What happened
On 29 November 2023, an unmanned MQ-9A, tail number 13-4226, experienced a critical propulsion system anomaly shortly after takeoff. The aircraft was being operated remotely by a Launch and Recovery Element from the 12th Expeditionary Special Operations Squadron, part of Air Force Special Operations Command (AFSOC), within the United States Africa Command (AFRICOM) Area of Responsibility.
Following a normal takeoff sequence, the pilot transitioned from autopilot to manual control. Approximately 14 seconds after liftoff, the aircraft experienced a sudden drop in engine torque. This loss of power led to an immediate reduction in airspeed and an inability to maintain altitude, triggering 'Aileron Tip Stall Override' warnings on the heads-up display. The pilot attempted to manage the stall by lowering the nose and identified a nearby area of debris as the safest site for a forced landing. Roughly 44 seconds after takeoff, the aircraft impacted the ground several miles east of the runway, resulting in the complete loss of the MQ-9A. There were no fatalities and no reported injuries or damage to civilian property.
The investigation
The Abbreviated Accident Investigation Board examined the mechanical systems and maintenance history of the aircraft. Investigators found that all preflight procedures, mission planning, and maintenance inspections were performed correctly, and the aircraft was not overdue for any scheduled services.
Because the aircraft was destroyed during the forced landing, investigators were unable to perform a direct physical inspection of the engine components. To compensate, the manufacturer conducted re-creation testing to identify potential failure points within the Fuel Control Unit (FCU). This testing narrowed the possible mechanical origins down to two specific internal issues: a torque motor failure or a pressure failure in the P3 line.
Findings
- The primary cause of the mishap was an undetermined mechanical failure within the Fuel Control Unit (FCU), which triggered a sudden decrease in fuel flow and a subsequent loss of engine torque.
- This reduction in fuel flow prevented sufficient combustion, leading to the loss of altitude and aircraft stabilization.
- Due to the lack of wreckage for forensic analysis, the exact nature of the failure within the FCU could not be definitively established.