Accident Overview
A contract cargo flight operating under Instrument Flight Rules (IFR) at night departed on a scheduled route. About one minute after takeoff, the tower controller notified the pilot that the aircraft was transmitting an incorrect transponder code. The pilot reset the transponder to the correct code, but was again advised of the discrepancy. He then realized he had selected the wrong transponder unit and switched to the correct one.
Sequence of Events
During the time the pilot addressed the transponder issue, the aircraft drifted approximately 30 degrees to the right of its assigned heading. The pilot corrected the heading as he established communication with the departure controller. The departure controller cleared the aircraft to continue its climb and instructed a left turn of about 120 degrees, which the pilot executed. Approximately 40 seconds after initiating that left turn, while climbing straight ahead through an altitude of about 4,700 feet above ground level, the controller instructed a further left turn of 20 degrees. Almost immediately afterward, the aircraft began a right turn and then suddenly entered a rapidly descending right turn. The aircraft ultimately impacted the terrain in a nearly wings-level attitude with a nose-down angle greater than 45 degrees. At impact, the aircraft's heading was about 220 degrees to the right of its last stabilized course.
Investigation Findings
The investigation found no evidence of airframe, control system, or engine mechanical failure or malfunction that would have precluded normal flight. Autopsy and toxicological information could not be obtained due to the high energy released upon impact. The determination of the initiating event that led to the uncontrolled descent could not be established.