NTSB Identification: SEA04LA073.
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Accident occurred Monday, April 26, 2004 in Haines, OR
Probable Cause Approval Date: 12/28/2004
Aircraft: Hiller UH-12E, registration: N9785C
Injuries: 1 Minor.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot was descending through about 100 feet above the ground at 60 knots airspeed on approach to landing when he heard a loud bang. He immediately transitioned into an autorotation but as he flared prior to touchdown he had insufficient rotor RPM and the helicopter landed hard with the main rotor blades severing the tailboom. The pilot reported that as the helicopter impacted the ground he noted the Rolls Royce (Allison) 250-C20B engine spooling up. He also stated that he did not hear any audible engine out alert during the entire sequence and that the helicopter was not equipped with an auto-relight system. A post-crash test run of the engine revealed no abnormalities. The height-velocity diagram for the helicopter indicated that a successful auto-rotation could be accomplished at an elevation of 100 feet for airspeeds of 41 knots and above.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

A momentary partial loss of power for undetermined reason(s) and the pilot's failure to maintain adequate RPM during his autorotation landing.

Full narrative available

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