What happened
On the evening of 29 April 2023, a surveillance flight involving a remotely piloted aircraft (RPA), registration ZT-XVM, ended in a crash in Vrede, Free State. The flight was being conducted under beyond visual line of sight (BVLOS) regulations during night-time visual meteorological conditions.
Following a successful pre-flight inspection, the Arace Sirin was launched at 1950Z with 98% battery power. As part of a standard stealth procedure for the surveillance mission, the pilot deactivated the aircraft's navigational lights once it reached 150 feet above ground level. Approximately ten minutes later, while the aircraft was 4 kilometers from the launch site, the controller unit alerted the pilot to a "potential loss of thrust." Immediately after this alert, the link between the controller and the RPA was severed. The aircraft's failsafe "return to home" function failed to activate. The pilot subsequently located the aircraft at its last known coordinates, where it had sustained substantial damage to its landing gear, one motor arm, and the propellers. No injuries were reported.
The investigation
SACAA AIID examined the pilot's credentials and the operator's certifications, finding that the pilot held valid Remote Pilot and BVLOS ratings, as well as a valid medical certificate. The operator's certificates and the aircraft's registration and approval documents were also found to be in order. The aircraft was also within its service interval, with 16.07 hours remaining before its next mandatory periodic inspection.
However, investigators were unable to perform a log analysis of the flight data. Although the memory card had been wiped 58 hours prior during a scheduled inspection, it had become full again by the time of the accident. This prevented the recovery of data necessary to identify the specific reason for the loss of thrust or the loss of command link.
Findings
- The primary cause of the crash was a loss of forward thrust and a subsequent disconnection from the controller unit.
- The specific reason for the loss of thrust remains unknown because the operator failed to ensure sufficient storage capacity on the memory card, rendering the flight logs unavailable for analysis.