On July 11, 2000, a Grumman G-164A (registration N897X) operated by Williams AG Service, Inc. was involved in an aviation accident near Gridley, CA. Investigators recorded the probable cause as: A partial loss of engine power due to the failure of an exhaust valve during an aerial application flight. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive; 1 related events involving the same aircraft type or operator are linked below.
An aerial application pilot experienced engine trouble, made a precautionary landing on a field road, and collided with a dirt berm during rollout. Engine inspection revealed a separated exhaust valve head.
Event Summary
While maneuvering during an aerial application flight, the pilot heard an unusual engine noise, experienced a loss of engine oil pressure, observed smoke, and lost partial power. The pilot made a precautionary landing on a nearby field road. During the landing rollout, the airplane collided with a dirt berm.
Engine Inspection
An inspection of the engine revealed that its No. 2 cylinder exhaust valve head had separated and subsequently broke the cylinder. The engine's total time was estimated at 9,300 hours, and it had been operated about 708.8 hours since last receiving a major overhaul.