Accident Sequence
The accident occurred on the first flight after a maintenance inspection. Company mechanics had left the flaps full down following the post-inspection. Witnesses observed the flaps in the full down position as the aircraft taxied for takeoff on runway 19L. After liftoff, the aircraft climbed steeply, reaching a pitch attitude of up to 60 degrees. It ascended to an estimated height of 200 to 500 feet above ground level before stalling and descending nose-down in a left turn. The aircraft crashed approximately 300 feet left of and 2,000 feet down the runway.
Investigation Findings
Examination of the wreckage revealed the flaps were fully extended. The scroll-type checklist was found positioned at the beginning of the takeoff check. The flight manual specifies a 10-degree flap setting for takeoff and prohibits takeoff with flaps full down. A review of previous DHC-6 accidents involving full-down flap takeoffs showed a pattern of steep climb and excessive pitch attitude leading to stalls. Additionally, the position of the control lock suggested it may have been in the locked position during the takeoff. The pilot, the sole occupant, was killed.
Probable Cause
The official finding stated that the pilot inadvertently misused the flaps by failing to set them to the proper setting; the flaps were set full down. This caused the aircraft to pitch up steeply after liftoff. Additionally, the flight control lock was probably installed during some portion, if not the entire flight, which prevented flight control operation. The pilot subsequently failed to maintain adequate flying speed and the aircraft stalled. Contributing factors were the pilot's inattention and his failure to adequately use the checklist.