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An aircraft is flying straight and level at 280 kt with a CL of 0.3. The crew are warned of turbulence ahead and reduce speed to 220 kts, the turbulence penetration speed for their aircraft.
Determine the new value of CL:
  • A
    0.24
  • B
    0.28
  • C
    0.38
  • D
    0.49

Coefficient of lift decreases as speed increases. In other words, it is inversely proportional to the square of the speed change.

The new CL can be calculated using the following formula:

New CL = Old CL x 1 / (change in speed)2
New CL = 0.3 x 1 / (220/280)2
New CL = 0.49

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