Top Overhaul vs. Full Overhaul

Crashnburn

Crashnburn

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I was pursuing some aviation related porn and saw a plane with an engine with about 2300 hours, with a Top Overhaul with about 320 hours.

What are the ramifications of not doing a full overhaul around 2000 hours?

Is a top OH vs. full OH on an IRAN basis?
 
There's really no such thing as a "top overhaul." The manufacturers and the FAA only have a provision for overhauling the entire engine. A "top" means that they replaced or looked at just the cylinders. It largely is a meaningless number without knowing that work was actually done. It does nothing for TBO (though TBO itself is largely meaningless for private operations).
 
Crashnburn said:
What are the ramifications of not doing a full overhaul around 2000 hours?

Is a top OH vs. full OH on an IRAN basis?
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As above, plus the seller will have to put up with offers that assume a timed-out engine which will require an complete overhaul at any point after purchase.

They probably pulled the cylinders, inspected the cams and were satisfied with what they saw, and decided to keep going without splitting the case. Maybe they replaced all four cylinders, but I would absolutely confirm that and not assume.
You're still on borrowed time, though. As an owner, I'd probably replace/overhaul cylinders if they're weak, assuming the crank and cam look ok. But while that might make sense for me as an owner of an engine that doesn't owe me anything, you as a buyer should still make an offer that assumes the engine can give up at any point.
 
AV8R_87 said:
As above, plus the seller will have to put up with offers that assume a timed-out engine which will require an complete overhaul at any point after purchase.

They probably pulled the cylinders, inspected the cams and were satisfied with what they saw, and decided to keep going without splitting the case. Maybe they replaced all four cylinders, but I would absolutely confirm that and not assume.
You're still on borrowed time, though. As an owner, I'd probably replace/overhaul cylinders if they're weak, assuming the crank and cam look ok. But while that might make sense for me as an owner of an engine that doesn't owe me anything, you as a buyer should still make an offer that assumes the engine can give up at any point.
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Thanks.
 
The problem with overhauling is there’s been a backlog of parts since Covid, so an overhaul could take a long time, I would call some engine shops to see expected time to overhaul.
 
Crashnburn said:
Is a top OH vs. full OH on an IRAN basis?
Click to expand...
A "top" is technically a repair so any and all work performed should be detailed in the logbook. Usually when you see cylinder work on a 2000 hr lower end points to someone who either wants to get every last bit out of it or someone planning to sell the aircraft. With most bets pointing to the latter. And depending on the aircraft model it will probably sell.
 
My experience with the term "top overhaul" means that the cylinders were removed and disassembled. Valves out. Dimensional checks on the cylinder, piston, valves, valve springs, rockers, pins and guides. Hone the cylinders to break the glaze. Clean the pistons and install new rings. Grind the valves. Replace the guides if out of limits, and ream to size. Grind the valves. Reassemble the cylinders, reinstall on the crankcase with new seals. Install rockers and check dry tappet clearances, adjust rods as necessary.

Anything less than that is not an overhaul of any sort and is a waste of time and money.
 
Depends on how long your going to keep the airplane,some say do you feel lucky.
 
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