What happened
This accident occurred during the second leg of a non-scheduled cargo operation. The flight had commenced the previous evening, with a refueling stop occurring approximately three and a half hours into the mission. Following a one-hour period on the ground for fuel, the aircraft departed for its final destination.
As the flight approached its destination, the crew initiated a cruise descent roughly 39 miles from the airport. The pilots notified air traffic control that they were performing a wide base turn and were subsequently granted clearance for a visual approach and landing. While the crew acknowledged the landing instructions, no additional radio communications were made. The aircraft was briefly tracked on radar on final approach before contact was lost.
Shortly before reaching the runway, the aircraft struck trees and terrain approximately 0.5 miles short of the threshold, eventually coming to a stop in a parking lot belonging to a trucking company. The impact was followed by a fire. Investigation of the wreckage showed the landing gear was extended during the collision, though the state of the wing flaps remained undetermined. Discrepancies in propeller blade angles were attributed to the impact sequence and the encounter with the wooded area.
Findings
Analysis of radar data indicated that the airspeed of the aircraft decreased to between 70 and 75 knots during the final approach. This velocity was at or below the aerodynamic stall speed for the aircraft in its landing configuration.
No mechanical failures involving the engines, propellers, or airframe were identified. However, investigators determined that the flight crew's performance was likely compromised by fatigue. This impairment was attributed to the extended duration of the overnight flight schedule and the timing of the approach, which occurred during the circadian low. This fatigue likely prevented the crew from maintaining sufficient airspeed and recognizing the onset of an aerodynamic stall.