What happened
On the morning of 30 April 2023, an Arace Sirin remotely piloted aircraft (RPA), registered ZT-XNI, was performing night-time railway surveillance operations near Vryheid, KwaZulu-Natal. The mission was being conducted under beyond visual line of sight (BVLOS) regulations.
Following a successful pre-flight inspection and launch with 98% battery power, the aircraft reached its operational altitude. However, during a return flight approximately 8km from the launch site, the pilot experienced a screen freeze on the remote controller unit. This was immediately followed by a loss of the command-and-control link. Although the pilot attempted to use navigational lights to locate the aircraft, the programmed failsafe mode failed to initiate a return-to-home sequence. The pilot subsequently located the aircraft at its last recorded coordinates, where it had sustained substantial damage to its landing gear and propeller blades after impacting a mountain.
The investigation
SACAA AIID investigators reviewed post-accident logs provided by the operator to reconstruct the flight path. The data confirmed that the aircraft ascended to 230 feet for the mission. Analysis of the flight logs revealed that 19 minutes into the flight, the aircraft lost communication with the ground station and attempted to switch to return-to-launch (RTL) mode. One minute later, the aircraft struck a mountain. The investigation also confirmed that the GPS signal had remained within normal operating parameters during the flight.
Findings
- The primary cause of the incident was a loss of the command-and-control link, which severed communication between the pilot and the aircraft.
- The aircraft's failsafe mechanism failed to execute the programmed return-to-home procedure following the link loss.
- The pilot held a valid Remote Pilot Licence with the necessary BVLOS and aircraft type endorsements.
- The operator maintained all required certifications, including a valid Operating Certificate and landowner permission.