Could a drone really bring down a plane?

All flights from Gatwick Airport were grounded this morning, and incoming aircraft diverted, after two drones were spotted hovering in the vicinity. 

Around 10,000 passengers were affected by Gatwick's response to the threat, an unprecedented move which implies that the remote controlled devices present a very serious danger indeed.

What would happen if a drone hit a plane?

We know that bird strikes can do a surprising amount of damage to an aircraft, especially when they hit an engine - though serious incidents are very rare.

Drones, however, present a greater risk. Saj Ahmad, chief analyst at StrategicAero Research, explained: "Any object that hits a plane is a serious event. Obviously, the bigger the object, and depending on the size of aircraft, the consequences can be catastrophic.

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"It's fair to draw similarities with bird strikes, but the impacts of drones is less clear because some are big, heavy and have combustible electrical components which could cause an uncontained fire if it hit an engine or punctured a fuel tank."

This year, the University of Dayton Research Institute conducted lab simulations to compare the impact of a drone strike against a bird strike and found the drone to do considerably more damage.

To conduct the experiment, the DJI Phantom 2 drone (a popular model among hobbyists) was fired at the wing of a Mooney M20 (a small propeller aircraft) at a speed of 238mph, the approximate closing speed you'd expect with a collision of this kind. Footage of the strike is alarming, with a sizable hole being torn out of the wing.

Kevin Poormon, group leader for impact physics at the research institute told AINtv: "The drone did not shatter apart, it completely penetrated and was buried inside the wing, causing substantial damage."

A gelatin model was used to mimic the weight and speed of a bird and was fired from the canon in the same way. Although it crushed a portion of the wing's outer casing, it did no internal damage.

Poormon believes the aircraft would have survived the impact of a drone but for a faster plane, the results could have been worse. A plane travelling twice as fast could have suffered a punctured fuel cell, for example.

What does the law say about drone use?

As of July 30 2018, new laws came into force which ban all drones from flying above 400ft and within 0.6 miles (1km) of airport boundaries.

Drone users who flout the height and airport boundary restrictions or fly negligently could face an unlimited fine, up to five years in prison, or both.

Has a drone ever hit a commercial aircraft?

No. However, drone near-misses with planes have more than tripled in two years, new figures show. Some 92 incidents were recorded in 2017, according to analysis of UK Airprox Board (UKAB) data. This is compared with 71 during the previous 12 months and 29 in 2015.

Former RAF and British Airways pilot Steve Landells, flight safety specialist at pilots' union Balpa, described the figures as "very worrying".

But as for whether a drone strike has ever caused a significant safety breach, Ahmad states: "Thankfully there's not yet been any such incident, but there have been many close calls."

In October of this year, a Virgin Atlantic plane came within just 10 feet of a drone - the closest ever near-miss involving a passenger jet and one of the gadgets in UK airspace, according to UKAB.

It happened as the Virgin Atlantic jet, a Boeing 787-9 Dreamliner capable of carrying up to 264 passengers, was flying at around 250mph over residential streets just north of Clapham Common on its approach to land at Heathrow. It managed to land without hitting the drone - and the owner of the device was never located.

Are there any other associated dangers?

Even in the event of a near-miss, when no collision occurs, the sudden presence of a drone is distracting to a pilot whose concentration must be at its most focused upon take-off and landing.

There's also the issue of what more sophisticated drones could be carrying - in the worst case scenario, a bomb or chemical weapon.

"There is obviously nothing stopping someone using a drone equipped with some form of weaponry," Ahmad says. "But thankfully, that hasn't happened."

As for whether they have the ability to interfere with radio communications or Air Traffic Control, it's a no. They aren't that advanced, Ahmad remarks.

What can be done to lower the risks?

"What we need to do is look at how the drones are constructed," Poormon suggests. "Perhaps make them more frangible and act more like birds do - break apart upon impact. I think that's the key for minimising the risks."