aileron flutter !!!! help !!!

[mikegregory]

hi all , i have a mk 2 kitfox , & had the fright of my life today !! i took off as normal (not flown for several months ) & was climbing out at around 300ft when all of a sudden the aircraft started to shudder badly , the port wing ( i didnt notice the starboard wing ) started to flutter as did the ailerons , very badly !!! the instrument panel also shuddered badly ! i couldnt control it , & the plane started to drop to the left ! i closed the throttle & tried to slow it down , ( the speed had creeped up to over 80mph ) the engine stopped , i thought my time was up !!! but i managed to restart the engine & gently increased power so i could nurse it back into normal flight , the flutter seemed to stop , but still seemed like it wanted to turn , i very nervously nursed it back around & landed safely , but , ive not got a clue why it happened ? ground running after showed no issues , i taxied it & checked everything , but all seems ok ?? im very reluctent to try flying again untill i have some idea of what happened ?? could it have been some kind of high speed flutter ? as i had let it creep up over 80mph on full power ? but if so , why did the instrument panel shudder also ?? could it have been engine related ?? but why does it seem to run ok after ?? any help gratefully recieved
mike

[Danzer1]

Didn't you have some of these issues before? Have you completely gone through the rigging and controls to make sure everything is correct per the manufacturers specs?

Also as the engine stopped - is it possible you had a little bit of water in the fuel - as you haven't flown it for some time? If it was fuel starved - it could cause shuddering.

Also keep in mind an engine will act/run differently when running under load (in the air) than it will static (not moving on the ground).

[mikegregory]

hi danzer , thanks for your reply , no , never had any issues before , ive not long , only done less than 10 hours in it , but never had any issues at all before ! all rigging etc seemed ok , i fold the wings for hangerage , but as usual it was simply putting the wing pins in & putting the turtledeck on , i checked everything after , but cant see anything obvious , i guess water could have been an issue ?? but why would it make the wings / ailerons shudder so bad ?? thanks anyway
regards
mike

[Danzer1]

Mike,

This thread was yours: http://www.teamkitfox.com/Forums/showthread.php?t=4739 You mentioned some of that same issue today "& the plane started to drop to the left".

If the engine is running rough for any reason, the resulting vibration amplifies the further away it gets from the source and to the components that flex the most - so seeing it outboard on the wings would not be out of line.

Good Luck

[mikegregory]

danzer , thanks again , yes thats right it did used to drop a left wing , but i believe that was due to it being set up for a previous owner who flew from the right seat , i adjusted the incidence a little & now its ok ? i think ? but today it was definate flutter on the ailerons , but as you said , & now thinking about it , the instrument panel shuddered badly also , so maybe it was water ? rough running engine ? that shook the whole airframe & made the ailerons flutter so badly ???
regards
mike

[Geowitz]

If the engine shut off on it's own I would start there. Something intermittent could be going on with your ignition or fuel delivery. Engine problems can definitely create a lot of vibrations in these planes and make it look like something else. I doubt this is a flutter or rigging issue. Your previous issue was about a heavy wing/incidence and again, I doubt it has anything to do with this. I'm betting on bad ignition connections, but check fuel too.

[mikegregory]

Hi av8 . Thanks for your help . Can I ask how do I check all these bearings ? What exactly am I looking for. There is dome play with ailerons. But hard to determin what's acceptable & what's not ? Even my inspector just said "check everything" . But I'm not sure exactly what to check ?

Regards
Mike

[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?