What happened
On 17 March 2025, a Velos V3 unmanned aircraft (UA) was conducting a training mission near Onllwyn, Neath Port Talbot. The flight was designed to test the aircraft's response to breaching a predefined geofence. During the mission, the aircraft successfully navigated several waypoints but experienced multiple radio failsafe errors.
As the aircraft reached a pre-programmed rally point, the pilot attempted to resume the automated flight sequence. However, the aircraft experienced an uncommanded change in flight mode, followed by several critical errors including potential thrust loss and velocity variance. The aircraft subsequently dropped to the ground, and a post-impact fire resulted in the destruction of the aircraft.
The investigation
The investigation focused on the flight and control data recovered from the control unit. Analysis revealed that at the time of the incident, ten out of twelve data channels recorded values that were outside the specified operating range. This included erroneous data for several channels that were not even in use at the time.
Testing performed by the manufacturer demonstrated that if the communication link had been completely lost, the system would have maintained the last known valid values. Because the errors were inconsistent across different channels, investigators concluded that the aircraft was likely experiencing electromagnetic interference rather than a total loss of connectivity. The investigation also examined the regulatory oversight regarding the use of the ADS-B Mode S transponder recently fitted to the aircraft.
Findings
- The aircraft was subject to electronic interference that caused erroneous flight channel inputs, making sustained flight impossible.
- The source of the interference was likely the newly installed 1090 MHz ADS-B Mode S transponder, which had a high transmission power better suited for high-altitude operations.
- The regulator's assessment process for the operator's Operational Authorisation did not fully evaluate the specific technical details or the impact of the transponder's power output on the aircraft's systems.