Rotax 912UL crank failure



The 94 S7 had been operated for most of its life on amphib floats. There was no record of any prop strike during that period (and also very unlikely) nor during the short period that the last owner operated it on wheels. It had well under 1000hrs on it when it suffered an engine failure on take off. The pilot made a reasonably safe landing but the aircraft subsequently burned.


You can read the NTSB report here:


This is what was left after the owner chopped it up and I purchased it:

Picture soon


The engine was examined and disassembled. Internally there appeared to be no failure but it was extremely difficult to rotate the crank. After splitting the case and pulling the crank it is clear that the two part crank slipped at the join. If you look at the two faces of the lobes between the crank pairs you can see they are not parallel by about 10 degrees. This shift would put the three lobes out of alignment and cause excessive friction and, perhaps, the seizure.

It is unclear what caused the subsequent fire.



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