What happened
During a night cargo operation, an aircraft departed into weather conditions characterized by haze and an overcast ceiling. Shortly after takeoff, the aircraft began executing significant deviations in airspeed, altitude, and heading. When air traffic control questioned the erratic flight path, the pilot reported experiencing issues with the aircraft's instruments. An attempt was made to return to the departure airfield, but the aircraft entered a near-vertical descent and struck the terrain.
Findings
Investigation into the aircraft's electrical systems revealed that the inverter system, which provides power to the pilot's flight instruments, was not functioning at the time of impact. This specific aircraft was one of only two in the operator's fleet equipped with an inverter system. The loss of electrical power rendered the pilot's attitude indicator and horizontal situation indicator inoperative, displaying warning flags on the panel.
While the co-pilot's vacuum-powered instruments remained functional, the pilot likely experienced spatial disorientation due to the combination of marginal visibility and the loss of primary flight instrumentation. The pilot's history of procedural and flying skill deficiencies was noted, suggesting a failure to either activate the inverter during pre-flight or switch to a secondary inverter during the flight. Although toxicology reports showed trace amounts of ethanol and morphine, the ethanol levels were likely postmortem, and the impact of morphine on the pilot's impairment could not be determined. The high-energy nature of the crash was consistent with a loss of control following disorientation.