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An aeroplane flying at 200 kt in straight and level flight is subjected to a disturbance that suddenly increases the speed by 80 kt. Assuming the angle of attack remains constant, the load factor will initially:

  • A

    remain unchanged, since the angle of attack does not change.

  • B

    increase to 1.4.

  • C

    increase to 1.96.

  • D

    increase to 1.8.

Load factor is defined as:

n = Lift / Weight

Expanding the Lift Formula:

L = ½ x ρ x V2 x S x CL

n = (½ x ρ x V2 x S x CL) / W

By removing all the constants, we can say that:

n ∝ V2

To find the change in load factor (nΔ), we have to divide nNEW by nOLD:

nΔ = nNEW / nOLD

nΔ = VNEW2 / VOLD2

Where, VNEW = 200 kt + 80 kt = 280 kt and VOLD = 200 kt

nΔ = 2802 / 2002

nΔ = 1.96 g

Knowing now that accelerating from 200 kt to 280 kt, we can conclude that after passing the disturbance the load factor increased to 1.96 g.

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