Loose Ailerons?

[Kerbs]

I have noticed recently quite a bit of play in both ailerons on my '46 BC12D. This seems to be between the bracket that attaches to the aileron and the aileron itself where there are bolts that go into the aileron to hold the bracket on. The bolts are difficult to access too tighten without pulling the ailerons. I am also not sure if its a plate or nuts that are on the other side of the bolts behind the fabric inside the ailerons. I do not have any inspection holes on the ailerons.

My father who used to own the plane, told me the previous owner to him told my father the ailerons are suppose to be loose and don't listen to anyone that says otherwise. This is all new to me so I thought I would check and see if anyone else has run into this. I can get pictures tomorrow if it is helpful.

[3Dreaming]

The bracket should not be loose on the aileron. The bolts likely have nuts on the back side, so I doubt you can tighten themwithout cutting access in the fabric. The question to ask is why are they loose.

Another point of looseness I've seen is the pin in the aileron bracket. This happens when the pin turns in the bracket instead of the bushing like it is supposed to.

The looseness the previous owner may have been speaking is the control cables. They don't work well if tightened like cables in other airplanes.

[Hank Jarrett]

I think the prior owner was talking about the ailerons being "loose" in that the cables aren't overly tight. When the wheels are in neutral you should be able to lift each aileron a little (both sides at once) without the wheel moving. The looseness of the pushrod fitting on the aileron is a completely different problem. The prior owner is completely right that you SHOULD NOT tighten the cables until there is no play in the wheel to aileron. YOUR problem seems to be looseness in the pushrod fitting attach to the aileron spar. That is usually because someone in the past over tightened the bolts, slightly crushing the wood in the spar. The solution IS NOT to tighten the bolts more. You will just crush the spar more. If the spar is crushed down it will require a proper repair. That may require cutting into the aileron fabric to get to the nuts and washers inside the aileron. A bit more complex repair.

Hank

[Kerbs]

Thanks guys. Yes, it's the fitting attached to the aileron spar. Sounds like I am going to likely have to cut fabric. Are there typically inspection holes on the ailerons or no?

[Scott]

Sometimes there are access holes, sometimes not. Mine had 1" holes with chassis plugs/caps at the centre hinge/pushrod location but nothing at the outer hinge location.

How long have the ailerons been in service since last recover?
As has already been suggested, the most likely cause is crushed/rotten spars. Depending on how the fabric was install, there's lots of opportunity for moisture ingress and associated rot at the pushrod location.

If its ten years or more since the last recover (maybe less if the aircraft has been parked outside) the spars probably look like this:

[Mark Bowden]

Stu, it's good you are looking at things in detail.
If you are "in for a penny, you should be in for a pound", in that you need to examine all sources of aileron looseness. If there is one issue there could likely be others.

Other spots to examine "while your at it".

1. The aileron actuator bracket pin bolt. This part is installed it the actuator bracket and connects to the aileron push pull tube. It can wear and or be loose in the bracket. * regular lube point
2. The aileron push/pull tube. This assembly has two cups on each end that can wear and are adjustable. * regular lube point
3. The control yoke universal joints. These have two bolts in each that can wear and make for slop. * regular lube point
4. The control yoke sprockets. These teeth wear just like bike chain sprockets. * regular lube point
5. Aileron Sector, pivot shaft and bolt bushings. *regular lube point, protective cork cap on pivot shaft is usually long gone
6. Make sure the "bump stop" bumpers are in place so the yoke sprocket bolt doesn't crash in the the fuselage frame structure

The following photos are credited to Rob Lees and his Top Ten Maintenance presentation at https://www.taylorcraft.org.uk/
Also check Scott's aileron section in his blog at: http://c-fclr.blogspot.com/p/ailerons.html

[N96337]

Mine were like Scott's above...only MUCH worse! They'd been tightened/squashed until there wasn't 1/4" of thickness left in places.... I'll have to pull one down and get a picture if I think of it. I kept them to show people when I was teaching covering classes.
John

[skip]

Six years ago when I did my wing rebuild the ailerons were actually in worse condition than the wings. Years outside had not been kind. There was a little aileron up/down movement at the fitting (not the trailing edges from appropriate cable tension). Turns out someone had really torqued the bolts over time crushing the aileron spar and plywood plates. Also the plywood plates just fell off the spar when the bolts were removed. there is no trace of any glue on the plywood or the spar. On my rebuilt ailerons, the plates are on with resorcinol and I added a .067 backing plate on the rear of the aileron spar to help distribute bolt loads.
My ailerons seem to be original and so this problem probably shows up once in a while.

Skip Egdorf
N34237 - 1946 BC12D

[N96337]

I'm thinking it's probably a great spot to use some good epoxy resin after everything is glued, to seal it, as well as add a little strength. At least that's the plan on mine.
John

[Scott]

Yes I think the epoxies available now are considerably better than the glues of the past. The two part urethane varnishes are equally tough. Thin the first couple of coats 50% and the varnish penetrates well, sealing the wood and providing excellent adhesion for the top coats. Can also thin epoxy glue with denatured alcohol and brush on like a varnish.

In the area of the pushrod, with the spruce doubler, plywood front and back epoxied, and 4 coats of varnish, you end up with kind of a composite build that is/should be more resistant to moisture. I also put chromate past on the bolts to seal them too.

[PA1195]

A one piece metal backing plate is a good idea. Large area washers not so much.

Other potential sources of wood crushing are snow and wind loads on the ailerons when parked. I've seen them both droop more than an inch under a good load of built up snow. Over a few years one finally broke the bell crank on a local F-19. Wind from behind can work them up and down banging against the stops, or if restrained by the control wheel being tied pressure is applied at the pushrod attachment. Better to use gust locks at both ends of the control.

Gary

[Robert Lees]

I also had bad crushing to my aileron spars



So I made new.

I also added 0.080 aluminium plates with floating anchor nuts behind the spars, so that no cutting of the aileron fabric would be required in the future. I am sure that if CG Taylor expected his aircraft to last so long, he would have done the same.



Here's the result:



Blog here for those interested.

I can do this legally in the UK (perhaps Scott can in Canada too) but in the US is a different matter because you insist on keeping unsupported types certified {?)

[PA1195]

This is as good as or better than...excellent fix Rob. In 50 years someone will think that's how they are all done.

Gary

[Scott]

I considered following your lead Rob and use nutplates. While any modifications to a spar would be considered a major modification, my intention was to treat it as a substitution of hardware and I'm sure no one would have given me any grief.

However in the end I didn't want to encourage potential future problems. I was fooled by someone before me tightening the bolts instead of investigating the root cause. The root cause being moisture induced rot of the spar. Once the bolts are tightened and the spar crushed, there's really no way to detect the problem (until the bolts shank out perhaps).

My sense is that if the spar is rot-free, the hinge and pushrod brackets won't be loose. I.e. if you find looseness assume more significant problems that can't be properly solved just by tightening the bolts.

Having said all that, this is clearly a common problem (both the rot and the crushing due to bolt tightening) and it would appear there haven't been critical failures, so we can add it to the list of things to be aware of as opposed to some sort of fleet-wide airworthiness issue.

[N96337]

Exactly right Scott! The old varnish wasn't great to start with, and from everything I've been told by a guy that used to work at Taylorcraft in the 40's, they were ALWAYS broke, so you used everything very sparingly. I totally agree with the theory of a backing plate, but wouldn't do the nutplates for the same reason as you...it's just going to make it too easy to just snug them up again instead of finding the problem.
John