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Drones over London caused aviation chaos, pilots' reports reveal

Heathrow flights were diverted to avoid errant UAVs

A pair of errant drones over East London caused so much airspace disruption that flights to Heathrow had to be diverted for fear of collision, it has emerged.

Airprox reports filed by captains of airliners flying over London on 20 November last year, freshly published by the UK Airprox Board (UKAB), reveal how air traffic controllers were forced to divert flights passing over the London City Airport area after "multiple pilots reported sighting a drone or 'something'.”

An Airbus A320 pilot reported that as he was descending through 6,200ft, heading south over London and turning west on to the Heathrow approach, he spotted "two white, orb shaped objects, with no lights or visible markings".

"The objects did not move, despite the wind," said the UKAB summary of his report, which noted that the wind was blowing 30kt due west. One drone was thought to be at around 5,500ft with the second around a thousand feet below it. Neither was big enough to trigger the Airbus's automated Traffic alert and Collision Avoidance System (TCAS).

Just 20 minutes later, an air traffic controller coming on duty at Swanwick's London Terminal Control Centre, which controls all London-bound air traffic below 24,500ft, immediately began receiving more reports from pilots of sighting a drone. One described the drone as five feet across, while another said it passed within 50 metres of his airliner.

A Boeing 777 pilot reported a "large white drone, about 2m across and with four 'prongs'" passed down the right-hand side of his aircraft within no more than half a nautical mile. He assessed the risk of collision as "medium".

"The drone operator could not be traced," noted the UKAB. It also reported that one pilot said, after landing, that he thought the drones may have been balloons – something the A320 crew also thought, until the pilot realised they were "twice the size of a standard child's helium balloon" as they passed between 500m and 800m from his aircraft.

Drones flying outside the permitted limits (generally 400ft and within visual range for drones under 7kg in weight) is an increasing problem. Airprox reports in particular are dominated by airliner pilots, normally around airports or preparing to land, filing reports of drones buzzing about. Many of these sightings are at very high altitudes; one pilot reported a drone at 10,000ft.

EU regulators are proposing strict rules which would snuff out hobbyist drone flying unless operators choose to register themselves with the authorities. Model aircraft fliers also believe that proposed EU drone regs will capture their hobby and effectively make it uneconomic for them to fly their replicas around fields. ®

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