Mooney M20C N6581U accident near Lewisburg, West Virginia

Probable cause

The pilot's failure to maintain airspeed while maneuvering, which resulted in the airplane exceeding its critical angleofattack and experiencing an aerodynamic stall. Contributing to the accident were abnormal engine operation due to improper magneto-to-engine ignition timing and the pilot's failure to have the airplane inspected before the flight as required by the special flight permit.

NTSB analysis

The private pilot/owner purchased the airplane 1 month before the accident flight; the airplane had no associated maintenance logs. The pilot applied for and received a special flight permit to ferry the airplane to a facility where maintenance could be performed with the stipulation that a qualified mechanic inspect the airplane before the flight to ensure that it was safe for flight; however, the pilot failed to have this inspection performed.

According to one witness, the taxi, takeoff roll, and initial climb of the accident flight appeared and sounded normal. After reaching about 200 ft above ground level, the airplane leveled off and continued to fly over the runway centerline. Before reaching the end of the runway, the airplane entered a slight left bank, which quickly steepened; the airplane's nose dropped and then returned to a level attitude before it descended out of view. Another witness stated that, about the time that the airplane entered the left bank, it sounded like the engine had lost power but that, shortly thereafter, full engine power appeared to have been restored. A third witness stated that the airplane descended as it oscillated left to right at a relatively steep angle, leveled again, and pitched up and then down just before impact.

Postaccident examination of the airframe revealed no evidence of any mechanical anomalies. During examination of the engine, the magneto-to-engine ignition timing was found to be significantly out of specification for both magnetos, which likely resulted in abnormal engine operation during the climb and may account for the observed leveling off of the airplane just after takeoff; however, it could not be determined whether this was due to reduced engine power output or the pilot's response to an observed anomaly. The witnesses' observations of the takeoff and left turn indicated that the pilot may have been maneuvering for a forced landing or returning to the airport. Their observations are also consistent with the pilot failing to maintain adequate airspeed and the airplane exceeding its critical angle-of-attack and experiencing a subsequent aerodynamic stall.

Text from the NTSB. Open the NTSB docket for ERA15FA049 for the full record.