Changed my mind about using a borescope on every inspection

I was doing a 100 hour on a Cessna 172 in Phoenix last summer, and I skipped the borescope on the cylinders because the engine ran smooth. A week later, the owner called back with a rough mag drop. Turns out, a small crack was starting in the number three cylinder head, right where you can't see it without the scope. I had to eat the cost of the tow back to the shop. Now I run the scope on every cylinder, every time, no exceptions. How many of you make the borescope a non-negotiable step for pistons?

2 comments

2 Comments

schmidt.grant13d ago

Ever have one of those moments where you try to save five minutes and it costs you five hundred bucks? That was me, but with a valve guide. Now the scope comes out even if the engine sounds like a sewing machine.

thomaslewis12d ago

Man, that's rough. I feel you on the mag drop surprise. But honestly, @schmidt.grant, even a smooth running engine can hide stuff. I found a tiny bit of fretting on a barrel once that you'd never catch by ear or compression check. It wasn't bad yet, but it was a sure sign things were getting loose. That's the whole point of the scope, right? It's not for the obvious problems, it's to spot the small stuff before it leaves you on a taxiway somewhere.