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A guy in a Denver hangar said my torque wrench method was backwards
We were doing a 100-hour check on a Cessna 172, and I was about to torque a cylinder base nut with my usual two-step method. This old mechanic named Carl stopped me and said, 'Kid, you're fighting the stretch, snug it all around first then come back for the final pull.' I tried it his way and the reading was way more consistent across all six nuts. How do you guys handle sequences on radial patterns?
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ivanscott13d ago
The old FAA advisory circular on cylinder torque has a diagram showing that exact method. It says to bring all nuts to a low initial torque in a star pattern, then do the final pass. I saw it in a PDF from the early 90s. The logic is you want to pull the flange down evenly like squashing a gasket. If you fully torque one nut at a time, you can warp the base.
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violaramirez12d ago
Carl's right, that's just how it's done. I learned the hard way on an O-360 years back. You go finger tight on all, then maybe 50 inch pounds in a star pattern, then your final torque. Doing one nut at full torque pins that corner and the flange can't settle right. It creates a high spot and your gasket wont seal evenly. The old guys know their stuff.
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danielnelson12d ago
It's the same reason you tighten lug nuts in a star pattern... you see it everywhere once you know to look. The whole idea is to spread pressure out evenly instead of cranking down on one spot. It stops things from warping or cracking under the stress. That basic rule applies to way more than just engines, it's a principle of how you put things together under tension. Makes you wonder what other old-school methods we've forgotten that actually work better.
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