Airprox between Desert Hawk 3 and Apache helicopter on Salisbury plain

UK Newspaper The Guardian reports an airprox on Salisbury Plain earlier this year. The incidents are from this report.

Two official safety inquiries took place into the military use of drones over southern England after near-collisions with helicopters, the Guardian can reveal.

The investigations are the first of their kind involving unmanned aerial vehicles (UAVs), which are increasingly being flown in British civilian airspace after extensive use in Iraq and Afghanistan.

The inquiries by Airprox, the body that investigates reports of near-collisions, relate to flights on 12 February by a Desert Hawk 3 (DH3) drone owned and used by the army. The drone was being flown in military airspace over Salisbury Plain and operated from the ground.

In each case Airprox concluded that action taken by the operator on the ground prevented collision with the helicopter. However, it made recommendations and said there were “many lessons learned” in the first inquiries involving unpiloted aircraft, which can fly below radar altitude.

The areas in Wiltshire over which military drones are permitted to fly have been significantly extended since then. They were widened on 1 July to enable testing of Watchkeeper UAVs – winged drones that are based on Israeli military technology and operated by the Royal Artillery as remote spotter and targeting planes.

Announcing the additional “danger areas”, the Civil Aviation Authority (CAA) circular warned: “The unmanned aircraft that will be operating within this airspace are not capable of independently detecting or avoiding other aircraft (ie there is no pilot on board to ‘see and avoid’).

“In addition, their colour scheme and relatively small size may result in them being difficult for other pilots to acquire visually when airborne. Pilots who may be unable to comply with the conditions … should not request a crossing clearance.”

There is growing concern over the dangers of drones. Several police forces, government agencies and commercial operators are testing or using them.

Most have shown interest in microdrones: rotor-propelled aircraft that hover at heights of about 60 metres and can be fitted with video cameras, thermal imaging devices, radiation detectors, mobile phone jammers and air sampling devices. They weigh less than 20kg and, when used for surveillance, require a licence to fly.

They are said by manufacturers to be virtually invisible from the ground, making them ideal for covert surveillance. The Home Office endorses their use. In a statement to the Guardian it said: “UAVs can be a useful tool for law enforcement agencies in fighting crime and safeguarding the public, but their use is subject to strict Civil Aviation Authority safeguards and must be necessary and proportionate.”

The CAA, which regulates UK airspace, last week warned that misuse of drones could lead to deaths. “In the wrong hands or used irresponsibly in built-up areas, or too close to other people or property, they represent a very real safety risk,” it said.

The first UAV incident investigated by Airprox occurred when the DH3, which looks like a model aeroplane and is operated with controls like those on a games console, sought to land after running out of battery at 488ft.

An Apache helicopter escorting a Chinook on a simulation exercise entered the landing zone and was at one stage “on a collision course” with the drone, the report said. Last-minute manoeuvres by the UAV controllers prevented a collision.

Three hours later a Sea King helicopter entered the same drone’s airspace and came within 300 metres of it. The UAV operator spotted the helicopter and avoided collision with an “emergency orbit”. “This was a very close encounter and had the [UAV operator] not reacted so quickly a mid-air collision could have occurred,” the report said.

The Ministry of Defence said in a statement that neither incident posed a danger to personnel or aircraft. “On both occasions Desert Hawk 3 was operating safely under remote pilot control when a manned aircraft incorrectly entered the dedicated air space allocated to it,” it said.

DH3s are manufactured by the US aerospace company Lockheed Martin. They have been used extensively in Afghanistan and Iraq for “over the hill reconnaissance” by Royal Artillery soldiers.

The CAA tightened regulations surrounding the use of drones this year, requiring all UAVs to be licensed before use. Merseyside police was forced to halve flights of its drones in February after the Guardian revealed it had used an unlicensed UAV to pursue a 16-year-old suspected car thief into some bushes, where he was found hiding. The force has since been given permission to resume flights.