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At a wing loading of \( 5.0 \) kN/m\(^2\) with \( C_{L,max} = 2.6 \) in the landing configuration and \( \rho = 1.225 \) kg/m\(^3\), the stalling speed is

  • A.39.6 m/s
  • B.79.2 m/s
  • C.28.0 m/s
  • D.56.0 m/s

Answer: D

Correct answer: 56.0 m/s

The stalling speed follows from equating lift to weight at maximum lift coefficient:

\[ V_s = \sqrt{\frac{2(W/S)}{\rho C_{L,max}}} = \sqrt{\frac{2 \times 5000}{1.225 \times 2.6}} = \sqrt{3140} = 56.0\ \mathrm{m/s} \]

Note the wing loading must be in newtons per square metre, not kilonewtons. The distractor \( 79.2 \) omits the \( C_{L,max} \), and \( 28.0 \) halves the result. This relation is what turns the landing requirement into a vertical line on the diagram: fix the approach speed and \( C_{L,max} \), and the wing loading is bounded.

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