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4 Answers

Crosswind Component Calculation

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General Aviation, Private Pilot

When calculating the crosswind component should the sustained wind or gust wind speed be used?

Example:

Wind Direction: 190

Runway: 22

Wind Speed: 17kts           Xwind: 10kts

Gust Speed: 27kts           Xwind: 15.9kts

In my Cessna 172 with a demonstrated crosswind of 15kts I would be good without considering the gust factor.

Thanks

 

mm

 

4 Answers



  1. Chris Carlson on Jan 28, 2013

    There are two answers to this question.

    The first, and more technical answer, is that the POH has a demonstrated maximum crosswind, not an absolute maximum cross wind. The plane can handle a stronger crosswind, but it is not known, because they never tested it during the pre-airworthiness testing. That being said, these tests were done in brand new airplanes with pilots who are very good at what they do.
    I guess you could think of it on a specific time scale, where if the gust happens to be going during the landing, then you are landing with more than 15kt crosswind, but if the gust isn’t going, you aren’t. But the wind could change at anytime.

    The second answer is a reality answer. The plane isn’t brand new, you and I, are not Cessna test pilots who have literally put our lives on the line for Cessna, and know them inside and out, and the weather predictions aren’t perfect either. Gusty wind makes the airplane rapidly change the aerodynamic forces, and it can be detrimental. The FAA calls it wind shear, and stresses about its dangers. If you are coming down crabbed, on a strong crosswind, and slow, and just during your flare, as you parallel your longitudinal axis on the runway, the gust picks up, will you be ready to go around, or will you get pushed in a way you didn’t expect.

    In short, the plane could probably handle it, but don’t push the airplane to its limits if you don’t have to, and be conservative in your own limits, especially in the early stages.

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  2. Mark Kolber on Jan 29, 2013

    >>In my Cessna 172 with a demonstrated crosswind of 15kts I would be good without considering the gust factor.<<

    If, in the course of your flare to landing you were hit with a 15.9 KT direct crosswind gust, would you be able to handle it?

    I'm not sure what the purpose of your question is. Depending on what it is, the answer might be different:

    1. As Chris pointed out, the "max demonstrated crosswind component" is not an aircraft limitation, so from a FAR 91.9(a) regulatory standpoint, it doesn't matter which number you use.

    2. If it's about safety and determining your personal limitations and whether you should attempt a landing, think about the question I asked at the beginning of this comment.

    3. If it's about crosswind limitations placed upon a student pilot certificate or a flight school, club or FBO policy, those are the ones to ask. Most I'm familiar with would use the gust factor number since that's the safety consideration. I've also seen crosswind limitations that specifically discuss the gust factor.

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  3. Jim F. on Jan 29, 2013

    Looking at it from a safety/practical standpoint, I do my preflight calculation with both the sustained winds and the gust factor. That way I know the sustained x-wind factor, as well as what the x-wind factor would be during a gust. If I’m not comfortable with the worst case, x-wind gust scenario, then I’m not gonna do it.

    As for what you feel comfortable with, you’ll need to practice and push your comfort zone a bit (with an instructor, of course.) Find an airport that will offer you a good x-wind, but you still have an “out” on another runway that will offer a good, straight headwind.

    (Runway 226? Did I miss the memo from the FAA about a new runway naming system? :) )

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  4. Tarek on Jan 31, 2013

    how can i make or fill a flight planning by my hand, not to use any help from anywhere, by other word manually?

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