Accident Hiller UH-12E N689SB, Tuesday 10 October 1989

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Date:	Tuesday 10 October 1989
Time:	20:27 LT
Type:	Hiller UH-12E
Owner/operator:	West Farm Air Inc.
Registration:	N689SB
MSN:	1475
Engine model:	Lycoming VO-540
Fatalities:	Fatalities: 0 / Occupants: 1
Other fatalities:	0
Aircraft damage:	Substantial
Category:	Accident
Location:	Yuma, AZ - United States of America
Phase:	Manoeuvring (airshow, firefighting, ag.ops.)
Nature:	Agricultural
Departure airport:	Somerton, AZ
Destination airport:
Investigating agency:	NTSB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
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.

Probable Cause: 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.

Accident investigation: