ce-461 ce-461 runway length

7/24/2019 CE-461 CE-461 Runway Length

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Transportation Engineering - II

Runway Length

Dr. Indrajit Ghosh

Assistant Professor

Department of Civil Engineering

Indian Institute of Technology Roorkee


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Lecture Outline

Basic Runway Length

Corrections to basic runway length


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Basic Runway length

Length calculated under the following assumed

conditions:

Airport is situated at sea-level

Standard temperature of 15o

C at the airport Runway is leveled in longitudinal direction

Zero effective gradient

No wind is blowing on runway

Aircraft is loaded to its full loading capacity No wind is blowing on the way to destination

Standard temperature exists along the way


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Basic Runway Length: Factors Affecting

Determination of basic runway length

Performance characteristics of aircrafts using the

airport

Manner in which an aircraft actually performs landingand take off operation

Consideration of following cases

Normal Landing

Normal Take-off

Engine Failure


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Normal Landing

The aircraft should come to a stop within 60 percent

of landing distance assuming that the pilot makes an

approach at the proper approach speed and crossesthe threshold of the runway at a height of 15 m (50

ft)

The runway of full strength pavement is to be

provided for the entire 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: Calculations

Field length (FL) = Landing distance (LD)

LD = Stopping distance (SD) / 0.60

Length of full strength runway (FS) = LD


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Normal Take-off

Take-off distance must be, for a specific weight of

aircraft, 115 percent of the actual distance the aircraft

uses to reach a height of 10.5 m (35 ft) It requires a clearway at the end of the runway in the

direction of take-off

This should not be less than 150 m wide

It is kept free from obstructions

The upward slope of clearway from the end of the

runway shall not exceed 1.25 percent


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Normal Take-off


10.5m

Lift off distance

115% 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

Clearway

A rectangular area at the end of landing strip in the direction of

take off

Centrally located about extended centre line of runway

Selected or prepared as suitable area over which an aircraft

may take a portion of its initial climb to a specified height

Under the control of airport authorities


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Normal Take-off: Calculations

Field length (FL) = Full strength runway (FS) + Clearway

(CW)

Take-off distance (TOD) = 1.15 D10.5m Clearway (CW) = 0.5[TOD - 1.15(LOD)]

Take-off Run (TOR) = TOD - CW

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


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Engine Failure

If the engine fails at a speed, less than designated

engine failure speed, pilot decelerates the aircraft and

makes use of a stopway If, however, engine fails at a speed higher than the

designated speed, there is no other option to the pilot

except to continue to take-off

Pilot may later take a turn in turning zone and land again for anormal take-off

Requires either a clearway, or a stopway, or both


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Engine Failure

Stopway

A rectangular paved area at the end of runway in the direction

of take-off in which an aircraft can be stopped after aninterrupted take-off due to engine failure

Its width is at least equal to the width of runway

It is centrally located in alignment with centre line of runway

Used for decelerating aircraft and bringing it to a stop during

an aborted take-off

Strength of stopway pavement should be just sufficient to

carry the weight of the aircraft without causing any structural

damage to aircraft


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Engine Failure

Decelerate - Stop Distance


10.5

m

Lift off distance

Stop way

Accelerate - Stop Distance

Take-off Distance

(distance to 10.5 m height)

Engine Failure

Accelerate to V1

Lift-off

Point

Clearway > Half this

distance


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Engine Failure

Runway (Full Strength)

Clearway

minimum

150 m

Stopway


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Engine Failure: Related calculations

Take-off proceeded case

Take-off distance (TOD) = D10.5m

Clearway (CW) = 0.5 [TOD - LOD]

Take-off Run (TOR) = TOD - CW

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

(TOR)

Field length (FL) = Full strength runway (FS) +

Clearway (CW)


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Engine Failure: Related calculations

Take-off aborted case

Field length (FL) = Full strength runway (FS) +

Stopway (SW)

FL = Accelerate stop distance (ASD)


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Basic Runway length

Required runway length

In case of Jet engine aircrafts

All the three conditions are considered

The case giving the longest runway length isfinally recommended


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Basic Runway length

Required field length and other components

Field length = max {LD, TOD2, TOD3, ASD}

Full strength runway = max {LD, TOR2, TOR3}

Stopway = ASD - max {LD, TOR2, TOR3} Clearway = min {(FL - DAS), CW2, CW3}

Stopwaymin= 0

Clearwaymin= 0

Clearwaymax= 300 m

If both ends of runway are to be used by aircrafts

Field length components must exist in each direction


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Basic Runway length

ICAO Specifications for Field Runway

Length

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 Length

Specify 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 will

include 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 Length

Specify 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 for

approaches made to the threshold.

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

provided


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Basic Runway length

ICAO declared distances

C L


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Basic Runway length



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Basic Runway length



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Basic Runway length

Example problem

Determine the runway length requirement for

turbine powered aircraft. Following aircraft

performance characteristics are observed. Normal landing

Stop distance = 1500 m

Normal take off

Lift off distance = 2100 m

Distance of 10.5 m height = 2400 m


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Basic Runway length

Example problem (continued)

Engine failure take off

Lift off distance = 2460 m

Distance of 10.5 m height = 2730 m Accelerate stop distance = 2850 m

Engine failure aborted take off

Accelerate stop distance = 2850 m


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Basic Runway length

Corrections for Elevation, Temperature and

Gradient

Basic runway length is for mean sea level

(MSL) elevation Have standard atmospheric condition

Have zero effective gradient

Necessary corrections are applied Any change in elevation, temperature and gradient

for the actual site of construction


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Basic Runway length

Correction for elevation

Elevation increases

Air density reduces

Reduces the lift on wings of aircrafts Require greater ground speed to rise to air

Need longer length of runway

ICAO recommendation

Basic runway length should be increased

At rate of 7 percent per 300 m rise in elevation of

airport above mean sea level


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Basic Runway length


Airport elevation = 100 m

Basic length of runway = 600 m

Calculate actual length of runway.


= (7/100)* (100/300) * 600

= 14 m

Length of runway after correction for elevation

= 600 + 14 = 614 m


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Basic Runway length

Correction for temperature

Rise in airport reference temperature hassame effect as that of increase in elevation

above MSL ICAO recommendation

Initially basic runway length is corrected forelevation of airport

Basic runway length is further increased at rate of 1percent for every 10 C rise in airport referencetemperature above standard atmospherictemperature at that elevation


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Basic Runway length


Airport Reference Temperature AFT = T1+

1/3 (T2- T1)

T1= Monthly mean of average dailytemperature for the hottest month of the year

T2= Monthly mean of the maximum dailytemperature for the same month


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Basic Runway length


Airport Reference Temperature

Daily temp. data for hottest month of a year

for a given airport siteDate Temp Date Temp

Max Avg. Max Avg.

1 48.0 27.7 16 47.7 26.8

2 47.3 27.5 17 48.5 27.2

. .

15 46.5 27.1 30 46.1 27.3


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Basic Runway length

Temperature

Standard Temperature at airport site at anelevation (in o C)

STE = [Temp at MSLrate of change of temp.x elevation]

= (15 - r x h )

Standard temperature at MSL is 15oC

r is rate of change of temperature with heightabove MSL 6.50 C / 1000 m rise in elevation

h is height above MSL in meters


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Basic Runway length

Correction for elevation and temp.



Airport reference temp. = 28o C

We found earlier,

Length of runway after correction for elevation

= 600 + 14 = 614 m

Standard temp. at airport site

= 15(6.5*100/1000) = 14.35 o C


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Basic Runway length


Rise in temp. = 28 -14.35= 13.65 o C

Correction for temp.

= (1/100 * 614) *13.65 = 83.81 = 84 m

Corrected runway length after elevation plus

temp. correction

= 614 + 84 = 698 m


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Basic Runway length

Check for total correction for elevation plus

temp.

ICAO recommendation

Total correction should not exceed 35 percent of

basic runway length

If exceeds, the corrections should then be further

checked up by conducting specific studies at the

airport site by model sites


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Basic Runway length


Corrected runway length after both corrections

= 698 m

Total correction in percentage

=(698600)/600 * 100

= 16.33% < 35%

Hence, OK

Not done now


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Basic Runway length

Correction for gradient

Runway Gradient

Runway gradients are of two types:

Longitudinal gradient

Transverse gradient

Quick disposal of water from the pavement surface


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Basic Runway length


Runway Gradient

Longitudinal gradient

If the gradient is steep it may cause pre-mature lift-off

or may induce structural defects

It will cause more consumption of energy and will

require longer length of runway to attain the desired

ground speed


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Basic Runway length


Runway Gradient

ICAO does not recommend any specific correction

FAA recommendation

Runway length to be increased at a rate of 10 percent

for every 1 percent of the effective gradient


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Basic Runway length


Runway Gradient

Effective longitudinal gradient

Average gradient, computed based on difference in

maximum and minimum elevation along the runway

and divided by the total length of runway


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Basic Runway length

Correction for elevation, temp. and gradient



Airport reference temp. = 28o C

Highest point along length = 98.2 m

Lowest point along length = 95.2 m


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Basic Runway length

Correction for elevation, temp. and gradient

Effective gradient = (98.2 - 95.2 )/600

= 3/600 = 0.5%


= 10/100 * 698 * 0.5

= 34.9 = 35 m

Actual length of runway

= 698 + 35 = 733 m


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Basic Runway length

Corrections to basic runway length Elevation correction

Temperature correction

Gradient 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 rate

le= 7 percent per 300m rise above MSL

Temperature Correction rate

lt= 1 percent for every 1orise in ART above Std.

Atmospheric temp at that elevation

Gradient Correction rate

lg= 10 percent for every 1 percent of effective gradient


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Basic Runway length

Example problem

Longitudinal section of runway provides

following data:

Calculate effective gradient of runway.

End to end of runway (m) Gradient (%)

0 to 200 +1

200 to 600 -1

600 to 1200 +0.8

1200 to 1600 +0.2


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Example

Mean of avg daily temp = 40 degree C

Mean of max daily temp = 50 degree C

Site is at MSL

Basic runway length = 800 m

Determine actual runway length.

Runway is on a level surface

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