N51MJTolle Alan E VANS TOLLE RV-6A · 1991

On March 8, 2015, about 1520 Pacific daylight time, a Vans RV-7A, N51MJ, experienced a total loss of engine power during descent to Dayton Valley Airpark (A34) Dayton, Nevada. The commercial pilot and passenger sustained minor injuries; the airplane sustained substantial damage to the right wing and rudder. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was operated on a visual flight rules flight plan. The flight originated from Auburn Municipal Airport (AUN), Auburn, California at an unknown time.

The pilot reported that he departed the airport and cruised at 11,500 feet. About 10 miles from his destination airport he started the descent to the traffic pattern altitude of about 6,000 feet. About 3 miles from the airport, he realized that the engine had quit without any indications or warning. The propeller was still windmilling, and he checked the engine gauges; the oil pressure and temperature was good. He switched fuel tanks and tried to restart the engine, but to no avail. Unable to make the runway, he landed in a field just short of the runway surface. The main landing gear touched down uneventfully; when the nose wheel touched down, the airplane flipped onto its back and came to rest.

Postaccident examination of the engine by a Federal Aviation Administration Inspector revealed no anomalies that would have precluded normal operations.

During a post-accident telephone conversation with the pilot, he reported that he usually keeps the mixture control lever about ½ to ¾ of the way out almost the entire time he flies. He stated that the airplane operates best at this mixture level, and the only time he ever needs to change it is while flying above 14,500 feet.

Review of the Lycoming Operator's Manual for the O-360 and associated models revealed "Improper fuel/air mixture during flight is responsible for engine problems…," "On engines with manual mixture control, maintain mixture control in "Full Rich" position for rated takeoff, climb, and maximum cruise powers (above approximately 75%)". The operator's manual also states, "Always return the mixture to full rich before increasing power settings."