AAIB investigation to Experimental Drone Variant 4J, (UAS registration n/a)
Loss of navigational control, emergency flight termination, Salisbury Plain Training Area, Wiltshire, 11 December 2025
During a verification and validation test flight of a fixed wing UA command and control was lost. The flight was terminated when it was confirmed the UA was over a safe area. The UA descended to the ground and the wreckage recovered. A fault was found within its navigation module which caused it to breach the geofenced area in which it was flying. The operator has taken safety actions which introduce a fall-back logic within the system which can switch to other navigational sources and has modified the user interface to provide a clear alert to the remote pilot in the event of a positioning data anomaly.
Download the report:
Download glossary of abbreviations:
Updates to this page
Published 9 April 2026