aileron flutter !!!! help !!!

[Dave Holl]

Have the flaperons got the weights fitted and are they secure? I don't believe there should be any backlash in the aileron circuit. Get someone to hold the control stick central and then see how much lost movement in each of the flaperons I don't think there should be any

[Av8r3400]

First give it the "wiggle" test. There should not be any play in the bearings on the flapperons and the turtle deck bearings should be snug to the shaft passing through them.

Loose bearings on the turtle deck of the early models 1-3 have been known to cause flapperon flutter.

Broken rib tails have also been known to induce flutter.

Both of these are common issues that can be easily overlooked.

[Av8r_Sed]

Just checking, but you do have the flaperon mass balance counterweights installed, correct?

[Dave S]

Mike,

This may help with some your flutter question; it is a link to the FAA Advisory circular for testing home built experimental aircraft. On pages 52 & 53 as marked on the bottom of the page (pages 59 and 60 of the PDF document) there is guidance on analyzing and dealing with control surface flutter.

http://www.faa.gov/regulations_polic...a/ac90-89a.pdf

Not an exhaustive engineering piece by any means; but a good primer on the subject.

Sincerely,

Dave S
KF7 Trigear
912ULS Warp Drive
St Paul, MN

[jrthomas]

A friend of mine had a GSC wood 3 blade prop on a 582. One blade would slip and the pitch change would cause it to vibrate like crazy. Just a thought. Good luck. James Thomas

[mikegregory]

Thanks everyone do far . Yes there are counter weights on the flapperons & are secure . There is some play in the flapperons when the stick is held firm . Maybe this is an issue ? But if it is & I did experience flapperon flutter . Would the instrument panel shudder like it did ? . Mike

[Av8r3400]

Yes, I believe it would. The panel is not rigidly mounted and will move if the entire airframe is vibrating from a flutter.

We're you getting a vibration in the control stick, too?

You need to track down where the play in the stick is coming from. That's critical.

[mikegregory]

Hi av8 . Actually I font recall the stick shuddering at all . Which would suggest excessive playiI guess ? Maybe the engine cutting was an extra issue ? I'm not looking forward to flying it again !

[Dave Holl]

Hi
There has been some very good suggestions so far but before you fly the aircraft I think you must remove all play in the aileron circuit that probably means at least replacing all of the bolts in the pushrods and mixer circuit I would also critically inspect the rose joints and repace any that show any movement, check the rivet security on the flaperons torque tubes and ensure no movement in the removable connections.
It is possible it is engine related and if you have done the work on the flaperons circuit that would be one less thing to worry about as obviously flutter can cause an in flight break up very quickly.
I have experienced violent engine vibration and the inst panel really did shake(not on a kitfox though) and the fact that you had an engine issue is probably what caused the vibration but better safe than sorry.
Hope it goes ok
PS would be worth getting onto the mcbeens and get their views as I am sure john would give you some specific advice!

[Av8r3400]

I'd agree with Dave, now. Aileron flutter would shake the heck out of the stick. You'd remember that, I would expect.

Inspect for the play in the stick and repair that, but look to your engine for issues.