A MILITARY drone operating out of West Wales Airport at Aberporth crashed into the sea off the Cardigan coast while undergoing bad weather trials, a military inquiry has revealed.

The Watchkeeper unmanned aircraft was testing a new ice detection system when things went wrong on February 3, 2017 and it plunged into Cardigan Bay.

Wreckage from the crash was never found despite an extensive search involving underwater vehicles – Watchkeeper is not fitted with a ‘black box’ flight data recorder - though small parts of the aircraft were later washed up on shore.

Investigators concluded that a build-up of moisture in one of the Watchkeeper's pitot sensors used to calculate air speed and angle of attack caused its automated flight systems to start malfunctioning and ultimately led to the aircraft stalling and the crash.

The aircraft’s operators Thales, who are responsible for developing the Watchkeeper programme for the British military, came in for criticism in the report’s conclusions, which said “the design organisation (Thales) and the MOD not fully understanding how WK works, not making the most of simulation or from the exploitation of data and providing a disproportionate level of complexity to those who fly Watchkeeper.

“Watchkeeper was designed to deliver a flexible, 24-hour Intelligence, Surveillance, Target Acquisition and Reconnaissance (ISTAR) system for primary use in the land environment. Having the ability routinely to operate in cloud and precipitation throughout the year is therefore an important pre-requisite.

“The necessity to conduct icing trials is a given, but so should be confidence in the basic requirements to do so, such as the correct operation of the pitot system, prior to flight.

“There are other areas that demand attention — for the design organisation in improving its safe conduct of trials and for the MOD in providing effective 'operator' supervision.”

The report called for “a fully representative simulator for pilot and crew training. This is long overdue.”

The inquiry also said “a means of enabling its post-crash location should now be compelling.”

The crash was the third occasion an unmanned Watchkeeper drone ¬ which has a length of 6.50m, a wingspan of 10.95m and an overall height of 2.18m - had been lost in an accident.

It was to be followed some six weeks later by another, which crashed over Cardigan Bay on March 24, 2017, with a fifth going down near West Wales Airfield on June 13, 2018, which prompted calls for a safety review by many local residents. That crash is still under investigation.

Flights were temporarily grounded by the Ministry of Defence, though have since resumed.