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4 Answers

crosswind component confusion

Asked by: 4808 views , , ,
General Aviation, Private Pilot, Student Pilot, Weather

 

Determine the maximum wind velocity for a 45° crosswind if the maximum crosswind component for the airplane is 25 knots.

  

the options are 35, 29, and 25

How is it 35?

please help

Ben

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4 Answers



  1. Max Trescott on Oct 21, 2019

    It helps to have studied a little trigonometry in the past. You can get the crosswind component by taking the sin of the angle at which the wind is crossing the runway and multiplying that by the total wind speed. If the wind is straight down the runway, the angle at which it’s crossing the runway is zero, and the sin of 0 degrees is zero. So there’s no crosswind component. If the wind is a direct crosswind and is at a 90 degree angle to the runway, then sin of 90 degrees is 1.0. In that case, the crosswind component equals the wind speed. For a 45 degree angle, the sin of 45 degrees is 0.707. Since you already know that the crosswind component is 25 knots, take 25 and divide it by 0.707 to find out the total wind strength. The answer is 35.36 knots.

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  2. ben.mirsky on Oct 22, 2019

    Hi,

    Thank you for your reply! I appreciate the help. I ended up finding the answer by tracing up from the 25 mark until it intersected the 45 degree line and saw that it was indeed at the 35 on the wind velocity radial. Is this a viable solution as well?

    Ben

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  3. ayavner on Oct 22, 2019

    Definitely! The FAA doesn’t expect you to know or use trig to solve these problems – however, agreeing with Max here – the little bit of insight helps you to not only work the problem but to know intuitively whether your solution “makes sense”.

    Many ways to skin these cats! good luck!

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  4. KDS on Oct 22, 2019

    Those are all excellent answers, but let me toss this in. There is an old saying about measuring with a micrometer and cutting with a chainsaw. I think typically, pilots will know some basic numbers like 30 degrees is about half, 45 degrees is about 70%, and beyond that is almost the whole thing. If more math is required to see if it is within the pilot’s ability, then it’s a good time to think of a Plan B. That might be a different runway or a different airport.

    When might coming up with a near perfect answer matter? When taking an FAA written test. When showing an examiner how to come up with the numbers. When you want to figure how many degrees to swivel the landing gear on your B-52 before touchdown.

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