TWO PLANES ONLY narrowly avoided each other in a mid-air collision last year.

The collision was avoided as one of the aircraft initiated avoiding action following a Traffic Advisory System (TAS) warning warned of air traffic nearby.

The incident happened on 22 April 2013 over Knock Airport.

Metres apart

The Air Accident Investigation Unit Ireland stated it was a “serious incident” where the two planes missed each other by only a few hundred metres.

The report into the matter states that after midday the two planes, which each had three persons on board – two crew and one flight inspector – narrowly missed each other by just 0.42 nautical miles with no vertical separation.

The pilot of one of the flights, CLB205, said their approach to runway 9 was “uneventful” but on the go-around they became aware of another aircraft.

Previously, they had been instructed to maintain 3,000 ft. They requested permission to descend and the Air Traffic Controller cleared them for approach.

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The pilot then said he was alerted to air traffic on their Traffic Advisory System (TAS). The traffic was on a 90 degree intercept approaching from the left and 300 feet above them.

Just before 5 nautical miles, they received a ‘yellow warning’ on TAS indicating traffic was still approaching from the left, at a “co-altitude” (same altitude).

With this information the pilot deemed that both aircraft “were on a collision course”.

The pilot who was not flying called for an immediate right turn and climb. The flying pilot responded with an immediate right turn and on seeing a gap in the cloud, he descended.

Both aircraft landed without further incident. There were no injuries.

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In the report the Air Movements Controller (AMC) stated when flight CAL01 got airborne his initial plan was to hold the aircraft south of the airport until the CLB205 detail was complete.

Coast Guard

Around the same time an Irish Coast Guard Rescue helicopter (R118) en-route from Sligo to Galway Hospital requested clearance to route through the airport’s air space.

This was approved and traffic information was issued to R118 and the other two aircraft.

The AMC stated that he was anxious not to delay R118 and as such he originally planned to put CLB205 into the hold at 3,000 ft until R118 had passed the airport.

However, this plan was not implemented as the AMC made visual contact with R118 and
instructed the pilot to route directly overhead the airport.

At the same time CLB205 advised that they wished to commence descend.

As there was no longer a conflict with R118, the AMC cleared CLB205 for the approach and he passed on traffic information to CLB205 with regard to R118.

The AMC stated that to his mind when CAL01 advised that he was turning in behind the
number one (CLB205), this intimated to him that CAL01 had visual contact with the aircraft and would pass behind him.

Radar showing how close the planes got to one another. Air Accident Investigation Unit Ireland Air Accident Investigation Unit Ireland

Air traffic

He recognised that he could have verified that CAL01 actually had CLB205 in sight but he was very busy at the time monitoring the transit of R118 across the airport. He also was communicating with another aircraft and an engineering vehicle

The AMC stated that he had experience of aircraft conducting calibration flights before, but not with two aircraft at the same time.

He felt that in hindsight he should have grounded one until the first aircraft had completed its task.

At his previous location at Weston Airport there was a radar feed from Dublin Airport which was utilised solely as an advisory aid to the controllers. He considered that this was very beneficial to the operation, as they could verify position reports and compliance with
instructions given to aircraft, and it also served as a “second pair of eyes” for the controller.

The lack of radar information at the airport was determined by the investigators to be a contributory factor in the occurrence of the near miss.

A safety recommendation was made to the aerodrome licensee in conjunction with the IAA with regard to the provision of radar display information at the airport.

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