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That old timer's advice about torque on wing bolts saved my butt today
My mentor Lenny told me to always back off and re-torque after 50 flight hours on new fasteners, which I thought was overkill. I skipped it on a Cessna 172 last month and found three bolts half a turn loose during a routine inspection this morning in Phoenix. Has anyone else had a senior mechanic give you a tip that seemed pointless but turned out to be critical?
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stella2210d ago
Disagree with the wisdom here. I've been torquing fasteners my whole career and never once backed off after 50 hours on a new install. The spec is the spec, you torque it to the manual and it stays put. Bolts don't magically loosen unless something else is wrong like corrosion, vibration from a bad mount, or just using a cheap torque wrench that wasn't calibrated. Found three bolts half a turn loose on my Cessna 172 last year but that was because I used a Harbor Freight special instead of my Snap-on. You sure your mentor's not just repeating an old wives' tale from the 1950s when hardware was junkier? What did the bolt threads look like when you pulled them out?
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lee6899d ago
Oh man, I gotta chime in here... a buddy of mine had a similar setup on his old Piper and he was the same way, always trusting the torque wrench and never looking back. Well, he did a full engine mount swap on a Saturday, torqued everything to spec with his Matco wrench, and thought he was good. About 60 hours later he's doing a preflight and sees a weird oil stain near one of the bolts... pulled it and it was almost a full turn loose. Threads looked clean, no corrosion, just the nut had worked itself back a bit. He went back and checked the other mounts and found two more that were slightly loose too. He's not a young guy either, been wrenching since the 80s. So I don't know if it's old wives or not, but he sure won't skip that re-torque step now.
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Yeah, that thing about threads looking clean is interesting... I had the same thing happen on a pre-buy inspection a few years back. The bolt came out looking brand new, threads were perfect, but it had definitely backed off. Vibrations from the engine just work stuff loose over time, especially on a fresh install where things haven't had a chance to settle in yet. Your buddy with the Piper is smart to go back and check those mounts now, and I'd bet he'll never skip that 50 hour re-torque again. It's one of those things that sounds like overkill until you find one loose and realize how close you were to a bad day.
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