Geometric Design of Runway Part 1 of Airport Engineering
Geometric Design of Runway Part 1 of Airport Engineering, In Part 1, we set the stage by dissecting the foundational elements of geometric runway design. From the critical dimensions that govern runway length to the graceful curves and strategic alignments that guide every take off and landing, this is where the blueprint for aviation excellence takes shape.
Geometric Design of Runway
The runway is usually oriented in the direction of prevailing winds. The head wind that is the direction of wind opposite to the direction of landing and take-off. Head wind component provides greater lift on the wings of the aircraft while take-off and helps in causing braking effect, thus reducing the runway length. Whereas, if landing and take-off operations are done along the wind direction, then the required length of runway will be much higher.
Cross wind components
The normal component of the wind is called the cross wind component, and it may interrupt landing and take-off operations of the aircraft.
The maximum permissible cross wind component depends upon the size of the aircraft and the wing configuration.
Cross wind component, for small aircraft should not exceed 15 kmph whereas, for airports serving big aircraft, it should not exceed 35 kmph.
FAA recommends that the runway handling mixed air traffic should be as planned that for 95 percent of the time in a year, the permissible cross wind component does not exceed 25 kmph.
It is the percentage of time during which wind intensity remains less than 6.4 kmph at a location, and it does not influence the landing or take-off operation as the wind intensity is low.
The orientation of the runway should be in such a way that the crosswind component should exceed the head wind component.
basic runway length:
assumptions for deciding the runway length
- Airport altitude is at sea level
- Temperature at the airport is standard (15°C)
- Runway is levelled in the longitudinal direction
- No wind is blowing on the runway
- Aircraft is loaded to its full loading capacity
- Enroute temperature is standard
- There is no wind blowing enroute to the destination
The way an aircraft actually performs the landing and take-off operation will decide to large extend the length of the runway. The Following three cases will be considered:
- i) Normal landing
- ii) Normal take-off
- iii) Stopping in an emergency (engine failure case)
Longitudinal Section: Normal take-off
Plan: normal take-off
Longitudinal Section: Stopping in emergency
Plan: Stopping in emergency
aerodrome reference code
code element 1
|ARF Length (lARF)
|lARF < 800 m
|800 m <lARF < 1200 m
|1200 m < lARF < 1800 m
|1800 m and over
code element 2
|Wing Span < 15 m
|15 m < Wing Span < 24 m
|24 m < Wing Span < 36 m
|36 m < Wing Span < 42 m
|42 m < Wing Span < 55 m
|55 m < Wing Span < 80 m
ARF = Aerodrome Reference Code
Width of runways:
Following are the minimum limits for width of a runway:
Outer Main Gear Wheel Span (OMGWS)
|Up to but not
including 4.5 m
|4.5 m Up to but not
including 6 m
|6 m Up to but not
including 9 m
|9 m Up to but not
including 15 m
* The width of a precision approach runway shall be not less than 30 m where the code number is 1 or 2
Q 1) The percentage time period of a year in which the cross wind component remains within the limit is called
a) Wind coverage
b) Head wind
c) Prevailing wind
d) Cross wind
Sol: The percentage of time in a year during which the cross-wind component remains within the limit is referred to as wind coverage.
So, the correct option is a).
Q 2) Consider the following statement: Wind rose diagram is used for the purpose of
1) Runway orientation
2) Estimation of runway capacity
3) Geometric design of holding the apron
Which of these statements is/are correct?
a) 1 and 2
b) 2 and 3
c) 1 and 3
d) 1 only
Sol: The wind rose diagram is used only for the purpose of the runway orientation
There are two types of wind rose diagrams.
- i) Type I: It contains the information only about the direction and the duration of wind.
- i Type II: It contains information about the direction, duration and intensity of the wind.
So, option d) is correct.
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