Worn wing to fuselage bolt holes

[Hank Jarrett]

I am FINALLY ready to hang the wings back on my 41 BC-12-65 and was getting everything lined up and ready when I took a close look at the attach fittings on the fuselage. Typical of many of our older birds in areas that are covered a lot and don't get much cosmetic attention, the drilled ears had a LOT of layers of old paint and the bolts (which I had just put back in the holes without much thought to keep from loosing them when I took the wings off) were really covered with multiple layers of paint. Since I didn't want to use elastic stop nuts again and had new castellated nuts for cotter pins I took the old bolts and threw them in a jar of solvent (solvent REALLY messes up elastic nuts!). Then took my mighty #11 X-acto knife and scraped off about 10 layers of paint from the fuselage lug. When I did this (without breaking the ancient original primer I might add) a layer of paint IN THE HOLE also came out. When I took the now clean bolts back to the fuselage the rear spar bolts had enough clearance to "rattle" in the holes! The slop was being taken up by all the paint (they were tight before).
Now for the question (bet you guys thought I would NEVER get here). I KNOW lots of other planes must have had worn spar to fuselage holes. Should I;

1) Sleeve the hole and go back with the original bolts
2) Clean up the holes and go with 1 step oversize
3) Ream and go to the next size up bolt (anybody know what size was original? What is the max bolt size?)
4) Lay a weld bead in the hole and re-drill
5) Peen the lug so it is tight on the bolt again (No, I am NOT doing that, but have seen it done. Made my hair stand on end!)

What has been done in the past and how was it documented to the FAA?

Hank

[Pearson]

Re: Worn wing to fuselage bolt holes

Hank,

In my old copy of AC43.13, dated Sept 1998, it says on page 4-40, Elongated or worn bolt holes in fittings, which were designed without bushings, are not to be reamed oversize. Replace such fittings, unless the method of repair is approved by the FAA. Do not fill hles with welding rod, Acceptable methods of repairing elongated or worn bolt holes in landing gear, stabilizer, interplane, or cabane-strut ends are shown in figure 4-25. Figure 4-25 shows what appears to be welding a washer over the fitting. I think I would fabricate a piece out of 4130 rather than use a washer. I think I have seen this type of repair on attach fittings before, but I'm not 100% sure. I am sure one of the IAs reading this can chime in about the legality of such a repair. But from what I see in AC43.13, it looks like using oversized bolts or welding the hole smaller are not approved methods. For all the hassle of fabricating two "washers" out of 4130 and welding one on each side of the fittiing, you could make a new fitting and weld it on.

[Hank Jarrett]

Re: Worn wing to fuselage bolt holes

Got that. If it was the fitting on the wing I would put new fittings on. The problem is the oversize holes are in the lugs on the fuselage side. I seem to remember that the FAA didn't like welding on the lugs, which never made much sense to me since they are welded to the tubes 1/2" away from the holes. If they are worried about changing the temper from welding the holes, what about the weld bead attaching the lug to the tube?
Hank

[Buell Powell]

Re: Worn wing to fuselage bolt holes

Hank,
The original size bolts are AN4-13 rear spar and AN5-15 front spar. Have you tried new bolts yet or checked to see how they fit the wing fittings? Probably is the fittings but might be worth checking to see if the old bolts may be worn-if someone used lock nuts where they shouldn't may-be they also used some old worn bolts?

[Hank Jarrett]

Re: Worn wing to fuselage bolt holes

In the rear spar attach I tried new bolts and they were just as loose. Front ones aren't really that loose in the holes, but bad enough I want my IA to look at them. I haven't checked the wing fittings yet because the wings are still in the storage room and the root ends are against the wall. I was hoping to pull them out this weekend, but I don't want them taking up all the floor space if I need to do a lot of work on the fuselage (AGAIN!!!!) Tore the whole instrument panel, glare shield, windscreen, doors and interior apart last week to weld one stinking little crack in the door hinge!
Hank

[astjp2]

Re: Worn wing to fuselage bolt holes

I would first try and put some epoxy primer back in the hole, it worked for how many decades with no problems? But that is just me......One problem with the washer method is the lack of compression and friction holding the wing attach fittings tight when screwed down, all of the force would be on the washer. The wing attach fittings are sandwiched but can be crushed, so the only thing holding it is the direct shear of the bolt. Skip 43.13 and check cam 18, I would go oversize if there is enough bearing surface, that is the easiest option, if not then replace the fitting, and the cover and......you get the point, also flip the fuselage upside down, less chance of weld splatter hurting anything nearby. Tig with pre and post heat if you weld, that will help normalize it and use ER70S2 rod. You will also need to find out from Forrest if its 1020 or 4130

[mikeg]

Re: Worn wing to fuselage bolt holes

Hank,
Try a "close tolerance" 1/4" bolt. Their diameters tend to run a little larger.
Mike

[Pearson]

Re: Worn wing to fuselage bolt holes

Got that. If it was the fitting on the wing I would put new fittings on. The problem is the oversize holes are in the lugs on the fuselage side.

Hank, that is what I was referring to when I said it might be easier to just replace the fitting. They are just a square shaped U with a hole drilled through it and welded to the upper longeron. Obviously you would need to make sure if it is 4130 or 1020, or whatever.

[Robert Lees]

Re: Worn wing to fuselage bolt holes

And what is wrong with elastic stop nuts in a non-rotating shear situation?

[astjp2]

Re: Worn wing to fuselage bolt holes

Absolutely nothing!

[Hank Jarrett]

Re: Worn wing to fuselage bolt holes

Nothing really wrong with it. I had drilled bolts already, the old elastic nuts were encased in ancient paint (I never reuse elastic nuts anyway and if possible always replace them with mechanically locked nuts), it originally had castellated nuts and cotter keys and I am just a little anal about doing it original if I can.
I have been caught in the past with having to remove an elastic locking nut and not having a replacement. The manufacturer says you can use them twice, but how do you tell if the one you need to take off has already been removed once?
Hank

[astjp2]

Re: Worn wing to fuselage bolt holes

Hank, you can reuse them until the locking feature is no longer working, if it gets tight in the nylon, its still good. Tim

[Hank Jarrett]

Re: Worn wing to fuselage bolt holes

Yea, I am going by the military requirement we used at the NADEP where we overhauled aircraft. We were only allowed to reuse them twice. I never could get an answer as to how we would know how many times they had been used before "this time". We always just tossed them into a box when they were removed and used them on the facility bicycles, desks or GSE. No one was willing to reuse them. I just don't like them. I feel really secure looking at that cotter pin. Something I don't feel when I am looking at an old Nyloc.
Hank

[Buell Powell]

Re: Worn wing to fuselage bolt holes

Well--Just going by what I have seen used so far and my parts book listing the AN310-4 and AN310-5 castle nuts. I checked the Service Manuel and it does show elastic nuts so guess I have to admit they were used also and agree they should work OK-I agree with Hank though- the castle nuts and cotter keys just seem more secure in such a critical location.

[M Towsley]

Re: Worn wing to fuselage bolt holes

You only got to use them twice because the taxpayers were purchasing new ones from the supplier who was making campaign contributions to the senator who represented their area.

Sorry to get off-track, Hank. I wish I had the answer for you but I am sure someone will chime in.