YUMA, AZ, USA
N689SB
HILLER UH-12E
THE PILOT COMPLETED AN AERIAL APPLICATION OPERATION AT ABOUT 200 FT AGL WHEN HE NOTICED THE ENGINE RPM DECAYING. HE PROCEEDED TO AN OPEN AREA TO EXECUTE A PRECAUTIONARY LANDING. UPON ARRIVING OVER THE OPEN AREA AT ABOUT 100 FT AGL, THE ENGINE SUSTAINED A TOTAL LOSS OF POWER. THE PLT IMMEDIATELY EXECUTED AN AUTOROTATION, BUT FLARED TOO HIGH CAUSING THE TAIL ROTOR ASSEMBLY TO STRIKE THE GROUND. A WRECKAGE EXAM DSCLSD THAT THE ENGINE TORSIONAL COUPLING RUBBER MOUNTS HAD SEPARATED. THIS CONDITION CAUSED AN OVERSPEED WHICH ULTIMATELY SHUT DOWN THE ENGINE.
THE PILOT MISJUDGED THE FLARE ALTITUDE. CONTRIBUTING TO THIS ACCIDENT WAS THE FAILURE OF THE ENGINE TORSIONAL COUPLING WHICH ULTIMATELY CAUSED THE TOTAL LOSS OF POWER.
Source: NTSB Aviation Accident Database
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