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When compared to a clean configuration, how does flap setting usually affect the Runway Length Limited Take-Off Mass and the Climb Limited Take-Off Mass? The Runway Length Limited Take-Off Mass…
  • A
    increases, and the Climb Limited Take Off Mass increases.
  • B
    increases, and the Climb Limited Take Off Mass decreases.
  • C
    decreases, and the Climb Limited Take Off Mass increases.
  • D
    decreases, and the Climb Limited Take Off Mass decreases.

Refer to figure.

EFFECT OF FLAPS ON TAKE-OFF RUN AND CLIMB GRADIENT
The use of high life devices (Flaps) will have an impact on the take-off and Landing roll and climb gradient.


For a given runway length and airplane weight, selecting a greater flap setting will increase the lift coefficient, which reduces the stalling speed.
  • As a consequence, the take-off speeds are reduced (the same lift will be created at smaller air speed due to greater lift coefficient). This will reduce the take-off run.
The down side of the use of flaps is that it generates more parasite drag:
We get our best angle of climb and, therefore, our best gradient where there is the biggest gap between the thrust available and thrust required. The parasite drag from the extended flap closes the gap and the climb angle and climb gradient will reduce. Hence as soon as we can after take off we accelerate and retract the flap and climb clean.
=> Based on the above, we can conclude that the Runway Length Limited Take-Off Mass increases (due to the reduced take-off run required with the use of flaps) and the Climb Limited Take Off Mass decreases (due to the degraded climb performance).

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