Mid-Air Avoided Off Irish Coast  

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An error by Irish air traffic controllers put two jetliners on a collision course last September, but fast action by the pilots narrowly averted a mid-air tragedy by 17 seconds, according to Ireland's Air Accident Investigation Unit (AAIA).

The Ryanair Boeing 737 was enroute from Stansted to Cork with 179 passengers and the Flightline MD-83 with 164 customers onboard had departed Faro, Portugal for Dublin on Sept. 23, 2007.

The commercial transports came within 600 feet of each other vertically, some 400 feet closer than the allowed. They passed within three nautical miles of each other laterally versus the customary five.

Quick action by the pilots, reacting to onboard collision avoidance systems, saved the day.

The AAIA report said that "in spite of at least four warnings, one verbal and three electronic, the radar controller appeared not to comprehend the closing speeds of the two aircraft and allowed the higher one to descend and lose the required minimum vertical and lateral separation from the other. What ensued was a critical failure of the human element of the ATC system to rectify this situation.

"The last resort safety net in this extreme circumstance, each aircraft's on board Traffic Alert and Collision Avoidance System (TCAS), automatically activated with a commanded warning to each aircraft. The pilot of each aircraft reacted correctly to this TCAS warning, one climbed his aircraft as instructed by the system and the other descended his aircraft as instructed by the system.

"A potential mid-air collision was thus narrowly avoided due to the TCAS activation and the correct response of the pilots," the incident investigators concluded.

The report said "the safety of RYR 907 and FLT 1174 was seriously compromised by the failure of the radar controller to maintain a safe Flight Level between the two aircraft. There were no electronic/technical reasons that contributed to this failure. This was a human error. All air traffic management safety defenses, both human and electronic, were breached in this event. The safe resolution of this occurrence was ultimately resolved by the last line of defense, the aircraft's on board TCAS resolution advisories, and not by ATC intervention."

The AAIA recommended that:

1. The Irish Aviation Authority (IAA) review training procedures employed by radar and planning controllers and amend as necessary in the light of the identified events that led to this serious incident.

2. The IAA review the TRM Course content/frequency of delivery, with specific emphasis on the human factors contributing to this serious incident.

3. The IAA appoint a Standards Officer in Shannon, to interact between Operations and the Shannon Training Centre, to more effectively link Operational and Training areas of responsibility.

In a statement, the IAA, which controls airspace over Ireland, said it welcomed the AAIA report into the serious incident, accepting all of the safety recommendations made.

The radar and planning controllers involved in the near mid-air were temporarily relieved of their duties. "The radar controller involved underwent a training program tailored to the lessons arising from the event, and subsequently returned to operational duty," the IAA stated.