Primary finding
Probable cause
a loss of engine power due to a malfunctioning thermostat valve in the liquid cooling system.
Investigator assessment
Analysis narrative
According to the pilot's statement, the converted Ford V6 automotive engine overheated and seized when a malfunctioning thermostat valve allowed excess pressure to build up inside the coolant system. The resulting overpressure blew out a plug in a coolant outlet from the block, which is unused in this installation. The coolant was then pumped overboard and the engine seized. The aircraft collided with fence posts during a forced landing onto a road.
Source record
Factual narrative
On March 23, 1996, at 1230 hours Pacific standard time, a homebuilt Scheperle Mustang II Mod, N8180T, collided with ground obstructions during a forced landing attempt near Merced, California. The forced landing was precipitated by a loss of engine power. The aircraft was owned and operated by the pilot and was on a personal cross-country flight from Fresno to Napa, California. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was destroyed in the collision sequence. The pilot and passenger onboard sustained minor injuries. According to the pilot's statement, the converted Ford V6 automotive engine overheated and seized when a malfunctioning thermostat valve allowed excess pressure to build up inside the coolant system. The resulting over pressure blew out a plug in a coolant outlet from the block, which is unused in this installation. The coolant was then pumped overboard and the engine seized. The aircraft collided with fence posts during the forced landing attempt on a road. -