Uncontrolled Roll on Full Flaps

[Osprey220]

Hi Guys,

I'm a new member - in the Davis/Woodland California area.

I've been helping a friend get his Kitfox Model II (Rotax 582) flying and correctly rigged - and having lots of fun flying it too.

But with the fun has come a bit of undesired sphincter puckering excitement.

A couple of weeks ago, the flapperons went into full flutter at ~75mph! Recovered quickly with pulled power and gentle up roll. Yikes.

I found a lot of slop in the remarkably complex control linkages I could tighten and remove. Additionally, the shoulder bearings on the flappers were not tight and I've fixed that. So far, no more flutter.

BUT -

On full flaps, I get a uncommanded and _almost_ uncontrollable roll to the left. Almost full right aileron controls the roll, but it does not seem like a condition I would want to approach landing in! Half flaps seems fine with no roll tendency.

Any insights or suggestions?

I did a quick search and have seen that others mention limited roll authority on full flaps, but I've seen no mention of uncommanded roll.

I look forward to your input - I really need the help.

Also - if there are folks around wanting to fly out, get in touch.

Cheers,
Owen Hughes

Attached is a picture of the plane:

[jiott]

From your photo it appears there are no mass balance weights on the flaperons; there should be two, one in midspan, the other on outboard end. These weights are extremely important to prevent flutter, and I believe there was a factory bulletin put out to require their installation on the early models that didn't have them.

The uncommanded roll I have no idea about, except it sounds like maybe a very bad rigging problem.

[avidflyer]

Maybe I'm wrong, but I believe the early Kitfox models only used one balance weight per flaperon. They certainly should have them installed to prevent flutter though. JImChuk

[Osprey220]

There is one mass balance per flapperon.

[David47]

Uncontrolled roll to the left when flaps are deployed: I'd be checking for correct part numbers used in the flap/aileron control circuit first of all and if all looks ok, do a ground check to ensure the flaperon angles are the same on both sides for flaps deployed with no aileron. If that's ok, sounds like it could be a rigging issue as Jim suggests. In that case, check the rigging.

[TY2068]

http://kitfoxaircraft.com/images/ser...etins/SB-3.pdf