Engine Teardown
Nobody ever wants to tear down what appears to be a perfectly good engine but there are times when a teardown is absolutely the right thing to do.
If you’ve suffered a prop strike that requires prop removal or significant prop work, whether your engine was running or not, you are required to do a full engine teardown and NDT analysis of major components.
If your engine lost oil pressure in flight and a check of the the oil pressure signaling system shows it's working properly, you should do a teardown. The engine components most often damaged by loss of oil pressure are the connecting rod and crank shaft bearings and both can only be inspected through a teardown.
If your engine has operated for more than a few minutes with less than the manufacturer’s minimum oil quantity in the sump, you should do a teardown. Every engine is different, but for many engines the minimum is around 1.5 to 2 quarts
If your engine is showing unusual amounts of metal in the oil filter and analysis shows the metal to be from anything other than a piston pin plug, you should do a complete teardown.
What the Engine Manufacturers Say About Teardowns
Both Lycoming and Continental’s service bulletins provide very clear guidance when it comes to determining when a teardown is required.
Lycoming Service Bulletin SB533A
Continental Service Bulletin SB96-11B
We have our own simple rule regarding teardown inspections:
Any sudden engine stoppage or significant propellor impact, should trigger a teardown with complete NDT analysis. To do less, is to put lives at risk.
What About Engine Accessories?
What many pilots don't realize is that there are more components than just the engine that can suffer damage from a prop strike.
Every engine accessory must also be inspected for damage.
Some accessories - alternators for example - turn at at ratio of up to three times engine speed
That means a 2000 RPM prop strike causes the alternator goes from 6000 RPM to 0 in under a second. That's almost always guaranteed to break something.
Only through a full teardown and careful inspection of all components can we be sure that alternator won't explode inside your cowling a some later date, possibly taking your engine with it.
Teardown or Complete Overhaul?
Teardowns aren't cheap. They involve almost the same amount of labour as an overhaul.
What do you do if your engine's over half way to TBO? How do you decide whether to do a complete overhaul or not? There aren't any easy answers and from an owner’s perspective the decision can be an agonizing.
You've got to carefully weigh all the factors before deciding to go the overhaul route because it definitely adds cost. We'll give you all the technical advice and expertise we can, but in the end, only you can decide whether to set the engine's TBO clock back to zero, or put it back in service with repairs only to items the teardown inspection discovered.
This Lycoming O-235 suffered a prop strike. We did a teardown inspection and had to replace the crankshaft and a few other components. With only 400 hours on it, a complete overhaul couldn't be justified. Seen here, it's almost ready to go: the prop has yet to be hung and engine hoses, ignition leads and baffles still need to be installed.
Note the overhauled and freshly painted engine mount. An engine mount overhaul is often required after landing hard enough to cause a prop strike.
The engine's owner chose not to repaint the cylinders in order to save on the teardown and inspection cost. Our normal practice is to repaint all cylinders and crankcase whenever an engine is taken apart, be it for overhaul or teardown.
We're Here if You Need Us
If you find yourself facing a teardown after any sudden engine stoppage or prop damage, give us a call. We’ll keep you in the loop every step of the way. In fact, we encourage owners to visit the shop and actually see the engine components for themselves during the teardown process.
And, we'll do everything in our power to keep the cost as low as possible.