Flaperon Torque tube failure


12 posts in this topic

Posted (edited)

Continuing Airworthiness Notice - 27-012                  CAA of New Zealand.

Avid and Kitfox fitted with flaperon.

See attached report img057.pdf and images for report and notice.

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Edited by anders.stenhammar84@gmail.

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Posted

Thanks for posting this.  Sorry that you bent up a bird but glad you walked away from it!

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Posted

We would like to hear what you ended up doing for repairs to the flaperons.

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Posted

Thanks for posting anders. Was the aircraft exposed to moisture more than normal, parked outside for example? Also, how visible was the corrosion from a normal look? Do the parts need to be disassembled (rivets drilled out) to do a complete inspection? Thanks

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Posted

Have a question:  

I took a look at both of my model 1, and on mine that piece he is holding is rivited and hysol on it also. Mayb that would have helped the rivits some?  Mayb have takin some of the direct stress off of them? 

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Posted

Just for clarity, because I find the photos in the initial post to be unclear as to the actual failure, here is the picture from the New Zealand report. It appears that the tube itself sheared and separated, due to corrosion of the tube itself the rivets appear to have little to do with the failure. Is that correct anders?

failed flaperon control.jpg

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Posted

Very hard to see but can you confirm that it was built correctly?

What I am looking for is, You have the flaperon tube then there should be a piece of thin aluminum wrapped around the Horn so you dont need so much hysol then the horn slid in side of everything and glued solid. Thanks Let us know.

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Posted

Hello all.

Sorry for not responding. i have been away for christmas. It was not me flying this plane, I only got it sent to me on Yahoo group from a guy that's not so good at computers. 

This is a death trap. Its glued so its impossible to remove and inspect properly. If anyone have any suggestions how to inspect this without cutting and welding, I would very much appreciate it.

Here is some info from him:

To do the mod we bought 2 feet (use 1 foot each side) of 3/4 inch OD .095 wall thickness 4130 steel tube. Because the bellcrank is glued on to the aluminium spar tube it is impossible to remove it without damage so just cut the arm off the end of the steel tube. Cut as far out as possible so that the new one can be welded back on and the weld will be clear of the turtledeck bearing. Drill out all the rivets and clean out all the glue from inside the short steel tube and the aluminium spar tube. Turn down the 1 foot of 4130 steel tube so it will slide up inside the spar tube. The amount you turn off lengthwise will depend on how far the spar tube extends inside the stub of the bellcrank. Make up the new arm as shown in the photos including the short piece of 7/8 OD tube to make the assembly up to the same diameter as the bellcrank stub.  Slide the assembly up inside the spar tube, position everything correctly and drill new rivet holes in the 1 foot tube.  Remove again, clean everything thoroughly, then epoxy glue the new tube in place and replace all the rivets.  We also put two rivets through the skin and spar tube of the flaperon near the end of the inserted tube. Finally put a ring of weld around the end of the bellcrank stub with plenty of wet rags to keep your new glue and the plastic hanger bearing cool.  Before you cut the arm off the bellcrank you will need to make up some sort of a jig or take exact measurements so that the new assembly will end up in exactly the same place as the old one.  

The more people that know this is a potential problem the better.  One thing I forgot to mention is that you must cut a small chamfer on the end of the mod tube that goes up inside the flaperon spar tube. 
 
Brian
leach@farmside.co.nz

 

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Posted

I'm still unclear as to the failure? I don't have my airplane handy to make sense out of the photos. Did it break exactly at the splice? In other words was that two walls of tubing that failed or just the inner wall that failed at a splice point? If it's the latter of the two I don't think I would rely on a weaker turned down piece of tubing to fix it. It it is the latter I'd have turned down a piece of solid stock to fit instead of the tubing. The load would be mostly torsional in this application and a piece of solid stock would take much longer to fail in a corrosive environment. You have plenty of surface for bonding on the turned down part in your photo but the weak part would be the shoulder where the lathe work began.

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Posted

The flaperon has an aluminum tube that runs full length.  There is a steel bellcrank of just slightly larger ID that is glued and riveted to that aluminum tube.  The aluminum tube cracked off right at the end of the steel bellcrank tube.  The new steel bellcrank is obviously thicker walled and stronger even when turned down then the aluminum tube it goes inside.  My only concern would be corrosion from steel to aluminum touching.  Maybe if the steel has a good epoxy coating on it, it would prevent the corrosion.  When I first saw this, the first fix that came to my mind was to slide a thick walled aluminum tube inside the original aluminum tube that goes through the flaperon.  Of course any rivets would have had to be drilled out, and then replaced after the inner tube was in place.  JImChuk

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Posted

I assume the outer sleeve can be removed once the rivets are drilled and some heat applied to loosen the glue? I am helping return an avid with issues back to a fly able condition, this incident raises a red flag so best be sure.

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