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On a dry runway the accelerate stop distance is increased...
  • A
    by headwind.
  • B
    by a lower take-off mass because the aeroplane accelerates faster to V1.
  • C
    by uphill slope.
  • D
    by low outside air temperature.

Learning objective 032.02.03.01.03: Explain the effects of the following runway (RWY) variables on take-off distances: RWY slope; RWY surface conditions: dry, wet and contaminated; RWY elevation. 
Learning objective 032.02.03.01.06: Explain the effect of wind on take-off and landing distances, and determine the actual headwind/tailwind component given the runway direction, wind speed and direction, by use of wind component graphs, mathematical calculations, and rule of thumb.

The ASD is the accelerate-stop distance. This is the ground distance covered by an aircraft as it accelerates throughout the takeoff roll, up to VEF where an engine failure occurs, and then rejects the takeoff at V1 and slows to a full stop. There are obviously multiple different factors which affect the ASD, including:

  • Aircraft Mass/Weight: When the mass is higher, it takes longer for the aircraft to accelerate, and to decelerate, due to the higher momentum. This increases the ASD significantly
  • Outside Air Temperature (OAT): A higher OAT means that air density is reduced. This decreases the thrust developed by the engines, and increases the TAS and GS at which V1 occurs, so the aircraft must also accelerate to a higher speed. A high OAT increases the ASD.
  • Slope: The exact affects of an upslope are difficult to determine precisely, as the upslope makes it take longer to accelerate to V1, but helps the aircraft slow down after rejecting the takeoff. Generally, it is assumed that the affect during the acceleration is more significant, so an upslope increases the ASD.
  • Wind: V1 is a CAS. The actual speed of the aeroplane over the ground is its groundspeed (GS). A headwind will decrease the GS at which V1 occurs, meaning that the aircraft is actually travelling slower and has less momentum. This means a headwind decreases the ASD.

Referring specifically to the answers: 
On a dry runway the accelerate stop distance is increased...

by headwind. → INCORRECT

  • a headwind decreases the ASD

by a lower take-off mass because the aeroplane accelerates faster to V1. → INCORRECT

  • a lower mass decreases the ASD as the momentum is lower.

by uphill slope. → CORRECT

by low outside air temperature. → INCORRECT

  • A low OAT will reduce the ASD, as the engines develop more thrust and the TAS and GS at which V1 occurs are lower.

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