What happened
On the night of 26 June 2023, an Arace Sirin unmanned aircraft system (UAS), registered ZT-YWO, was being operated for a surveillance mission on a private farm in Embalely, Mpumalanga. The flight was being conducted under beyond visual line of sight (BVLOS) regulations. While the pilot noted intermittent altitude reading glitches during the pre-flight phase, all other systems, including GPS acquisition and battery levels, appeared normal.
Approximately 22 minutes into the mission, the aircraft lost connection with the remote pilot station. The pilot attempted to restore the link by climbing atop a vehicle and later driving closer to the aircraft's last known position, but the connection remained unstable. Upon reaching the final recorded coordinates, the pilot discovered the Arace Sirin had crashed, resulting in substantial damage to the aircraft. There were no injuries to any persons on the ground.
The investigation
SACAA AIID examined the flight logs and coordinated with the manufacturer to determine why the aircraft failed to initiate its standard failsafe return-to-launch (RTL) procedure. While the pilot initially believed the aircraft had simply disconnected, a technical review of the downloaded data provided a different sequence of events. The investigation focused on the interaction between the ground station commands and the aircraft's automated response to those commands.
Findings
Technical analysis by the manufacturer revealed that the aircraft was not simply drifting away due to a signal loss, but was actively responding to new instructions. The investigation established that the UAS was receiving continuous updates to its home point setting from the ground station. The pilot was repeatedly changing the home point, which caused the aircraft, while in RTL mode, to navigate toward these newly updated coordinates. This continuous relocation of the target landing site caused the aircraft to fly further away from the operator until the eventual crash.