tight flapperons

13 posts in this topic

Posted

Hi, I just boght an avid mark IV and am doing a condition inspection with my mechanic friend.  The controls seem to be pretty stiff.  It seems that it is mostly due to the flapperons not moving very easily.  We tried oiling the hinges and they are still pretty stiff.  Is this normal for an avid, or is there some way to fix this?  Also there is some play in the controls as well.  I tightened all the linkages and it is much better, but the stick still moves about an inch before the flapperons begin to move.  Is this normal?  Thanks for your help.

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Posted

Flaperons should move the second the stick is moved, Zero Play is always nice, Better look things over, something is still loose,

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Posted

A small amount of play is where flutter lives. This is not good!

Isolate each stage of the system and find it.   Disconnect the flapperons and move them to determine if they are binding.  Then the next link in the mixer-chain all the way to the sticks.  Find the tight/binding problem and wherever the play is before you fly again. 

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Posted (edited)

Yeah flutter SUCKS!   Been there... done that!

The faperons on my old kitfox 2 had what seemed to be a minor amount of play.  Out flying and encountered pretty bad flutter... not a good deal, was lucky to get back to the field.

So get the slack and play out as best you can.

And a lesson learned for my experience:  if you ever get flutter in flight, change something quick.  Like slow it up and stall it if you have to, or add some load (and take away slack) on both flaperons by putting in some flaps.  Whatever, but don’t continue flying around in a flutter like I did!!

 

Edited by MN Kitfox 2
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Posted

Yea flutter is REAL bad and can come from unlikely sources.I had a randome flutter in turbulence when I got negative or zero g, after much searching i replaced the turtledeck bushes as there was a very small movement,problem sorted!' Take the time to check and recheck,if it doesn't feel right there may be a real problem lurking.

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Posted

take the linkage off at the fuse and move just the flaperons by hand.  If they are stiff and will "cam" over center and snap to one side or the other of center then you have a flaperon mount drilled wrong and its not aligned.  I learned this the hard way.  If you find they are "caming" over center then pull the bolts one at a time till you find the offending hanger.  If you need to redrill you can fill the holes with a dowel and gorilla glue then redrill. 

You can also look down the flaperon and make sure it is straight and does not have a bow in it anywhere.

Make sure you get the slop figured out before you fly, that is not good at all!

 

:BC:

 

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Posted

take the linkage off at the fuse and move just the flaperons by hand.  If they are stiff and will "cam" over center and snap to one side or the other of center then you have a flaperon mount drilled wrong and its not aligned.  I learned this the hard way.  If you find they are "caming" over center then pull the bolts one at a time till you find the offending hanger.  If you need to redrill you can fill the holes with a dowel and gorilla glue then redrill. 

You can also look down the flaperon and make sure it is straight and does not have a bow in it anywhere.

Make sure you get the slop figured out before you fly, that is not good at all!

 

:BC:

 

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Posted

I second that, when I drilled mine I set the most inner one and the most outer one then pulled a string right at the flaperon spar center spaced down 3/4 Inch,  then set the middle ones,

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Posted

One area that can manifest itself with slow response is the bushing areas on the turtle deck.  There can be some flex in the system when not supported by a good fitting set of bushings, especially when combined with slightly stiff flaperons.

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Posted

Thanks for the help. This is all really good information.  I disconnected the flaperons from the mounts and there were several that were way off, which was actually causing the wing to warp when I turned the flaperons by hand.  I redrilled them in the correct locations and they move much easier now.  Also, after tightening every joint in the controls I am seeing much better response in the controls.  I also found a few parts that were slightly bent in the control linkages, probably due to the excessive pressure needed to move the controls.   Also good to be aware of the flutter situation.

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Posted

Hoping that the builder put the counter weights on the flaperons - They are supposed to be on there for a good reason (flutter).   EDMO

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Posted

Some of the push pull rods under the seat have a small bend for clearance,is this what you are referring to?Any other bending done would take a massive effort with the stick,if that is the case a thorough inspection of all fittings etc would be a good idea.

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Posted

There was a rod end which connects the rod connecting the 2 control sticks to the L shaped rod that was bent due to the 2 rod ends that connect to the control sticks being installed in the wrong order.  I reversed them and the controls move much more smoothly.  I also had to trim a plate that the throttle mounts to which was interferring with the control sticks when moved all the way to either side.  Also all the linkages in the control system were loose, and after tightening and re cotter pinning have almost no play.  The flapperon mounts were also not all drilled in a streight line, causing the wing to warp when the flapperons move up and down.  It turned out to be a combination of many things which needed to be corrected, but I am feeling much better about the controls now.  Thank you for all your help.

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