To be fair, I mentioned the overhaul example as a gotcha, and not as some illegal thing.. most reputable shops (at least the ones I know of in the UK) would definitely supply new cylinders as part of an overhaul. When someone doesnt even replace the cheap hose in an overhaul, it must make you wonder what else they were cheap about. That’s definitely part of doing your home work.
the stuff that should be “illegal” is something like claiming an aircraft has a fresh annual when it is in fact not airworthy (or at least borderline) on inspection.
I don’t think that’s a negative approach – this is a highly regulated industry. If that aircraft crashes, people on the ground could die as well, not just the “dumb” pilot who bought it.
Say you later discover corrosion in an inner part of the engine
This happens to be exactly my case. Corrosion a while back led to undetected wear, which when my mechanic investigated and found it, requires a complete overhaul. The engine wasn’t far from TBO anyway, so I was prepared for it – although I hoped it would be a couple of years away. The only way to have detected it during a pre-buy would be to take a cylinder off and borescope the whole inside of the crankcase. Would any owner accept that in a prebuy? I certainly wouldn’t.
So what can I do? I very much doubt that the previous owner had any idea the problem was that serious. The only real symptom was that the plane wasn’t as fast as it should be by a few knots. The actual corrosion most likely happened two or three owners ago.
Suppose I decided to try and get compensation from the previous owner – an aeroclub whose finances are no better than any other aeroclub. If I could find a French lawyer to take the case on – dubious in itself – I’d face years of stress and unpleasantness. Probably in the end I’d get nothing, though for sure I’d have plenty of new enemies in the tiny and well-connected world of French private flying. It would frankly be an insane thing to try and do.
So I suck it up, and look forward to getting my plane back with a good few extra HP.
Rami1988 wrote:
the stuff that should be “illegal” is something like claiming an aircraft has a fresh annual when it is in fact not airworthy (or at least borderline) on inspection.
If it was signed off for an Annual, it has an Annual by definition. All that means is that it was certified as airworthy on the day it was inspected – there is no warranty on an Annual. You can however factor in the depth and scope of the Annual logbook entry, try to talk to guy that did it, and so on. That’s basic stuff, and well worth doing.
I doubt a corroded engine will be making a few kt less due to corrosion.
The few kt is worth a lot of HP. At 745.7W per HP, even 10HP is 7.5kW which is a huge amount of extra heat to be getting rid of. If the engine ran ok, with normal CHTs and oil temp, then you would not have had significant extra friction.
What is possible is a half-eaten camshaft, reducing valve lift, but that would have been seen in the valve lift, plus a ton of metal in the filters. I know few people do oil analysis but every mechanic who is not a complete chimp will check the filters.
Also from what I have seen, an engine with corrosion in the bores (the usual case of low use engine) will have fairly clean bores in the piston ring contact area, which is where it matters.
So if your plane is not making the book speed, and the fuel flow is right, and the fuel and rpm instruments are right, and you are flying at peak EGT, then the plane is probably “bent” (out of trim).
In the aeroclub scene down where you are, working against the system is going to get you massively slagged off, and if you upset somebody badly you will get stabbed in the back. Even the DGAC can do that (to an instructor they don’t like). I am familiar with another situation… It’s bad enough in the UK but your scene is much more connected-up.
Peter wrote:
I doubt a corroded engine will be making a few kt less due to corrosion.
I agree, the more typical effect will be on oil consumption, when corroded bores eventually wear the rings. If the cam were corroded, it would reduce power but most other corrosion will have limited effect on power output. The concern is when corrosion advances to the point that the engine goes ‘boom’ someday, as might occur with advanced bearing corrosion, or that it renders the crankshaft unsuitable for overhaul.
Bear in mind that most waste heat goes out the exhaust pipe.
Peter wrote:
They can be forged, especially computer ones, and frequently are especially with hangar queens where the buyer will be looking for fairly regular flights.
OK, if we’re going down the document forgery route, all bets are off. Flight frequency or lack thereof can easily be established via FR24 or FlightAware, at least here in the US. Talking to others on the field usually also yields some info.
Other than that, pretty much what @Silvaire says. You’re buying an old piece of equipment that usually has had several owners of varying attention to maintenance. Caveat emptor.
I’m not saying any more. tbh I regret saying what I already did. I would not be at all unhappy if Peter deleted my entry there.
johnh wrote:
I’m not saying any more. tbh I regret saying what I already did. I would not be at all unhappy if Peter deleted my entry there.
Why? You essentially exonerated the previous owner by saying: I very much doubt that the previous owner had any idea the problem was that serious.
