My plane is in for its annual inspection and I just got off the phone with the shop manager. The good news is that they're making good progress on the plane, and both the landing light and trim tab piece arrived in time. I do need to take the books out to the shop, which I will do tomorrow afternoon.
The not so good news is that they found some metal in the oil. When I had the pre-buy inspection performed back in January, I had them change the oil as well. The note in the engine log book states that no metal was found in the filter. If metal is in the filter now, that indicates that some unexpected wear has occurred.
As far as I know, the engine has been running fine. So I have no real idea what might be causing this. Thinking about it, though, there is one potential cause, though it seems strange to me that it might be related.
Several flights ago, when I was performing the magneto check during the run-up, I accidentally turned the ignition switch one step too far and turned it completely off briefly. I immediately turned it back on and the engine restarted, but it seemed to, for lack of a better phrase, hit "hard". I suspect there was a bit of extra fuel in one or more cylinders due to fact that the mixture was not at lean cut-off like it would be during a normal shut-down. I suppose it's possible that there was an unusual amount of pressure in the cylinder for one cycle, and that may have caused some damage to the rings or the piston. I don't think it's likely but, while I have an excellent understanding of the operating principles of an internal combustion engine, I'm not an expert on this kind of thing.
The plan is to finish the inspection, and then run the engine for around five hours. Then we'll do another inspection of the oil filter to see if any more metal is ending up in it. If it looks okay, we'll do it again at around 25 hours, than again at 50.
The engine has close to 1600 hours since it was overhauled. It *should* be good for at least another 400 hours or more, but sometimes things happen and it doesn't last as long. We'll have to see how it goes. Obviously I hope that no major repair will be required, let alone an overhaul or replacement. That's when you start talking real money. If it comes to that, though, well, I knew that there was some risk in purchasing an airplane of this vintage, regardless of how well-maintained it's been and how good a condition it's in. I'll just have to deal with it as it comes.
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