By Chris Stokel-Walker
For the second time in less than a month, suspected drone sightings have shut down a UK airport. On 8 January flights out of London Heathrow were suspended for over an hour. And between 19 and 21 December, more than 140,000 people at London Gatwick had their travel plans disrupted after drones were spotted above the airport.
How can drones cause so much disruption?
Airports operate on a just-in-time basis, with Heathrow moving a plane onto or off its runways every 45 seconds on average.
A drone could interrupt this flow if planes have to reroute. Air traffic control can’t know what a drone will do or where it will fly so have to be cautious if one is sighted.
Are we even sure there were drones at Gatwick and Heathrow?
It’s uncertain, but probably. A Sussex police officer said before Christmas that it was a “possibility” no drone existed at Gatwick – and two people arrested in connection with the incident were released without charge. However, 67 sightings were reported over the course of the Gatwick shutdown. Heathrow was shut down after a supposed drone sighting that had also been seen by a BBC cameraman.
What would happen if a drone hit a plane?
It could be nasty. Researchers at the University of Dayton Research Institute tried firing a 1 kilogram commercial drone into the wing of a plane at nearly 400 kilometres an hour and it wasn’t pretty. The leading edge of the wing tore apart. The researchers chose the wing and the drone to mimic those on standard planes and the kind of drones easily available online.
Can drones be stopped from flying over airports?
In principle, yes, but it’s tricky in practice. Drones are too small to be picked up by traditional radar. This means they often have to be spotted by eye and so any action to stop them is slow and inaccurate.
During the incidents at London airports, dozens of police officers were deployed to search for the drones.
Shouldn’t we just shoot the drones out of the sky?
Doing this runs the risk of stray bullets landing in odd places and the falling drones could also cause damage. What goes up must come down. The technique would also rely on getting someone with a gun near enough to the drone, which so far has proven difficult.
Are there other options?
Radio jammers can disrupt drones from 2 kilometres away. The devices stop signals used by remote controls. This triggers a drone’s in-built return to home function allowing it to land safely.
Many drones also contain geofencing software, which prevents pilots from flying into sensitive airspace, such as over airports, military bases and national parks. “But if you are technologically-savvy and want to cause disruption, you can get around that by building your own drone and tweaking the firmware and software,” says Andrew Heaton, an independent drone expert.
Dutch police have also tried training eagles to snatch drones from the sky, but had to abandon the project because the eagles rarely followed orders.
How far away can the drone pilot be?
Pilots are also meant to keep drones in sight at all times to legally fly drones – meaning they can’t fly more than around 500 metres away from where the pilot is standing. However, some drones can beam back signals to the pilot from 2 kilometres away, and there’s an aftermarket of signal boosters that allow drones to be flown at illegally long distances.
Some drones can also be set pre-programmed paths to fly autonomously.
Do airports currently have any protections?
In the aftermath of the Gatwick disruption, the airport installed a £1 million protection system. It comprises 360-degree radar and thermal imaging systems, as well as a radio jammer. It’s one of a number of systems set up at airports around the world. For example, Ronald Reagan National Airport in Washington DC has a 30-nautical mile network of radio jammers to try to stop drones entering the airport’s airspace.
However, a deliberate attack would be able to circumvent such systems, says Owen McAree at Liverpool John Moores University. “The only sure fire way to stop them without risking collateral damage is to stop people with nefarious intentions from getting hold of the drones in the first place,” he says.