N201MMMooney M-18C 55 · 1955

On May 25, 2023, about 1846 Pacific daylight time, a Mooney M-18C, N201MM, was substantially damaged when it was involved in an accident near Napa, California. The sole occupant on board sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he departed Ed Carlson Memorial Field - South Lewis County Airport (KTDO), Toledo, Washington, for a multi-leg cross-country flight destined for Napa County Airport (KAPC). During the approach to land at KAPC, about 8 miles north of the airport and 3,000 ft agl, the engine lost all power. The pilot cycled the throttle control to full, but the engine did not restart and the propeller continued to windmill. He then declared an emergency and initiated a forced landing onto an open field about 5 miles north of runway 19R. During the landing roll on unimproved terrain, the left wing struck a large rock and came to rest nose down. Subsequently, the left wing sustained substantial damage. Recovery of the airplane revealed that the airplane had about 13 gallons of fuel in its main tank and 7 gallons in its auxiliary tank.

A postaccident examination of the airplane and engine did not reveal any preimpact mechanical anomalies. The fuel system was traced from each wing tank to the carburetor at the engine through the fuel selector, which rotated normally and was unobstructed. The fuel lines that had not been damaged from impact or removed to transport the airplane were secure.

Mechanical continuity of the engine was established throughout the rotating group, valvetrain, and accessory section as the crankshaft was manually rotated at the propeller by hand. Thumb compression was achieved at all four cylinders and the valves displayed normal lift when the crankshaft was rotated. Examination of the cylinders’ combustion chamber interior components using a lighted borescope revealed normal piston face and valve signatures, and no indications of catastrophic engine failure.

At 1754, the weather reported at KAPC, about 6 miles south of the accident site, included a temperature of 63°F and a dew point 52°F; the calculated relative humidity was about 67%. Review of the icing probability chart contained within FAA Special Airworthiness Information Bulletin CE-09-35 revealed that the atmospheric conditions at the time of the accident were "conducive to serious icing at glide [idle] power." The pilot added that he did not use carburetor heat during the descent and approach into KAPC and that he should have used a prelanding checklist.