Aileron hinge mount movement

[Steve Ahrens]

After a little help please.

I have been having a close inspection of my aileron hinges and mounting, and noticed the centre hinge mount to the wing is firm and solid, but the 2 outer mounts to the wing have movement up and down.

Is this normal?  

[Andy Gelston]

Nope!  The plywood pieces that the hinges attach to can break free as the old resorcinol (the ONLY wood glue that is legal to use on certificated aircraft, and fortunately, the best wood glue available, next to TiteBond 3) glue has become brittle and broken.  It happened to 41VT. 

This is a major repair, as it's on a primary control surface and is a structural repair, so you'll need an IA to help you with the FAA Form 337 for it. I fixed 41VT by removing the aileron and, using a 2-1/4" hole saw to cut access to the bay, right behind the hinge (you need an aileron drawing, it will help a LOT). Go VERY slow with the hole saw, as you just want to cut through the plywood on the bottom side of the aileron. You just need to glue the plywood piece back in place, unless it is punky. I also glued in a piece of 1/4" birch ply, oriented vertically fore/aft, so it bisected the bay, right under the center of the access hole, to reinforce and stiffen the attachment of the piece that became loose.

Once the hinge attach and stiffener is glued back in and solid, scarf the edge of the hole and make a 2-1/2" diameter plywood (birch or mahogany) disc, with the edge scarfed to match the hole, and glue it into the hole. Cover with a 4-1/2" diameter patch of fabric (pink the edge) and finish that are compatible with the existing covering system.

I hope this helps...

[Steve Ahrens]

Thank you for the reply Andy.

I’ve been back out to the plane to investigate further. All the timber appears to be in very good condition, so I tightened the hinge attaching bolts through the small inspection holes at the rear of the wing. I had to remove the aileron and cut the fabric to achieve this. The bolts did’nt take much to tighten but it was enough to remove movement of the hinge bracket.

Andy Gelston said:

Nope!  The plywood pieces that the hinges attach to can break free as the old resorcinol (the ONLY wood glue that is legal to use on certificated aircraft, and fortunately, the best wood glue available, next to TiteBond 3) glue has become brittle and broken.  It happened to 41VT. 

This is a major repair, as it's on a primary control surface and is a structural repair, so you'll need an IA to help you with the FAA Form 337 for it. I fixed 41VT by removing the aileron and, using a 2-1/4" hole saw to cut access to the bay, right behind the hinge (you need an aileron drawing, it will help a LOT). Go VERY slow with the hole saw, as you just want to cut through the plywood on the bottom side of the aileron. You just need to glue the plywood piece back in place, unless it is punky. I also glued in a piece of 1/4" birch ply, oriented vertically fore/aft, so it bisected the bay, right under the center of the access hole, to reinforce and stiffen the attachment of the piece that became loose.

Once the hinge attach and stiffener is glued back in and solid, scarf the edge of the hole and make a 2-1/2" diameter plywood (birch or mahogany) disc, with the edge scarfed to match the hole, and glue it into the hole. Cover with a 4-1/2" diameter patch of fabric (pink the edge) and finish that are compatible with the existing covering system.

I hope this helps...

[Andy Gelston]

An easy fix? That's not supposed to happen with aircraft! 

The wood probably shrunk over the years, so I'm glad you were able to tighten up the bolts and be done with it, other than a bit of fabric patching.

Cheers!