What happened
On 2 August 2022, a DJI Matrice 200 (registration ZT-XDC) was conducting a Beyond Visual Line of Sight (BVLOS) surveillance mission at the Gamsberg Mine in the Northern Cape. The mission involved flying a manual grid pattern over a tailings dam.
As the flight progressed, the pilot noted that battery levels had dropped to approximately 43% and initiated the Return-to-Home (RTH) function to return to the launch point. While the aircraft was roughly 428 metres from the pilot, it began to shake violently. The pilot observed the aircraft enter a right-hand spiral toward the earth. Despite immediate attempts to regain manual control and correct the descent using the control sticks, the aircraft could not be stabilized and impacted the ground. The impact resulted in the destruction of the aircraft, though no injuries were reported to personnel on the ground.
The investigation
The investigation examined the pilot's credentials, the aircraft's maintenance history, and the flight telemetry. The pilot held a valid Remote Pilot Licence and a current medical certificate. Records indicated that a mandatory periodic inspection had been performed on the aircraft earlier that year, with no propulsion system issues noted at that time.
Analysis of the flight logs revealed that the pilot was operating under pressure to complete the surveillance tasks, which led to suboptimal mission planning. During the critical Return-to-Home phase, the pilot's attention was divided as they began preparing new batteries for a subsequent flight, reducing the level of focus on the aircraft's telemetry and position.
Findings
- The aircraft experienced erratic yawing and a continuous right-hand spin during the descent.
- A failure of an Electronic Speed Controller (ESC) is the most likely cause of the uncontrolled descent.
- The pilot's focus on preparing for the next flight leg contributed to a reduction in monitoring the aircraft's flight path during the RTH sequence.