Accident Summary
On 22 August 2023 at 02:02:44 Zulu time, an unmanned MQ-9A Reaper, tail number 14-4267, impacted and departed Runway 08 at Kanoya Air Base, Japan. The collision sheared off a portion of the left wingtip, bent the propeller blades, and collapsed the landing gear, resulting in the complete loss of the aircraft. The mishap aircraft was operated remotely by a Launch and Recovery Element consisting of a mishap pilot and a mishap sensor operator. There was no reported damage to civilian property, no injuries, and no fatalities. The loss of government property was valued at $21,500,000.
Sequence of Events
At 02:02:11 Z, the aircraft's landing gear touched down normally on the runway. The mishap pilot moved the throttle lever in the ground control station to the ground idle position per procedure, and the aircraft began to decelerate. Three seconds later, the ground control station lost uplink to the aircraft, indicated by a loud audible beep, a red display warning showing "LOS uplink-LOST", and the camera switching from daylight TV to infrared. The aircraft entered high speed lost link logic (HSLLL), automatically setting engine power to full to initiate a go-around maneuver without pilot input. The pilot's throttle lever remained in the ground idle position. The HSLLL accelerated the aircraft to takeoff airspeed, and it lifted off the runway. Six seconds after liftoff, uplink was restored. Control automatically transferred back to the pilot, and the aircraft reverted to the ground idle throttle position. This caused the airspeed to drop, resulting in a stall. Four seconds after uplink restoration, the aircraft stalled and began to descend. At 02:02:40 Z, 17 seconds after liftoff, the pilot commanded the throttle lever full forward and a steep pitch up. This excessive pitch increase exacerbated the stall. At 02:02:44 Z, the aircraft impacted the runway and came to rest in the infield.
Causes and Contributing Factors
The Abbreviated Accident Investigation Board President found, by a preponderance of the evidence, that the mishap had two causes: (1) the loss of uplink from the ground control station to the aircraft upon landing touchdown, and (2) the pilot's failure to execute the go-around procedure and the sensor operator's failure to verify the throttle and pitch setting while the aircraft lost uplink and executed a high speed lost link logic go-around. Additionally, three factors substantially contributed to the mishap: (1) a poor environment for datalink integrity, (2) the mishap crew overlooked a caution/warning, and (3) once the pilot recognized the aircraft was in a stall, the pilot over-controlled the aircraft, exacerbating the stall.
Conclusion
The investigation concluded that the accident resulted from a combination of a loss of uplink and crew errors during the go-around. No other causes or contributing factors were identified.