Several factors affect the length of the runway (runway) airports:
- Surface wind (surface wind)
- Runway slope (slope)
- The height from the sea level airfield / elevation (MSL)
- Runway surface conditions
Calculations in planning a runway using standard ARFL (airplane reference field lenghth). According to ICAO, ARFL is the minimum required runway for takeoff at max certificated take-off weight, elevation sea level, standard atmospheric conditions, a state with no wind blowing, no runway slope (slope = 0). Each plane has ARFL others as published by the manufacturer.
1. Temperature (temperature)
At higher temperatures, long shelf needs to be longer, because the low air density at high temperatures, produce lower thrust output. As standard the selected temperature above the temperature at sea level:
59 ° F = 15 ° C.
According to ICAO runway length should be corrected for temperature increase by 1% for every increase of 1 ° C or 0.56% per 1 ° F, while for every increase of 1,000 m from sea level the average temperature decline of 6.5 ° C or every rising 1000 feet temperature decreases to 3.6 ° F. On the basis of the ICAO recommended temperature correction count Ft (temperature conversion factor).
Ft = 1 + 0.01 (T – (15 to 0.0065 h) metric
Ft = 1 + 0.0056 (T – (59-.0036) imperial
Aerodrome reference temperature T =
2. Altitude (Altitude)
Based on ICAO recommendations, that ARFL increased by 7% every rise 300 m (1000 ft) is calculated from the height of the sea surface. So the formula is Fe (elevation correction factor).
Fe = 1 + 0.07 x (h/300) metric
Fe = 1 + 0.07 (h/1.000) imperial
h = elevation aerodrome
3. The slope of the runway: runway gradient
Airports that have upward slope requires a longer runway than the runway is flat or declining.
Criteria planning airfield runway slope limit of 1.5%. Slope correction factor (Fs) is equal to 10% per 1% slope for the plane take off conditions.
Fs = 1 + 0.10 S
S = slope (%)
4. Surface wind (surface wind)
Necessary foundation shorter when the wind blew the bow (head wind), otherwise if the wind blows the stern (tail wind) required a longer runway. Tail wind (tail wind) blowing the maximum allowed by the power of 10 knots. These estimated effects of wind on runway:
5. Runway surface conditions
The runway surface with a thin puddle of water (standing water) is avoided, as this may endanger aircraft operations. Standing water causes the surface to be slippery for aircraft wheels that make braking power to be ugly.