On August 18, 1994, at 2042 Pacific daylight time, an Aero Commander S2R airplane, N8843Q, collided with a highway signpost during a forced landing near Firebaugh, California. The forced landing was precipitated by a complete loss of power. The aircraft was owned and operated by Tri Air, Inc., of Firebaugh, California, and was engaged in an aerial application operation. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft incurred substantial damage to the left wing. The certificated commercial pilot, the sole occupant, was not injured. The flight originated from the Firebaugh airport on the evening of the accident at about 2030 hours as a local area aerial application flight. The pilot stated he was in cruise flight when the engine lost all power. He landed on the shoulder of a major interstate highway and the left wing collided with a highway signpost. Postaccident inspection of the aircraft revealed that the number 2 cylinder head was cracked.