Cessna 501 N212M accident near Detroit Lakes, Minnesota

Probable cause

A loss of airplane control due to an undetermined avionics malfunction and the pilots’ inattention, which resulted in excessive airframe forces during the unusual attitude recovery. The reason for the avionics malfunction could not be determined because postaccident testing did not reveal any anomalies that would have precluded normal operation.

NTSB analysis

While climbing on a night, instrument departure, with the autopilot most likely engaged, the airplane entered into an unusual attitude. Although both pilots recalled a left climbing turn that transitioned into a left descending spiral, air traffic control radar information indicated a right climbing turn that transitioned into a right descending spiral. Both pilots stated that their attention had been focused away from the attitude indicators during the time immediately before the unusual attitude began. The pilot-in-command disconnected the autopilot and recovered the airplane by referencing the standby instruments. During the recovery, as the pilot pulled up from the nose-low attitude, both wings sustained structural damage.

Examination of the airplane revealed that the nose radome quick release latches were not water tight and that gaps in these latches allowed precipitation to enter the forward avionics bay. Although, avionics testing did not reveal any anomalies consistent with an uncommanded flight maneuver by the autopilot, moisture conditions were not introduced during any of the tests. While it is possible that the moisture caused a malfunction of the avionics, it could not be definitively determined.

Text from the NTSB. Open the NTSB docket for CEN13FA101 for the full record.