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Airport Engineering

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Syllabus

Functional areas of airports- Runways, Taxiways,

Aprons, Terminal buildings; Classifications of Airports;

Airport site selection; Design of Runway, Runway

orientation, Wind Rose diagram; Design of Taxiway and

Terminal building.

Books1. Airport Planning and Design – Khanna, Arora & Jain

2. Airport Engineering – Rangawala

3. Air Transportation Planning & Design – Virendra Kumar & SatishChandra

4. Reference Book: Planning & Design of Airport – R. Horonjeff & F.X. Mckelvey

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Introduction1.1 Characteristics of Air Transportation

Advantages of Air TransportationI. Speed:- High Speed among all the transport modeII. Accessibility:- Open up any region that is inaccessible by

other means of transport e.g. Hill areaIII. Continuous Journey:- Movement is possible continuous over

land and water unlike other modesIV. Aerial PhotographyV. Military useVI. Encourage Trade and commerce:- More opportunities for

businessVII. Agricultural sprayingVIII. Impact on Economic and Social life of countryIX. Safety:- Safer than road way travel. Fatal air accident is less

than 20% of that of highway accident.

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Disadvantages are

1. High Cost

2. Noise Pollution

3. High Energy Consumption: Per passenger fuel consumption is 10 times more than bus

1.2 Air Transport in India & Abroad

• History of Development of Air Transport and its characteristics.

• Different Stages and modification in Air Transport mode.

• Present Scenario of worldwide Air Traffic.

• Development of Air Transportation in India.

History and Back Ground

Operational Development

Present Private and Govt. Participation in operation of Domestic as well as International Air Transportation

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1.3 Elements of Air Transport

Airport: It is an area of land and water which is to be regularly used for commercial purposes for arrival, departure and movement of aircrafts.

Aerodrome: Any defined area of land or water intended to be used for arrival and departure of aircraft is called aerodrome.

Any airport is largely divided into three major components:

• The air side: this consists of airfield and landing take-off area i.e. runway and taxiway

• The land side: this consists of terminal areas i.e. apron, hanger, terminal building.

• Air traffic control: this consists control movement of aircraftsin airspace surrounding the airport.

Airport Engineering deals with first two components

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C

A

B B B B

E

F

D

A : RunwayB: TaxiwayC: ApronD: HangerE: Terminal BuildingF: Car parking Zone

Fig. Schematic Diagram of an airport

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Runway: • Long and comparatively narrow strip of land which is used for

landing and take-off of aircraft along its lengths.• Paved.• More than one runway.

Taxiway:• Access of the aircraft from runway to apron or hanger.• Speed of the aircrafts are less than runway.• Less thick pavement.

Apron:• Paved portion in front of the terminal building or adjacent to

hanger.• Space for parking of aircrafts.• Size of the apron depends upon aircraft volume• Paved space provided near the runway is known as holding

apron.• Apron exclusively used for fueling purpose is known as

fueling apron

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Hanger:

• Space for servicing, overhauling and repairing of aircrafts• Important airports may have more than one hanger

Terminal Building:• Building complex mainly used for passengers, airliners and

airport administration facility.

• Passenger facilities for convenient and direct access to ground

transportation and parking area.

An airport encompasses a wide range of activities which have different and conflicting requirements. As they are interdependent, a single activity may limit capacity of entire complex.

The airport activity system is shown in the next slide

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Enroute Airspace

Terminal Airspace

Runway

Holding Apron Exit Taxiway

Taxiway

Apron/Gate Area

Terminal Building

Vehicular Circulation Parking

Airport Ground Access System

Airfield Surface System

Air side

Land side

Aircraft flowPassenger flowFig. Components of the airport

system for a large airport

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1.4 Classification of an Airport

1.4.1 International Civil Aviation Organization (ICAO)

– Most important international agency concerned with airport development.

– Specialized agency of UNO with head quarter at Montreal, Canada.

– 169 nations are members.

– The objective of ICAO are:

• Safe and orderly growth of international civil aviation.

• Aircraft design and operation for peaceful purpose.

• Development of airways, airports and air navigation facilities.

• Safe, regular, efficient and economic air transportation.

• Rights of the contracting nations are fully respected.

• Promotion of all aspects including safety of flight of international civil aeronautics.

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The document – “Aerodromes, Annex 14 to the convention on International Civil Aviation” issued by ICAO provides international design standards and recommended practicesapplicable to all international airports.

ICAO uses a two-element code to clarify geometric design standards at an airport. The code element consist of a numeric designator and an alphabetic designator. Aerodrome code numbers 1 through 4 classify the length of runway available or the reference field length.

Aerodrome code letters A through F classify the wingspan and outer main gearwheel-span for the aircraft for which the airport has been designed.

This aerodrome reference code is shown in Table 1.0

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Reference Field Length: Actual Runway takeoff length converted to an equivalent length at MSL, 150C, and 0 percent gradient.

Wing Span: Distance between outside of two wings of the aircraft.

Outer main gear wheel span: Distance between outside edges of tyreson the main gear wheel.

Table 1.0 ICAO Aerodrome Reference Code

14-<1665 - <80F

9-< 1452 - < 65E

9 - < 1436 - < 52D≥18004

6 - < 924 - < 36C1200 - <18003

4.5 - < 615 - < 24B800 - <12002

< 4.5< 15A<8001

Outer main gear wheel span (m)

Wing Span (m)

Aerodrome Code Letter

Reference field length (m)

Aerodrome Code No.

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(m)(m)

Table: Aerodrome Reference Code

Source: ICAO Annex 14, Aerodromes, Volume I, Aerodrome Design and Operation 4th edition

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1.4.2. Federal Aviation Administration (FAA)This is an agency which governs air transportation including airports in United States. It develops and establishes standards, governmentplanning methods and procedures, airport design, construction management, operation and maintenance. It clarifies airports forgeometric design purposes based upon airport reference code. It is based upon the aircraft approach category and the airplane design group to which the aircraft is assigned.

Utility Airport: Utility airports serves and accommodate small aircraft with

maximum take off weight of 12,500lbs. or less.

Transport Airport: Transport airports can accommodate large aircraft

with maximum take off weight in excess of 12,500 lbs.

FAA also defines five aircraft approach categories. The approachcategory is defined by aircraft approach speed which is defined as 1.3 times the stall speed in the landing configuration of the aircraft at the maximum certified landing weight.

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Stall Speed

• A stall is a sudden reduction in the lift forces generated by a airfoil.

• This occurs when the critical angle of attack of the airfoil is

exceeded,typically about 15 degrees.

• Typically it is the situation in aerodynamics and aviation where the

angle between the wing’s chord line and the relative incomong wind

(the angle of attack) increases beyond a certain point such that the

lift begins to decrease.

• The angle at which it occurs is known as the critical angle of attack.

• At the stall neither the engine(s) of the aircraft stopped working or

aircraft has stopped moving.

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≥ 166

141 - <166

121 - <141

91 - <121

<91

Aircraft approach Speed (Knot)

Transport Airport

Transport Airport

Transport Airport

Utility Airport

Utility Airport

Airport Category

E

D

C

B

A

Airport Approach Category

1 Knot = 1.87 km/hr.

Table 2.0 FAA Aircraft Approach Category Classification

214 - < 262171 - < 214118 - <17179 - <118

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Aircraft Wing Span (ft.)

Lockheed C5A

Boeing 747-400

Boeing 757, Lockheed 1011

Boeing 737, Martin-04

DeHavilland DHC-5 Gulfstream II

Beech Bonanza A 35 Learjet 25

Typical Aircraft

VIVIVIIIIII

Airplane Design group

Table 3.0 FAA Airplane Design Groups for Geometric Design of Airport

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1.4.3. Govt. of India, Dept. of Civil Aviation Classification.

I. a) Central Govt. Aerodrome

b) Privately owned licensed aerodrome

II. a) State Govt. Aerodromes maintained in a serviceable condition

b) State Govt. Aerodromes maintained not in a serviceable condition

iii. Air force aerodrome available for limited civil use

Airport configurationThe airport configuration is the number and orientation of runways

and the location of the terminal area relative to the runways.

The number of runways provided at an airport depends on the volume of traffic.

The orientation of these runways depends to a large extent on the direction of the prevailing wind patterns in the area, the size and shape of the area available for airport development, and land-use or airspace restrictions in the vicinity of the airport

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RunwaysIn general, runways and connecting taxiways should be arranged so as to-

• Provide adequate separations between aircraft in the air trafficpattern.

• Cause the least interference and delay in landing, taxing, and takeoff operations.

• Provide the shortest taxi distance possible from the terminal area to the ends of the runways.

• Provide adequate taxiways so landing aircraft can exit the runways as quickly as possible and follow the shortest possible routes to the terminal area.

• At busy airports, holding or run-up aprons should be provided adjacent to the takeoff ends of the runways – these aprons should be designed to accommodate three or possibly four aircraft to bypass one another.

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TaxiwaysThe principal function of taxiways is to provide access between runways and terminal area and service hangers

• Taxiways should be arranged so that aircraft which have just landed

do not interfere with aircraft taxiing to take off.

• At busy airports where taxiing traffic is expected to move

simultaneously in both directions, parallel one-way taxiways should

be provided .

• Taxiway should be located at various points along runways so that

landing aircraft can leave the runways quickly to clear them for use

of other aircraft – commonly known as exit taxiways.

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Runway ConfigurationThe basic runway configuration are

• Single runway.

• Parallel runways.

• Dual-lane runways.

• Intersecting runways.

• Open or V-runways.Single runway: This is the simplest of the runway configurations.Parallel runways:The capacities of parallel runway systems depend a

great deal on the number of runways and on the spacing between them.The spacing is classified as close, intermediate, and far depending on the C.L. seperation between two parallel runways.

Close parallel runways – seperations 700 ft to < 2500 ft.Intermediate parallel runways – seperation 2500 ft to < 4300 ft.Far parallel runways – seperation at least 4300 ft.

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Intersecting runways: When two or more runways in different directions crossing each other the intersecting runways formed.

Intersecting runways are necessary when relatively strong winds come from more than one direction, resulting in excessive crosswinds when only one runway is provided.

When winds are strong only one runway can be used.

If the winds are relatively light, both runways can be used simultaneously.

The capacity of the intersecting runways depends on the location of intersection (i.e., midway or near the ends), the manner in which runways are operated for takeoffs and landings (runway-use strategy) and the aircraft mix.

The highest capacity is achieved when the intersection is close to the takeoff and landing threshold. (Figure 1.e)

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Open-V runways:: Runways in different directions which do not intersect are known as open-V runways

The strategy which yields the highest capacity occurs when operations are away from the V, which is referred as a diverging pattern (Fig 1h).

When the operations are towards the V , it is reffered as a converging pattern (Figure 1i).

Combinations of runway cofigurations

Single direction-runway configuration is most desirable from the view point of capacity and air traffic control.

The open-V runway pattern is more desirable than an intersecting-runway configuration

If intersecting runway is not avoidable, then the intersection be placed as close as possible to their thresholds.

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Figure 1: Runway configurations

(a) Single runway

(b) , (c), (d) Parallel runways

(e) , (f), (g), Intersecting runways

(h) , (i), open-V runways

S= close, intermediate, or far

TO – takeoff

L - Landing

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RUNWAY ORIENTATION

• Runway is usually oriented in the direction of prevailing wind. If the take off is performed in the direction opposite to the direction of wind flow, greater lift on the wings of the aircraft is available.

• Due to the force applied by the wind, the aircraft can rise above the ground much earlier and therefore a shorter length of runway is required.

• This wind, directly opposite to the movement of the aircraft, is called head wind.

• During landing the wind provides a breaking effect and the aircraft comes to a stop within a shorter distance requiring a shorter length of runway.

• Thus, shorter runway length is required if the landing or take-off operation is performed along the head wind direction

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Wwsinθθ

wcosθ

wTakeoff

Landing

w Wind Direction

However, this is not always possible to have the wind blows in the direction of runway as the direction of wind is not same through out the year.

When the wind direction meets the runway at angle θ, its components along the runway centre line will be wcosθ and perpendicular to the runway centre line will be wsinθ. This perpendicular components of wind is referred as Cross Wind.

This cross wind components interrupts the landing and take off operation of the aircraft on runway. The excessive cross wind may put off the aircraft away from runway.

Therefore the runway or system of parallel runway should be directed in such a way that the cross wind component does not cross the specified limit most of the time in a year.

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The percentage of time in a year during which the cross wind components remain within the specified limit is called wind coverage or usability factor of airport.

ICAO recommended a minimum wind coverage of 95%.The permissible cross wind components on different runway length as recommended by ICAO are

19 km/hr.(10 knot)

24 km/hr.(13 knot)

37 km/hr. (20 knot)

Maximum cross wind component

Less than 1200m

1200m – 1499m1500m or over

Reference FieldLength

This 95% criterion suggested by ICAO is applicable to all conditions of weather. When a single runway or a set of parallel runways cannot be oriented to provide the required wind coverage, one or more cross wind runway should be provided.

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The period during which wind blows at a velocity below 6.4 km/hr is called calm period. This intensity does not influence the aircraft operation.

Maximum allowable cross wind component depends upon size of aircraft, wing configurations and pavement surface.

The Federal Aviation Administration (FAA) recommends that runways be oriented so that aircraft may be landed at least 95%of the time with allowable crosswind components do not exceeding specified limits specified by the airport reference codes

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WIND ROSE DIAGRAM

• The wind data and its direction, duration and intensity are represented by a diagram called ‘wind rose’.

• This wind rose is used to analyze the wind data graphically to determine the best runway orientation.

• The wind data should be collected preferably for a period of 10 years and at least for 5 years.

• The wind rose diagram are of two types and there are two methods to determine the runway orientations.

• The wind data for preparation of wind rose diagram should provide:

a) Direction of wind preferably in 16 directional segments each covering 22.50. and

b) Duration of wind in % of the total time in different velocity group and at least three group should be taken starting from 6.4 kmph.

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Table: Typical Wind Data: Percentage of time that Winds Come from Particular Directions at Various Velocities in All Weather Conditions

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N NNENE

ENE

E

ESE

SE

SSES

W

WIND ROSE TYPE IIn this method the duration and direction of wind are used, but data on velocity of wind is not required

This is not very accurate method. The radial lines indicate the wind direction and the duration is marked in this radial line to some suitable scale.

All plotted lines are joined by straight lines. The best runway orientation is usually along the direction of the largest line on the wind rose diagram.

In the figure the best orientation is along EW direction.,

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Wind Rose Co-ordinate system Cross wind components template showing limits of 15 mi/h

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• The type II wind rose diagram shows information of wind on direction, duration and intensity.

• This diagram is used for orientation of runway.

• The wind rose diagram consists of a number of concentric

circles, each circle represents the wind intensity to same scale.

• The circles are divided into number of segments, preferably 16 segments, each covering 22.50.

• Each segment represents a direction of wind flow.

• The duration of wind flow as a percentage of time in a year is noted in segment representing the respective direction of wind flow.

WIND ROSE TYPE II

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40Wind rose type II

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RUNWAY ORIENTATION

Step I : Draw the equi-spaced parallel lines on a transparent paper

strip. The middle line represents the runway centre line and the

distance between it and each of the out side lines is equal to the

allowable cross wind component.

Step II : Place the transparent strip on the wind rose so that the middle

line passes through the centre of the wind rose.

The procedure for determining the orientation of runway with thehelp of wind rose diagram is described in the following steps

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Step III : Rotate the strip with respect to the pivot until the sum of the

percentage between the outside lines is a maximum. When the strip

covers only a fraction of a segment, corresponding fractional part of

the percentage shown should be used. The sum of percentages

between the out side lines indicate the percentage of time that the

runway with the proposed orientation will conform with cross wind

standard.

Step IV : Note the direction of runway and calculate the wind coverage.

RUNWAY ORIENTATION

43Wind coverage for runway 9-27

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44Wind coverage for runway 3-21

45Wind coverage for runways 9-27 and 3-21

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1. Plot the wind rose diagram under VMC

2. Determine the best orientation of primary runway at this airport. Permissible cross wind component 15km/hr

Wind Data for day light hours for visual meteorological conditions for an airport

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RUNWAY GEOMETRIC DESIGN

Runway LengthLength of runway depends upon various factors

– Characteristics of airport– Trip length– Environmental factors

The length of the runway under the following assumed condition is known as the basic runway length

1) No wind is blowing in the runway.2) The aircraft is loaded to its full loading capacity.3) The airport is situated at sea level.4) The standard temperature of 150C exists in the airport.5) The runway is leveled in the longitudinal direction.6) There is no wind blowing enroute to the destination.7) Enroute temperature is standard.

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• The basic runway length depends upon the performance characteristics of the aircraft using the airport

• As a guide to the airport planners, FAA has published the runway length requirements for air carriers and general aviation aircraft

• The information from the aircraft manufacturer can be obtained for this purpose also.

•The necessary correction required for any change in elevation, temperature and gradient for the actual site of construction should be done

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Correction for Elevation

Reason: The density of air reduced with increase in elevation and the aircraft requires longer length of runway for taking off.

ICAO Recommendation:

The basic runway length should be increased @ of 7% per 300m rise in elevation above MSL

Correction for Temperature

Reason: The higher the temperature longer the runway required, because high temperatures reflect lower air densities, resulting in lower output thrust.

ICAO Recommendation:

The basic runway length should be increased @ of 1% for every 10C rise of airport reference temperature (ART) above the standard equivalent atmospheric temperature at that elevation.

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Airport Reference Temperature (ART)

= TA+ (TM – TA)/3

TA = Monthly mean of average daily temperature for the hottest month of the yearTM = Monthly mean of maximum daily temperature for the same month of the year

Standard Equivalent Atmospheric temperature

= 150C – [6.5h]/1000Where; h = rise in altitude(in m) above MSL

[Standard temperature = 150C, Decrease @ 6.50C per 1000m rise in elevation]

If the total correction for elevation plus temperature exceeds 35% of the basic runway length then this should be checked by specific studies

Check:

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Correction for Gradient

An uphill gradient requires more runway length than a level or downhill gradient. Though ICAO does not specifically provides any correction for gradient, it suggest the FAA recommendation for correction on runway gradient

It is recommended that the runway length after having been corrected for elevation and temperature should be further increased @20% for every 1% of effective gradient.

Effective gradient is the maximum difference in elevation between the highest and lowest point of runway divided by total length of runway

Problem:

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TAXIWAYSThe main function of a taxiway is to provide access to the aircrafts from the runways to the loading apron or hanger and back.

Dual Parallel Taxiway:Two taxiways parallel to each other an which airplane can taxi in opposite direction.

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Apron TaxiwaysIt is the taxiway located on the periphery of an apron in order to provide a through taxi route across the apron

Taxi lane: It is a portion of the aircraft parking area used for access between the taxiway and aircraft parking position

ExitTaxiway: Taxiways provided at various points along the runway help to divert the landing aircraft quickly.

Figure: Exit Taxiway

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Separation Criteria

To provide a margin of safety in the airport operating areas, the taxiways must be separated sufficiently from each other and from each other and from adjacent obstruction.

ICAO Recommendation

Taxiway to taxiway separation

Taxiway to taxiway separation

STT = WS + 2U1 + C1

Where;

STT = Minimum centre to centre distance between two adjacent taxiwayWS = Wingspan of the most demanding aircraft

U1 = Taxiway Edge safety margin i.e. the minimum clearance between edge of each taxiway and the outer main gear wheel

C1 = Minimum wing tip clearance

STT

C1

U1

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Taxiway and Fixed or movable object

Taxiway and fixed or movable object separation

STO = 0.5WS + U1 + C2

Where,

STO = Minimum separation

C2 = Required clearance between wingtip and object

C2

C2

U1

ICAO Recommendation

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Taxiway Layout

Factors controlling layout of taxiway1. Arrangement: Aircraft which has just landed does not interfere with the

aircraft taxing to take off2. Busy Airport: Exit taxiway should be provided at various points. Parallel

one way taxiway should be provided.3. Crossing: Intersection of runway and taxiway should be avoided.4. Route: Route should be so selected that it provides shortest practicable

distance.

Geometric Design Standard

Length of the taxiway should be as short as practicable. No specific

guideline is available for length of taxiway. Other features like width,

sight distance etc as per ICAO is given in table below

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1.50%3.33%1.50%30m

1.50%3.33%1.50%30m

1.50%3.33%1.50%30m

3.0%4.0%2.0%25m

3.0%4.5%2.0%25m

GradientLongitudinal maximumLongitudinal maximum changePavement transverse maximum

Minimum length of vertical curve for 1% gradient change

3.0m300m

3.0m300m

3.0m300m

2.0m200m

1.5m100m

Sight DistanceHeight of objectClear distance

23444.57.512

18384.57.512

15253.04.57.5

10.5-

2.253.05.25

7.5-

1.53.04.5

WidthPavementPavement and ShoulderEdge Safety Margin

C1C2

EDCBAAerodrome Code

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Taxiway width

Depending on the code letter of the runway, minimum margins of safety between 1.5m to 4.5m should be provided between outer main gear wheel edge and the taxiway edgeWidth of taxiway is less than the width of corresponding runway because aircraft taxi speed is considerably slower than the speed on take-off or landing.

The taxiway width needs to be between 7.5m (code letter A) to 25m(code letter F).

The taxiway width, WT is based on the formula;

WT = TM + 2C

Where; TM = outer main gear wheel span

C = clearance between the outer main gear wheel and taxiway edge Fig Taxiway width requirements

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Fillets

Taxiway need to be widened with fillets where they have sharp curves so that the necessary safe separation distance between the outer main gear wheel edge and runway edge may be maintained

Fig: Taxiway widening to achieve minimum wheel clearance on curve

30106.0<10

60157.510 to 15

603022.515 to 20

>1350450 -1350<450

Angle of IntersectionWheelBase

(m)

Table: Fillet Radaii (m)

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60Fig: Typical runway and taxiway fillets for small airports

61Fig: Typical runway and taxiway fillets for large airports

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Turning RadiusHorizontal curve is to be provided whenever there is a change in the direction of taxiway

Circular curve of larger radius is most suitable

125fV2

=RWhere;

V = exit speed of aircraft

F = coefficient of friction between aircraft wheel tyre and taxiway pavement. The adopted value of f is 0.13

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Exit Taxiway

The function of exit taxiway or runway turn offs is to minimize runway occupancy by landing aircrafts.

Location of Exit taxiway

The location of exit taxiway depends on the following points:i. Mix of aircraftii. Approach and touchdown speediii. Point of touchdowniv. Exit speedv. Rate of decelerationvi. Pavement conditionvii. Air traffic control

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Fig: A 450 high speed exit taxiway for air craft category A and B (FAA)

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Fig: A 300 high speed exit taxiway for aircraft in category C, D and E (FAA)

Point of curvature

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Fig: A 900 exit taxiway (FAA)

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Mathematical model are developed to determine the location of exit taxiway

Simplified method may be:

D = Dtd + De Where: D = distance from runway threshold to exit

Dtd = distance from the runway threshold to point where air craft touches down.

De = distance from touchdown point to exit

De = (Vtd2 – Ve2)/2a Where:

Vtd = aircraft speed at touch down

Ve = exit speed

a = deceleration rate which should not be more than 1.5 m/s2 for passenger comfort

Location of exit taxiway

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Location of High speed Exit taxiway

V1V2

V0= 0

D S2

S1Fig.1 High speed exit taxiway distance from a threshold

The location of the start of a high speed exit taxiway may be derived by assuming a constant retardation ‘a’

The following shall apply for such movement.

a;2dt

s2ddtdv

== ∫ +== 1Cata.dtv(t)

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∫ ++=+=∴ 212

1 CtCa.t21)dtC(a.tS(t)

With the beginning of path S=0 to the point with speed v=0 in the moment then C1= C2 = 0 and the following expression is generally valid:

a.t;V(t) = 2a.t21S(t) =

If the direction to the right of the full-stop point (i.e (S(0) = 0) is considered to be positive and at the same time the ‘acceleration ‘a’ negative. This is illustrated in Fig. 1 and the meaning of which is expressed by the following:

;at21S 2

11 = ;atV 11 = aVt 1

1 =

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aV

21

aVa

21S

21

2

11 =⎟

⎠⎞

⎜⎝⎛=∴

As an analogy we can derive;a

V21S

22

2 =

The Final Expression is:

2aVVSSD

22

21

21

−=−=

71Figure 2. Exit Taxiway