Aileron Hinge/Spar Inspection/Corrosion

[R. JOHNSON]

In the Sept/Oct 2003 issue of Cub Clues there is a piece on Aileron spar and hinge corrosion. Then during a pre-flight inspection of our J-3 I discovered a severe crack in the aileron spar at the center hinge. Removal of the aileron and closer inspection revealed more cracking. We cut off the fabric and drilled the thing apart and found badly corroded spar and the center hinge also had severe corrosion where it came in contact with the aluminum spar, and the spar was corroded in three spots, where it came in contact with the hinges (dissimilar metals). Also sandblasting of two of the hinges revealed a cracks in each of those. Because of what I seen on this aileron we'll be taking the other one apart for inspection as well, I would highly suggest this to anyone rebuilding their Cub. Also to help prevent corrosion at contact of dissimilar metals spray a "bed" of primer (we used zinc chromate) on the part of the hinge that is to come in contact with the spar and on the same place on the spar, then rivet the hinge in place while still wet to "mate" the surfaces of primer forming a corrosion barrier (thes pieces already had been primed once as well). Just be sure to carefully inspect your ailerons.

[Steve Pierce]

I brought this up the winter before last when rebuilding a SC. Found the same thing. Use a good epoxy primer. Zinc chromate is not a good primer for steel. This area is perfect for corrosion having a piece of aluminum sandwiched between two pieces of steel and prone to get moisture. Check in those aileron hinge channels also. I have a bunch of them in the scrap pile too.

[HydroCub]

Check in those aileron hinge channels also. I have a bunch of them in the scrap pile too.

They should have a small drain hole drilled in them so they don't hold water.

[cub_driver]

I had the same trouble with my flaps a few years back. The spar had all but corroded away where the flap hinge was rivited to the spar.

I noticed the flaps had started to drop I though it was just a weak return spring but after a closer inspection we removed the flap and tore it down that is when we found the corrosion.

I was real close to having a inflight failure most of the rivits had already pulled through the corroded spar and the remaining rivits had very little spar left to support the flaps.

Cub_Driver

[Steve Pierce]

They should have a small drain hole drilled in them so they don't hold water.

I agree this should be done and the holes kept clear. The problem I have seen is moisture collecting just inside the false spar of the aileron/ flap well and corroding the hinges there. It is hard to see cause there is usually a bunch of dope and stuff built up right there.

[RPURCELL]

When I took my hinges out of my flaps and ailerons I found that all four with the pushrod attachment had cracks. Corrosion was not present so I cleaned everything up, primed the aluminum and powdercoated the steel. I could not see the cracks under the old fabric glue, paint, etc. Years of stress cycles takes it's toll.

[Big AK]

Along with the corrosion in these areas is the effects of wind damage when you don't use gust locks on ails. and flaps.

Also, wind damage to the inboard flap hinge, flap cove sheet metal, and especially, the wing butt/root rib attachment brackets to the aft spar.

If your airplane has enough time on it to have found corroded ail. and flap fittings and cracked spars, it probably has sheared screws and cracked-out brackets on the butt rib at the aft spar.

Don't forget to notice the cracks in the aileron and flap nose ribs in the corner where the rivet-flange bend is located, They ARE cracked if you've found these other issues.

Good Luck. DAVE