# Airport Engineering MCQ – Set 5

This set of Airport Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Runway Length and its Corrections”.

1. What is the temperature at which the runway length is calculated?
a) 15°C
b) 13°C
c) 34°C
d) 27°C

Explanation: The temperature at which the runway length is calculated is 15°C. This temperature is considered as 15°C because that is the standard temperature at mean sea level. If the temperature is any different, the appropriate correction methods are applied.

2. Runway length is the length of runway under the assumed conditions. Which of the following is not a condition which is assumed to calculate the runway length?
a) Airport altitude at sea level
b) No wind is blowing on the runway
c) Aircraft is not loaded
d) En-route temperature is standard

Explanation: While calculating the runway length, it is assumed that the aircraft is loaded to its full carrying capacity. Runway length is the length of runway under the assumed conditions that the airport altitude is at sea level, temperature at the airport is standard 15°C, the runway is levelled in the longitudinal direction, no wind is blowing on the runway, the aircraft is loaded to its full loading carrying capacity and that the en-route temperature is standard.

3. Which of the following is not a type of correction done while calculating the runway length?
a) Correction for temperature
b) Correction for elevation
c) Correction for gradient
d) Correction for time

Explanation: Correction for time is not done or valid during the calculation of the runway length. Correction for temperature is done when the airport temperature is not 15°C. Correction for elevation is done when the airport is not at mean sea level and the correction for gradient is done when the runway is not levelled in the longitudinal direction.

4. Which formula is used to calculate the correction for temperature in runway length?
a) Ta + 1/2 (Tm – Ta)
b) Ta + 1/3 (Tm + Ta)
c) Ta + 1/3 (Tm – Ta)
d) Ta + 1/3 (Tm x Ta)

Explanation: Ta + 1/3 (Tm – Ta) is used to calculate the correction for runway length. Airport reference temperature is defined as the monthly mean of average daily temperature (Ta) for the hottest month of the year plus one third the difference of this temperature (Ta) and the monthly mean of the maximum daily temperature (Tm) for the same month of the year. The ICAO recommends that the basic runway length after having been corrected for elevation, should be further increased at the rate of 1 percent for every 1°C rise of airport reference temperature above the standard atmospheric temperature at that elevation.

5. Which of the following formulae is used to calculate the Standard Temperature at an Elevation?
a) STE = {15/h X r}
b) STE = {15 X h X r}
c) STE = {15 +/- h + r}
d) STE = {15 +/- h X r}

Explanation: The Standard Temperature at an Elevation is calculated using the formula STE = {15 +/- h X r} where ‘h’ is the height above MSL in meters, ‘r’ is rate of change of temperature with height or depth above/below MSL, in °C / m and where 15 is the standard temperature at MSL. In the formula, ‘+’ is taken if temperature is increasing with height or depth and ‘-’ is taken if temperature is decreasing with height or depth with respect to MSL.

6. Under normal take-off calculations, which of the following formula is used to calculate the field length?
a) FL = FS -CW
b) FL = FS + CW
c) FL = FS / CW
d) FL = CW – FS

Explanation: Under normal take-off calculations, the field length (FL) is calculated using the formula, FL =FS + CW where FS stands for full strength runway and CS stands for clearway. The 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 10.5m. It also requires a clearway at the end of the runway in the direction of take-off. This should not be less than 150m wide.

7. The ICAO recommends that the basic runway length should be increased at the rate of 2 per cent per 600m rise in elevation above the mean sea level.
a) True
b) False

Explanation: The ICAO recommends that the basic runway length should be increased at the rate of 7 per cent per 300m rise in elevation above the mean sea level. The correction for elevation is necessary because as the elevation increases, the air density reduces. This is in turn reduces the lift on the wings of the aircraft and the aircraft requires greater ground speed before it can rise into the air. Hence, to achieve greater speed, longer length of runway is required.

8. Which of the following is the aircraft type which the airport is intended to serve and which requires the greatest runway length?
a) Critical aircraft
b) Average aircraft
c) Jet aircrafts
d) Long aircrafts

Explanation: The critical aircraft is defined as being the aircraft type which the airport is intended to serve and which requires the greatest runway length. To identify the critical aircraft, flight manual performance data of a variety of aircraft are examined.

9. What is the maximum difference in elevation between the highest and lowest points of runway divided by the total length of runway called?

Explanation: The maximum difference in elevation between the highest and lowest points of runway divided by the total length of runway is called effective gradient. Steeper gradient results in the greater consumption of energy and as such longer length of runway is required to attain the desired ground speed.

10. The FAA does not recommend any specific correction for the gradient while calculating the runway length.
a) True
b) False

Explanation: The ICAO does not recommend any specific correction for the gradient. The FAA recommends that the runway length after having been corrected for elevation and temperature should be increased at the rate of 20 % for every 1 percent of increase in effective gradient.

Sanfoundry Global Education & Learning Series – Airport Engineering.

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