What happened
On 11 June 2019, a DJI Matrice 210 was being operated by the police for emergency services duties over a congested area at Hammond Court, Norwich. The unmanned aircraft, equipped with both thermal and optical imaging cameras, had ascended to an altitude of approximately 80 meters.
After maintaining a stable hover for nearly ten minutes with a battery level of 68%, the aircraft's cameras began to rotate unexpectedly. Simultaneously, a 'motor overload' alert appeared on the pilot's display. Following this alert, the drone entered an uncontrolled anticlockwise spin and descended rapidly, eventually crashing in an open space. The impact resulted in the destruction of the aircraft, specifically damaging the motor arms, body, battery casing, and cameras. There were no injuries to persons and no damage to property.
The investigation
The investigation was based on the aircraft accident report submitted by the pilot. The pilot had assessed the weather conditions prior to flight and determined that the light rain forecast fell within the manufacturer's operational parameters.
During the post-accident review, the pilot suggested that the failure might have been linked to a motor or Electronic Speed Controller (ESC) malfunction. The pilot also noted that the thermal camera was positioned away from the aircraft's centre of gravity, which may have introduced additional load to the propulsion system. The pilot also highlighted the extreme lack of warning, noting that control was lost only one second after the error message appeared.