What was found
PILOT REPORTED THAT IN FLIGHT, ENGINE MADE SOME NOISES FOLLOWED BY LOSS OF ENGINE POWER, LT ENGINE. PROP WENT TO UN-COMMANDED FEATHER WITH A SUDDEN INCREASE IN RPM BEFORE ENGINE STOPPED RUNNING. INVESTIGATION ON THE GROUND REVEALED NO MOVEMENT OF THE PISTONS IN CYLINDERS 3, 4, 5, 6 ON LT ENGINE WITH PROP ROTATION, BUT PISTONS IN NR 1 AND 2 CYLINDERS ARE MOVING WITH PROP ROTATION. NO DISASSEMBLY OF ENGINE HAS BEEN DONE, BUT SUSPECT THAT THE CRANKSHAFT HAS BROKEN BETWEEN CYLINDERS 1 AND 2 AND 3 AND 4.