A mid-air crash between two passenger aircraft carrying more than 350 people over the south coast of Ireland was narrowly averted after an error by air traffic controllers, a report published today reveals.
The Ryanair Boeing 737 and Flightline MD-83 were flying in opposite directions last September 23 rdwhen they narrowly avoided a collision, air accident investigators said. They were just 17 seconds from a crash after air traffic control issued conflicting instructions to the two pilots.
There were some 179 passengers on the Ryanair flight and 164 on the Flightline aircraft, with six crew on each.
The planes came within 600 feet of each other vertically, some 400 feet closer than the allowed minimum. They passed within three nautical miles of each other laterally, although international aviation rules say aircraft should be separated by at least five.
Quick action by the pilots, who were forced to respond to crash-avoidance warning systems on their aircraft, helped to avert tragedy.
Accident investigator Frank Russell
A report by the Air Accident Investigation Unit (AAIU) says that air traffic control (ATC) at Shannon cleared the Ryanair flight travelling from Stansted to Cork to descend from 30,000 feet to 29,000 feet and then 10,000 feet.
However, this path "conflicted" with the clearance given to the northern-bound Flightline craft travelling from Faro to Dublin.
"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," the report said.
"What ensued was a critical failure of the human element of the ATC system to rectify this situation."
AAIU investigator Frank Russell said the "last resort" safety net in this "extreme circumstance", was the automatic activation of an onboard traffic alert and collision avoidance system (TCAS).
"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. With separation subsequently re-established by ATC, both aircraft continued onwards and landed at their respective destinations."
In a statement, the Irish Aviation Authority, which employs air traffic controllers and manages the airspace over Ireland, said it welcomed the AAIU report into the serious incident and that it had accepted all of the safety recommendations made.
The recommendations included a review of training procedures and the appointment of a standards officer in Shannon to interact with the air traffic controller training centre.
"Safety is the IAA's number one priority. The IAA, and Ireland, has an excellent air safety record and, as acknowledged in the report, the AAIU has not investigated an incident of this seriousness in the previous seven years," the IAA said.
The incident was immediately reported to the duty station manager and the controllers involved were relieved of their positions and their licences to operate were withdrawn in line with normal procedure.
"Following this serious incident, the radar controller involved underwent a training programme tailored to the lessons arising from the event, and subsequently returned to operational duty."