That moment I found a cracked engine mount on a Cessna 172

I was doing a routine annual inspection at our shop in Phoenix last week and noticed a weird hairline crack near the left engine mount bracket. Took a closer look with a borescope and sure enough it was a solid fracture about 2 inches long. Had to pull the whole mount off and send it out for welding which cost about $400 and grounded the plane for three days. Anyone else run into hidden cracks that weren't obvious from a quick glance?

3 comments

3 Comments

masonbell1mo ago

Wait, did you actually send a cracked engine mount out for welding? I thought the standard practice was to replace those things, not repair them. Like I'm pretty sure the FAA considers engine mounts a critical safety item and welding them is usually not approved unless it's a very specific manufacturer approved procedure. I've seen A&P guys just swap them out for new ones to avoid the liability and paperwork headache. Was this a field repair or did you have some kind of special approval for that? Just seems like a risky move on a part that holds the whole engine on the plane.

hill.andrew1mo ago

Did you ask your A&P if he had the manufacturer's specific repair data for welding that mount? Because I've seen guys try to go off a generic AC 43.13-1B repair and that definitely won't fly for something like this, not on a critical part. The local FSDO here will red tag the whole plane if they catch a welded mount without an approved engineering order or a direct OEM repair letter. Did the shop actually produce any paperwork showing it was okay?

betty_palmer1mo ago

Oh man, you hit the nail on the head with "pretty sure the FAA considers engine mounts a critical safety item" because yeah, that's exactly what I was thinking when I saw that. I had a similar thing happen a few years back with a Cessna 172, and my A&P flat out refused to even look at welding it. He said it's not worth the paperwork and liability, and he just ordered a new one instead. I mean, I get that some shops might have the approval for specific repairs, but honestly it feels like a huge gamble for something that literally holds the whole engine on the plane. Idk, maybe it's just me but I'd rather spend the extra money and sleep better knowing it's not going to crack again mid-flight.