NTSB Identification: LAX97LA224.
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Accident occurred Wednesday, June 25, 1997 in RIVERSIDE, CA
Probable Cause Approval Date: 02/02/1998
Aircraft: Enstrom F-28-F, registration: N99YC
Injuries: 3 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.

During takeoff, the helicopter lost power and landed hard. Postaccident examination revealed the No. 2 cylinder intake valve rocker shaft migrated out of the shaft bosses of the cylinder head. The shaft, cover, and nuts were found; the washers were not. According to owner/pilot there were internal star washer imprints on the cover plate commonly caused by torque or tightening of the nut. The helicopter had 61.5 total hours since new, and received one 50-hour inspection since delivery to the owner/pilot. The owner/pilot changed the oil and filter just prior to the inspection.

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

failure by unknown maintenance personnel to retorque the nuts on the retainer cover.

Full narrative available

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