Airport Environmental Conditions

Several factors affect the length of the runway (runway) airports:

  1. Temperature
  2. Surface wind (surface wind)
  3. Runway slope (slope)
  4. The height from the sea level airfield / elevation (MSL)
  5. 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.

Operational jet limited to the height of standing water 1.27 cm (0.5 “). The jet must be reduced by the time it take off (take off weight) in order to avoid accidents, when standing water reaches a thickness of 0.6 to 1.27 cm. To anticipate this, the airport requires a good drainage system.

Wheel rotating plane above a thin layer of water is called hydro planning, braking coefficient in this condition is very bad, because the coefficient of friction is reduced, which in turn led to lost steering ability.

Thick layer effect hydro planning, influenced by:

  1. Shape tread
  2. Tire condition
  3. Runway surface texture



  • Planned length of runway required to take off = 3200 m
  • Elevation above sea level = 120 m
  • The temperature at the aerodrome = 28 ° C
  • Runway slope = 0.6%

What is the length of the runway when the plane took off in ARFL?


Fe = 1 + 0.07 x (h / 300) = 1 + 0.07 x (120/300) = 1.028

Ft = 1 + 0.01 (T – (15 to 0.0065 xh) = 1 +0.01 (28 – (15 – 0.0065 x 120) = 1.122

Fs = 1 S = 1 + 0.10 + 0.1 x 0.6 = 1.060

ARFL = 3200 / (1.028 x 1.122 x 1.060) = 2618 m


Reference code used by ICAO to facilitate reading the relationship between several specifications planes with different physical characteristics of the aerodrome. The code can be read for the elements related to the characteristics of the aircraft capability and aircraft measurements. Element 1 is a number based on the Aeroplane Reference Field Length (ARFL) and element 2 is a letter based on the characteristics of the aircraft. Code letters and numbers selected for planning purposes, linked to the characteristics of the critical aircraft will be served by the planned runway

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