LANGLEY AIR FORCE BASE, Va. – -- An Air Combat Command Accident Investigation Board completed its investigation into an RQ-4B that crashed into a field near Grand Forks Air Force Base, North Dakota, August 6, 2021.
Around 6:16 a.m. local time, the aircraft was flying a mission in the local military operating area when the mission control element experienced a workstation lockup, requiring the aircraft to return to base on an autonomous, preprogrammed route. However, the aircraft did not descend as planned because the mission control element pilot failed to sever the ground communications interface with the RQ-4 before it reached the initial approach fix. This initiated the aircraft’s autonomous missed approach route.
As the aircraft began the missed approach route, it descended, passing over the final approach fix. When the aircraft passed the final approach fix, the mission control element pilot disconnected the ground communications interface. Soon thereafter, a second pilot in the launch and recovery element and an instructor pilot reestablished connection with the aircraft.
The launch and recovery element pilot did not configure his workstation in a timely manner, delaying positive control of the aircraft. Instead of commanding a new flight route to the aircraft, the pilot commanded an altitude override command, which resulted in the RQ-4 being approximately 4,000 feet too high at the final approach fix. Neither the launch and recovery element pilot nor instructor pilot were aware of the discrepancy in altitude. Additionally, the launch and recovery element pilot and the instructor pilot were not aware of the missed approach logic, which required starting a new flight route after crossing the final approach fix a second time. The aircraft commenced an approach to land at Grand Forks Air Force Base, but overshot the base and crashed into a farm field 6.8 miles north of the runway.
The AIB president found that the cause of the crash was both the pilot’s incorrect selection of aircraft flight commands, which resulted in the aircraft’s controlled flight into terrain, and the instructor pilot’s failure to provide sufficient inputs to the pilot to prevent the aircraft’s controlled flight into terrain.
Additionally, the president found that the mission control element pilot failed to follow established procedures, resulting in the aircraft’s delayed descent and preprogrammed selection of a go-around/missed approach route, significantly contributing to the mishap. Similarly, the pilot workstation lockup, including the lack of documented procedures regarding requesting numerous detailed status requests within a short timeframe, resulted in the mission control element pilot’s inability to positively control the aircraft, resulting in the aircraft’s execution of preprogrammed logic and return to base, which significantly contributed to the mishap.
The aircraft, valued at approximately $64 million when acquired in 2012, was destroyed. There were no reported injuries or fatalities.
For more information, contact Air Combat Command Public Affairs at (757) 764-5007 or via email at accpa.operations@us.af.mil.