What happened
Prior to the accident, the pilot arrived at the airport to perform a quick turnaround, which included refueling the aircraft and loading cargo. During this period, the pilot interacted with three employees at the fixed base operator, who noted that the pilot appeared awake and alert. After the necessary fuel and cargo were secured, the flight departed. Approximately one minute after takeoff, the aircraft crashed.
At the time of the incident, the flight was operating under night visual meteorological conditions. Data from a GPS and simulation study of the aircraft performance revealed that the plane entered a right bank immediately following liftoff. The aircraft performed a 4-degree right turn and continued to accelerate, with groundspeed increasing from approximately 75 knots at liftoff to roughly 145 knots at the moment of impact. The aircraft reached a maximum altitude of approximately 260 feet above the ground while climbing at a rate of 500 to 700 feet per minute before beginning its descent.
Findings
An examination of the engine and airframe showed no mechanical failures or malfunctions that would have prevented the aircraft from operating normally. The gas generator speed remained steady at approximately 93 percent throughout the flight. Analysis of the load factor vectors suggests that the pilot may have experienced a somatogravic illusion, perceiving a climb while the aircraft was actually descending. Given the combination of degraded visual references at night and these physical forces, it is believed the pilot suffered from spatial disorientation, resulting in an unintentional descent into the terrain.