What happened
On the morning of 30 September 2022, a DJI Phantom 4 (registration ZT-UKH) was conducting an aerial mapping mission over the Cooke Randfontein Surface Operations mine dump in Gauteng. The flight was being operated under beyond visual line of sight (BVLOS) regulations during clear daylight conditions.
After successfully completing two surveillance passes, the aircraft encountered issues during its third flight. Approximately five minutes into the mission, the pilot observed the drone had ceased all movement on the controller unit. Attempts to regain control via the return-to-launch (RTL) function and the manual attitude (ATTI) mode were unsuccessful. The pilot subsequently located the aircraft on the ground, roughly 0.3 nautical miles from the launch point. The impact resulted in substantial damage to the camera and landing skids, though no injuries were reported on the ground.
The investigation
SACAA AIID investigators examined the aircraft's maintenance history and flight logs. Records indicated that the drone had experienced similar issues recently; specifically, maintenance entries from late August 2022 noted uncommanded landings and weak GPS signals. Although a technician had replaced the GPS tracking module and updated the firmware just weeks prior to the accident, the instability persisted.
Findings
- The investigation determined that a secondary GPS tracking module (a Trackimo device) was mounted on top of the aircraft.
- This secondary device interfered with the primary GPS signals of the DJI Phantom 4, leading to degraded signal strength and flight instability.
- The placement of the tracking module caused erroneous GPS data recording within the flight logs.