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5 Answers

Speed acceleration on final.

Asked by: 8133 views Aerodynamics

here is the scenario. Your on final, we are having gust but you are holding it pretty steady. We are in a CE172 approaching at 60-65 when all of a sudden it jumps to 70-75 then right back down again. The question is did I have a head or tail wind. What happened?

Tommy Eldridge

www.PrivatePilotInsider.com

 

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5 Answers



  1. John D. Collins on Jul 07, 2011

    From the information you provided, one can’t determine if the aircraft was experiencing a head wind or a tail wind, but the gust was either a temporary increase in a head wind or a temporary decrease in a tailwind.

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  2. Jon on Jul 11, 2011

    If he was on final, it better have been a headwind. I posted a response on Saturday, but it seems to have disappeared. The long and short of it was that you experienced a gust from the front (headwind). The momentum of the aircraft keeps it moving through the air pretty steadily (from a second-to-second perspective). The increase in indicated airspeed was direct indication that more air was pushing on the pitot tube, i.e. headwind.
     
    Jon

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  3. Nathan Parker on Jul 11, 2011

    I suspect the genesis of the question is that some people have the idea that an increase in tailwind would “push” on the airplane and make it go faster.  This isn’t a proper model of what an airplane experiences in flight.
     
    An aircraft in flight always experiences a self-generated wind from the direction the airplane is flying.   A steady tailwind has no effect on this self-generated wind, but changes in tailwind do, briefly.  The effect of an increase in tailwind is to slow down the velocity of the self-generated wind, but it doesn’t change the fact that it still comes from ahead of the airplane.

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  4. Tommy D Eldridge on Jul 13, 2011

    Thanks to all that responded,
    It’s pretty clear now that it was a head wind. I don’t believe I ever thought it was a tail wind but maybe more so a negative air pocket with a reduction in drag. Don’t laugh I guess I never thought the scenario through in detail. You guys have made it make a lot of sense. Thank you.
    It seems backwards from the way you would think it should be. This is one more area this pilot is a little more clear.
    Jon, I saw your post Saturday before it was deleted. Great reply! I have been having a lot of problems with my post as well. (Paul has been in contact with me working very hard to get it fixed).
    Thank you all,
    Tommy Eldridge
    http://www.PrivatePilotInsider.com

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  5. Brian on Jul 18, 2011

    To help come to terms with what’s being discussed here one might consider what they feel while walking down the street. Assume we are walking at a constant pace down the street when suddenly a blast of headwind hits us in the face. For this brief moment, could we say that we felt more like we were running than walking? In other words, this introduction of wind makes us feel as though we picked up our speed even though we did not.
     
    Good luck. 

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