British pilots are calling for urgent research into what would happen if a drone hit an aircraft, following 23 near misses in just six months.
They also say stricter rules governing where drones can be flown, compulsory insurance and registration for drone owners, and technology that prevents drones being able to fly close to commercial traffic is critically needed.
"We must act now to protect passengers and flight crew and make sure a catastrophic crash does not happen," said Steve Landells, a Flight Safety Specialist from the British Airline Pilots Association (Balpa). A drone hitting an airliner could result in uncontrolled engine failure or a smashed cockpit window, he told the BBC.
The UK Airprox Board (UKAB) has published reports on 23 incidents between April 11 and October 4 last year when drones nearly hit aircraft.
Four incidents were given a category A designation, meaning a serious risk of collision existed.
In one incident on September 22, a drone passed within 25 meters of the right-hand side of a Boeing 777 shortly after it had taken off from Heathrow Airport. A police report was made but the drone operator was not traced.
Just over a week later, a drone flew within a few meters of a passenger jet on the final approach to land at the west London airport. The pilot of the Airbus A319 said the drone may have been just six meters above and 20 meters to the left when it passed by.
In another incident, a silver drone passed within two wing lengths of a Beech 200 private aircraft as it was coming in to land at Southampton Airport. "Chance had played a major part" in a collision being avoided, said investigators.
Mr Landells, Balpa's flight safety specialist, told the BBC there was a large amount of data on the effects of bird strikes on planes, but specific drone research was needed because "birds don't have a big lump of lithium battery in them." Lithium could start an engine fire.
Many pilots think it's only a matter of time before a drone strikes a plane, wrote the BBC's Transport Correspondent Richard Westcott — "yet no one has any real idea what would happen if it did."
Balpa is worried that unsafe incidents could rise further over the next few months, "as people take their new Christmas presents in to the air for the first time, often with little or no handling experience or understanding of the rules of the air," it said in a statement. Stricter rules and a registration system would allow drone operators to be easily traced and prosecuted for any irresponsible flying, it said.
"Pilots also want technology to stop drones from being able to fly in areas where they could meet commercial traffic to be routinely fitted to the devices," said Balpa.
The association wants the government and the Civil Aviation Authority, the UK's air safety regulator, to pay for tests to see how serious a drone strike could be.
People who fly drones too close to planes can face prosecution for endangering the safety of an aircraft, which has a maximum prison sentence of five years — but only if they can be traced.
Britain's Civil Aviation Authority launched a campaign for safe drone flying last July. Its operating rules for drones are as follows:
- An unmanned aircraft must never be flown beyond the normal unaided 'line of sight' of the person operating it. This is generally measured as 500m horizontally or 400ft vertically.
- An unmanned aircraft fitted with a camera must always be flown at least 50m distance away from a person, vehicle, building or structure.
- An unmanned aircraft fitted with a camera must not be flown within 150m of a congested area or large group of people, such as a sporting event or concert.
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