Plane and helicopter 'came close' over Aberdeenshire, official probe into incident reveals
A helicopter and a plane came close over Aberdeenshire in an incident where safety had been "reduced", an official probe has revealed.
Investigators also rapped the Aberdeen Air Traffic controller whose instructions placed the aircraft "onto converging tracks".
The incident happened on April 8 at between 1000 feet and 1600 feet with one estimate that they were just 250 feet apart.
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A Sikorsky S-92 (S92) received a traffic alert warning soon after take off and a Piper PA-28 Cherokee was observed passing below the nose of the helicopter from right-to-left.
The chopper pilot assessed the risk of collision as "medium".
The PA28 pilot said that they were conducting an instructional trial-flight, the student's first flight.
On reaching Stonehaven harbour, they were instructed to proceed to the Bridge of Don. But there, they encountered other traffic, the departing S92 and an inbound helicopter from Balmedie to the north.
On becoming visual with the inbound helicopter, they were cleared to join downwind to pass behind.
"They turned right to join downwind, passing well behind. At that time, they were approximately 1200ft..... On rolling level, the student, in the left-hand seat, spotted the S92 and brought it to [the PA28 pilot's] attention, as was part of their pre-flight briefing," said the report.
"At that point, the S92 was above and passing behind by a safe distance.
"The S92 may have been in front and below [of the PA28] initially with [the PA28 pilot's] attention drawn to looking for the inbound traffic off to their right. During the turn, the S92 may have been about the same level as, and obscured by, the port wing when turning right to join the downwind leg.The pilot assessed the risk of collision as 'low'."
Members of the UK Airprox Board - which investigates near misses - agreed that the pilot of the PA28 had not had specific, "but only generic, situational awareness" of the position of the S92 and had not known that it had been on a converging track from their left.
"Members noted that the pilot of the PA28 had not visually acquired the S92 until after the moment of closest point of approach and agreed that that, effectively, constituted a non-sighting. Notwithstanding, members wished to applaud the 'good spot' by the passenger in the PA28 and commended the pilot of the PA28 for having briefed their passenger thoroughly before their flight," said the Board.
"Members next turned their attention to the actions of the Aberdeen controller. It was agreed by members that separation standards are not prescribed for application by Air Traffic Control between Visual Flight Rule (VFR) and Instrument Flight Rules (IFR) flights in Class D airspace.
"Nevertheless, members agreed that the Aberdeen controller had had a responsibility to prevent a collision between known flights and that, for them to have discharged that responsibility, the passage of sufficient Traffic Information to the pilot of the PA28 had been required.
"Members agreed that, although the pilot of the PA28 had received traffic information regarding the inbound helicopter, traffic information had not been passed on the S92. It was therefore agreed by members that the Aberdeen controller had not fully complied with the regulation pertaining to the control of VFR flights in Class D airspace."
Members pondered the instruction passed for a left turn after departure from rather than a right turn as had been expected by the pilot of the S92.
"Although the reason for a left turn after departure was not available for members to have assessed, it was agreed that the instruction passed by the Aberdeen controller to the pilot of the S92 to turn onto a track of 040 , in conjunction with the instruction to the pilot of the PA28 to pass behind the inbound helicopter, had brought the S92 and PA28 into confliction," said the Board.
"Members therefore concluded that the instructions passed by the Aberdeen controller had contributed to the Airprox. Further, members agreed that the Aberdeen controller had made an incorrect assumption that the flight profiles would not have conflicted.
"Concluding the discussion, members were in agreement that the instructions passed by the Aberdeen controller had placed the S92 and PA28 onto converging tracks. It was agreed that, although safety margins had been reduced, other safety barriers had prevented a more serious outcome.
"It was agreed that the pilot of the S92 had been alerted to the presence of the PA28 and it had been visually acquiredin time for the safest course of action to have been taken. Members agreed that there had not been a risk of collision during the encounter and assigned Risk Category C to this event."