What happened
On the evening of 26 April 2023, an Arace Sirin unmanned aircraft system, registered ZT-YJG, was performing a beyond visual line of sight (BVLOS) surveillance mission at the Sibanye Stillwater mining site in the Hexriver dumping area, Rustenburg. The flight was being conducted under Part 101 regulations.
Approximately 18 minutes after takeoff, the pilot received an urgent text message on a cellular phone from a team member. While attempting to read the message, the pilot accidentally pressed the acrobatic (ACRO) button on the remote control station. This action transitioned the aircraft from its stable GPS flight mode into ACRO mode, which requires manual stick input to maintain attitude.
As the pilot attempted to revert the aircraft to GPS mode, the Arace Sirin entered a steep dive. The airspeed increased rapidly, and the link between the remote station and the aircraft was lost. The drone impacted the ground, resulting in a post-impact fire—likely caused by a battery explosion—that destroyed the aircraft. No injuries to personnel or damage to ground property were reported.
The investigation
SACAA AIID investigators confirmed that the pilot held a valid Remote Pilot Licence with the necessary BVLOS ratings and a current medical certificate. The aircraft's maintenance records showed it had undergone a mandatory periodic inspection recently and was within its operational airframe hour limits.
Investigators noted that the flight log was lost due to the fire at the crash site. The investigation also reviewed the technical specifications of the ACRO mode, noting that unlike GPS mode, this setting does not provide automatic leveling or position holding, making it highly sensitive to pilot input.