What happened
On 6 October 2019, a DJI Matrice 210 was being operated in manual flight mode over the Backwarden Nature Reserve in Danbury, Essex. The flight was being conducted in support of police operations. While the aircraft was hovering at an altitude of approximately 54 metres, the ParaZero SafeAir M200 ballistic recovery parachute system activated without warning.
Following the deployment, the aircraft's motors ceased operation, and the drone descended under the parachute until it became stuck in a tree. While the pilot initially believed no damage had occurred upon landing, the aircraft sustained damage during the recovery process from the trees. At the time of the incident, the aircraft's batteries were at 87% charge.
The investigation
The investigation involved a detailed analysis of the flight logs from both the aircraft and the parachute system. The parachute manufacturer conducted various tests, including 24 hours of continuous vibration testing and flight tests using a similar DJI Matrice 200 model. These tests failed to replicate the unexpected deployment or identify any mechanical or electronic malfunctions within the parachute system.
The AAIB reviewed the onboard data and noted that the aircraft's flight log ended abruptly. While the aircraft manufacturer suggested a hardware issue or an internal power failure might have occurred, they did not provide further supporting evidence. The investigation also noted that the aircraft's battery compartment module, batteries, and a power board were replaced during subsequent repairs.
Findings
- The investigation could not definitively determine if the parachute system activated erroneously, cutting power to the motors, or if an in-flight failure on the aircraft triggered the deployment.
- There was a discrepancy in the timing of acceleration data between the aircraft and the parachute system, making it difficult to correlate the exact moment of failure.
- The aircraft's flight log ended suddenly, and while a power failure could have triggered the system, a false-positive activation by the parachute system could not be ruled out.
Safety action
- The parachute manufacturer is aware of the data synchronization challenges between their system and the DJI Matrice 200 series. New designs for the DJI Matrice 300 series will feature direct communication with the aircraft to allow power to remain active for continued data logging and more accurate synchronization.