The UAS, a DJI M600 Pro, was being operated in an automated flight mode to survey a construction site when a GPS-compass error caused the aircraft to revert to a flight mode that required manual control. By the time that the pilot and observer realised that it was not responding to the return-to-home (RTH) function, visual line of sight was lost when the aircraft drifted with the wind beyond a line of trees. It subsequently collided with the roof of a house before falling into the property's rear garden. No persons were injured.
The pilot, and the observer who was also a pilot, had operated UASs since 2018 and had the required permissions from the UK CAA. Both pilots had relied predominantly on the automated flight capability of their aircraft and had not, nor were required to have, practised for emergencies since completing their flying training in 2018.
One Safety Recommendation is made to the UK CAA to require that operators issued with a Permissions for Commercial Operations (PfCO) include in their operations manuals the need to practise routinely the actions to take in the event of emergencies, and specify how pilots will remain competent at maintaining manual control of their aircraft in the event that automated flight modes are lost.
