What happened
On 8 February 2020, a DJI Inspire 2 was being operated for aerial work at a construction site located at Sampson House, London. The pilot had already completed five successful flights from a northern takeoff area that day but had relocated the takeoff and landing area (TOAL) to the southern quadrant to maintain safe distance from a crane.
During the initial flight checks of the sixth flight, the unmanned aircraft began behaving erratically. The pilot attempted an immediate landing, but the situation worsened when the landing gear was deployed. In an effort to move the aircraft away from nearby railways, roads, and buildings, the pilot attempted to climb and direct the drone toward the River Thames. However, the aircraft became uncontrollable and struck a concrete core located in the center of the site, resulting in extensive damage to the drone.
The investigation
The investigation examined flight logs and the circumstances surrounding the takeoff. While the pilot's pre-flight checks suggested a full GPS signal had been acquired and the home-point was correctly set, subsequent analysis of the flight data revealed that the home-point was actually set outside of the operational site. Furthermore, the logs indicated that the distance data recorded during the flight was inaccurate.
Investigators also found that the drone was experiencing poor GPS and compass signal strength from the start of the flight. The pilot noted that they may have overlooked the incorrect home position on the interface, potentially relying instead on the aircraft's navigational lighting and the automated messages indicating the drone was ready for flight.
Findings
- The primary cause of the loss of control was the drone failing to correctly establish the home-point, despite the pilot's perception that it was positioned correctly.
- Poor GPS and compass signal strength contributed to the erratic maneuvering and the subsequent fly-away behavior.
- Extensive safety mitigations were in place, including the use of a sterile operational zone and staff stationed to monitor the area, which prevented any risk to the public or vehicles during the collision.