What happened
On 16 March 2019, a DJI Matrice 210 was being used for a commercial filming operation at an outdoor athletics event in Temple Newsam, Leeds. The mission involved capturing video of a cross-country championship attended by hundreds of people. While the aircraft had been flying successfully earlier in the day, rainfall intensified during the flight.
As the pilot attempted to return the aircraft to the landing site due to the worsening weather, the drone began to wobble. While descending at a height of approximately 3 m, the aircraft suddenly flipped upside down and struck the ground. The impact caused significant damage to the propellers, rotor arms, and the camera payload. There were no injuries to any persons on the ground.
The investigation
The investigation examined the aircraft's flight data and physical condition. Analysis of the onboard logs revealed fault messages regarding the No 4 motor electronic speed controller (ESC) and a 'link down' message for the No 3 ESC. Upon physical inspection, investigators found evidence of liquid residue and moisture ingress on the No 3 ESC circuit board.
While the manufacturer identified a failure in the No 4 ESC as the primary cause, the investigation noted that the manufacturer's IP43 rating for the Matrice 200 series was not tested with propellers installed, potentially leaving the ESC chambers vulnerable to moisture. The investigation also reviewed the risks associated with flying such aircraft over people, noting that a falling drone of this mass could cause fatal injuries.
Findings
- The primary cause of the accident was a fault in the No 4 motor ESC.
- Moisture was present on the No 3 ESC circuit board, likely entering through unsealed areas near the antenna case during the increased rainfall.
- The aircraft's IP43 protection rating may not have been fully validated for real-world conditions involving propellers and active rain.
- The flight occurred in an environment where the aircraft was positioned over people, presenting a high risk of injury should a technical failure occur.
Safety action
- The AAIB made a recommendation to the CAA to notify users of the Matrice 200 series regarding the risk of moisture ingress and sudden loss of control during rain.
- A recommendation was also made for the CAA to define specific conditions required for the safe overflight of people using unmanned aircraft.