TBO and rental ops

[NYCPilot]

A freshly overhauled engine (regardless of who did it) is much more likely to fail durring it's first 100 hours.

I think I've heard this before, but what are the general reasons or causes for an engine to fail after an overhaul within the first 100 hrs.

 

[avbug]

And as a side note, a zero-time factory overhaul is beyond nebulous, and into the realm of downright deceptive. Zero time engines are assembled from piles of major components of completely unknown history. your "zero time" engine may have case halves with 15,000 hours and a crank that has 10,000, rods that have 17,000. You don't know, and neither does the factory because the records have been discarded.

True story. Overhaul doesn't mean much...the parts have been inspected and meet tolerance, and that's about it. A factory job may have new parts, but a lot will be reused...most major parts, in fact.

Even a typical "top" overhaul reuses the second most stressed part of the engine...the connecting rods as a matter of course.

Ignorance, for most, is bliss.

Why do engines tend to fail more right off the bat? Most things fail new...they haven't been proven yet. Older equipment, excepting unusual streses or undetected design or manufacturing flaws, tends to be more tried and tested, and whatever is going to break has already broken. Very notable exceptions to that exist, but it's those first few hours out of the shop when thing begin to loosen, parts begin to work against each other that haven't done so before, and stresses can become manifest.

All a new engine says to me is "guess which part is gonna break first?"

 

[pilotmiketx]

There is a reason why that TBO is established. Especially in an environment where the engine is getting abused I am not even sure if an engine can make it to the TBO in a very healthy manner.

The engines that make it to TBO and past are the ones that are run hard and run regularly. I don't expect the engine on my 170 that flies less than 100 hrs/yr to make it anywhere near TBO (nor do I plan on owning it that long.) All of the 135 freight and flight school planes that I flew would make it past TBO. It wasn't magic, they were just flying 100 hours/mo.