A small remotely operated aircraft nearly collided with a passenger jet near Heathrow Airport

Radars to prevent drone-aircraft collisions already in testing

Technology that could have allowed air-traffic controllers to spot a small drone dangerously close to a passenger Airbus near Heathrow airport already exists, a leading expert has said.

As revealed by the Sunday Times, the incident that took place this July is the first near miss between a passenger jet and a drone in the UK.

Having escaped the air-traffic control radars, the small unmanned aircraft was only noticed by a pilot of the Airbus when flying at 700 feet, sparking calls for stricter regulations for the booming technology.

However, radars capable of detecting common unmanned aerial systems that can be purchased by hobbyists are already in testing.

“The common air-traffic control radars are designed for detecting, surveying and tracking large aircraft at ranges of many hundreds if not thousands of kilometres,” Peter Doig, a defence technology consultant at Plextek Consulting told E&T.

“They are not designed to look for something like a quadcopter or a small one or two metre fixed-winged aircraft, which could comfortably fly at 700 feet. These UAVs have a very small radar cross-section as they are predominantly made of non-metallic materials, such as plastics, which don’t have a very big return from radar.”

However, as Doig explained, Plextek has already been trialling local airspace monitoring radars for defence applications capable of keeping track of small drones up to the distance of 20km.

“The system is based on electronic scan frequency modulated continuous wave Doppler technology,” Doig described. “We have done trials both in the UK and internationally and we have demonstrated the ability to detect and track small unmanned air systems, like a quadcopter or a two-metre fixed winged aircraft and even distinguish them from birds to reduce false alarm rates,” he said.

Similar technology is already used at many airports for ground surveillance purposes, mostly for monitoring of fenceless perimeters.

Although primarily designed to help armed forces detect spy drones sent out by the enemies, the Plextek system could help protect civilian aircraft from collisions with drones – a danger that is bound to increase with the growing popularity of various remotely controlled aircraft. Apart from amateur UAV pilots, the technology has been tested by companies like Amazon and DHL for parcel delivery and some researchers believe that personal drones will become a major trend in the not-so-distant future.

“Drones are certainly going to become more prevalent in civilian airspace,” Doig said. “People can easily purchase them on the Internet for a couple of hundred or a couple of thousand pounds. However, the existing regulations should be enough to prevent them from interfering with the safety of civilian aircraft.”

According to the UK Civil Aviation Authority, small unmanned aerial systems not equipped with radar transponders and thus invisible to air-traffic controllers, could be either operated within segregated airspace or within the line of sight of the operator up to a maximum altitude of 400 feet.

“If that person has been sticking to that regulation that incident would likely have not happened,” Doig commented.

The UK Airprox Board (UKAB) is expected to publish results of the incident inquiry on Friday.

According to available information the board rated the July incident as A, meaning the highest level of collision risk on a five degree scale.

The owner of the drone has never been identified.

Earlier this year the UK airline pilots' association Balpa called for better protection against the risks posed by unmanned aircraft to civilian aviation.

Balpa said remotely operated aircraft flown in airspace used by passenger planes should meet the same standards as those binding for piloted aircraft with their operators obliged to undergo similar training to pilots.

''The UK should become a 'safe drone zone' so we can make the most of the major business and leisure opportunities offered by remotely piloted aircraft, while protecting passengers, pilots and residents,” said Balpa general secretary Jim McAuslan.

''The technology is developing quickly and we could see remote aircraft the same size as a Boeing 737 being operated commercially in our skies within 10 years.''

According to a report published by the University of Birmingham in October, the hazards posed by unmanned aerial systems could go beyond accidental encounters. The technology, the report suggests, could be used to carry out deliberate attacks on aeroplanes and should thus be subject to stricter control. 

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