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Thread: Uncontrolled Roll on Full Flaps

  1. #11
    ppilotmike's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    On flutter, have you removed the flaperons and verified that the "mass balance" weights truly balance the flaperons. I would suspect the uncontrolled roll is due to a rigging problem, Jims post is a good way to check that.

  2. #12
    kitfoxjim's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    As I recall many years ago, when I did the rigging on my Model 2 (90-91) there was a possibility that one of the aileron push rods could go over centre if the flap handle was not limited in travel. Went back to look at the manual rigging instructions but that section is now missing.
    I would suggest looking at the aileron mixer assembly while deploying full flaps as there may be this over centre condition.
    The aileron push rod could be too short but the best cure would be to limit flap handle travel.
    Jim
    Jim Corner
    KF2 582 1150 hrs
    KF5 O-360 1150 hrs

  3. #13
    Guy Buchanan's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    Two possibilities for uncontrolled role. Miss-rigging, which you seem to have eliminated, and un-symmetric stall. It's possible that one of your flaperons is stalling. It's also slightly possible you're getting a partial stall on one wing, though I'm not really seeing how that would happen. As for the stalled flaperon, the most likely culprit would be a bad airfoil, possibly a kink or other hard edge on the top of the leading edge somewhere. It wouldn't have to be the entire flaperon. I can't remember if the 3 flaperons were symmetric but if they weren't you'd want to check to make sure they weren't installed upside down.
    Guy Buchanan
    San Diego, CA
    Deceased K-IV 1200 / 912uls / 70" Warp 3cs

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  4. #14
    Senior Member
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    Default Re: Uncontrolled Roll on Full Flaps

    The Kitfox 1 to 3 model flaperons all have flat bottoms. Also, it would be pretty near impossible to install them up side down. JImChuk

  5. #15
    Senior Member HighWing's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    I am likely revealing my age, but back in the really olden days when these puppies were being actively built, it was common practice to put an Adel Clamp on the sloping tubing next to the flap handle that limits the flap function of the flaperons to 20 degrees only. I don't remember if the uncontrolled roll was the gremlin, but I did it on my first IV and the one I fly now. Never an issue.
    Lowell Fitt
    Goodyear, AZ


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  6. #16
    Senior Member LSaupe's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    My Model III never had an issue (though I had the same Adel clamp at 20 degrees like he describes, also a stop at zero)). Along with High Wing's comments I did ensure max deflection of 20 degrees though (in case you havent yet looked at this). I do remember something about flapperon stall being mentioned for deflections above that value. I set my zero degree using a laser bolted to the bottom of the flapperon to ensure a certain distance below the leading edge (per build manual and subsequent service letter - forget that value now, the value was increased above the initial build manual value).

    Fix the control stick to prevent side to side movement, then add in your 20 degrees and ensure both are the same (at 20 degrees).

    In reality, the only time I used flaps was when I was two up (used 50% for take off and 100% for final). When flying single never used them except for short fields (would just float otherwise). I did have the enlarged elevator which helped with a 3 point with full flaps.

    Please keep us posted with what you find out. Could always put some tell tails on your dropping flap to see (maybe) if your flap is stalling more compared to the other.

  7. #17
    Senior Member TJay's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    If the center mixer that controls the flaps is not level in the plane one side might drop further than the other. I would check that first also if you have one flap bearing on the wing that needs oil it may cause the stick to move when pulling on the flaps. But most of all you keep the plane level with your feet not the stick. If it starts to roll step on the pedal dont be shoving the stick around that will just make it worse ( adverse Yaw)

  8. #18
    Senior Member LSaupe's Avatar
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    Default Re: Uncontrolled Roll on Full Flaps

    In addition to my previous, there is also a criteria for max flap extension whereby you set your stick to full deflection to left or right and pull flaps on until the stick starts to move towards center. That becomes your new max flap extension, which might be less than 20 degrees. 20 degrees or stick motion being the limiting factor.

  9. #19

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    Default Re: Uncontrolled Roll on Full Flaps

    I read were some guys with early models would tweak the trailing edges of the Flaperons (one up, one down) to help with wing drop. I guess doing that was a last resort when nothing else helped. I'd also guess some of these planes were slapped together and not assembled correctly.

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