On February 12, 1993, a Boeing A75N1 (registration N62733) operated by Grauf Flying Service, Inc. was involved in an aviation accident near Hughson, CA. Investigators recorded the probable cause as: The fracture of an engine intake valve, which resulted in a loss of engine power and a subsequent forced landing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A light aircraft suffered a loss of power shortly after takeoff from a private airstrip due to a fractured engine intake valve, resulting in a nose-over landing.
What happened
The incident occurred shortly after the airplane departed from a privately owned airstrip. Immediately following departure, the engine began running roughly before experiencing a complete loss of power. The pilot attempted to execute an emergency landing in a nearby cultivated open field. Upon touchdown, the main wheels sank into the soft terrain, causing the aircraft to nosed over.
The investigation
A post-acc examination of the aircraft's engine was conducted to determine the cause of the power loss. The inspection revealed that an intake valve had fractured during operation. This mechanical failure is consistent with the reported rough running and subsequent loss of power experienced by the pilot during the initial climb phase.
Findings
The primary factor contributing to the accident was the structural failure of the engine's intake valve. The fracture led to a catastrophic loss of engine power, leaving the pilot with no option but to land in an unprepared area. The soft ground conditions of the cultivated field exacerbated the damage by causing the nose gear to collapse upon impact.
Probable cause
The fracture of an engine intake valve, which resulted in a loss of engine power and a subsequent forced landing.