American crew assumed Wick was a 'sleepy little airport' before potential near-miss
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The crew of an American military plane assumed Wick was a “sleepy little airport” before becoming involved in a potential near-miss with a helicopter off the east coast of Caithness, it has emerged.
The US plane, a C-12 Huron, was on a training flight when the incident occurred seven months ago. The helicopter was a Sikorsky S92 which was heading to a ship.
A report found that the C12 pilot took action after finding that "they were nearly 500ft below the assigned altitude".
The incident occurred 14 miles south-southeast of Wick at around 9.20am on Wednesday, October 20.
It was investigated by the UK Airprox Board, whose role is to enhance air safety through lessons learned from airprox occurrences within UK airspace.
An airprox is defined by the board as "a situation in which, in the opinion of a pilot or air traffic services personnel, the distance between aircraft as well as their relative positions and speed have been such that the safety of the aircraft involved may have been compromised".
The incident off Caithness was deemed class C, which means “no risk of collision”.
A newly issued Airprox Board report states that Wick air traffic control (ATC) cleared the C12, which was on the same track and same position as the helicopter, to descend to 4000ft. On its traffic alert and collision avoidance system (TCAS), the S92 crew watched a contact descending within one nautical mile.
"The rate of descent was rapid and eventually indicated less than 1000ft to their level," the report says. "They communicated their avoiding descent with ATC and expedited to altitude 2000ft, remaining in VMC [visual meteorological conditions].
"They levelled at 2000ft and the contact continued to descend and came within 500ft of their level.
"ATC repeated the clearance to the C12 pilot who climbed back to altitude 4000ft. Based on their TCAS observation and the C12 pilot’s communication, the S92 crew surmised that the C12 pilot did not comply with their clearance and descended rapidly through the S92’s level and within one nautical mile."
Although the helicopter crew did not see the C12, and no alert was activated, they "perceived that the C12 was behind them throughout the event". The helicopter pilot assessed the risk of collision as high.
According to the report, the pilot of the US plane "had to admit that, at the time, they considered that because of the ‘sleepy little airport of Wick and the Scottish controllers out in the middle of nowhere’ maybe the controllers were just a bit relaxed. In retrospect, the pilot considered that it was in fact themself who was ‘just a bit relaxed’."
The Airprox Board commended the S92 crew “for their presence of mind”.
The report says: “It was apparent that the C12 pilot had descended below their cleared altitude having set the incorrect altimeter pressure setting.”
On the question of risk, it was agreed that "there had not been a risk of collision but also that normal procedures had not been complied with".
Gary Cobb, chief operating officer at Highlands and Islands Airports Ltd (HIAL), said: “The UK Airprox Board found that the primary cause was the pilot of the C12 aircraft not adhering to the Wick air traffic controller’s instruction to descend and maintain altitude.
"Aviation safety is our number one priority and HIAL takes on board the learnings gained as a result of this incident and these will be implemented as part of our continuous review of training and processes.”
