Tests must be done into what would happen if a drone hit a passenger jet, say airline pilots following a recent spate of near misses.
The British Airline Pilots Association (Balpa) wants the Department for Transport (DfT) and the Civil Aviation Authority (CAA) to back research into the possible consequences of such a collision.
The former RAF and British Airways pilot Steve Landells warned that a drone hitting an airliner could result in an uncontrolled engine failure or a smashed cockpit windscreen.
Twenty-three near misses between aircraft and drones were investigated by the UK Airprox Board (UKAB) in just six months according to its latest reports, including 12 given an A rating – meaning there was a serious risk of collision.
Landells, Balpa’s flight safety specialist, said although there was a large amount of data on the effects of bird strikes on planes that was not a true representation of what would happen with a drone because “birds don’t have a big lump of lithium battery in them”.
He said it was “very likely” that the battery of a standard quadcopter drone entering the core of a jet engine would cause an uncontained engine failure, as happened to a BA plane which became engulfed in flames and smoke as it was taking off in Las Vegas last September.
“You end up with very high velocity bits of metal going anywhere they like. That could be through fuel tanks, through hydraulic lines and even into the cabin,” he said.
“Losing the engine is not going to cause an aircraft to crash because they are designed to fly with one engine down. But an uncontained engine failure is going to be different every time. That could be very serious indeed.”
Landells said he wanted testing with drones to be carried out because it appeared none had been done before.
“The first thing we want to do is get a drone or at least the critical parts of a drone flying at a windscreen of an aircraft. The indications so far with computer modelling are that you’ll end up with penetration of a windscreen.
“One possibility is that the battery smashes the windscreen and the inside layer of the windscreen shatters and you end up with a lot of glass in the cockpit, probably moving at quite high speed.
“As a pilot, I don’t want to be sitting there when that’s going on.”
He added: “There’s also a possibility that it might just bounce off. We don’t know at the moment.”
Landells said the initial tests could cost about £250,000.
Philippa Oldham, the head of transport and manufacturing at the Institution of Mechanical Engineers, described the consequences of a drone hitting an airliner as “such an unknown thing” that would depend on a number of factors including the size and speed of the drone and the location of the collision.
“There’s a lot of scenario planning going on around that at the moment,” she said. “The impact potentially could be anything from nothing to a destruction of an engine.”
People who fly drones close to planes could be convicted of endangering the safety of an aircraft, which has a maximum prison sentence of five years, the CAA said.
A CAA spokesman said the regulator had a number of ongoing schemes aimed at raising awareness of the safety requirements for using drones, such as its Dronecode campaign.
He added: “We are already working alongside the DfT and industry partners to better understand the potential risks and outcomes of a drone hitting a manned aircraft.”
The DfT said in a statement: “Public safety is our first priority and we are working very closely with the Civil Aviation Authority, industry and airline operators to improve our understanding and knowledge of this emerging technology.
“It is important to ensure that clear and proper regulations are in place and we will set out more details in a government strategy on the use of drones later this year.”
There were 23 near-misses between aircraft and drones in just six months, according to aviation investigators.
The UK Airprox Board (UKAB) has published reports on the incidents, which took place between 11 April and 4 October last year.
Here is a summary of the 12 which were put in the most serious risk category:
A military Lynx helicopter was forced to conduct an “evasive manoeuvre” to avoid hitting a drone over Hambrook, Gloucestershire.
The pilot said the object passed just one rotor span away down the side of the helicopter.
The pilot of an autogyro was on a training flight over Detling, Kent at 450 metres (1,500ft) when he encountered a drone.
The aircraft missed the drone by around 20 metres and the pilot assessed the risk of collision as high.
Both members of the flight crew on an RJ1 aircraft spotted a drone at an altitude of 1,200 metres over Detling, Kent.
It passed 18 metres below the left wing.
The UKAB concluded that it would have been “impossible” for the drone to have been flown legally because at that height it could not be seen by an observer on the ground.
A silver drone passed within two wing lengths of a BE200 aircraft as it was coming in to land at Southampton airport.
Investigators found that “chance had played a major part” in a collision being avoided.
A Chinook pilot was carrying out a simulated engine malfunction near RAF Odiham, Hampshire when a quadcopter drone with an attached camera was seen around 25 metres to its side.
The pilot of a Dornier Do328 short-haul jet – which typically has capacity for around 30 passengers – was at 850 metres on the approach to Manchester airport when he spotted a bright blue drone.
The UKAB determined that the drone was not permitted to be within that airspace.
A Boeing 737 suffered a near-miss with a drone shortly after taking off from Stansted airport, Essex.
The incident happened “so quickly” that there was no time to take avoiding action, the pilot said.
In the skies above the Houses of Parliament a drone came within 20 metres of an Embraer 170 jet on its approach to London City.
The UKAB considered that the drone operator was the cause of the near miss.
Shortly after a Boeing 777 had taken off from Heathrow airport a drone narrowly passed down the right hand side of the airliner.
Investigators concluded that the drone was at the same height and within 25 metres of the jet.
A report was made to police but the drone operator was not traced.
A drone was flown within a few metres of a passenger jet landing at Heathrow.
The pilot of the Airbus A319 stated that the drone may have been just six metres above and 23 metres to the left when it passed by the aircraft.
The jet was flying at an altitude of 150 metres and was on the final approach to the west London airport when the drone was spotted.
A Dornier Do328 pilot assessed that there was a high risk of collision when a drone passed his left wing by less than 15 metres.
The incident occurred at an altitude of 900 metres shortly after take-off from Manchester airport.
A PA28 light aircraft pilot was flying over Otherton airfield, Staffordshire as a drone passed about six metres from his wing tip.