Airplanes are huge, massive machines. What could a tiny toy drone even do to a big plane, you might wonder? Spoiler: massive damage. Researchers at the University of Dayton wanted to know exactly that. In a lab they simulated a midair collision between a small two pound hobby drone and the wing of a commercial aircraft.      

Instead of breaking into pieces, the drone ripped through the leading edge of the wing and did "substantial damage to the wing," including to the main spar — the structure carrying the majority of the forces during a flight. At nearly 240 mph (380km/h) the researchers shattered the idea that bigger is always better — or stronger.

"So far, we've just been lucky," Torsten Kretschmann from Germany's air traffic control Deutsche Flugsicherung (DFS) tells DW. He's in charge of finding a suitable drone detection system to protect the 16 international airports DFS controls in Germany, the largest of which is Frankfurt International. As drone sales rise, so does the risk of collisions, Kretschmann says.

 

A drone or a plastic bag?

Germany's airports registered 158 air traffic disturbances caused by drones in 2018, up from 88 in 2017 and only 15 back in 2015. Frankfurt tops the list. Planes were in fact grounded there three times in 2019 due to drones — or what were thought to be drones.

"We actually don't know if there really were drones," says Kretschmann, "they might have been plastic bags for all we know." Traffic controllers receive sightings mostly from pilots or staff on the ground. There is no technology in place that would detect drones, let alone do something about them.

Easy to lose control

"It's really easy to lose control of a drone," says Thorsten Chmielus, CEO of Aaronia, a radio technology company from Germany that offers drone detection and defense systems. Chmielus points out that even without malicious intent, drones can become a danger for air traffic. "We lose one about every two months. They just stop functioning properly and drift off," he says. At full speed with charged batteries a drone can fly 20 or 30 kilometers and could easily become an issue for an airplane during takeoff or landing, the most dangerous phases of flight.

What few hobby drone flyers know: a dangerous disturbance of air traffic that can easily be caused with a drone could put you behind bars for up to ten years in Germany. Suddenly, snapping a quick shot of a pilot in mid-air for your social media sounds a lot less fun, doesn't it? There is actually a no-fly-zone of at least 1.5 kilometers around airports.

Stopping air traffic is costly

Current strategy at airports is to stop air traffic when a drone is sighted, wait for about 30 minutes until the drone battery has likely run out, then reopen if there are no further sightings. That's all but a satisfying strategy for Kretschmann at the DFS, airport operators or airlines who face the costs of having to divert planes to other airports, rerouting customers and so on.

The worst incident of this kind in Europe so far? It occurred at London Gatwick airport in 2018 in the run-up to Christmas. Of all times. The airport was closed for 36 hours. To this day, there is doubt about whether there actually were drones present. Around 1000 flights were cancelled and an estimated 140,000 passengers affected.

Finding a suitable system

Kretschmann is looking for a detection system that could help identify a drone earlier, which might give clues about the whereabouts of the drone pilot and allow them to reopen traffic sooner. He and his colleagues have found around 30 operators with solutions or partial solutions in Europe and will be testing seven of them in 2020.

"We need a system that can spot a drone in a radius of 18 kilometers," Kretschmann says. "So far, I have seen systems identify drones in a distance of 70 meters without doubt." He's laid out a road map for dealing with drones that also includes public awareness campaigns for hobby drone operators. "I expect it will be 2027 until we have systems in place at all our airports that meet all our requirements," he says.

Depending on the test results, DFS may start with cheaper and smaller systems which can at least handle many of the toy drones or they may put money into more sophisticated systems or even their development. "If we can prevent grandpa and his grandchildren from accidentally endangering air traffic that might be a first step," Kretschmann says, "plus, we would finally have some more reliable data."

Integrating drones in air traffic management

Several European airports already use detection systems, but there is doubt about their effectiveness. Since London Gatwick introduced a system after 2018, there have been more reports of near collisions. The ideal, Kretschmann says, would be to just integrate drones into regular air traffic somehow.

DFS is responsible only for air traffic management at 800m and higher only, for now. Together with network operator Deutsche Telekom, they created a joint venture in early 2019. Their goal: develop an air traffic management solution for the space below that could include drones. "They're a totally useful tool and we need a way to integrate them fairly," Kretschmann says. "Just because there is a drone doesn't mean it's a bad one."

In fact, Frankfurt airport itself uses drones. No, they say they haven't created any disturbances. The airport operator uses drones to keep tabs on the building of a new terminal since 2018. "We use them for measuring and to document the construction process," says Yi-Chun Sandy Chen at Fraport AG, the company that operates Frankfurt International Airport. Currently, all their drones and flights are registered with DFS. With a common monitoring system in place, it could get easier to manage such commercial operations as well as drones that don't have any business around the airport.