NTSB Identification: DEN82DA089
14 CFR Part 91: General Aviation
Accident occurred Sunday, May 16, 1982 in MARMATH, ND
Probable Cause Approval Date: 05/16/1983
Aircraft: ENSTROM F-28C, registration: N8617J
Injuries: 1 Uninjured.

THE PILOT REPORTED THAT WHILE HE WAS IN FLIGHT AT ABOUT 75 TO 80 FT AGL, THE ENGINE LOST POWER. DURING AN AUTOROTATIVE LANDING IN AN OPEN PASTURE, A SKID DUG INTO THE GROUND AND THE HELICOPTER ROLLED OVER. A SUBSEQUENT ENGINE TEARDOWN REVEALED EVIDENCE THAT THE ENGINE HAD BEEN OPERATED IN AN OVERSPEED CONDITION OVER A PROLONGED PERIOD OF TIME. THERE WAS EVIDENCE OF HIGH VALVE SEATING VELOCITIES AND BOUNCING, THE UPPER SPRING SEATS HAD BEEN STRIKING THE TOPS OF THE VALVE GUIDES, FATIGUE FAILURE OF THE KEEPERS HAD OCCURRED, AND SUBSEQUENTLY, A VALVE FAILED FROM FATIGUE.

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

ENGINE ASSEMBLY,VALVE,INTAKE..FATIGUE

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

POWERPLANT CONTROLS..IMPROPER USE OF

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