the thing i was dead wrong about was composite repairs on aluminum airframes

Been turning wrenches since 1999 and I spent years thinking fiberglass patches on metal skins was just a bandaid. Then about 5 years ago I had an MD-80 with a belly skin that looked like swiss cheese from corrosion in the galley area. My lead handed me a 3M scotchbrite pad and some epoxy and I was ready to fight him over it. That repair held for 4 more years until we retired the plane. What made me go from hater to believer? Actually watching a bonded doubler distribute load across a crack on a test coupon. Has anyone else here had to eat crow about a repair method they swore was garbage?

2 comments

2 Comments

the_joel1mo ago

...and what really sealed it for me was watching a bonded patch hold up to a full pressure cycle test. I had the same fight with my old boss over a Cessna 340 wing skin repair back in 2003. He wanted to drill out the whole area and put in a riveted doubler. I was like no way I'm trusting glue to hold a wing together at 200 knots. But he made me sit through a factory training on bonded repairs and I saw them rip a test panel apart with a hydraulic pull tester. The parent metal failed before the bond line did. After that I stopped arguing and started paying attention to surface prep. You gotta scuff it right, keep it clean, and watch your cure temps. Still hate doing it in cold hangars in January though.

allen.cole1mo ago

Buddy of mine had the exact same awakening. He was restoring a Piper fuselage, old corrosion damage. Refused to use anything but rivets for weeks. His lead mechanic finally got fed up. Dragged him over to a scrap wing section they were about to scrap. Made him sand down a spot, apply a test patch. Cured it in a homemade oven bag setup with heat lamps. Next day they clamped it in a vise and hit it with a sledgehammer. The aluminum tore around the patch, bond line held perfect. Now he won't shut up about surface prep and cure times.

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