What happened
On the evening of 30 November 2022, a DJI Matrice 300 RTK remotely piloted aircraft, registered ZT-WWH, was conducting night aerial surveillance at the Simunye Colliery in Secunda, Mpumalanga. The operation was being performed under visual line of sight (VLOS) protocols for industrial monitoring.
Following a successful pre-flight inspection and a manual test at low altitude, the pilot ascended the aircraft to approximately 120m (394 feet) AGL. While the drone was hovering, the pilot and ground crew heard a loud screeching noise. Immediately following this sound, the aircraft suffered a total loss of control and entered an uncontrolled descent, impacting the ground. The impact resulted in the destruction of the aircraft, though no injuries to persons or damage to ground property were reported.
The investigation
SACAA AIID examined the wreckage and the digital flight logs of the drone. The investigation confirmed that the aircraft's maintenance was up to date, with the most recent check performed less than a month before the accident. The pilot held a valid Remote Pilot Licence and the necessary medical certification.
Analysis of the flight data revealed that the aircraft experienced a specific propulsion error while at altitude. The logs indicated that the drone attempted to stabilize itself while tumbling downward at a vertical speed of approximately 22.4 kph. The investigation concluded that the incident was not caused by pilot error or incorrect manual inputs.
Findings
- The primary cause of the accident was a propulsion error occurring at 120m AGL.
- This error was likely triggered by a malfunction within either the motor or the Electronic Speed Control (ESC).
- The aircraft was operating with 94% battery power at the time of the failure.