Learjet Coldwxops

Winter Operations ..................... 1

Exterior Inspection..................... 1

Engine Start............................... 2

Taxiing ....................................... 2

Pre Take-off Conditions............. 3

Take-off ..................................... 3

After Take-off............................. 3

En Route.................................... 3

Before Landing .......................... 3

Landing...................................... 4

After Clearing Runway .............. 4

Shutdown and Post Flight ......... 4

References ................................ 5

Slush on the Runway and what it does to Aircraft Performance.............................. 7

Winter Operations Eff. All Models By Scott Simpson – Technical Specialist, Maintenance Engineering &

Technical Support

Once again, it is time to issue a reminder on cold weather operations. Operational problems related to cold weather can occur unless proper preflight and inspection procedures are accomplished. Additionally, operational difficulties due to ice, snow, slush, or water accumulation may be encountered. The following instructions supplement the normal procedures and, when followed, will help ensure satisfactory operation of the aircraft and its systems in cold climatic conditions. Please keep in mind the aircraft flight manual takes precedence to the recommendations below. Exterior Inspection 1. Conduct normal exterior inspection as defined in Section II – Normal

Procedures of the AFM.

2. Check the entire aircraft for ice, snow, and frost. Brush off light snow and frost. Remove all encrusted snow and ice. Ice may be removed by spraying with suitable de-ice fluid. Refer to the latest Ground De-icing/Anti-Icing Addendum.

3. Remove ice, snow, and dirt from landing gear shock struts and wheel wells.

Check gear doors, position switches, squat switches, wheels and tires. 4. Carefully inspect engines for frozen precipitation in fan duct and tailpipe.

Under certain climatic conditions, ice can form on the back of fan blades and cause vibration during start.

5. Inspect area behind aircraft to ensure that loose snow or ice will not be

blown at personnel, other aircraft, or equipment during engine start or initial taxi thrust.

6. Specific preflight attention should be given to upper surfaces of the

horizontal stabilizer and elevator. This will mean getting out a stand or ladder to inspect and de-ice, if necessary.

7. It might be wise to spray the landing gear, squat switch, and door hinges

with de-ice fluid prior to taxi. Note: do not apply de-ice fluid to the brakes on 40 series aircraft.

Learjet 2009-2010 Cold Weather Operations

INFOSERVICE / 2009-2010 Cold Weather Operations / Page 2

Exterior Inspection (Cont…) 8. In addition to the visual check, a tactile check of the wing leading edge and wing rear upper surface is done during the

external walk around inspection to determine that the wing is free of frost, ice, snow or slush when the outside air temperature is 41°F (5°C) or less, or if it cannot be determined that the wing fuel temperature is above 32°F (0°C) and there is visible moisture (rain, drizzle, sleet, snow, fog, or water) present on the wing, or the difference between the dew point temperature and outside air temperature is 5°F (3°C) or less, or the atmospheric conditions have been conducive to frost formation. It should be noted that ice and frost may continue to adhere to wing surfaces for some time even at outside air temperatures above 41°F (5°C).

Type II, III or IV fluids are designed to shed from the aircraft during flight. However, residue may accumulate in “Aerodynamically Quite” areas leaving a dry powder or gel like substance. If not removed the residue may re-hydrate during flight and form a gel several times it original thickness which can refreeze and restrict flight control surface movement. On the Learjet product line, the residue is prone to accumulate around the aileron brush seals where the fluid cannot drain easily. Please pay particular attention to this area and remove any residue prior to reapplication of additional fluid. The frequency of residue removal should be based on the particular operator’s experience. The FAA maintains that crews must use the “clean aircraft” concept. Federal Aviation Regulations (FARs) specify that no pilot may take-off in an airplane that has snow or ice adhering to the wings, stabilizer, or control surfaces. Make sure your airplane is clean.

Engine Start Review the AFM regarding cold weather engine starts and use of ground power units (GPUs). During engine starts in cold weather, engine acceleration can be much slower than normal, and ITT/EGT has a tendency to increase more rapidly due to slower spool-up time. Higher than normal oil pressure can be expected which may exceed the maximum allowable transients. On Learjet 31/31A, Learjet 35/36, Learjet 45 and Learjet 55 Series aircraft, exceeding idle power with oil temperature below 86°F (30°C) is not recommended. However, if ambient temperature prevents attainment of 86°F (30°C), idle power may be exceeded, as required, to further warm the oil to normal operating limits prior to take-off. Remember that you will need to operate the engines a minimum of three minutes to bring the hydraulic system up to normal operating temperature. Taxiing Make sure wheels are not frozen to ramp. Brake heat can melt snow and ice on ramp.

• Use normal taxi procedures if the ramp and taxiways are clean and dry. If it is necessary to taxi on ice, snow, slush, or water, taxi at reduced speed and allow greater distance for braking.

• If taxi is to be accomplished through slush or snow, use the brakes to create some friction induced heating of the brake discs to prevent the brakes from freezing.

• Use both engines for taxi on slippery surfaces. Directional control may be difficult to maintain during one-engine taxi on a slick surface.

• Use anti-ice systems as required. • Insofar as possible, taxi on snow or slush covered surfaces should be accomplished with the flaps up. • Avoid taxiing in the exhaust wake or propeller-wash of another aircraft on other than hard packed or dry surfaces. • Taxi slowly on snow or ice covered surfaces; you might need to stop. • If you have been de-iced, or have taxied in snow/slush, consider an extra control check before take-off. • If airport operations/local traffic permits, taxi on the runway. It may have less snow/slush than ramps and taxiways. • If you must taxi through snow/slush and the runway is reasonably clear, consider stopping at the end of your taxi and

removing snow/slush from the landing gear, wheel wells and brakes. When operating on airports with minimal services, it might be necessary to request that you be taken physically out to the runway to accurately assess the runway conditions; i.e. deep drifts, pools of slush, etc.


Pre Take-off Conditions Snow, slush, or water on the runway will decrease acceleration and increase stopping distance. Runway requirements will be greater than normal balanced field lengths. Flight Crews should evaluate each airport as to terrain, obstacle clearance, runway slope, wind, and runway length. Is there additional stop way if it becomes necessary to abort? What about the terrain at the end of the runway if a stop cannot be made? What is the condition of the runway? Is there snow, slush, or water on the runway? How much – a little, a lot, how deep, etc. Occasionally, it may be necessary to delay take-off and wait for improved conditions. Make sure that runway conditions are satisfactory at your alternate airport, and be sure to have enough fuel for alternates in the event weather prohibits landing at the destination. Take-off Use normal take-off procedures if runway is clean and dry.

• If anti-ice systems are required for take-off, the systems should be energized prior to setting take-off power.

• Do not take-off with runway water or slush accumulation in excess of ¾ inch.

• Do not take-off with frost, snow, or ice on the wings or aircraft control surfaces, including the horizontal stabilizer and elevators.

WARNING: Even small accumulations of ice on the wing leading edge can cause aerodynamic stall prior to activation of the

stick shaker, nudger, and/or pusher. These ice accumulations can also cause angle-of-attack indicator information to be unreliable.

• When operating on icy ramps and taxiways, make sure that the parking brakes are fully released prior to take-off.

• If a drag chute is installed, preplan its use in case of abort.

• Be alert for engine compressor stall during take-off run.

After Take-off After take-off from a snow-covered or slush-covered runway, delay retracting landing gear for at least a minute to allow residual slush to be thrown or blown off.

On Learjet 28/29, Learjet 31, Learjet 31A, Learjet 55, Learjet 55B/C and Learjet 60 models, wing heat bleed air exits overboard through the center wing/wheel well area. If take-off was made from a snow or slush covered runway, activation of wing heat for approximately 10 minutes will help clear moisture from the wheels and brakes.

On aircraft with radome anti-icing, do not forget to use anti-icing in climb and descent to prevent radome icing.

En Route

• Keep informed of changing weather at destination and alternate.

• Use anti-ice systems before entering icing conditions.

Before Landing

Prior to landing after gear is extended: 1. On aircraft equipped with Hydro-Aire anti-skid system, set ANTI-SKID system to OFF.

NOTE: On aircraft equipped with the Hydro-Aire system, it is permissible to turn the system off after take-off and use the anti-skid system lights to serve as a reminder to pump the brakes prior to landing. However, regardless of the procedure used, the pilot must ensure that the anti-skid system is turned ON prior to touchdown.

2. Apply brakes six to ten times. Brake application will tend to crack any ice existing between the brake discs and between the discs and wheels. Note: This procedure is not recommended for 40 series aircraft.

3. Prior to touchdown, set ANTI-SKID switch ON and check ANTI-SKID GEN lights out.


Landing Use normal landing procedures if runway is clean and dry. For landing on a slippery runway, minimum ground roll can be realized when the following procedure is used: 1. Final Approach Speed – VREF. 2. Make firm touchdown and extend spoilers immediately after touchdown. 3. Brakes – As required.

NOTE: The anti-skid system will automatically modulate wheel brake pressure to prevent skids and provide maximum braking for any runway surface condition.

4. Thrust Reverser – As required. 5. Do not try to use asymmetrical thrust reverse should you start to slide sideways on a slippery runway. Instead, move

thrust reverser levers from Reverse to Idle/Deploy. After Clearing Runway Aircraft without digital nose wheel steering should avoid use of nose wheel steering about 10 knots during moderate or heavy braking action on patchy snow or ice. For taxi after landing on a slush or snow covered field, it is recommended that the flaps not be retracted above 20 degrees. This will protect flaps and wings from damage in the event ice or snow has accumulated on the flaps. Shutdown and Post Flight When the aircraft must be parked outside in extremely cold or fluctuating freeze/thaw temperatures perform the following in addition to the normal shutdown and post-flight procedures: 1. Chock main gear wheels before releasing parking brake. Do not leave aircraft parked for extended periods in subfreezing

weather and parking brake set. 2. Remove ice, snow, and dirt from landing gear shock struts and wheel wells. Check gear doors, position switches, squat

switches, wheels and tires. 3. Remove ice, snow, and dirt from flaps and flap tracks before retracting flaps. 4. If the aircraft is to remain in subfreezing temperatures for an extended period, remove water and beverage containers

from the aircraft. Crew masks should be stowed in a heated room or the cabin should be warmed to at least 20°F (6.7°C) before flight. Remove toilet tank and reservoir fluid from aircraft or add ethylene glycol base antifreeze containing antifoam agent to the flush fluid.

5. Install aircraft protective covers. If the aircraft will be exposed to extremely cold temperatures for an extended period, it is recommended that the batteries be removed and stored in a warm area if possible.


References Please refer to and be familiar with the information contained in the AFM, Ground De-Icing/Anti-Icing addendum, and in the Chapter 12 of the AMM. Cold Weather Operation Recommendations During winter, flight crew and maintenance personnel must pay particular attention to the hazards imposed by the season. The following additional information is available for your reference:

• Learjet 40/45/XR & Learjet 60/60XR Smart Card Handbook Deicing Guidelines for the Learjet 40/45/XR and Learjet 60/60XR aircraft models have been created and are part of the Smart Card Handbook. Handbooks are available for ordering through Technical Publications at: International Customers: 1-316-946-6100 option 4, then 1

Domestic Customers: 1-866-538-0247 option 4, then 1 Fax Orders: 1-316-946-2580.

• Icing Awareness Pre-flight Considerations Training There is a free web-based training Icing Awareness: Pre-flight Considerations course now available on the Bombardier Customer Training website at http://www.batraining.com. The objectives of this course are:

• To enhance risk awareness related to operations when airframe contamination may exist. • To ensure all individuals involved with aircraft operations make informed decisions concerning:

The identification of airframe contamination Appropriate actions before flight.

Further reference information can be obtained from: Transport Canada Winter 2008-2009 Holdover Time (HOT) Guidelines AC 0072R (Advisory Circular) Ground De-icing/Anti-icing With Engines Running 0135R Union Carbide Type lV & lll Anti-icing Fluid Difficulties To obtain copies: http://www.tc.gc.ca/CivilAviation/commerce/HoldoverTime/menu.htm and http://www.tc.gc.ca/CivilAviation/commerce/circulars/menu.htm

For any other information contact: Email: [email protected] Phone: 613-990-2309 TTY: 1-888-675-6863 Fax: 613-954-4731 / 613-998-8620

Mailing Address: Transport Canada 330 Sparks Street Ottawa, ON K1A 0N5 Attention: Commercial and Business Aviation Issues Officer

U.K. Civil Aviation Authority (CAA) A winter operations reference page can be found at the following link: http://www.caa.co.uk/ and search for “Winter”.

CAA focal points for winter operations and icing: Flight Operations Phone 01934 529852 Fax 01934 529850 Continuing airworthiness (including maintenance) Phone 01293 573766 Fax 01293 573984

Design and continued airworthiness Phone 01293 573309 Fax 01293 573976 Research Phone 01293 573462

Fax 01293 573981


References (Cont’d) Federal Aviation Administration (FAA) A winter operations reference page can be found at the following link.

http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2006/safo06002.pdf http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/deicing/


Slush on the Runway and what it does to Aircraft Performance By Gerard van Es, Senior Research Engineer, Flight Testing & Safety Department, National Aerospace Laboratory NLR, The Netherlands. Analysis of accidents that occurred in the last 20 years has shown that the risk of overrunning the end of a slush- or water-covered runway is about eight times higher than on a dry runway. The hazardous effect of slush on aircraft field performance was first brought into prominence after an accident involving a BEA Airspeed Ambassador aircraft, in which 23 people were killed, in Munich in 1958. The introduction of tricycle under carriages and higher operating speeds of modern aircraft in the late 1950's were associated with this new hazard to aircraft operations. In the early 1960's, investigations on the effects of slush were carried out in the United States, the United Kingdom and France. Tests were conducted using catapult-driven test carriages as well as full-scale aircraft. These early tests gave a clear picture of what slush does to an aircraft that takes off or lands. It was found that the acceleration during takeoff was reduced due to an increase in total drag acting on the aircraft. This increase in drag was caused by the tires displacing the slush and the impingement (interference, intrusion) of the spray of slush on the airframe thrown up by the tires. It was shown that the additional drag increased with increasing slush depth. It was also discovered that there was a considerable possibility of loss of engine power, system malfunctions and structural damage due to spray ingestion or impingement. Furthermore, the problem of very low braking friction between the tires and surface was identified in which aquaplaning of the tires plays an important role. The problem of slush is more acute for aircraft with turbine engines than for aircraft with piston engines because of the higher operating speeds and increased susceptibility to ingestion and impingement due to geometrical characteristics of aircraft with turbine engines. Let us have a look at some typical numbers with respect to the effect of slush on takeoff performance. Just 13 mm (0.5 in.) of slush can subject a large jumbo jet to a drag that is equal to approximately 35% of the thrust of all its four engines. This number increases to 65% for 25 mm (1 in.) of slush, making it impossible to take off. In general, for a multi-engine transport aircraft, just 13 mm (0.5 in.) of slush can increase the take-off distance by some 30-70%. Slush can have an adverse effect on the landing performance. Braking friction can be low because aquaplaning is likely to occur on slush-covered runways. This will increase the landing distance compared to a dry runway. Although it sounds strange, a thicker layer of slush can be better than a thin layer because the drag from the slush helps stop the aircraft. The more slush you have on the runway, the higher the drag on the aircraft. This also applies to rejected takeoffs and can lead to strange performance restrictions when taking off from slush-covered runways. For instance, more slush can give lower take-off weight penalties. What about regulations for operating on slush-covered runways? In 1992, the Moshansky Commission of Inquiry into the Air Ontario crash at Dryden, made several recommendations regarding operations on contaminated runways. The commission recommended that Transport Canada should require that Aircraft Flight Manuals (AFMs) contain guidance material for operating on wet and contaminated runways and that operators provide adequate training to their crews with respect to the effects of contaminated runways on aircraft performance. At the present time, Canadian Operational Regulations do not provide for a Canadian operator of turbo-jet aircraft to have any information in the manuals for operating on contaminated runways. But on the other hand, effective August 1992, an AFM associated with a new type approval must have performance advisory material that deals with operations on contaminated runways. What is this situation elsewhere in world? In Europe, any commercial operator whose principal place of business is in a Joint Aviation Authorities (JAA) Member State must comply with the operational regulations, JAR-OPS 1, which formalize requirements for operational performance information. JAR-OPS 1 requires that an operator account for the effect of contaminated runways on take-off and landing performance. Several non-European countries have adopted JAR-OPS 1. At present the regulations in the United States do not address performance on contaminated runways. The Flight Test Harmonization Working Group will address harmonization of this issue with the JAA in the future. However, this is awaiting harmonization of the associated operating rules by the Airplane Performance Harmonization Working Group. Transport Canada and Canadian operators are some of the members of this last working group. There are more problems caused by slush than described here. For instance loss of directional control when operating in crosswind and the accumulation of slush in the main landing gear bay areas that could freeze and interfere with the landing gear, just to name a few. Remember that slush on the runway today is as big a risk to aircraft operations as it was 40 years ago. Fly safely in the remainder of this and all upcoming winters! You can read about some real-life occurrences in which slush was a factor in Transportation Safety Board of Canada (TSB) accident reports with numbers A98O0034, A96A0047 A96A0050, A96C0232 (see www.tsb.gc.ca).

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Learjet Coldwxops