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The following parameters affect the take-off ground run:

1.decreasing take-off mass
2.increasing take-off mass
3.increasing density
4.decreasing density
5.increasing flap setting
6.decreasing flap setting
7.increasing pressure altitude
8.decreasing pressure altitude

Which parameters will decrease the take-off ground run?

  • A
    2, 4, 5 and 7
  • B
    2, 3, 6 and 7
  • C
    1, 3, 5 and 8
  • D
    1, 4, 6 and 8

Refer to figure.

FACTORS AFFECTING TAKE-OFF DISTANCE REQUIRED
The take-off ground run and, consequently, the take-off distance required (TODR) varies with aerodrome conditions, aeroplane mass, and aeroplane configuration.

AEROPLANE MASS
An aeroplane with a higher mass will have more inertia, decreasing acceleration. This results in a longer take-off distance required.
=> Therefore, decreasing take-off mass, will result in an increased acceleration and decreased take-off ground run required.


AIR DENSITY
Density is determined by pressure, temperature and humidity. A low density of the air/high altitude, reduces engine and propeller performance (the reduction in air density reduces the engine mass flow and, therefore, thrust, which results in slower acceleration). Consequences:
  • Higher take-off speed.
  • Longer take-off distance required.
=> Increasing air density and decreasing pressure altitude will result in a shorter take-off ground run.
WIND

Winds affect the true ground speed of the aeroplane for any given true airspeed.

  • Headwinds: reduce the ground speed at the required take-off airspeed and reduce the take-off ground run.
  • Tailwinds: higher ground speed and longer take-off ground run.

FLAP SETTINGS
Flap settings has an effect on the wing's lift coefficient and on the aerodynamic drag.
  • Increasing flap setting/flap angle increases the lift coefficient, which reduces stalling speed and take-off speed. This reduces the take-off ground run.

RUNWAY CONDITIONS
If the runway is sloping, a component of the weight acts along the runway and increases or decreases the acceleration force.
  • Downhill slope increases the accelerating force, and therefore reduces the take-off distance.
  • Uphill slope reduces the accelerating force and increases the take-off distance.
The runway surface condition has effect on the wheel drag. If the runway is contaminated by snow, slush or standing water, the wheel drag will be greater. Thus the accelerating force decreases and the take off distance required increases.
=> Based on the above, the correct option is: decreasing take-off mass (1), increasing density (3), increasing flap setting (5) and decreasing pressure altitude (8).

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