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I used to be dead set on using safety wire over cotter pins for castle nuts. Now I'm not so sure after a 767 job in Phoenix.
For the longest time I thought safety wire was the only way to go on anything that could vibrate loose. Cotter pins felt old school and kinda flimsy to me. But last month we had a 767 come in with a nose gear issue and the manual clearly called for a cotter pin on one of the main bolts. I fought it at first, but my lead told me to just follow the book. So I did. Used a proper cotter pin, spread the ends right. Three weeks later that plane is still flying without a hitch. Made me realize sometimes the old ways are there for a reason, not just because nobody updated the manual. Has anyone else had a moment where you switched your go-to method and it worked out better than you thought?
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lee8471mo ago
Three weeks ago I had almost the exact same thing happen on a 737NG main gear door actuator. I was dead set on safety wire for the castle nut, been doing it that way for years. My lead told me to check the IPC and sure enough it wanted a cotter pin. I grumbled but did it, spread the legs nice and even. That bird has been flying all over the west coast since and no issues. It really made me rethink the whole "newer is always better" mindset I had. Sometimes the engineers who wrote that manual knew what they were doing even if it looks old school. Now I check the book before I grab my wire twisters.
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davis.noah1mo ago
Hold on, I gotta push back a little here. I've seen just as many cotter pin failures from them being installed wrong or vibrating loose in high heat areas. In my experience, a properly twisted piece of safety wire is way more forgiving and you can actually see it holding tension long after a cotter pin might have started to wiggle. That 767 might be fine for now, but I'd be nervous relying on a cotter pin on a critical nose gear bolt where you can't really inspect it without pulling stuff apart. Your mileage may vary, but I've had to re-cotter pin stuff on the ramp that looked fine until I yanked on it and the leg popped right out.
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Fair enough Davis, but is a loose nose gear bolt really a make or break thing.
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