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How does the stall speed of a lightly loaded aircraft compare to that of a heavily loaded aircraft?

  • A

    It will stall at a higher speed.

  • B

    It will stall at the same speed, but at a higher angle of attack.

  • C

    It will stall at the same speed.

  • D

    It will stall at a lower speed.

Refer to figure.
A wing stalls when it reaches and exceeds the critical angle of attack. At this angle, the airflow separates from the top of the wing, such that a further increase in the AoA leads to a reduction in lift.

A stall speed is a speed that be calculated for straight and level flight, at the critical angle of attack, using the lift equation:

  • L = ½ρV2 S CL

In straight and level flight, L = W. At the critical angle of attack, CL = CLMAX. The speed at which this occurs is VS. We can then put these values into the equation, and re-arrange to find the stall speed formula:

  • VS = √ ((2W) / (ρSCLMAX))

What this tells us is that for an increase in weight (or mass), the stall speed increases. More lift needs to be created to hold the aircraft in the air, which will require a higher speed at the critical angle.

So comparing a lightly loaded aeroplane to a heavy one, It will stall at a lower speed (and the same angle of attack).

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