What happened
On 25 March 2025, a Phoenix Wings Orca was conducting a series of commercial UAS flights near Coombe Country Park, Warwickshire. The mission involved several flights between a farm and a site near Coventry Hospital to prepare for a Beyond Visual Line Of Sight (BVLOS) demonstration.
During the sixth flight of the day, the aircraft was cruising at approximately 60 m altitude when its electric propulsion motors suddenly lost power. This led to a stall and a rapid, uncontrolled descent. The aircraft struck the ground in a wooded area, resulting in the aircraft being damaged beyond economic repair. There were no injuries to persons on the ground or the flight crew.
The investigation
The investigation examined the aircraft's flight data, software, and operational procedures. Investigators found that while the aircraft was flying, the communication link between the aircraft and the Safety Remote Pilot (SRP) controller was re-established. At that moment, the SRP controller was set to the disarm position.
Crucially, the investigation identified that a software update implemented in November 2024 contained a signal filter designed to reduce signal glitches. However, this filter inadvertently caused the aircraft to respond to the disarm command immediately upon re-establishing the link. Furthermore, the investigation established that disarming the aircraft in flight also deactivated the Flight Termination System (FTS), preventing the emergency parachute from deploying.
Findings
- The primary cause was a software bug within a signal filter that caused the aircraft to unexpectedly disarm when the SRP controller came back into range.
- A loss of synchronisation occurred between the Remote Pilot and the Safety Remote Pilot, as the SRP controller remained in the disarm position during takeoff.
- The aircraft's emergency parachute system was rendered inoperable because the disarm function also disabled the FTS.
- The operator's checklist lacked a formal 'check and challenge' procedure to verify that the arm/disarm settings were synchronised between both controllers.
- The manufacturer had not tested the specific scenario of the aircraft re-establishing a connection with a controller set to the disarm position following the software update.