A Royal Artillery Thales Watchkeeper unmanned aerial vehicle (UAV) crashed in Wales after a computer glitch made it activate its landing procedures prematurely, an inquiry has found.
The director general of the Defence Safety Authority, Air Marshal Dick Garwood, said the crash showed the vehicle management system computer (VMSC) software was "not fit for purpose".
Details of the crash and a series of complex computer faults were revealed in a Service Inquiry report released on 12 August by the UK Defence Safety Authority.
According to the report, Watchkeeper WH031 crashed as it was making its final approach to the ParcAberporth airfield in Wales on 16 October 2014.
It was 20 feet above the ground when the UAV's VMSC registered a false "ground touch" signal, which activated its V-tail pitch down function. As a result, it nose-dived into the runway causing "considerable damage" to the fuselage. A photograph published in the report shows the UAV's undercarriage had collapsed and the fuselage broken apart just in front of its wings.
A laser altimeter registered a false height reading on the ParcAberporth wet runway as the air vehicle approached the airfield, said the report. Several safety functions that would have prevented the accident were disabled because the civilian crew from the Watchkeeper's manufacturer, UAV Tactical Systems Ltd, had activated overrides so they could rapidly land the air vehicle to avoid approaching bad weather.
The report cleared the crew of fault for the accident and blamed faults in the "logic" or software of the VMSC, which controls the air vehicle in flight, and said the Watchkeeper's automatic take-off and landing system had not been assessed in the process that had granted it an initial release to service (RTS) clearance for use by the British Army.
AM Garwood said the report highlighted a number of technical issues that "will need to be resolved", "if we are to avoid the loss of further platforms and release aspirations to operate [UAVs] outside military controlled airspace".
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