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Airport Geometric Standard
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Transcript of Airport Geometric Standard
Airport Geometric Standard
Topics to be coveredRunway lengthRunway widthSight distanceGrades and change of gradesTaxiwaysApronsOrientation of runwayWind Rose diagram.
Aircraft characteristics
1. Type of propulsion: the size of aircraft, its
circling radius, speed, weight carrying
capacity, noise and heat nuisance etc.
depends on type of propulsion.
Piston engine.
Jet engine.
2. Size of aircraft :
Wing span
Fuselage length
Height (empennage height)
Distance between main gear
Wheel base and
Tail width.
3. Minimum turning radius : is very essential in
order to decide the radius of taxiway,
position of aircrafts in landing aprons and
hangers and to establish the path of the
movement of the aircraft.
4. Circling radius : depends on type of aircraft,
air traffic volume and weather condition.
Micro-lites aircraft – 1.6km
Jet engine – 80km
5. Speed of aircraft : Cruising speed/ground speed – aircraft speed
w.r.t ground when aircraft is flying in air @ maximum speed.
Air speed – speed of aircraft relative to wind.6. Aircraft capacity : capacity of runway system
and passenger terminal.7. Weight of aircraft and wheel configuration :
structural design of runway, taxiway, apron and hangers.
8. Jet blast : causes inconvenience to the
passenger travelling in aircraft. Bituminous
flexible pavements are affected by the jet blast,
CC pavements @ touch down portion. For
location, position and size of gates.
9. Fuel spillage : bituminous flexible pavements are
seriously effected by the fuel spillage.
10. Noise.
Runway orientation• Runway is always oriented in the direction of
prevailing winds.• The direction of wind opp. to the direction of
landing and take-off (head wind) provide greater lift on the wings of aircraft when it is taking-off and during landing head wind provides a breaking effect and the aircraft comes to stop in a shorter length of a runway.
• Landing and taking-off along wind direction require longer runway.
Cross wind : If a wind blow making certain angle with a
center line of runway then it has two components, one along the direction of runway center line VcosƟ and normal to the direction of runway center line VsinƟ. Where V is the velocity of wind.
The normal component of the wind is called the cross wind component and may interrupt the safe landing and take-off of the aircraft.
Depends on size & wing configuration. Small aircraft <15kmph & mixed traffic <25kmph(FAA), big aircrafts <35kmph(ICAO)
Wind coverage : The percentage of time in a year during which
the cross wind component remains within the limits (as per FAA & ICAO specification) is called wind coverage.
A/C to FAA, the runway handling mixed traffic should be so planned that 95% of time in a year, the permissible cross wind component does not exceed 25kmph.
For busy airport, the wind coverage may be increased to as much as 98% to 100%.
Wind Rose• The graphical representation of direction, duration
and intensity of wind obtained from wind data is called wind rose.
• Wind data – at least 5yrs, preferably 10yrs.• Wind rose diagram helps in analyzing the wind data
and obtaining the most suitable direction of the runway.
• The percentage of time during which the intensity of wind is < 6.4(6)kmph is called calm period.
• Wind rose diagram is plotted in two types• Type I: showing direction and duration of wind• Type II: showing direction, duration and intensity of
wind
Wind rose diagram - Type I• The radial line indicate the wind direction and
each circle represents the duration of wind.• The values of percentage of time in a year during
which wind blows from different direction are plotted along the corresponding directions. All plotted points are then joined by straight line.
• The best direction of runway is usually along the direction of longest line on wind rose diagram.
• Does not account the effect of cross wind component.
Wind rose diagram – Type II• Circle represents the wind intensity to some scale. The values in each
segments represents the percentage of time in a year during the wind blows with particular intensity form the respective direction.
• The procedure for determining the orientation of runway is as follows:• Step1 : draw three equally spaced parallel lines on a transparent paper
strip in such a way that the distance between the two near by parallel lines is equal to the permissible cross wind component. This distance is measured with same scale with which wind rose diagram is drawn.
• Step2 : place the transparent paper strip over the wind rose diagram in such a way that the central line passes through the centre of the diagram.
• Step3 : with the centre of the wind rose, rotate the tracing paper and place it in such a position that the sum of all values indicating the duration of wind, with in two outer parallel lines, is the maximum. The runway should thus oriented along the direction indicated by central line. The wind coverage can be calculated by summing up all the percentages shown in segment. The percentage value is assumed to be equally distributed over the entire area of the segment.
Change in direction of runway• Obstructions
• Excessive grading
• Noise nuisance
Length of runway
• Selecting the length of a runway is per haps
the important decision which must be made in
the planning of landing area.
• Length of runway depends on
1.The type of aircraft
2.Its payload
Basic runway lengthIt is the length of runway under the following
assumed condition at the airport:1.Airport altitude at sea level2.Temperature at airport is standard (150 c)3.Runway is leveled in the longitudinal direction4.No wind is blowing on runway5.Aircraft is loaded at its full loading capacity6.There is no wind blowing en route to the
destination7.En route temperature is standard
• The following case are considered for
determining the basic runway length
1.Normal landing case
2.Normal take-off case
3.Engine failure case
The cases which works out the longest
runway length is finally adopted
Jet engine
Piston engine
1. Normal landing case• The normal landing case requires that an air
craft should come to a stop within 60% of the landing distance. The runway of full strength pavement is provided for the entire landing distance.
15 m
stop
60% of landing distance
landing distance
Runway
2. Normal take-off case
• The normal take-off case requires a clearway which
is an area beyond the runway and is in alignment
with the centre line of runway. The width of
clearway is not <150m and is kept free from
obstruction. The clearway ground area or any
object on it should not protrude a plane inclined
upward at a slope of 1.25% from the runway.
Lift-off distance
115% of Lift-off distance
Distance to 10.5m height
115% of distance to 10.5m height ( take-off distance)
Clearway ≤ ½ of this distance
10.5m height
Longitudinal section
Runway Clearway
Min 150m
Plan
Normal Take-off Case
3.Engine Failure Case• The engine failure case may require either a clearway, or
a stop way, or both.• Stop way is an area beyond the runway and centrally
located in alignment with the centre line of runway. • Stop way is used for decelerating the aircraft and
bringing it to stop during aborted take-off.• If the engine has failed at a speed, less than the
designated engine failure speed, the pilot decelerate the aircraft and make use of stop way.
• If however, the engine fails at a speed higher than the designated speed, there is no other option to the pilot except to continue take-off. The pilot may later take a turn in the turning zone and land again for a normal take-off.
Lift-off distance
Accelerated stop distance
Distance to 10.5m height ( take-of distance )
Clearway ≤ ½ of this distance
10.5m height
Longitudinal section
Runway
Clearway Min 150m
Plan
Engine Failure Case
Engine Failure
Decelerated – stop distance
Stop wayClear way
Stop way
Correction for Elevation, Temperature and Gradient
• The basic runway length is for mean sea level
elevation having standard atmospheric
conditions.
• For any change in elevation, temperature and
gradient for actual site of construction,
necessary corrections are to be applied to
obtain the length of runway.
Correction for Elevation• The air density reduces as the elevation
increases, this in turn reduces the lift on the
wings of the aircraft and the aircraft requires
greater ground speed before aircraft becomes
airborne. To achieve greater speed, longer length
of runway is required.
• ICAO recommends that basic runway length
should be increased at the rate of 7% per 300m
rise in elevation above MSL.
Correction for Temperature• The rise in airport reference temperature has the same
effect as that of the increase in elevation.• Airport reference temperature
Ta = monthly mean of avg. daily temp. for the hottest month of the year.
Tm = monthly mean of the maximum daily temp. ICAO – 1% for every 10c rise in airport reference temp. Further the temp. gradient of the standard atmosphere
from the mean sea level to the altitude at which the temp becomes 15.60 c is 0.00650 c per meter.
= Ta + (Tm – Ta )/3
Check for total correction for elevation plus temperature
• ICAO further recommends if the total
correction for elevation plus temp. exceeds
35% of the basic length, these correction
should be further checked up by conducting
specific studies at the site by model test.
Correction for gradient• Steeper gradient results in greater
consumption of energy.• ICAO does not recommends any specific
correction for the gradient.• FAA – Runway length after being corrected for
elevation and temp. should be further increased at the rate of 20% for every 1% of specific gradient.
• Specific gradient – is the max. difference in elevation between the highest and lowest point of runway divided by the total length of runway.