An $11 million Air Force Reaper UAV stalled and spun to the ground because the pilot was fixated on completing a checklist, ignoring audible and visual stall warnings, according to the Air Force Aircraft Accident Investigation released Thursday. Immediately after receiving control of the aircraft from the launch team, the pilot of the unmanned turboprop was confused about the aircraft’s autopilot mode and disconnected the autopilot, while continuing to complete the handoff checklist. The Reaper’s stall protection is disabled in the manual, landing configuration mode. Then in manual flight mode, the pilot left the aircraft in a 9.5 degree nose-up attitude and 30% power, which led to a stall. Rather than lower the nose, the mishap pilot increased the power to full, which caused the aircraft to enter a spin.
In the incident report, the accident board found “that the cause of the mishap was the combination of the pilot’s misprioritization to complete the handover checklist, and the pilot’s failure to observe prior warnings of reduced energy state and stall, and timely implement stall recovery procedures.” The report continues, “By commanding landing configuration, the pilot was manually operating the aircraft. The pilot was responsible for monitoring altitude and air speed. The pilot was also responsible for taking precautionary measures to prevent the aircraft from stalling and taking corrective measures in the event the aircraft stalled. On two separate occasions in between 22:27:11 GMT and approximately 22:29:20 GMT, the pilot received visual and audible warnings that the aircraft was stalling. However, the pilot prioritized completing his handover checklist and increased airspeed instead of accomplishing the stall recovery checklist. As a result, the aircraft stalled and impacted the ground.”
