NTSB Identification: SEA95LA119.
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Accident occurred Thursday, June 15, 1995 in HELENA, MT
Probable Cause Approval Date: 01/29/1996
Aircraft: GRUMMAN G-164B, registration: N6669Q
Injuries: 1 Uninjured.

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

WHILE MANEUVERING IN CLOSE PROXIMITY TO THE GROUND, THE ENGINE BACKFIRED TWO OR THREE TIMES AND SUDDENLY LOST POWER. THE PILOT ATTEMPTED TO LEVEL THE WINGS AND EXECUTE A FORCED LANDING, BUT THE AIRPLANE IMPACTED TERRAIN IN A BANK. EXAMINATION OF THE ENGINE REVEALED THAT THE CRANKSHAFT WAS BINDING DURING ROTATION, THE NO. 5 CYLINDER HEAD WAS CRACKED, AND THE CRANKSHAFT WAS EXPOSED TO HEAT DISTRESS. NO EVIDENCE WAS FOUND TO INDICATE THAT THESE DEFICIENCIES OCCURRED AFTER THE ACCIDENT. POSTIMPACT AND THERMAL DAMAGE TO THE ENGINE PRECLUDED A COMPLETE FUNCTIONAL TEST AND EXAMINATION OF THE ENGINE.

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

THE LOSS OF ENGINE POWER FOR UNDETERMINED REASONS.

Full narrative available

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