lecture-6 final - airport

8/12/2019 Lecture-6 Final - Airport

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CE-363

Lecture 6: Runway Length

Dr. Ankit Gupta, Assistant ProfessorDepartment of Civil Engineering

National Institute of Technology Hamirpur


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Lecture Outline

Basic Runway LengthCorrections to basic runway length


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Basic Runway length

Length calculated under the following conditions No wind is blowing on runway.

Aircraft is loaded with full loading capacity.

Airport is at sea-level.No wind is blowing on the way to destination.Runway is leveled, i..e zero effective gradient.Standard temperature of 15 oC at the airport.Standard temperature exists along the way.


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Basic Runway length

Factors affecting the basic runway length Aircraft characteristicsSafety requirements

Airport Environment


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Basic Runway Length: Factors Affecting

Aircraft CharacteristicsPower and propulsion system

Type of an aircraft

The critical aircraft is defined as being the aircrafttype which the airport is intended to serve and whichrequires the greatest runway length. To identify thecritical aircraft, flight manual performance data of a

variety of aircraft are examined. Having determined thecritical aircraft, the longest distance determined fromanalyzing both takeoff and landing performance is used


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Aircraft CharacteristicsGross Take-off and landing weights of the aircraft

Aerodynamic and Mechanical characteristics


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Safety RequirementsNormal LandingNormal Take-off

Stopping in Emergency


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Normal LandingThe aircraft should come to a stop within 60 percentof landing distance assuming that the pilot makes an

approach at the proper speed and crosses thethreshold of the runway at a height of 15 m.The runway of full strength is to be provided for theentire landing distance


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Normal Landing

Runway (Full strength)

15mStop

60% of landing distance

TouchdownPoint

RunwayThreshold

Landing Distance


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Normal Landing: CalculationsField length (FL) = Landing distance (LD)LD = Stopping distance (SD) / 0.60

Length of full strength runway (FS) = LD


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Normal Take-offThe take-off distance must be, for a specific weight ofaircraft, 115 percent of the actual distance the aircraft

uses to reach a height of 10.5 m.the distance to reach a height of 10.5 m should beequal to 115 percent of the lift-off distanceIt requires a clearway at the end of the runway in the

direction of take-off. This should not be less than 150m wide. The upward slope of clearway from the endof the runway shall not exceed 1.25 percent.


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Normal Take-off


10.5m

Lift off distance115% of LOD

Distance to reach a height of 10.5mTake-off Distance

(115% of distance to 10.5 mheight)

Clearway >Half thisdistance

Clearway


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Normal Take-off

Runway (Full+ Strength) Clearway

Min. 150 m


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Normal Take-off: CalculationsField length (FL) = Full strength runway (FS) + Clearway(CW)

Take-off distance (TOD) = 1.15 D 10.5m Clearway (CW) = 0.5[TOD - 1.15(Lift-off distance, LOD)]Take-off Run (TOR) = TOD - CWLength of full strength runway (FS) = Take-off run (TOR)


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Stopping in EmergencyFor the engine failure case, the take-off distance is thebefore coming actual distance required to reach a

height of 10.5 m with no percentage applied.

The aircraft accelerates to a speed V 1 before findingthat the engine has failed and then it starts

decelerating to stop at the end. Therefore, it requires astopway along with a clearway.


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Stopping in EmergencyStopway is defined as a rectangular paved area at theend of runway in the direction of take-off in which an

aircraft can be stopped after an interrupted take-offdue to engine failure. Its width is at least equal to thewidth of runway.


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Stopping in Emergency

Decelerate - Stop Distance


10.5

m

Lift off distance

Stop way

Accelerate - Stop Distance

Take-off Distance

(distance to 10.5 m)

Engine Failure

Accelerate to V 1

Lift-off

Point

Clearway > Half this

distance


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Stopping in Emergency: calculations

Engine failure, Take-off proceeded caseField length (FL) = Full strength runway (FS) +Clearway (CW)

Take-off distance (TOD) = D 10.5m

Clearway (CW) = 0.5[TOD - LOD]

Take-off Run (TOR) = TOD - CW

Length of full strength runway (FS) = Take-off run(TOR)


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Stopping in Emergency: calculations

Engine Failure, take-off aborted caseField length (FL) = Full strength runway (FS) +Stopway (SW)

FL = Accelerate stop distance (DAS)


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Basic Runway length

Required runway lengthIn case of Jet engine

All the three conditions are considered

In case of Piston engineOnly first and third cases are considered

The case giving the longest runway length isfinally recommended


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Basic Runway length

Required runway lengthField distance = max {TOD 2, TOD 3, DAS, LD}Full strength runway = max {TOR 2, TOR 3, LD}

Stopway = DAS - max {TOR 2, TOR 3, LD}Clearway = min{(FL - DAS), CL 2, CL 3}Stopway min = 0Clearway min = 0Clearway max = 300 m


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Basic Runway length

ICAO Specifications for Field RunwayLength

Specify four Declared Distances as Takeoff run available (TORA)Takeoff Distance available (TODA) {=TORA +Clearway}

Accelerate Stop distance available (ASDA){=TORA + stopway}Landing distance Available (LDA)


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Basic Runway length

ICAO Specifications for Field Runway LengthSpecify five cases as

I: with no CL and SW and with no displaced threshold

the four declared distances are normally equal to thelength of runway

II: When runway is provided with a CL, TODA willinclude the CL

III: When runway is provided with SW, ASDA willinclude the length of SW


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Basic Runway length

ICAO Specifications for Field Runway LengthSpecify five cases as

IV: When runway has a displaced threshold, LDA will

be reduced by the distance the threshold is displaced.The displaced threshold at one end affects LDA forapproaches made to the threshold.

V: When a CL, SW and a displaced threshold isprovided


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Basic Runway length

ICAO declared distances


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Basic Runway length

Balanced field ConceptIn case of piston engine aircraft , the designatedengine failure speed is so chosen (by themanufacturer) that the distance required to stop fromthe point, where V f was reached, was equal to thedistance from the same point to reach specified heightof 10.5 m above the runway.This results in the shortest distance of runway


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Basic Runway length

Balanced field Concept: In case of turbine poweredaircraft


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Basic Runway length

Balanced field ConceptCase II: V < V f

FS = L c

FL = L e CW = L e - Lc SW = 0


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Basic Runway length

Balanced field ConceptIn case of turbine powered aircraft

Case III: V > V f

FS = L a FL = L f SW = L f - L a


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Basic Runway length

Airport Environment Atmosphere

Temperature

Surface Wind

Location and Condition of Runway

AltitudeRunway Gradient


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Basic Runway length

AtmosphereStandard Atmosphere

Temperature at MSL 15 oCPressure at MSL 760mm of Hg

Air density 1.225 kg/cu.m


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Basic Runway length

TemperatureStandard Temperature at an Elevation(in oC)

STE = {Temp at MSL +/ rate of change of

temp. x elevation}If h is height above MSL in meters; r is rate of change of temperature with heightor depth above / below MSL, in oC / m; and

Standard temperature at MSL is 15oC, then


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Basic Runway length

TemperatureEffect of Temperature

Reduces air density if airport is located withinstratosphere I.e. up to 11 km height above MSLfor which the temperature decreases with height.Thus reduces drag on aircraft while landing orrequires longer distance for producing necessarylift for the aircraft to fly

Increases basic runway length, the increasebeing 1% for every 1 oC rise in airportreference temperature above the standardtemperature at that elevation


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Runway length

Surface WindInfluence of Wind

HW

TW

W, speed V V sin


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Runway length

Surface WindHead Wind

Provides breaking during landing,

Greater lift during take-off,Reduces runway Length


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Runway length

Surface WindTail Wind

Pushes the aircraft if forward direction

generation of lift is difficultIncreases runway length by a large value


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Runway length

Surface WindCross Wind

It has two components, one along the aircraft and

other transverse to the aircraftThe component along the aircraft may act as headwind or as tail windThe component transverse to the aircraft produces

sway in the movement of the aircraft. If it is veryhigh then it may cause eccentric landing or take-off(away from air path)


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Basic Runway length contd.

Location and Condition of Runway Altitude

Affects air density, atmospheric pressure andtemperature

The reduction in air density or atmospheric pressurewith height above MSL affects the drag and lift forcesand subsequent requirement of length of runway

Rate of change of temperature with height- 6.5 oC / km height upto 11 km heightConstant at -56 oC 11 20 km height+ 1 oC /km height 20 32 km height


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Basic Runway length

Location and Condition of Runway Altitude

Requ ires long er run w ay leng th , incr easebeing 7% per 300m alt i tud e abo ve MSL


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Basic Runway length

Location and Condition of RunwayRunway Gradient

Longitudinal gradientIf the gradient is steep it may cause pre-mature lift-offor may induce structural defects.

It will cause more consumption of energy, therefore,will require longer length of runway to attain the

desired ground speed


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Basic Runway length

Location and Condition of RunwayRunway Gradient

Effective longitudinal gradient Average gradient, computed based on difference inmaximum and minimum elevation along the runwayand divided by the total length of runway.

Runway length to be increased at a rate of 20%

for every 1% of the effect ive gradient . (FAA)


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Basic Runway length

Corrections to basic runway lengthElevation correctionTemperature correction andGradient correction

These corrections have to be applied in the samesequence as listed above


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Basic Runway length

Corrections to basic runway length

Elevation Correction ratele = 7% per 300m rise above MSL

Temperature Correction ratelt = 1% for every 1 o rise in ART above std. Atmospherictemp at that elevation

Gradient Correction ratelg = 20% for every 1% of effective gradient


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Basic Runway Length

Procedure for calculating corrected lengthElevation correction

Find the required basic field runway length under

standard conditions LB Calculate elevation correction rate le and apply itto LB.

Add this value to LB. Lets denote it as LE.


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Procedure for calculating corrected lengthTemperature Correction

Calculate airport reference temperature (ART)

Calculate standard temperature at the givenelevation (ST).Calculate temperature correction rate lt and applyit to LE.

Add this value to LE. Lets denote this correctedlength as LT.


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Procedure for calculating corrected lengthCheck on combined correction for temperatureand elevation

Calculate percentage increase in length after thetwo corrections with respect to LB i.e. (l t + l e ).It is OK if less than and equal to 35%.If it is more than 35% then model testing has to be

carried out


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lecture-6 final - airport

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