Synopsis
A Boresight BQ400 Raider LR unmanned aircraft (UA) operating under the A3 Open Category experienced a loss of control shortly after being armed at Throckmorton Airfield, Worcestershire on 6 February 2025. The UA took off, climbed, veered away, and could not be steered via the pilot's controller. The pilot activated a termination function, causing the UA to fall approximately 320 m from its takeoff point. The UA struck the ground about 4 m from an uninvolved person, who was not injured. The UA was destroyed, with damage to its rotors and rotor arms.
History of the Flight
The flight was intended to support the development of processes for testing a ground-based product. The planned flight path was along one of the disused runways at Throckmorton, maintaining a horizontal distance of at least 150 m from residential, commercial, or recreational areas as required for A3 Open Category operations. The operator had conducted thirteen previous uneventful flights with this UA type; the accident flight was the first flight of this particular UA.
A flight team comprising a pilot and two observers prepared the UA at the intersection of two disused runways. Communication with the control system was established normally. Weather conditions included a gentle northerly breeze, visibility of about 600 m, and a temperature of 1°C. When the UA was armed for flight, it immediately took off and climbed to an estimated height of 20 m before veering west. The pilot attempted to command the UA via his controller but received no response. He then used a disarm function on a laptop hosting the control system, which successfully terminated the flight. The two observers ran toward the falling UA.
Aircraft Information
The BQ400 Raider is a quadcopter with a takeoff mass of 1.3 kg, powered by four electric motors. It is marketed as a disposable low-cost target for training and testing. The operator had attached a 3 m rope with a small metal weight to serve as a manual altitude indicator for the pilot; the combined weight was 122 g. Although this modification was novel, it had been used without incident on previous flights and there was no evidence to suggest it contributed to the accident.
Regulation
UAS operations in the UK are governed by UK Regulation (EU) 2019/947 and associated guidance. The pilot held a valid CAA Flyer ID. The planned flight path's horizontal distance from residential, commercial, industrial, or recreational areas exceeded the 150 m requirement for A3 Open Category operations.
Conclusion
The operator believes that the abnormal flight behavior was caused by a fault with the UA, which was brand new at the time of the accident. The root cause of the technical fault had not been determined at the time the investigation report was published. As a safety action, the operator has begun providing advance notification to businesses near the test site when UAS test flights are scheduled.