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Uncommanded Roll on Full Flaps


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Posted (edited)

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 other mention limited roll authority on full flaps, but no mention of uncommanded roll.

I've also posted this to the TeamKitfox forum - I really need the help.  Sorry if you've seen this twice.

I look forward to your input.  

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

Cheers,
Owen Hughes


Attached is a picture of the plane:

 

IMG_9672.jpg

IMG_9675.jpg

Edited by Osprey220

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Posted

Owen,

   Welcome to the forum. I'm hangared at Rio Vista O88. I would be weary of flying that bird anymore until you get to the bottom of this issue. People have been killed in these from flaperon flutter. Typically roll reversal happens at more than 15 degrees of flaps. In the Avid manual there are several warnings about this. The upper and lower bearings on the turtle deck where the flaperon rods come out of the fuse are critical! Shoot me a PM with your contact info and we can get together sometime. I fly out of University once in a while at the Cal Aggies.

Joey

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Posted

I concur with Joey"s sentiment.. Don't fly this plane until you get a full understanding of what is creating this anomaly and rectify it. I would suspect some sort of in congruent deployment of the flaps when the flaps are in full position deployment. What is causing it if it is the problem I couldn't tell you.... At a keyboard it is just all speculation. 

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Posted

Does he have the counter weights for the flaperons installed.  Sounds like you need to go back thru the controls and make sure they were put together properly and then re-do the flaperons rigging. If you can't find anything then it is probably best to get someone that knows these planes to come look at it Joey, maybe if he has the time..

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Posted

There is one flaperon mass balance per side (mounted near the outside end of each).

 

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