A MILITARY drone crash in Wales was caused by computer failure, an official investigation has found.

Inadequate training also contributed to the accident near the Welsh coastal village of Aberporth, which has seen five drone crashes in recent years including one near the local primary school.

A new report by the Defence Safety Authority (DSA) examined the fourth crash, in which an unmanned Watchkeeper drone ploughed into Cardigan Bay on March 24, 2017 – just 20 minutes into a training flight.

The drone, WK043, took off from West Wales Airport at 10.36am in fair weather and was flown remotely by Royal Artillery pilots under instruction from French defence contractor Thales.

Almost immediately the army pilots battled with “abnormal” engine revolution “fluctuations” forcing them to head out to sea and follow emergency procedures.

The pilots received a series of error messages including “throttle stuck” until “data-links were lost.”

Observers then saw the drone “spiral downwards” in a “barrel roll” as it crashed in the sea.

The main wreckage has never been located by salvage teams although some small items have “sporadically washed ashore.”

Investigators now believe the crash was caused by a fault in the drone’s “Vehicle Management System Computer” which houses the “essential electronic installations” and carries out “top level tasks.”

DSA head Lieutenant General Richard Felton said this crash also highlighted “the urgent need for a fully representational simulator for crew and support training.”

“The advantages must now be compelling in minimising risk and cost,” he said.

Other reports suggest the series of crashes could have cost as much as £30 million.

He also warned that the Watchkeeper drone “is largely crewed by non-commissioned officers from the Royal Artillery, whose selection and assurance is set for them to operate at a level below that for pilots of manned aircraft.

“Yet the plethora and complexity of information available to them would challenge the most competent manned-aircraft pilot.”

He said the drone’s manual was over three times longer than the guidance for pilots flying the army’s Wildcat helicopter.

And even then the drone manuals were “not good enough,” he concluded.

A Ministry of Defence (MoD) spokesperson told the Morning Star: “The MoD and Thales acknowledge the findings of the Watchkeeper Service Inquiries.

“Actions have already been taken to address issues identified in the reports and we are considering all of the recommendations.”

Military journal Jane’s claims that the Watchkeeper fleet is now at “full operational capability.”