My old foreman told me to always torque a prop bolt twice, and I just found out why

Back at my first job in Tulsa, my foreman insisted on torquing the prop bolts on a Cessna 172, waiting ten minutes, and hitting them again. I thought it was overkill until I skipped it on a rush job. Next inspection showed two bolts had backed out a quarter turn. He said the aluminum hub settles under initial load. Now I hear some shops call that second pass a waste of time. What's your take on the double-torque method for props?

2 comments

2 Comments

simonh741d ago

My buddy Mike at a small field in Wyoming had a Beechcraft come back after an annual with a prop vibration. They pulled the spinner and found three bolts just finger tight. The shop that did the work swore they torqued them once to spec. Mike's old boss made them redo it with a second pass after a coffee break, and it never happened again. Seems like that settling is real, so why risk it for ten minutes of extra work?

thompson.nathan23h ago

Yeah, that's everywhere. You see it with lug nuts after a tire rotation if you don't recheck them in a week, or even a new deck where the wood shrinks and all the screws need another pass. It's like anything under tension finds a tiny bit of give once it settles. Skipping that second check just assumes everything is perfectly rigid, which nothing ever is. Ten minutes to be sure beats the time and cost of fixing the problem later.