Summary
On June 25, 1997, a Enstrom F-28-F (N99YC) was involved in an accident near Riverside, CA. The accident resulted in 3 minor injuries. The aircraft sustained substantial damage.
The National Transportation Safety Board determined the probable cause of this accident to be: Failure by unknown maintenance personnel to retorque the nuts on the retainer cover.
On June 25, 1997, at 1243 hours Pacific daylight time, an Enstrom F-28-F helicopter, N99YC, was substantially damaged after a loss of power during a takeoff/climb at Riverside, California. The pilot and two passengers received minor injuries. Visual meteorological conditions prevailed for the local flight and no flight plan was filed. The flight was destined for Corona Airport, Corona, California.
According to the pilot, the loss of engine power occurred less than 200 feet agl. He attempted an auto rotation and landed hard. Postaccident examination of the engine revealed that the 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.
This accident is documented in NTSB report LAX97LA224. AviatorDB cross-references NTSB investigation data with FAA registry records to provide comprehensive safety information for aircraft N99YC.
Accident Details
Probable Cause and Findings
failure by unknown maintenance personnel to retorque the nuts on the retainer cover.
Aircraft Information
Registered Owner (Current)
Analysis
On June 25, 1997, at 1243 hours Pacific daylight time, an Enstrom F-28-F helicopter, N99YC, was substantially damaged after a loss of power during a takeoff/climb at Riverside, California. The pilot and two passengers received minor injuries. Visual meteorological conditions prevailed for the local flight and no flight plan was filed. The flight was destined for Corona Airport, Corona, California.
According to the pilot, the loss of engine power occurred less than 200 feet agl. He attempted an auto rotation and landed hard. Postaccident examination of the engine revealed that the 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. The pilot stated that there were internal star washer imprints on the cover plate that is commonly caused by the torque or tightening of the nut. The helicopter had 61.5 total hours since new and received one inspection at 50.9 hours since delivery to the owner/pilot.
The owner/pilot changed the oil and filter prior to the formal 50-hour inspection by a private contractor. The inspection form revealed no specific inspection of the retainer plates are required except for a general condition inspection of the engine, accessories, and of the fluid systems for leaks.
Data Source
Data provided by the National Transportation Safety Board (NTSB). For more information on this event, visit the NTSB Records Search website. NTSB# LAX97LA224