A helicopter flew within 300 feet of a glider and its towing plane, an official report has heard.
The incident happened over Loch Leven in Perthshire on May 22 at around 1,750 feet and investigators said safety had been “degraded.”
The Eurofox light aircraft pilot assessed the risk of collision as “high.”
He said that he was the duty tug pilot for the evening flying and the incident occurred on the second tow.
He took off at 4.31pm with an ASK21 glider attached. The glider had an experienced pilot and a student on board.
He climbed by routing along the eastern edge of Loch Leven and made a couple of ‘S’ turns from 600ft upwards as he searched for the best lift.
The pilot said he had been established in a left-hand climbing turn for about 20 seconds and his main focus was looking out for several other gliders known to be within two miles at similar levels.
As he steadied on a heading of 270° a helicopter suddenly appeared from under his left-hand engine cowling, 100m (328ft) in front.
“It was now flying away, having passed directly below with 150ft vertical separation,” he said
Despite his extensive continuous look-out (because he knew he was in a high traffic density environment), he had no prior knowledge of the helicopter before it passed underneath.
The pilot assessed the risk of collision as ‘high,’” said the report by the UK Airprox Board, which investigates near misses.
The pilot of the Eurocopter AS365 said he was transiting from a private site near Leuchars. He was aware of the gliding site at Portmoak so he turned further north and was in the process of changing to Edinburgh when he spotted a glider and tug, about four miles away, climbing out on a westerly heading from Portmoak.
The tug initially climbed straight ahead before turning right, towards his track, and then in an easterly direction.
The recorded vertical separation between the aircraft was 300 feet.
The report said: “The board assessed the risk and agreed that because the AS365 pilot was visual with the tug and glider, there had been no risk of collision.”