NTSB Identification: LAX03TA043.
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Accident occurred Sunday, December 01, 2002 in Panaca, NV
Probable Cause Approval Date: 12/28/2004
Aircraft: Bell 47G-3B-1, registration: N48020
Injuries: 1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.
The helicopter experienced a loss of engine power and landed hard during an autorotation, severing the tail boom. The number 6 cylinder's intake valve separated, with the valve's head wedged in the intake valve seat bore. Removal of the rocker box cover on that cylinder revealed that the spring retainer was broken into numerous pieces. The piston head showed over 15 impressions consistent in dimension to that of the valve head. After examining the number 6 cylinder, a metallurgist determined that the valve failed in between the intake valve head and the valve stem.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: separation of the no. 6 cylinder intake valve head from the valve stem, which resulted in a loss of engine power. The mechanism responsible for the valve failure is unknown. Full narrative available
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