Is my engine scrap?!

If this is the only indication of trouble, I agree with you to run the engine for at least 3 hours (I would be inclined to maybe run it for 25 hours) and check it again. That plug is easy to check, so maybe after 3-5 hours is not a bad idea. I also agree with you that if anything serious was going on, it would show up in the oil filter inspection. I also agree with Rotax guidelines that if that much debris is showing on the magnetic plug, it should not be ignored and the reason must be found.

This would be from the gear box not the engine. The oil filter is the place to look for engine metals.

James Ott wrote:

If this is the only indication of trouble, I agree with you to run the engine for at least 3 hours (I would be inclined to maybe run it for 25 hours) and check it again. That plug is easy to check, so maybe after 3-5 hours is not a bad idea. I also agree with you that if anything serious was going on, it would show up in the oil filter inspection. I also agree with Rotax guidelines that if that much debris is showing on the magnetic plug, it should not be ignored and the reason must be found.

Yes it's the only indication of trouble, I'd love to run it for longer but because of this it's no longer airworthy (I'm in the UK so rules may be different to your location), so I have to sit there on the ground for 3+ hours varying the RPM and then inspect the mag plug.

Ronald Lane wrote:

This would be from the gear box not the engine. The oil filter is the place to look for engine metals.

As the oil is shared with both engine and gearbox why do you say this? All the oil passes through the filter.

From my personal experience of running 2 different 912 engines over nearly 20 years, I can say that every periodic service results a small amount of ferrous metal on the end of the magnetic plug. If I hadn't cleaned it off in over 500 hours then it is quite likely that the cumulative mass of particles on the end of the magnet would be similar to that shown in your photos.

What I cannot work out is how large those particles are, mine were always very short and very fine. If yours had larger, thicker filaments that were one single piece then you may have more of a problem.

If the latter is not the case, then I would do what you have proposed: clean the plug, run the engine and then inspect it again. I have no idea how long you would have to run it for to get a meaningful result but if all of that metal was formed recently then it will probably be shedding at a reasonable rate.

Could you get a borescope in one of the access holes to have a look, or even just pull the gearbox off for a proper inspection?

Given the financial implications of condemning the engine, I would spend some time investigating the root cause first.