All-in-all the entire incident left much to be desired. Only six days before Christmas, and one of its busiest times of the year, London’s Gatwick Airport, south of the capital and the second-busiest in the UK was closed for two days. Official figures state that over 140,000 passengers were stranded and over 1,000 flights were either cancelled or disrupted. The cause of this mayhem? Numerous reports from the public that a drone had been spotted flying within 0.5 nautical miles (one kilometre) of the airport. The decision was taken to close Gatwick’s two runways in a precautionary step to prevent the drone colliding with any aircraft landing or taking off.
One month since and little remains known about the drone in question. What is not in dispute is that the drone’s operator wanted to intentionally disrupt flights, as every time the airport was about to reopen the drone was sighted again. Moreover, local police reported that the drone was an industrial design, rather than a hobby aircraft, corroborating the intentional nature of the flights. Following the first reported sightings on 19 December 2018, the Royal Air Force (RAF) Regiment, the air force’s land component, was deployed to help police to bring the situation under control.
Initial reports said the regiment had deployed its Rafael Advanced Defence Systems’ DRONE DOME Counter-Unmanned Aerial Vehicle (CUAV) system. The UK procured six systems which use a combination of optronics and radar detection to locate a drone. Although DRONE DOME can use a laser to down the aircraft, the UK has instead procured an electronic attack capability collocated with the system to break the Radio Frequency (RF) link between the aircraft and operator. The media stated that at least one DRONE DOME was deployed to Gatwick on 21 December. This was later denied by the UK Ministry of Defence (MoD), which said that as DRONE DOME was not yet delivered, an alternative had been deployed.
Pictures from the incident show what appears to be a radar and optronics system positioned on a rooftop, along with a Yagi-Uda antenna presumably to detect the drone’s RF signals. The deployment of this system may have occurred too late as by then the drone sightings had ceased. Alternatively, it may have had a deterrent effect persuading the operator to cease their activities knowing that they could now be disrupted. The military deployment ceased on 3 January following news that Gatwick Airport would procure an unnamed CUAV system.
The British government can be commended for their quick response to the crisis. The airport must also take credit for their decision to procure a CUAV system. Nonetheless, the incident raises some questions.
To be fair, the airport’s management had little choice but to close the runways, despite the disruption this caused to thousands of passengers. The loss of an aircraft to a drone could have caused hundreds casualties. Yet there were serious shortcomings in that the airport had no CUAV system in the first place. The absence of this capability is all the more striking when one realises that Gatwick airport had suffered two similar incidents on 3 July and 9 July 2017.
These occurred against a backdrop of warnings sounded by aviation experts over the past ten years concerning the danger posed by flights of unmanned aircraft near airports.
While on this occasion the military were deployed with a CUAV system to help bring the crisis to an end, one worrying aspects was local law enforcement seemingly lacked a capability to detect and locate the aircraft. This was surprising as Gatwick Airport resides in Sussex Police’ jurisdiction, alongside several other airfields in the counties of East and West Sussex in southern England.
Yet as David Stupples, professor of electronic and radio systems at City, University of London, and director of electronic warfare systems research told MONch, detecting a drone is not an easy task: “Being able to locate it is quite difficult. You need a staring radar, one that is not scanning, but constantly looking in all directions. As the radar is staring, it can detect small objects which might be missed by a scanning radar, which may only see the drone sporadically.”
He added that the physically small size of such drones makes them hard to see with a radar: “Spotting is much more difficult than it first appears, as you’re dealing with a very small target.”
Detecting the drone though its RF link is similarly challenging, Prof. Stupples continued: “The drone itself may not be communicating with the ground, and maybe following a pre-programmed flight path using GPS (Global Positioning System) coordinates.”
Moreover, civilian drones typically use frequencies of 2.4 gigahertz/GHz as their air-to-ground/ground-to-air link, and 5.4GHz to transmit video to the ground: “The problem is that the 2.4GHz waveband is very crowded. For example, you have garage remote controls working in this band.”
He added that, “you’ll need some very smart software to tease out the drone signal from the rest of the noise on 2.4GHz … The drone signal may have some specific characteristics which will allow you to recognise this, but it is still not an easy task.”
Arrests were made of two individuals on 21 December 2018 whom were later released without charge, and seem to have become suspects on the strength of one of them being a drone enthusiast. Such mistakes can happen when the authorities lack the electronic means of detecting and locating a drone.
During the incident at Gatwick, law enforcement relied on a physical search of the airport’s locale using officers and a police helicopter. As drones proliferate, there will be more compunction on police across the UK to ensure they can detect and stop such flights in a timely fashion, particularly when they cause disruption at major airports. Investing in the technologies recommended by Prof. Stupples and other experts would be a step in the right direction.
Dr Thomas Withington