Overhauling GA aircraft engines
 

A wee quick Question regarding the more common 4/6-Cylinder General Aviation piston engines, e.g. Lycoming 0-235, 0-360, various 4/6-cyl. Continentals etc., just out of pure interest.

In most piston-engined GA light aircraft the engine is overhauled every 1800 hours or 2000 hours. What is actually involved in this overhaul? I take it this is when major components are replaced, e.g. gaskets, cylinder head etc.? Are there any other parts which are replaced between the overhauls? Like I say, I ask this out of pure interest, I don't actually need to know it but I am learning to fly so I am just interested in the workings of the aeroplane (I'm an apprentice engineer you see so I'm fascinated).

Cheers

Smithy

There are two overhaul limits used with these engines.
New limits
Service limits.
If you pay more, you receive an engine overhauled to new limits.
Items routinely replaced.
All gaskets, internal hardware (including counterweight bushings), case thru-bolts, etc.
The crankshaft is inspected and reground, if nesessary.
Same for the camshaft.
The engine case is sent out for inspection and line boring, if needed.
Cylinders can be overhauled if desired, and this would normally include new pistons, rings, valves, valve springs/rotator cuffs.
The starter adapter is overhauled.
The magnetos are overhauled.
The propellor governor is overhauled.
The fuel injection system is overhauled.
The engine is then assembled and test run.
Note that accessories are generally not included, such as alternator, vacuum pump, turbocharger, however these can be overhauled at extra cost.
Cost, an interesting subject.
Take a typical engine, say a TCM IO520.
Field overhaul to service limits, $13k
Field overhaul to new limits, $16k
Rebuild by the engine manufacturer, $19k
Note that with the rebuilt engine from the manufacturer, a new engine log is issued, indicating ZERO time.

Thanks for that, most thorough explanation there.

Bit pricey too... although it seems like a pretty major job!

Smithy

Might appear pricey, but then a car overhaul will simply roll to a halt if it goes badly wrong, a single engined aircraft will not and on some twins if you lose an engine the other one will simply fly you to the crash site.

If you go for the likes of the engine in say a Beech Baron twin and for a new item you would be looking at the best part of £50,000 for one.

Most engines on I have had overhauled have new cylinder assemblies fitted as part of the job.

BTW the overhaul period on a 0-235 (dependant on pistons fitted) is 2400 plus up to a 20% extension ( Engineers Discretion) giving it a life of 2880 hrs... there is a new ruling now as well of a 12 year dependant on usage.

Good look with the flying, its always refreshing to find a pilot taking the time to find out more about the aircraft he flies.

I know of a few owners who are having brand new factory engines sent to certain overhau shops, RAM and Victor Aviation come to mind for custom blueprinting jobs. Is tere any payback on the cost , something like 25% of the cost of a new engine for these super expensive rebuilding.