My old boss told me to always torque a prop bolt cold, but I tried it warm once

He said it at my first job in Wichita, that you have to let the engine sit overnight before final torque on a Lycoming. I followed that for years. Then last month on a tight turn, I torqued it after a short ground run, just to see. The reading was exactly the same as the cold spec. Maybe it's just me, but I think that old rule might be more about habit than fact. Has anyone else checked this on a piston engine?

4 comments

4 Comments

the_lee1mo agoMost Upvoted

Good point on "metal expands evenly" - that's the tricky part with mixed metals in an engine case vs steel bolts, but with modern tolerances I bet the difference is negligible for most of us.

kimmurphy2mo ago

So we're just out here ignoring decades of aviation wisdom now? Guess I'll go warm up my torque wrench and see what else I was wrong about.

william_garcia2mo agoMost Upvoted

Decades of wisdom" sounds heavy, but sometimes it's just old guys being stubborn. Your test seems pretty solid to me.

phoenixw112mo ago

Old habits die hard. Your test makes sense though, metal expands evenly. Might have been more important with older engines or different metals.