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2 Answers

Why is C-172′s flap loose?

Asked by: 8329 views Aerodynamics, Aircraft Systems, Flight Instructor

I've been always wondering during preflight, why is Cessna 172's flap loose? not tight? You know what I mean? During preflight, flaps all the way down and check the flaps? Maybe it's not only cessna 172....Dows anyone know why?   :-) Thanks,

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2 Answers



  1. Micah on Dec 07, 2010

    You’ll can probably get a more specific answer, but I imagine this specifically minimizes the possibility of the stuck flap.  The track that the flap travels is curved and the arm appears to have a different travel (straight) through the wing.  Presumably, if the two tracks were identical then the flap could move without risk of getting stuck (unless there is any foreign object in the way).  Having some “play” when the flap moves should allow for less risk of friction during extension and retraction.  Have you ever watched a flap that didn’t roll along the track but instead was “dragging?”  Not a pretty preflight inspection.

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  2. Kent Shook on Dec 07, 2010

    How loose is “Loose”? I’ve flown a lot of Cessnas and I don’t think I’ve ever seen one where the trailing edge of the flap moves more than 1/8″, certainly not more than 1/4″.
     
    However, the feel of it being “loose” in that it moves is simply because the flaps do not have a single hinge point the way the ailerons do – They ride on tracks. The small amount of motion when they’re down is just the little bit of play in the hardware attaching the control rod to the flap.
     
    All controls will have a tiny bit of play like this, it’s just easier to tell on the flaps because they’re held rigidly in place. If you put the control lock in and try to move the ailerons, you’ll get a similar feeling with a little bit of play as you do with the flaps.
     
    If the flap is truly “loose” – As in, the trailing edge moves 1/2″ or more – Then check the flap rollers, as one of them is likely broken. But, I’m guessing that what you’re seeing is the normal slight amount of play as I’ve explained above, and that both flaps behave similarly (as well as the ailerons if you do the control-lock exercise), and that is normal.

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