One certainly could, but it makes little sense financially and increases the risk.
For example the OH on an IO540-C4 is of the order of GBP 30k including shipping and VAT.
That makes it 15 quid per airborne hour.
So running to say 2200hrs rather than 2000hrs saves you only about 1.5 quid an hour, which is below trivial. It is around 1/40 of the fuel cost.
Most of the scenarios where people run “on condition” are where they
It’s more important to be able to get the job done in a convenient way and get some extra value out of the downtime. One would pick a horrible winter, and if possible sync it with a major avionics job e.g. 2 × IFD540 
That means the plane has to be left at a heated hangar. Avionics work is very tough in -5C (been there, done it).
If you have a well working engine, at best you get an equally well working engine after overhaul.
So not much reason to overhaul. Enough data and experience available to safely operate on condition.
One certainly could, but it makes little sense financially and increases the risk.
It’s not only about the money. It’s about avoiding the hassle.
I would not overhaul an engine at 2000 hours just because it has 2000 hours.
Nor would I but one needs to do it sometime, and it is better to do it at a time of your choosing i.e. in the winter.
Whereas if you wait for a problem to develop you lose that option.
Peter wrote:
Nor would I but one needs to do it sometime, and it is better to do it at a time of your choosing i.e. in the winter.Whereas if you wait for a problem to develop you lose that option.
You are right if you have a long term plan to keep the aircraft. If you have a 10-year plan, then you might as well do the overhaul soonish at some convenient point as you are going to need to do it sometime (FWIW this is how I think personally). Time of your choosing is pretty desirable – but place of your choosing is a lot more important!
However, if there is any doubt about future ownership, doing an overhaul is a bad idea as its true value is not realisable in the market – so doing the overhaul now harms the option of selling the aircraft next year.
Peter wrote:
For example the OH on an IO540-C4 is of the order of GBP 30k including shipping and VAT.That makes it 15 quid per airborne hour.
So running to say 2200hrs rather than 2000hrs saves you only about 1.5 quid an hour, which is below trivial. It is around 1/40 of the fuel cost.
REALITY CHECK – MATH ERROR
Err, that’s £15.00 / hour for a total of £3,000 over 200 hours.
Not 1/40 of the fuel cost, but closer to 1/4th.
Not exactly “trivial” …
Yes but only over those 200hrs.
The long term saving is still what I said.
Your case is correct if you bought the plane at 2000hrs and sold it (for the same money) at 2200hrs.
Michael wrote:
REALITY CHECK – MATH ERROR
Not really, you’re just distributing the cost savings differently.
Peter distributes them over the whole engine lifetime, so it indeed reduces hourly operating cost by roughly 1.5 quid.
You however keep the operating cost constant for 2000 hours, then fly for free.
How old is the engine now? Isn’t it on condition already due to the 12 year recommendation?
And has it not been apart a while ago because of the crankshaft replacement? How many hours ago was that?
It is really interesting to see the discussions we have re engines and on condition running, the big hooray when EASA finally went the way and allowed it like the US have been doing for ever, only to find that in the end there are people out there who are scared into doing a full overhaul by a RECOMMENDATION without any valid reason other than that recommendation?
So why do we bother to get the CAA’s to finally reckognize that neither is a full overhaul any guarantee for less trouble with an engine and that a well maintained engine can run perfectly for a lot over the recommended TBO, if we don’t believe in it ourselfs?
My engine came out to overhaul with 2500 hrs when there were indications for it to be worthwile. Before that, our maintenance crew had a very close look at the engine every time they saw it and pronounced it fit to continue.
Clearly, it is your decision what to do, if you feel better than by all means do it. And yes, there is a clear advantage of doing it at a time of your choosing. But just because of 2000 hours I would not dream of spending this kind of money if I can continue to operate the engine safely for 3-5 years unless I was trying to sell the airplane. Then a zero time engine is a huge advantage.
Peter wrote:
Your case is correct if you bought the plane at 2000hrs and sold it (for the same money) at 2200hrs.
Let me put it differently:
You keep books on your plane and you budget routine maintenance, fixed costs and reserves for engine and prop.
You’ve budgeted the engine based on £30K / 2000 hours, hence £15/h engine “reserve”.
You now elect to extend the engine life by 10% (200 hours) your books will show a net positive of £3,000 on the engine reserve.
If the plane is actually rented out and generating income, that’s a real take-it-to-the-bank 3 grand Sterling .
