Is my engine scrap?!

Kevin Stewart wrote:

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.

The gearbox is off but I get the impression my Rotax engineer is reluctant to find the cause as the procedure here in the UK seems to be just scrap it and replace, it's being reassembled for me to come and ground run it and inspect.

I'm a 4 hour round trip away from the AC so cannot easily inspect further myself.

Hi Karl,

My understanding of magnetic plug inspection is -

The residual oil should be removed by soaking in petrol/carb cleaner BEFOR making an assessment of the amount of ferrous "swarf" held by the magnet.

The photo you have supplied looks like the oil has not been removed, making the amount of swarf appear very much more than it actually is.

Further,

The inspection of the magnet is subjective and should ALWAYS be viewed alongside other indicators  eg  service hours, clutch wear assessment, unusual noise or vibration, ferrous chips, etc. If all other indicators are acceptable the generation of swarf should be monitored during the next in service interval (as you suggest)

Your gearbox inspection (1200hrs) is due in 400 hr - it is possible that your concerns about the previous owners attention to maintenance may have resulted in accelerated wear - The Rotax Maintenance Manual has test procedures for this.😈

So not sure if it has been inspected in hundreds of hours?  Really, this is called out for inspection at every annual.  Simply plug the material off into your fingers.  if it has any particles that are more than 3 mm (⅛ inch) you might have an issue.  If it is just magnetic ferris metal, normal from the gearbox wear over time, you have no issue.  As others suggested, change the oil and filter and clean off the mag plug.  Run it 25 hours and check again.  I doubt you have anything to worry about.  I would personally have the gearbox reshimmed at this many hours anyway.  That is the only sure way to check for wear internally in the gearbox. 

Cheers

Yes it certainly looks like it hasn't been soaked in anything and literally just pulled from the engine.

I do know the 600 hour gearbox service was done as it's in the log book and the invoice from Airmasters UK (where it's at right now) is present.

We'll see what happens when I get up there next week.

I cannot run it for 25 hours as it cannot be flown, Airmasters will not permit it without either a new engine or knowing this one is safe.

The previous owner of 18 years had done almost nothing, even basic things like tyres were down to the cords and perished, the brakes were through to the backing plates, all wheel bearings where shot to bits, fuel was leaking from both wing tanks, he'd wired a second battery inside the cabin glued to a car cleaning sponge under the passenger seat instead of replacing the failed one in the engine bay! This is just some of the problems it came with... truly horrendous!

The magnetic plug detect metallic parts from the GB so have look to it before saying the engine is dead at 800h  and remember that the normal check of the GB is 1000h so you you are not so far…