timeand count each swell system.

3. Obtain the swell period by dividing the time inseconds by the number of waves. For example, 5waves in 30 seconds equates to a swell period of6 seconds.

4. Determine the swell velocity in knots by multi-plying the swell period by 3. In this example, 6seconds multiplied by 3 equals 18 knots.

Resultant Wave

Wave A Wave B

Resultant Wave

Wave A Wave B

Figure 8-3. Wave interference.

Swell Period

Swell Velocity Swell Period x 3 knots

Swell Length Swell Period2 x 5 Feet

Time in SecondsNumber of Waves Counted

Figure 8-4. Rules of thumb to determine swell period,velocity, and length.

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SELECT TOUCHDOWN AREAOn final approach, select the touchdown area bysearching for a null or smooth area in the swell sys-tem, avoiding rough areas if possible. When doing so,consider the conditions discussed in the followingsections.

LANDING PARALLEL TO THE SWELLWhen landing on a swell system with large, widelyspaced crests more than four times the length of thefloats, the best landing heading parallels the crests andhas the most favorable headwind component. In thissituation, it makes little difference whether touchdownis on top of the crest or in the trough.

LANDING PERPENDICULAR TO THE SWELLIf crosswind limits would be exceeded by landing par-allel to the swell, landing perpendicular to the swellmight be the only option. Landing in closely spacedswells less than four times the length of the floatsshould be considered an emergency procedure only,since damage or loss of the seaplane can be expected.If the distance between crests is less than half the lengthof the floats, the touchdown may be smooth, since thefloats will always be supported by at least two waves,but expect severe motion and forces as the seaplaneslows.

A downswell landing on the back of the swell is pre-ferred. However, strong winds may dictate landing intothe swell. To compare landing downswell with landinginto the swell, consider the following example.Assuming a 10-second swell period, the length of theswell is 500 feet, and it has a velocity of 30 knots or 50feet per second. Assume the seaplane takes 890 feet and5 seconds for its runout.

Downswell Landing—The swell is moving with theseaplane during the landing runout, thereby increas-ing the effective swell length by about 250 feet andresulting in an effective swell length of 750 feet. If

the seaplane touches down just beyond the crest, itfinishes its runout about 140 feet beyond the nextcrest. [Figure 8-5]

Landing into the Swell—During the 5 seconds ofrunout, the oncoming swell moves toward the seaplanea distance of about 250 feet, thereby shortening theeffective swell length to about 250 feet. Since the sea-plane takes 890 feet to come to rest, it would meet theoncoming swell less than halfway through its runoutand it would probably be thrown into the air, out ofcontrol. Avoid this landing heading if at all possible.[Figure 8-6]

If low ceilings prevent complete sea evaluation fromthe altitudes prescribed above, any open sea landingshould be considered a calculated risk, as a dangerousbut unobserved swell system may be present in theproposed landing area. Complete the descent andbefore-landing checklists prior to descending below1,000 feet if the ceiling is low.

LANDING WITH MORE THAN ONE SWELLSYSTEM Open water often has two or more swell systemsrunning in different directions, which can present aconfusing appearance to the pilot. When the second-ary swell system is from the same direction as thewind, the preferred direction of landing is parallelto the primary swell with the secondary swell atsome angle. When landing parallel to the primaryswell, the two choices of heading are either upwindand into the secondary swell, or downwind anddownswell. The heading with the greatest headwindis preferred; however, if a pronounced secondaryswell system is present, it may be desirable to landdownswell to the secondary swell system and acceptsome tailwind component. The risks associated withlanding downwind versus downswell must be care-fully considered. The choice of heading depends onthe velocity of the wind versus the velocity and theheight of the secondary swell. [Figure 8-7]

Direction ofSwell Movement

Direction ofSwell Movement

Direction ofSwell Movement

Position of Swell HalfwayThrough Runout

Position of Swell atEnd of Runout

Position of Swellat Touchdown

Figure 8-5. Landing in the same direction as the movement of the swell increases the apparent length between swell crests.

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Due to the rough sea state, landings should not beattempted in winds greater than 25 knots except inextreme emergencies. Crosswind limitations for eachtype of seaplane must be the governing factor in cross-wind landings.

EFFECT OF CHOP Chop consists of small waves caused by local winds inexcess of 14 knots. These small waves ride on top ofthe swell system and, if severe, may hide the underly-

ing swell system. Alone, light and moderate chop arenot considered dangerous for landings.

NIGHT OPERATIONSNight landings in seaplanes on open water areextremely dangerous with a high possibility of damageor loss of the seaplane. A night landing should only beperformed in an extreme emergency when no otheroptions are available. A night landing on a lighted run-way exposes the seaplane to much less risk.

Directionof Swell

Directionof Swell

Directionof Swell

Position of Swellat Touchdown

Position of Swellat End of Runout

Position of SwellHalfway ThroughRunout

Land

ing

Headin

g

Land

ingHea

ding

PrimarySwell Direction

Primary SwellDirection

SecondarySwell Direction

Figure 8-6. Landing against the swell shortens the apparent distance between crests, and could lead to trouble.

Figure 8-7. Landing heading in single and multiple swell systems.

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If operating at night, equip the seaplane with parachuteflares, smoke floats, glow sticks, or other markers.

SEA EVALUATION AT NIGHTBefore attempting a night landing, perform a sea stateevaluation as described in previous sections. If anemergency occurs shortly after nightfall, a landingheading can be determined by estimating the currentconditions from those conditions prevalent beforenightfall. If the pilot has no information to form an esti-mate of the conditions, the information must beobtained from other sources or determined by the pilotfrom a sea state evaluation by flare illumination ormoonlight. If near a ship, sea weather conditions and arecommended landing heading may be obtained fromthe ship. However, a landing heading based on suchinformation is subject to error and should only be usedas a last resort. A pilot evaluation is preferred and canbe accomplished by performing the teardrop patternnight sea evaluation as follows:

1. Set a parachute flare and adjust the altitude sothat the flare ignites at 1,700 feet. Altitude shouldbe as close to 2,000 feet as possible.

2. After the drop, adjust altitude to 2,000 feet andmaintain the heading for 45 seconds.

3. Turn back 220º, left or right, until the flare isalmost dead ahead. The sea becomes visible afterthe first 70º of the turn is completed, allowingapproximately 90 seconds for sea evaluation. Usestandard rate turn (3º per second).

4. Immediately after passing the flare, if it is stillburning, the pilot may circle to make additionalevaluation during remaining burning time.

If both pilot and copilot are present, the pilot should flythe seaplane and the copilot should concentrate on thesea evaluation. If only two flares are available and seaconditions are known or believed to be moderate, itmay be advisable to dispense with the sea evaluationand use both flares for landing.

NIGHT EMERGENCY LANDINGA night landing should be performed only afterexhausting all other options. Be sure all occupants arewearing life vests and secure loose items prior totouchdown. Remove liferafts and survival equipmentfrom their storage containers and give them to thoseoccupants closest to the exits. Prior to the landing pat-tern, unlatch the doors to prevent jamming that maybe caused by airframe distortion from a hard landing.If time permits, make distress calls and activate theemergency locator transmitter.

LANDING BY PARACHUTE FLAREWhen a landing heading has been determined and allemergency and cockpit procedures have been

accomplished, the landing approach with the use ofparachute flares is made as follows:

1. Establish a heading 140º off the selected landingheading.

2. Lower the flaps and establish the desired landingpattern approach speed.

3. As close to 2,000 feet above the surface as possi-ble, set the parachute flare and adjust the altitudeso the flare ignites at 1,700 feet.

4. Release the flare and begin a descent of 900f.p.m. while maintaining heading for 45 seconds.If the starting altitude is other than 2,000 feet,determine the rate of descent by subtracting 200feet and dividing by two. (For example, 1800feet minus 200 is 1600, divided by 2 equals an800 f.p.m. rate of descent).

5. After 45 seconds, make a standard rate turn of 3ºper second toward the landing heading in linewith the flare. This turn is 220º and takes approx-imately 73 seconds.

6. Roll out on the landing heading in line with theflare at an altitude of 200 feet. During the lasttwo-thirds of the turn, the water is clearly visi-ble and the seaplane can be controlled by visualreference.

7. Land straight ahead using the light of the flare.Do not overshoot. Overshooting the flare resultsin a shadow in front of the aircraft making depthperception very difficult. The best touchdownpoint is several hundred yards short of the flare.

A rapid descent in the early stages of the approachallows a slow rate of descent when near the water. Thisshould prevent flying into the water at a high rate ofdescent due to faulty depth perception or altimeter set-ting. [Figure 8-8]

LANDING BY MARKERSIf parachute flares are not available, use a series oflighted markers to establish visual cues for landing.When a landing heading has been determined and allemergency and cockpit procedures are completed, usedrift signals or smoke floats and perform the landingapproach as follows:

1. Establish a heading on the reciprocal of the land-ing heading.

2. Drop up to 20 markers at 2 second intervals.

3. Perform a right 90º turn followed immediatelyby a 270º left turn while descending to 200 feet.

4. Slightly overshoot the turn to the final approachheading to establish a path parallel and slightlyto the right of the markers.

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5. Establish a powered approach with a 200 f.p.m.rate of descent and airspeed 10 percent to 20 per-cent above stall speed with flaps down, as if fora glassy water landing.

6. Maintain the landing attitude until water contact,and reduce power to idle after touchdown.

Do not use landing lights during the approach unlessconsiderable whitecaps are present. The landing lightsmay cause a false depth perception. [Figure 8-9]

EMERGENCY LANDING UNDERINSTRUMENT CONDITIONSWhen surface visibilities are near zero, the pilot hasno alternative but to fly the seaplane onto the water byinstruments. A landing heading can be estimated fromforecasts prior to departure, broadcast sea conditions,or reports from ships in the area. Obtain the latest localaltimeter setting to minimize the possibility of altitudeerrors during the approach.

Due to the high possibility of damage or capsizingupon landing, be sure all occupants have life vests onand secure all loose items prior to touchdown. Removeliferafts and survival equipment from their storagecontainers and give them to those occupants closest tothe exits. Prior to the landing pattern, unlatch doors toprevent jamming caused by airframe distortion from ahard landing. If time permits, transmit a distress calland activate the emergency locator transmitter.

After choosing a landing heading, establish a finalapproach with power and set up for a glassy waterlanding. Establish a rate of descent of 200 f.p.m. andmaintain airspeed 10 to 20 percent above stall speedwith flaps down. Establish the landing attitude byreferring to the instruments. Maintain this approachuntil the seaplane makes contact with the water, oruntil visual contact is established.

140°

220°73 Seconds

45Seconds

200Feet

TouchdownZone

2,000Feet

LandingHeading

Figure 8-8. Landing by parachute flare.

LandingHeading

TouchdownZone

200 f.p.m. Rate ofDescent 10% to 20%Above Stall Speed.Flaps Down

90°

270°

200 Feet

Figure 8-9. Landing by markers.

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ESCAPING A SUBMERGED SEAPLANEIf a seaplane capsizes, it is absolutely essential thatboth pilot and passengers understand how to exit theseaplane and find their way safely to the surface. Pilotsshould become thoroughly familiar with possibleescape scenarios and practice to the extent possible sothat they will be able to react instantly in an emergency.Passengers can not be expected to have any prior train-ing in water survival, and an actual emergency is not agood time to try to instruct them. Therefore, a completebriefing before takeoff is very important. At a mini-mum, the portions of the passenger briefing that dealwith escaping from the seaplane in an emergencyshould cover orientation, water pressure issues, the useof flotation equipment, and both normal and unusualmethods of leaving the seaplane.

ORIENTATIONMany of those who have survived seaplane accidentsemphasize how disorienting this situation can be.Unlike the clear water of a swimming pool, the wateraround a seaplane after an accident is usually murky anddark, and may be nearly opaque with suspended silt. Inmost cases the seaplane is in an unusual attitude,making it difficult for passengers to locate doors oremergency exits. In a number of cases, passengers havedrowned while pilots have survived simply because ofthe pilots’ greater familiarity with the inside of theseaplane. Use the preflight briefing to address disorien-tation by helping passengers orient themselvesregardless of the seaplane’s attitude. Help thepassengers establish a definite frame of reference insidethe seaplane, and remind them that even if the cabin isinverted, the doors and exits remain in the samepositions relative to their seats. Also, brief passengerson how to find their way to the surface after gettingclear of the seaplane. Bubbles always rise toward thesurface, so advise passengers to follow the bubbles toget to the surface.

WATER PRESSURE The pressure of water against the outside of the doorsand windows may make them difficult or impossible toopen. Passengers must understand that doors and win-dows that are already underwater may be much easierto open, and that it may be necessary to equalize thepressure on both sides of a door or window before itwill open. This means allowing the water level to riseor flooding the cabin adjacent to the door, which can bevery counter-intuitive when trapped underwater.

FLOTATION EQUIPMENTPersonal flotation devices (PFDs) are highly recom-mended for pilots and all passengers on seaplanes.

Since the probability of a passenger finding, unwrap-ping, and putting on a PFD properly during an actualcapsizing is rather low, some operators encouragepassengers to wear them during the starting, taxiing,takeoff, landing, and docking phases of flight.

Not all PFDs are appropriate for use in aircraft. Thosethat do not have to be inflated, and that are bulky andbuoyant all the time, can be more of a liability in anemergency, and actually decrease the wearer’s chancesof survival. Many of the rigid PFDs used for waterrecreation are not suitable for use in a seaplane. In gen-eral, PFDs for aircraft should be inflatable so that theydo not keep the user from fitting through small open-ings or create buoyancy that could prevent the wearerfrom swimming downward to an exit that is underwa-ter. Obviously, once the wearer is clear of the seaplane,the PFD can be inflated to provide ample support onthe water.

The pretakeoff briefing should include instructionsand a demonstration of how to put on and adjust thePFD, as well as how to inflate it. It is extremely impor-tant to warn passengers never to inflate the PFD insidethe seaplane. Doing so could impede their ability toexit, prevent them from swimming down to a sub-merged exit, risk damage to the PFD that would makeit useless, and possibly block the exit of others fromthe seaplane.

NORMAL AND UNUSUAL EXITSThe briefing should include specifics of operating thecabin doors and emergency exits, keeping in mind thatthis may need to be done without the benefit of vision.Doors and emergency exits may become jammed dueto airframe distortion during an accident, or they maybe too hard to open due to water pressure. Passengersshould be aware that kicking out a window or thewindshield may be the quickest and easiest way to exitthe seaplane. Because many seaplanes come to rest ina nose-down position due to the weight of the engine,the baggage compartment door may offer the best pathto safety.

In addition to covering these basic areas, be sure totell passengers to leave everything behind in the eventof a mishap except their PFD. Pilots should neverassume that they will be able to assist passengers afteran accident. They may be injured, unconscious, orimpaired, leaving passengers with whatever theyremember from the pilot’s briefing. A thorough brief-ing with clear demonstrations can greatly enhance apassenger’s chance of survival in the event ofa mishap.

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Helicopters are capable of landing in places inaccessi-ble to other aircraft. In addition to rooftops, mountaintops, pinnacles, and other unprepared locations, thereare times when a pilot may have to operate a helicopterin areas that do not offer a solid place to land. For thoseoperations, the normal skid gear configuration can bereplaced with a set of floats for water operations or skisfor winter operations.

Note: In this chapter, it is assumed that the helicopterhas a counterclockwise main rotor blade rotation asviewed from above.

FLOAT EQUIPPED HELICOPTERSUnlike airplanes, there is no additional rating requiredfor helicopter float operations. However, it is stronglyrecommended that pilots seek instruction from aqualified instructor prior to operating a float equippedhelicopter. Check the Pilot’s Operating Handbook(POH) or Rotorcraft Flight Manual (RFM) for anylimitations that may apply when operating with floatsinstalled. [Figure 9-1]

CONSTRUCTION AND MAINTENANCEHelicopter floats are constructed of a rubberizedfabric, or nylon coated with neoprene or urethane, andmay be of the fixed utility or emergency pop-out type.Fixed utility floats typically consist of two floats thatmay have one or more individual compartmentsinflated with air. Fixed floats may be of the skid-on-float or the float-on-skid design. [Figure 9-2]

A skid-on-float landing gear has no rigid structure inor around the float. The float rests on the hard surfaceand supports the weight of the helicopter. With this

type of design, be aware of differences in float pres-sure. While the pressures are usually low, a substantialdifference can cause the helicopter to lean while on ahard surface making it more susceptible to dynamicrollover.

A float-on-skid landing gear has modified skids thatsupport the weight of the helicopter on hard surfaces.The floats are attached to the top of the skid and onlysupport the weight of the helicopter in water. A floatwith low pressure or one that is completely deflatedwill not cause any stability problems on a hard surface.

Emergency pop-out floats consist of two or morefloats with one or more individual compartments perfloat, depending on the size of the helicopter. [Figure9-3] They are often inflated with compressed nitrogenFigure 9-1. Float equipped helicopter.

Figure 9-2. Skid-on-float and float-on-skid landing gear.

Figure 9-3. Pop-out float equipped helicopter.

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or helium and are deployed prior to an emergencylanding on water. The aircraft’s maintenance manualstates that the pop-out floats must be tested periodicallythrough a deployment check, a leak check, and a hydro-static check of the compressed gas cylinder.

To maintain the floats in good condition, perform thefollowing tasks before and after every flight:

• Inflation—Check each float compartment forproper inflation. Record the pressure to obtain atrend over time to help recognize leaks.

• Condition—Inspect the entire float assembly forcuts, tears, condition of chafing strips, andsecurity of all components.

• Clean—Wash oil, grease, or gasoline from thefloats, since they deteriorate the float’s material.

• Flush—If the helicopter has been operated onsalt water, flush the entire helicopter, includingthe float assembly, with plenty of fresh water.

• Storage—Avoid placing the floats in directsunlight when not in use.

OPERATIONAL CONSIDERATIONSHelicopter floats have only a mild effect on aircraftperformance, with just a slight weight penalty andreduction in cruise speed. However, the large surfacearea of the floats makes the helicopter very sensitive toany departure from coordinated flight. For example, incruise flight, any yawing causes the helicopter to roll inthe opposite direction, as shown in figure 9-4. A failureof the engine requires immediate pedal application toprevent an uncontrollable yaw, with a resulting roll.

Similarly, a tail rotor failure in cruise flight requiresimmediate entry into autorotation to prevent a yaw andthe subsequent roll. Corrections to this rolling momentcan exceed rotor limits and cause mast bumping ordroop stop pounding.

Helicopters equipped with skids-on-floats are limitedin ground operations. Minimize horizontal movementduring takeoffs and landings from hard surfaces toavoid scuffing or causing other damage to the floats.Perform approaches, in which hover power may not beavailable, by flaring through hovering altitude in aslightly nose-high attitude to reduce forward motion.Just prior to the aft portion of the floats touching down,add sufficient collective pitch to slow the descent andstop forward motion. Rotate the cyclic forward to levelthe helicopter, and allow the helicopter to settle to theground, then reduce collective pitch to the full downposition. In helicopters with low inertia rotor systems,an autorotation to a hard surface requires a moreaggressive flare to a near-zero groundspeed to ensureminimal movement upon landing. A running takeoff orlanding on a hard surface is not recommended inhelicopters equipped with skids-on-floats.

Helicopters equipped with floats-on-skids are capableof performing running takeoffs and landings, andautorotations to hard surfaces require the sameprocedures as non-float equipped helicopters. Thesurfaces should be flat and clear of objects that maypuncture, rip, or cause other damage to the floats. Donot attempt to land on the heels of floats-on-skids asthey may cause the tail boom to kick up and be struckby the rotor.

Helicopters equipped with stored emergency pop-outfloats are operated with the same procedures as ahelicopter without floats. When emergency floats aredeployed, the helicopter may have similar characteris-tics to a helicopter with fixed floats and should beflown accordingly. If emergency floats are deployedduring autorotation, the increased surface increasesparasite drag with a resulting reduction in airspeed. Toregain the recommended autorotation airspeed, thenose must be lowered.

Effects on aircraft performance must also be consid-ered during water operations. Air is often cooler nearbodies of water, thus decreasing the density altitude butalso increasing humidity. Although the higher humidityof the air has little effect on aerodynamic performance,it can reduce piston engine output by more then 10percent. Properly leaning the mixture might possiblyreturn some of this lost power.

Turbine engines experience only a small, often negligi-ble, power loss in high humidity conditions.

RightRoll

YawLeft

Intended Flightpath

Figure 9-4. Float instability.

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STARTINGA helicopter on a hard surface has the friction of theskids or floats to counter the torque produced whenthe rotor is engaged. Therefore, you have more controlover the helicopter if you can engage the rotors whileit is sitting on a hard surface. On water, little or no anti-torque control is present until the rotor system hasaccelerated to approximately 50 percent of its normaloperating r.p.m. A heavily loaded helicopter’s floatssit deeper in the water and create more resistance tothe turning force than a lightly loaded helicopter. Thusa helicopter turns less when heavily loaded and morewhen lightly loaded.

To overcome the spinning and to prevent drifting, tiethe helicopter securely to a dock or to the shore usingthe fore and aft cross tubes if not otherwise indicatedin the POH or RFM. If help is not available for castingoff, it may be necessary to paddle to a clear locationwell away from the shoreline for a safe start. Windand water currents may cause the helicopter to turn ordrift a considerable distance before control is obtained.To compensate, use a starting position upwind andupcurrent of a clear area.

Illusions of movement or non-movement can make itdifficult to maintain a fixed position during rotorengagement and runup. Techniques to overcome theseillusions are discussed later.

TAXIING AND HOVERINGWhere possible, it is usually more convenient andsafer to hover taxi to the destination. However, due topower limits, local restrictions, noise, water spray, orcreating a hazard to other vessels or people, it may benecessary to water taxi the helicopter. To taxi in water,maintain full rotor r.p.m. and use sufficient up collec-tive to provide responsive cyclic control to move thehelicopter. Never bottom the collective pitch while thehelicopter is in motion to avoid momentarily sinkingthe floats or capsizing the helicopter. Float equippedhelicopters should be taxied with the nose in thedirection of movement. Maximum taxi speed isattained when the bow wave around the nose of thefloats rises slightly above the normal waterline.Beyond this speed, the bow wave flows over the frontportion of the floats, and this severe drag may capsizethe helicopter. When the helicopter is heavily loaded,it is restricted to a slower taxiing speed than whenlightly loaded.When taxiing in small waves, point thehelicopter into or at a slight angle to the waves. Neverallow the helicopter to roll in the trough. In someinstances, increasing collective can produce enoughdownwash to create a slight smoothing effect on wind-produced waves.

A ground swell can be dangerous to the tail rotor whilethe helicopter is riding up and pitching over the swell.

Warning: During water operation, if there is anypossibility that the tail rotor struck the water, do notattempt a takeoff. Although a tail rotor water strikemay not show any visible evidence of damage, a tailrotor failure is likely to occur.

PREFLIGHT INSPECTIONThe preflight inspection consists of the standardaircraft inspection with a few additional itemsassociated with the floats. When performing a preflightinspection, follow the manufacturer’s recommenda-tions. A typical inspection of the floats includes:

• Visual Inspection—Examine the floats for cuts,abrasions, or other damage.

• Inflation Check—Although proper inflation canbe checked by hand feeling for equal pressureand firmness, a pressure gauge is the preferredmethod to check for the correct pressure listed inthe POH or RFM. For flights to higher altitudes,adjust float pressure before takeoff so thatmaximum pressure is not exceeded, unless thefloats are equipped with pressure relief valves.

• Valve Checks—Check the air valves by fillingthe neck with water and watching for bubbles.Examine fittings for security and, if operated insalt water, inspect for corrosion.

• Float Stabilizer, if equipped—Examine the floatstabilizer and other float related surfaces forsecurity and condition. Any indication of watercontact requires, at a minimum, a visual inspec-tion of the tail surfaces, tail boom, and mounts.Consult the aircraft’s maintenance manual forany additional required inspections.

• Float and Skid Freedom—In cold weather, it iscommon for floats and skids to freeze to thesurface. Inspect the floats and skids for freedomof movement and obstructions. To help preventthis problem, try to park on a dry surface withproper drainage.

• Secure—Ensure all equipment is secure andproperly stowed including survival equipment,anchors, tiedowns, and paddles. If possible, stowitems inside the helicopter that could becomeloose and fly into the rotors.

• Survival Equipment—Check the quantity andcondition of survival equipment including flota-tion devices, liferafts, provisions, and signalingdevices.

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Approach the swell at a 30º to 45º angle and use collec-tive pitch to minimize bobbing. If it becomes obviousthat continued water taxi could lead to a seriousproblem, lift the helicopter off and reassess thesituation. It might be possible to land in an area thatdoes not contain the same conditions.

When hovering over or taxiing on water, movement ofthe helicopter may be difficult to judge. The ripplingeffect of the water from the downwash makes it appearas if the helicopter is moving in one direction when it isin fact stationary or even moving in the oppositedirection. To maintain a fixed position or maintain astraight course while taxiing and hovering, use a fixedreference such as the bank or a stationary object in thewater. When reference points are not available, judgemovement by swirls, burbles, or slicks seen around thefloats.

Hovering a helicopter over open water can createdeceptive sensations. Without a reference point,extensive or rapid helicopter movements may gounnoticed. Very smooth and very rough wateraggravate this situation. The most desirable waterconditions are moderate ripples from a light breeze. Anodd sensation, similar to vertigo, is sometimesproduced by the concentric outward ripples resultingfrom the rotorwash, and pilots must keep their eyesmoving and avoid staring at any particular spot. Theinexperienced pilot may choose to initiate a slightforward movement when taking off into or landingfrom a hover. This guards against undesirablebackward or sideward drift during takeoff or landing.With smooth water conditions, the usual tendency is tohover too high because the outward-flowing ripplesfrom the rotorwash gives the pilot the sensation ofbeing in a bowl and descending.

TAKEOFFA float equipped helicopter can perform a normaltakeoff from a hover or directly from the water. If thereis insufficient power available for a normal takeoff, arunning takeoff from a slow forward taxi may be anoption. However, remember that water creates drag, sowith insufficient power, a running takeoff may not bepossible either.

The preferred method for taking off from water is tomove forward into translational lift without pausing tohover after leaving the water. This type of takeoff issimilar to a normal takeoff from the surface.

A normal takeoff from a hover over water is similar tothe same type of takeoff over a hard surface. Acommon problem is poor judgment of altitude and rateof acceleration, which causes the pilot to increase speedwithout an increase in altitude. This causes thehelicopter to enter the high speed portion of the

height/velocity diagram, reducing the probability of asuccessful autorotation in the event of an enginefailure. Also, be aware of possible restricted visibilityduring takeoff from water spray produced by therotors. To help alleviate these problem areas, as thehelicopter begins to move forward, use referencepoints some distance in front of the helicopter.

Over water, ground effect is reduced from the absorp-tion of energy in the downwash. This increases thepower required to hover and with other factors mayexceed the power available. When this occurs, performa slow taxi to a takeoff to take advantage of thetranslational lift produced from the forward motion.Remember, translational lift is also affected by anywind that is present. Apply sufficient collective pitchto keep the floats riding high or skimming the surface.While skimming the surface, float drag increasesrapidly, and the takeoff must be executed promptlysince a further increase in speed, with the floatsplowing in the water, is likely to exceed the limit of aftcyclic control or cause the floats to tuck under thewater. The speed at which the floats tuck under is themaximum forward speed that can be attained and isdetermined by the load and attitude of the helicopter.Never lower the collective during this procedurebecause doing so could bury the nose of the floats inthe water and possibly capsize the helicopter.

LANDINGPilots performing glassy water landings may experi-ence some difficulty in determining their altitudeabove the surface. The recommended procedure is tocontinue an approach to the surface with a slow rate ofdescent until making contact, avoiding any attempt tohover. The helicopter’s downwash creates adisturbance in the water as concentric ripples movingaway from the helicopter. Although this provides thepilot with a visual reference, it may also cause thesensation of moving backwards or descending rapidly.A natural tendency is to apply too much collectivepitch in an attempt to halt the perceived descent. Toovercome the effects of these visual illusions, avoidstaring at the water near the helicopter and maintainforward and downward movement until contacting thewater. When making approaches to a landing on alarge body of water when land areas or other fixedobjects are not visible, occasionally glance to eitherside of the horizon to avoid stare-fixation. Anothertechnique some pilots use when fixed objects are notavailable, and the water is glassy, is to make a low passover the area to create a disturbance on the surface.This disturbance remains for a while giving the pilot areference to help determine distance.

When landing on water with a slight chop, bring thehelicopter to a hover and descend vertically with no

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horizontal movement. This procedure is similar tolanding on a hard surface.

Make a running landing on water when high densityaltitude or a heavy load results in insufficient power tohover. Perform this type of landing when sufficientpower is not available to reduce the speed to 5 knots orless. When approaching with greater than 5 knots ofspeed, hold a slight nose-high attitude to allow the aftportion of the floats to plane. Maintain collective pitchuntil the speed reduces to below 5 knots, and the heli-copter settles into the water. At zero groundspeed,slowly lower the collective into the full down position.Lowering the collective or leveling the helicopter tooquickly may result in the floats tucking, which cancause the helicopter to capsize.

Caution: The following discussion deals with land-ing in heavy seas. Use these procedures only in anemergency.

Landing the float helicopter becomes risky when theheight of short, choppy waves exceed one half thedistance from the water to the helicopter’s stinger, andthe distance from crest to crest is nearly equal to or lessthan the length of the helicopter. These waves causethe helicopter to pitch rapidly and may bring the rotorblades in contact with the tail boom or the tail rotor incontact with the water. In addition, avoid landingparallel to steep swells as this could lead to dynamicrollover. [Figure 9-5]

If landing on waves higher than half the distance fromwater to stinger, the following techniques apply:

• Land the helicopter 30º to 45º from the directheading into the swell. This minimizes the foreand aft pitching of the fuselage, reducing thepossibility of the main rotor striking the tailboom, or the tail rotor contacting the water. Thisalso minimizes the possibility of dynamicrollover.

Perpendicular to Swell

Parallel to Swell

Angled 30° to 45°to Swell

Rotor StrikesTail Boom

DynamicRollover

Tail Rotor Strikes Water

Figure 9-5. Effect of landing heading relative to waves.

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• When landing with power, maintain rotor r.p.m. inthe normal operating range. This permits a quicktakeoff if the helicopter begins to pitch exces-sively or when an especially high wave becomesa hazard.

• When landing without power in high waveconditions, hold the desired heading as long asdirectional control permits. As the rotor r.p.m.decreases to the point that the desired headingcannot be maintained, bring the rotor to a stop asquickly as possible to avoid rotor contact with thetail boom.

AUTOROTATIONAn autorotation to water is similar to one performed ona hard surface except that during touchdown, thehelicopter is kept in a slight nose-high position. Forgreater safety, slow to around 5 knots of forward speed.However, if this is not possible, maintain a slightnose-high attitude and full-up collective to allow thefloats to plane until the speed decelerates below 5knots. As the helicopter settles to the surface and slowsto zero knots, level the helicopter with cyclic and lowerthe collective. Do not lower the collective or level thehelicopter until the speed has reduced sufficiently orthe floats may tuck causing the helicopter to capsize.Hold a pitch attitude that keeps the tail from contactingthe water.

Autorotations to smooth, glassy water may lead todepth perception problems. If possible, try to land neara shoreline or some object in the water. This helps injudging altitude just prior to touchdown.

SHUTDOWN AND MOORING Although a helicopter can be moored prior toshutdown, it is preferable to fly to a landing spot on thedock or shore prior to shutting down. The helicoptercan then be parked there. If mooring is the only option,be aware of any posts or pillars that might extend abovethe main dock level. Even though there may be plentyof blade clearance when the rotor is at full r.p.m., bladedroop due to low r.p.m. could cause the blades to comeinto contact with items on the dock. Also be aware ofwind and waves that could tilt the helicopter and causethe blades to contact objects. If near an ocean or largebody of water, tides could change the water levelconsiderably in just a few hours, so anticipate anychanges and position the helicopter to prevent anydamage due to the changing conditions.

When mooring the helicopter prior to shutting down,arrange the mooring lines so the tail cannot swing intoobjects once the rotors stop. Some pilots prefer to moorthe helicopter nose in to protect the tail rotor.

If there is sufficient room to allow for drift andpossible turning or weathervaning, the helicopter maybe shut down on open water, but wind and water cur-rents may move the helicopter a considerable distance.When shutting down on open water, do so upwind orupcurrent and allow the helicopter to drift to the moor-ing buoy or dock. It might be necessary to use a paddleto properly position the helicopter.

Because of the great danger from the main rotor or tailrotor of the helicopter to personnel, docks, or vessels,pilots should never attempt to water taxi up to a dockor vessel. In addition, loading or unloading passengersor freight from a partially afloat helicopter with therotors turning is extremely dangerous. When loadingor unloading passengers, the helicopter should beresting on a hard surface, either on the shore or on ahelipad on a dock or on a boat. Passengers shouldalways:

• stay away from the rear of the helicopter,

• approach or leave the helicopter in a crouchingmanner,

• approach from the side or front, but never out ofthe pilot’s line of vision,

• hold firmly to loose articles and never chaseafter articles that are blown away by the rotordownwash, and

• never grope or feel their way toward or awayfrom the helicopter.

GROUND HANDLINGOn helicopters equipped with floats-on-skids, groundhandling usually can be performed with normal orslightly modified ground handling wheels. With theground handling wheels kept onboard, the helicoptercan be handled at any landing facility. On helicoptersequipped with skids-on-floats, the helicopter must betransported by a special dolly or wheeled platform onwhich the helicopter lands. Unless a dolly or platformis available at the destination, the aircraft usuallyremains where it lands.

SKI EQUIPPED HELICOPTERSSki equipped helicopters are capable of operating fromsnow and other soft surfaces that might otherwiseinhibit conventional gear helicopters. [Figure 9-6]Snow can greatly reduce visibility causing pilot disori-entation; therefore, special procedures are used whenoperating in snow.

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CONSTRUCTION AND MAINTENANCEREQUIREMENTSHelicopter skis are made from plastics and compositematerials such as fiberglass with steel and aluminumhardware. Steel runners on the bottoms of the skisprotect them during hard surface operations.Excessive wear of these runners can lead to wear ordamage to the skis.

All of the steel bands securing the skis to the skidsshould have a protective rubber lining preventing thebands from wearing into the skids. This lining shouldbe replaced if it becomes brittle or shows signs ofwear.

Have any damage to the skis repaired before flighteven if the skis are not needed, or simply have the skisremoved. A cracked ski could break off and damagethe helicopter or injure people on the ground.

OPERATIONAL CHARACTERISTICSApart from the small weight penalty and slight reduc-tion in speed, a ski equipped helicopter operatesexactly like one with no skis. The main concern whenoperating with skis is to avoid operations that maydamage the skis, such as landing on rocks or roughhard surfaces.

PREFLIGHT REQUIREMENTSThe preflight inspection consists of the standardaircraft inspection and includes additional items asso-ciated with the skis. The POH or RFM contains theappropriate supplements and additional inspectioncriteria. Typical inspection criteria include:

• Hardware—Inspect all of the steel bands andbolts securing the skis to the skids for security.Check for any movement of the skis on the skids.A torque stripe can help determine if any move-ment has occurred.

• Liner—Inspect the rubber liner between thesteel bands and the skids.

• Runners—Inspect the steel runners on thebottoms of the skis.

• Condition—Inspect the skis for cracks andcheck the edges for separation of fiber layers.

• Clean—Remove all snow and ice from the skiswhich could break off and cause damage to thetail rotor during flight.

• Ski Freedom—In cold weather, it is common forthe skis to freeze to the surface. Inspect the skisfor freedom of movement.

STARTINGHelicopter starting procedures on snow and ice areidentical to a hard surface starting procedure exceptthat care must be taken to maintain antitorque controlon a slippery surface. When performing thefree-wheeling unit check on ice, place the pedals in theautorotation position to prevent the helicopter fromspinning.

TAXIING AND HOVERINGWhen hovering over snow, the rotorwash may create awhite-out condition if sufficient loose snow is present.Blowing and drifting snow may give the illusion ofmovement in the opposite direction. When operatingin snow, it is vital to select a reference point tomaintain situational awareness and take off directly toa high hover at an altitude that allows visual contact tobe maintained. When performing a hover taxi, selectthe speed just above effective translational lift to helpkeep the blowing snow behind the helicopter. If loosesnow is less than 6 inches, it may be possible to applycollective pitch to create enough rotorwash to blowaway the majority of the snow before lift-off. Ifmoving the helicopter a short distance, and especiallywhen around other aircraft, it might be preferable tosurface taxi on the skis.

When taxiing wheel-equipped helicopters on snow andice, use caution when applying the brakes. If thehelicopter begins to skid sideways, lower thecollective, which places all of the weight on the wheelsand move the cyclic in the opposite direction of theskid. If the skid continues, the best option at that pointis to bring the helicopter into a hover, but be aware ofobjects that could lead to a dynamic rollover situation.

TAKEOFFNormal takeoff procedures are used in snow and ice,but before startup, check the departure path for anyobstructions that may be obscured by blowing snow.Powerlines are difficult to see in the best conditionsand nearly impossible to recognize through blowingsnow.

Perform a takeoff from a hover or from the surface byfairly quickly increasing speed through effectivetranslational lift and gaining altitude in order to fly out

Figure 9-6. Ski equipped helicopter.

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of the low visibility conditions. A takeoff from icerequires slow application of power and proper pedalapplication to prevent spinning. At certain tempera-tures, the skis may freeze to ice surfaces. If this occurs,a slight left and right yawing with the pedals may breakthe helicopter free. If this does not free the skids, shutdown the helicopter and free them manually. Excessivepedal application could damage the skids.

LANDINGAs with takeoffs, landings in snow can prove to beextremely hazardous if reference points are notavailable. When possible, land near objects that won’tbe easily obscured by blowing snow. If none areavailable, drop a marker made from a heavy object,such as a rock tied to a colored cloth; then retrieve itafter landing.

When the snow condition is loose or unknown, make azero-groundspeed landing directly to the surfacewithout pausing to hover. A shallow approach andrunning landing can be performed when the snow isknown to be hard packed and obstacles are not hiddenunder the snow. The lower power required in a runninglanding reduces the downwash and the forward motionkeeps blowing snow behind the helicopter until aftersurface contact.

If the surface conditions are unknown, a low reconnais-sance flight might be appropriate. This could befollowed by a low pass. A low pass might blow awayloose snow and keep the debris behind the helicopter. Ifthe surface appears appropriate for a landing, make anapproach to a high hover to blow away any remaining

loose snow and begin a vertical descent to the landing.If the surface appears to be deep hard-packed snow orice, lower the collective slowly on landing and watchfor cracking in the surface. Should one skid breakthrough the surface, a dynamic rollover is likely tofollow, so be prepared to return to a hover if thesurface is unstable.

Skis are also very useful for landing on uneven or soft,spongy surfaces. They provide a larger surface area tosupport the helicopter, thus assisting in stability. Besure that the skis are not hooked under roots or brushduring lift-off.

AUTOROTATIONUse normal autorotation procedures in ski equippedhelicopters. Perform practice autorotations on snow orsod to reduce the wear on the skis.

GROUND HANDLINGShut down before loading and unloading. If shuttingdown is not feasible, load and unload passengers onlyfrom the front during snow and ice operations. Thisprevents the main rotors from striking an individualshould one landing gear drop through the snow or ice.Beware of loading and unloading while running indeep snow as the rotor clearance is reduced by theheight of the snow above the skids.

Most skis for skid-equipped helicopters allow use ofstandard or slightly modified ground handling wheels.Skis for wheel-equipped helicopters often havecutouts to allow the wheels to protrude slightly belowthe ski for ground handling.

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AMPHIBIAN—A seaplane withretractable wheel-type landinggear that can be extended to allowlandings to be made on land.

ANCHOR—A heavy hook con-nected to the seaplane by a line orcable, intended to dig into thebottom and keep the seaplanefrom drifting.

AUXILIARY FIN — An addi-tional vertical stabilizer installedon some float planes to offset theincreased surface area of the floatsin front of the center of gravity.

BEACHING—Pulling a seaplaneup onto a suitable shore so that itsweight is supported by relativelydry ground rather than water.

BEAUFORT WIND SCALE—Astandardized scale ranging from0-12 correlating the velocity ofthe wind with predictable surfacefeatures of the water.

BILGE—The lowest pointinside a float, hull, or watertightcompartment.

BILGE PUMP—A pump used toextract water that has leaked into thebilge of a float or flying boat.

BULKHEAD—A structural parti-tion that divides a float or a flyingboat hull into separate compartmentsand provides additional strength.

BUOYANCY—The tendency of abody to float or to rise whensubmerged in a fluid.

BUOYS—Floating objects mooredto the bottom to mark a channel,waterway, or obstruction.

CAN BUOYS— Cylindrical buoysmarking the left side of a channelfor an inbound vessel. They haveodd numbers which increase fromseaward.

CAPSIZE—To overturn.

CAST OFF—To release or untie avessel from its mooring point.

CENTER OF BUOYANCY—Theaverage point of buoyancy in float-ing objects. Weight added above thispoint will cause the floating objectto sit deeper in the water in a levelattitude.

CHINE—The longitudinal seamjoining the sides to the bottom of thefloat. The chines serve a structuralpurpose, transmitting loads from thebottoms to the sides of the floats.They also serve a hydrodynamicpurpose, guiding water away fromthe float, reducing spray, and con-tributing to hydrodynamic lift.

CHOP— A roughened condition ofthe sea surface caused by localwinds. It is characterized by itsirregularity, short distance betweencrests, and whitecaps.

COMBINATION SKI— A type ofaircraft ski that can be used on snowor ice, but that also allows the use ofthe skiplane’s wheels for landing onrunways.

CREST—The top of a wave.

CURRENT — The horizontalmovement of a body of water.

DAYBEACONS — Unlightedbeacons.

DAYMARKS—Conspicuousmarkings or shapes that aid inmaking navigational aids readilyvisible and easy to identifyagainst daylight viewing back-grounds.

DECK—The top of the float,which can serve as a step or walk-way. Bilge pump openings, handhole covers, and mooring cleats aretypically located along the deck.

DISPLACEMENT POSITION—The attitude of theseaplane when its entire weight issupported by the buoyancy of thefloats, as it is when at rest or dur-ing a slow taxi. Also called theidling position.

DOCK—To secure a seaplane to apermanent structure fixed to theshore. As a noun, the platform orstructure to which the seaplane issecured.

DOWNSWELL—Motion in thesame direction the swell is moving.

FETCH—An area where wind isgenerating waves on the water sur-face. Also the distance the waveshave been driven by the windblowing in a constant directionwithout obstruction.

FLOATPLANE — A seaplaneequipped with separate floats tosupport the fuselage well above thewater surface.

FLOATS—The components of afloatplane’s landing gear thatprovide the buoyancy to keep theairplane afloat.

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FLOATS-ON-SKIDS—A type ofhelicopter float design where thefloats sit on top of the fully func-tional skids. During water opera-tions, the floats support the weightof the aircraft, and on hard surfacesthe skids support the weight of theaircraft.

FLYING BOAT—A type of sea-plane in which the crew, passengers,and cargo are carried inside afuselage that is designed tosupport the seaplane on thewater. Also called a hull seaplane.

GLASSY WATER—A calm watersurface with no distinguishablesurface features, with a glassy ormirror like appearance. Glassywater can deceive a pilot’s depthperception.

HEIGHT-TO-LENGTHRATIO—The ratio between theheight of a swell to the lengthbetween two successive crests(swell length).

HYDRODYNAMIC FORCES—Forces relating to the motion offluids and the effects of fluidsacting on solid bodies in motionrelative to them.

HYDRODYNAMIC LIFT—Forseaplanes, the upward force gener-ated by the motion of the hull orfloats through the water. When theseaplane is at rest on the surface, thereis no hydrodynamic lift, but as theseaplane moves faster, hydrodynamiclift begins to support more and moreof the seaplane’s weight.

IDLING POSITION—The atti-tude of the seaplane when its entireweight is supported by thebuoyancy of the floats, as it iswhen at rest or during a slowtaxi. Also called the displacementposition.

KEEL—A strong longitudinalmember at the bottom of a float orhull that helps guide the seaplanethrough the water, and, in the caseof floats, supports the weight of theseaplane on land.

RAMPING—Using a ramp thatextends under the water surface asa means of getting the seaplane outof the water and onto the shore. Theseaplane is typically driven underpower onto the ramp, and slidespartway up the ramp due to inertiaand engine thrust.

SAILING—Using the wind as themain motive force while on thewater.

SEA—Waves generated by theexisting winds in the area. Thesewind waves are typically a chaoticmix of heights, periods, and wave-lengths. Sometimes the term refersto the condition of the surfaceresulting from both wind wavesand swells.

SEA STATE CONDITIONNUMBER—A standard scaleranging from 0-9 that indicates theheight of waves.

SEAPLANE — An airplanedesigned to operate from water.Seaplanes are further divided intoflying boats and floatplanes.

SEAPLANE LANDINGAREA—Any water area designatedfor the landing of seaplanes.

SEAWARD—The direction awayfrom shore.

SECONDARY SWELLS—Thoseswell systems of less height thanthe primary swell.

SISTER KEELSONS—Structuralmembers in the front portion offloats lying parallel to the keel andmidway between the keel andchines, adding structural rigidityand adding to directional stabilitywhen on the water.

SKEG—A robust extension of thekeel behind the step which helpsprevent the seaplane from tippingback onto the rear portion of thefloat.

LEEWARD—Downwind, or thedownwind side of an object.

MOOR—To secure or tie theseaplane to a dock, buoy, orother stationary object on thesurface.

NUN BUOYS—Conical buoysmarking the left side of a channelfor an inbound vessel. They oftenhave even numbers that increase asthe vessel progresses from seaward.

PLAIN SKI—A type of aircraft skithat can only be used on snow or ice,as compared to combination skis,which also allow the use of theskiplane’s wheels for landing onrunways.

PLANING POSITION—The atti-tude of the seaplane when the entireweight of the aircraft is supportedby hydrodynamic and aerodynamiclift, as it is during high-speed taxi orjust prior to takeoff. This positionproduces the least amount of waterdrag. Also called the step position,or “on the step.”

PLOWING POSITION—A nosehigh, powered taxi characterized byhigh water drag and an aftward shiftof the center of buoyancy. Theweight of the seaplane is supportedprimarily by buoyancy, and partiallyby hydrodynamic lift.

POP-OUT FLOATS—Helicopterfloats that are stored deflated on theskids or in compartments along thelower portion of the helicopter, anddeployed in the event of an emer-gency landing on water.Compressed nitrogen or heliuminflates the floats very quickly.

PORPOISING—A rhythmic pitch-ing motion caused by an incorrectplaning attitude during takeoff.

PORT—The left side or thedirection to the left of a vessel.

PRIMARY SWELL—The swellsystem having the greatest heightfrom trough to crest.

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SKIDS-ON-FLOATS—A type ofhelicopter float design where therigid portion of the landing gearrests on the floats. The floats sup-port the whole weight of the heli-copter in water or on hard surfaces.

SKIPPING — Successive sharpbounces along the water surfacecaused by excessive speed or animproper planing attitude when theseaplane is on the step.

SPONSONS—Short, winglike pro-jections from the sides of the hullnear the waterline of a flying boat.Their purpose is to stabilize the hullfrom rolling motion when the flyingboat is on the water, and they mayalso provide some aerodynamiclift in flight. Tip floats also aresometimes known as sponsons.

SPRAY RAILS—Metal flangesattached to the inboard forward por-tions of the chines to reduce theamount of water spray thrown intothe propeller.

STARBOARD—The right side orthe direction to the right of a vessel.

STEP—An abrupt break in thelongitudinal lines of the float orhull, which reduces water drag andallows the pilot to vary the pitchattitude when running along thewater’s surface.

STEP POSITION—The attitude ofthe seaplane when the entire weightof the aircraft is supported byhydrodynamic and aerodynamiclift, as it is during high-speed taxi orjust prior to takeoff. This positionproduces the least amount of waterdrag. Also called the planing posi-tion.

SWELL—Waves that continueafter the generating wind has ceasedor changed direction. Swells alsoare generated by ships and boats inthe form of wakes, and sometimes

by underwater disturbances such asvolcanoes or earthquakes. Thewaves have a uniform and orderlyappearance characterized bysmooth, rounded, regularly spacedwave crests.

SWELL DIRECTION — Thedirection from which a swell ismoving. Once set in motion, swellstend to maintain their original direc-tion for as long as they continue indeep water, regardless of winddirection. Swells may be movinginto or across the local wind.

SWELL FACE—The side of theswell toward the observer. The backis the side away from the observer.These terms apply regardless of thedirection of swell movement.

SWELL LENGTH—The horizon-tal distance between successivecrests.

SWELL PERIOD — The timeinterval between the passage of twosuccessive crests at the same spot inthe water, measured in seconds.

SWELL VELOCITY — Thevelocity with which the swelladvances with relation to a fixedreference point, measured in knots.There is little movement of waterin the horizontal direction. Eachwater particle transmits energy toits neighbor, resulting primarily ina vertical motion, similar to themotion observed when shaking outa carpet.

TIDES—The alternate rising andfalling of the surface of the oceanand other bodies of water connectedwith the ocean. They are caused bythe gravitational attraction of thesun and moon occurring unequallyon different parts of the earth. Tidestypically rise and fall twice a day.

TIP FLOATS—Small floats nearthe wingtips of flying boats orfloatplanes with a single main float.The tip floats help stabilize the air-plane on the water and prevent thewingtips from contacting the water.

TRANSOM—As it applies toseaplanes, the rear bulkhead of afloat.

TROUGH—The low area betweentwo wave crests.

UPSWELL—Motion opposite thedirection the swell is moving. If theswell is moving from north tosouth, a seaplane going from southto north is moving upswell.

VESSEL—Anything capable ofbeing used for transportation onwater, including seaplanes.

WATER RUDDERS—Retractable control surfaces on theback of each float that can beextended downward into the waterto provide more directional controlwhen taxiing on the surface. Theyare attached by cables and springsto the air rudder and operated bythe rudder pedals in the cockpit.

WEATHERVANING—The ten-dency of an aircraft to turn until itpoints into the wind.

WINDWARD—Upwind, or theupwind side of an object.

WING FLOATS—Stabilizer floatsfound near the wingtips of flyingboats and single main float float-planes to prevent the wingtips fromcontacting the water. Also called tipfloats.

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AAids for marine navigation 1-2Altimeter setting 6-7Amphibians 2-1, 6-2Anchoring 6-9Autorotation 9-2, 9-6, 9-8Auxiliary fin 2-4, 5-2

BBeaching 6-8, 6-10Bilge pump 4-2Bilge pump openings 2-2, 4-2Bulkheads, float 2-2Buoyancy 2-2, 4-3Buoys 1-2, 1-3, 1-4

CCenter of buoyancy 4-4, 4-6, Center of gravity 4-1, 5-1, 5-2, 5-3, 7-7Centrifugal force (in turns) 4-6, 4-7, 4-14Certificate, limitations 1-1Chine 2-2Clamp-on ski 7-1Coast Guard rules 1-2Combination ski 7-1, 7-2Confined area operations 4-16, 6-7Corrosion 4-1, 4-3Crosswind 4-12, 4-13, 6-3, 7-5Current 3-2, 4-8, 4-9, 6-5

DDaybeacons and daymarks 1-2, 1-3, 1-4Deck 2-2Density altitude 4-11, 4-12, 5-1, 6-8, 9-5Displacement 2-2, 4-3Displacement position 4-3

Displacementof float 2-2position or attitude 4-3, 4-10taxi 4-3

Docking 6-8, 6-10Downwind takeoff 4-14

EEscaping a submerged seaplane 8-8

FFetch 3-2, 8-1Float construction 2-2, 2-3, 9-1Float, weight-bearing capability 2-2, 9-1Floatplane defined 2-1Flying boat

definition 2-1handling 4-9, 5-3

GGlaciers 7-6Glassy water 3-3, 4-15, 6-5, 9-4Go-around 6-2, 6-8

HHovering 9-3, 9-7Hull 2-1, 5-3Hump (water drag) 4-9, 4-10, 4-11Hydrodynamic lift 2-2, 4-4, 4-10

IIce (in floats) 4-3Ice types 7-2Idling 4-3, 4-8Inland waters 1-2International waters 1-2

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KKeel 2-2

LLandings

confined area 6-7crosswind 6-3downwind 6-5, 8-4emergency 6-8, 7-8frozen lakes and rivers 7-6glaciers 7-6glassy water 6-5helicopter 9-4, 9-8night landing 6-8, 7-8, 8-5, 8-6normal 6-3open sea 8-1rough water 6-7, 8-1, 9-5skiplane 7-6, 7-7tundra 7-6

Launching 4-3Lighting conditions 7-6Limitations of sea rating 1-1

MMarine aids for navigation 1-2Mooring 6-8, 6-9, 9-6

NNight operations 6-8, 8-5, 8-6Noise 3-4, 4-12, 6-2Normal takeoff 4-12

OOn the step 4-4, 6-2

PParking 7-7Passenger briefing 4-3Penetration ski 7-2Plain ski 7-1Planing position 4-4

Plow turn 4-6, 4-7Plowing position 4-4Pop-out floats 9-1Porpoising 4-9, 5-3Preflight inspection

seaplane 4-1skiplane 7-3float equipped helicopter 9-3ski equipped helicopter 9-7

Privileges and Limitations 1-1

RRamping 6-8, 6-10Regulations 1-1Retractable ski 7-1Right-of-way rules 1-2Roll-on ski 7-1Rough water 4-16, 6-7, 8-1, 9-5Rules of the Sea 1-2Runup 4-12Runup (skiplane) 7-4

SSailing 4-8, 4-9Seaplane defined 2-1Seaplane landing areas

beacons 1-2chart symbols 1-2reconnaissance 6-1restrictions 3-4unplanned 5-2

Sister keelsons 2-2Skeg 2-2, 2-4Ski types 7-1Skids-on-floats 9-1, 9-6Skipping 4-10Snow types 7-2Sponson 2-1Spray damage 4-1Spray rail 2-2, 4-2Starting

seaplane 4-3skiplane 7-4helicopter 9-3, 9-7

Step 2-3, 4-4Step position 4-4Step taxi 4-5, 6-3Step turns 4-7Survival equipment 7-3, 7-4, 7-8Swell 3-2, 4-9, 6-2, 6-7, 8-1, 8-2, 8-3, 8-4, 8-5

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TTakeoffs

normal 4-12crosswind 4-12downwind 4-14helicopter 9-4, 9-7glassy water 4-15rough water 4-16, 8-1confined area 4-16skiplane 7-5

Taxiingseaplane 4-3skiplane 7-5float equipped helicopter 9-3ski equipped helicopter 9-7

Tides 3-3Tip floats 2-1Transom 4-2Turns 4-5, 4-6, 4-7

Types of ice 7-2Types of snow 7-2

WWarmup (skiplane) 7-4Water current 3-2, 4-8, 4-9, 6-5Water rudders 2-4, 4-2, 4-5, 4-12, 4-14, Water, characteristics 3-1, 8-1Watertight compartments 2-3, 4-2Waves 3-1, 6-3, Weathervaning 3-4, 4-5, 4-6, 4-13, 6-3Weight and balance 4-1, 5-1Wheel replacement ski 7-1Wing floats 2-1

YYaw instability 2-4, 4-6, 5-2, 9-2

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