USMCmech
Well-known member
- Joined
- Jan 7, 2005
- Posts
- 259
Overhauling an engine at TBO is not a requirement for pt 91 operators. Many pt 135 operators have extensions on their engines allowing them to run past the published TBO.
TBO is an "estimate" of when the engine will NEED to be overhauled. Nothing more nothing less. Some engines will break down before TBO, and some others will last much longer.
Most American males need to have their heart overhauled between 55-60. Does that mean that you will get bypass surgery at 60, even if your doctor says that your cholesterol is low, BP is fine, ect. Of course not! There is no more reason to overhaul an engine if it is not showing any signs of failure just because it has run for a certian amount of time. Some desiel generators have been running constantly for DECADES whitout ever being shut down much less overhauled.
I personally know a pilot who flys pipleine patrol in a C-172 with an engine that has 7500 hours SMOH. He has replaced 2 cylinders in the past 10 years, he flies it almost daily, it still makes good compression, shows no sign of metal in the oil, still makes full take off power, ect. In short it is as good as the day it came out of the shop. He has no plans to EVER split the case untill the engine shows some sign of a problem.
OTOH, any engine not makeing full power, showing metal in the oil, or has a prop strike, ect. needs to be overhauled imeadiately, regardless of the number of hours it has beeen running. I have seen a IO-540 that needed to be rebuilt after only 100 hours. A large amount of metal was showing up in the oil anylsis and the filter. The main bearings had been heavily worn and the camshaft showed serious spalling.
Don't ever say to your self, "it runs like crap, but it was just overhauled so it must be OK". That is an exact quote from a pilot who had to make a forced landing after that freshly overhauled engine blew an exauxst valve.
TBO is an "estimate" of when the engine will NEED to be overhauled. Nothing more nothing less. Some engines will break down before TBO, and some others will last much longer.
Most American males need to have their heart overhauled between 55-60. Does that mean that you will get bypass surgery at 60, even if your doctor says that your cholesterol is low, BP is fine, ect. Of course not! There is no more reason to overhaul an engine if it is not showing any signs of failure just because it has run for a certian amount of time. Some desiel generators have been running constantly for DECADES whitout ever being shut down much less overhauled.
I personally know a pilot who flys pipleine patrol in a C-172 with an engine that has 7500 hours SMOH. He has replaced 2 cylinders in the past 10 years, he flies it almost daily, it still makes good compression, shows no sign of metal in the oil, still makes full take off power, ect. In short it is as good as the day it came out of the shop. He has no plans to EVER split the case untill the engine shows some sign of a problem.
OTOH, any engine not makeing full power, showing metal in the oil, or has a prop strike, ect. needs to be overhauled imeadiately, regardless of the number of hours it has beeen running. I have seen a IO-540 that needed to be rebuilt after only 100 hours. A large amount of metal was showing up in the oil anylsis and the filter. The main bearings had been heavily worn and the camshaft showed serious spalling.
Don't ever say to your self, "it runs like crap, but it was just overhauled so it must be OK". That is an exact quote from a pilot who had to make a forced landing after that freshly overhauled engine blew an exauxst valve.
