Metal debris after 25 hours – 2 Engines

We found significant metal debris on the magnetic plug of our 915 Eurofox at the first 25-hour oil change, as did a sister gliding club with an engine 1 serial number different. Our experiences since then have been almost identical.

CFS, the UK Rotax agents requested that we remove the gearbox and send it for inspection as the most likely source of the metal. They stripped the gearbox and there were signs of the overload-clutch slipping, but it was confirmed that the debris did not come from the gearbox. This means that 2 engines each had the same 2 distinct problems – a slipping overload clutch and metal debris from an unknown source, which suggests a serious quality issue in Rotax’s manufacturing, assembly or QA processes.

The gearbox was returned with a new overload clutch and we were requested to do a 30-minute ground run and re-check the magnetic plug. If it was clear, then the aircraft was to be flown for a further 25 hours and another oil + filter change performed. In both cases, there was more metal debris after the 30-minute ground run, with one more than the other.

Has anyone else experienced this problem as it’s hard to imagine only 2 engines would be affected ? Also, the BUDS logs did not show any overspeed events, so the clutch must have been slipping, but not excessively. This may be a widespread problem that no-one knows about yet, but what are the long term implications ?

Disappointingly, CFS supposedly obtained approval in writing from Rotax to replace our engine and bizarrely withdrew this option, insisting we flew it for a further 25 hours – so much for “no-compromise warranty” !