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A single-engine class B aeroplane has the following wind limitations:

Crosswind: 17 kt
Headwind: 30 kt
Tailwind: 10 kt

Consider a take-off from runway 20 with wind from 255°.

Using trigonometry, determine the maximum wind speed which allows to stay below the crosswind limit of 17 kt and take-off.
(2 decimal places for the calculations)

  • A

    20 kt

  • B

    22 kt

  • C

    21 kt

  • D

    19 kt

Refer to figure.
The wind components may be calculated using sin or cos.
Sin a = opposite side / hypotenuse

The angle between the wind and the runway direction is 55°.

We need to calculate the hypotenuse of a triangle whose opposite side (crosswind) equals 17 kt:

  • Hypotenuse = 17 / sin 55° = 20.75 kt, to stay below the limit 20 kt would be the correct answer.

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