UK pilot representatives are emphasising speed reduction as the best strategy to lower the risks posed by an unmanned aerial vehicle collision threat.
Crews of commercial aircraft filed 92 reports of drone sightings in UK airspace last year, and cockpit union BALPA states that the structural composition of drones makes a collision potentially more damaging.
"It is important therefore to slow down to reduce the kinetic energy of a potential drone impact," it says, having drawn up guidance for pilots in co-operation with air traffic controllers guild GATCO.
When a drone report is received, says the union, pilots should decelerate to the "minimum clean" speed – the lowest speed an aircraft can fly in clean configuration – during climb and descent, and to 180kt during approach.
Although crews have claimed to sight drones above 10,000ft they are more likely to encounter them at lower altitudes, especially during approach and departure.
"The speed reduction should be requested first so [air traffic control] can assess the traffic situation and accommodate the request safely," says BALPA.
Pilots should pass as much information as possible to controllers if they sight a drone – partly to maximise support to law enforcement – and controllers should continue to notify pilots joining the radio frequency for 30min after the sighting.
BALPA's guidance also recommends that pilot should plan for adjustment of the flightpath and possible diversions.