I used to think a torque wrench was just a fancy ratchet until a gear bolt sheared on a Cessna 172

For years I would just pull on the wrench until it felt tight, maybe give it an extra tug for good measure. I figured the click was a suggestion, not a rule. Then last month I was doing a 100 hour on a 172 and found a sheared bolt on the nose gear steering assembly. The mechanic who worked on it before me had clearly over-torqued it, probably by a good 20 foot-pounds. The shop foreman pulled me aside, showed me the fracture surface under a glass, and said 'That's not a bad bolt, that's a bad habit.' It hit me that I'd been doing the same thing, just trusting my arm. Now I set the wrench, wait for the click, and stop. No more 'feel'. Has anyone else had a part failure that finally made the book procedure click for you?

3 comments

3 Comments

gray_hall425d ago

Exactly like @karenwest said, that manual is the law for a reason. Your arm is NOT a torque wrench.

daniel39125d ago

Yeah, that click is the whole point. Saw a prop strike once where a crank bolt backed out. Guy said he "felt" it was tight enough. The manual isn't just a guide, it's the only right answer. Now I double check the setting and listen for that click every single time. My arm isn't calibrated.

karenwest25d ago

I read a report from the NTSB about a small plane crash where a cylinder head stud failed. The investigation traced it back to improper torque during an overhaul, just one guy thinking he knew better than the manual. It's scary how one skipped step can chain into something that bad.