The July 2015 meeting of the UK Airprox Board assessed an airprox reported by a Royal Navy Lynx helicopter pilot flying at 2500ft just west of Bristol earlier this year which came within 30-50ft of a drone.
THE LYNX PILOT reports transiting to RNAS Yeovilton. The aircraft was descending from 2500ft to 1500ft when a small white ‘doughnut shaped’ UAV/drone was observed directly ahead at a range of approximately 100-200m. The pilot conducted an evasive manoeuvre, a right-hand break, and the UAV passed 30-50ft (approximately 1 rotor span) down the left-hand side. The pilot stated that the object appeared to be about 50cm across, with a mass of less than 7kg he estimated, and appeared to remain level without manoeuvring. It was difficult to see against an urban backdrop but a low cockpit workload allowed an effective lookout scan. The pilot also commented that had the UAV not been sighted through effective lookout, and evasive action not been taken, a mid-air collision would have occurred.
He assessed the risk of collision as ‘Very High’.
The full Airprox Report is available here: http://www.airproxboard.org.uk/docs/423/2015054v2.pdf