What happened
On 3 August 2021, at approximately 23:37 UTC, a DJI Matrice 300 RTK was being operated over Seymour Grove, Old Trafford, Manchester. The unmanned aircraft system (UAS) was engaged in commercial operations, specifically supporting Rescue and Fire Fighting Services (RFFS) in an effort to locate a missing person.
During the night-time mission, the aircraft had been airborne for roughly nine and a fraction minutes. While maintaining an altitude of 63 metres, the pilot and observer heard a sudden audible pop or bang. Immediately following this sound, the aircraft entered a three-rotor emergency landing sequence. The drone followed a rapidly descending arc before impacting the ground, resulting in the destruction of the aircraft.
The investigation
Following the incident, the aircraft and its digital logs were examined. An analysis of the flight data and a physical inspection by the UAS manufacturer revealed that the left rear frame arm had folded backward during the flight. This movement caused the arm to strike the motor, which subsequently led to the failure of the rotor and the activation of the emergency landing mode.
Findings
- The investigation established that the primary cause of the crash was the failure of the locking collar at the junction of the frame arm.
- There was a high likelihood that this locking collar had not been sufficiently tightened prior to flight, allowing the arm to fold back under operational conditions.