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:
http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20060519X00587&ntsbno=CHI06CA102&akey=1
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.
