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Which statements about an aeroplane entering ground effect are correct or incorrect?

1) The downwash angle remains constant.
2) The induced angle of attack decreases.

  • A
    1) is incorrect, 2) is incorrect.
  • B
    1) is incorrect, 2) is correct.
  • C
    1) is correct, 2) is incorrect.
  • D
    1) is correct, 2) is correct.

Refer to figure.
The question is asking what will happen to the downwash angle and the induced angle of attack when entering ground effect.

  • Downwash angle: When entering ground effect, the proximity to the ground reduces the effect of downwash, and therefore the induced drag. Meaning our downwash angle will reduce when entering ground effect.
  • Induced angle of attack: As you can see in figure 1, when entering ground effect the induced downwash will decrease, this leads to a decrease in the induced angle of attack (αi).

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