NTSB Identification: NYC90LA122.
The docket is stored on NTSB microfiche number 43535.
Accident occurred Thursday, May 31, 1990 in BECKET, MA
Probable Cause Approval Date: 12/14/1992
Aircraft: BELL 47G-3B1, registration: N39268
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.

THE HELICOPTER ENGINE LOST POWER AND THE PILOT AUTOROTATED INTO UNSUITABLE TERRAIN. THE CAUSE OF THE POWER LOSS WAS A OIL CHANNEL WHICH WAS BLOCKED WITH DEBRIS AND LED TO THE FAILURE OF THE NUMBER 4 BEARING AND CONNECTING ROD. THE ENGINE HAD BEEN OVERHAULED 6 YEARS AND 228.5 HOURS PRIOR TO THE ACCIDENT. LYCOMING SAID THEIR POST CRASH EXAMINATION OF THE ENGINE SHOWED THE OVERHAUL HAD NOT BEEN CONDUCTED IN ACCORDANCE WITH THEIR DIRECTIVES.

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

A POWER LOSS DUE TO OIL STARVATION, AFTER MAINTENANCE PERSONNEL FAILED TO COMPLY WITH LYCOMING DIRECTIVES DURING THE ENGINE OVERHAUL. FACTORS RELATED TO THE ACCIDENT WERE: IMPROPER ADJUSTMENT OF THE ENGINE OIL PRESSURE BY MAINTENANCE PERSONNEL AND UNSUITABLE TERRAIN.

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