Two aeroplanes full of passengers nearly collided at Dublin Airport as they were not on the same transmission frequency, an investigation has found.
A Boeing aircraft with 176 passengers passed in "close proximity" to the front of an Airbus aircraft carrying 137 passengers last May.
The commanding pilot of the Airbus had signalled to the oncoming Boeing to stop, but the Boeing did not receive the transmission, according to a report by the Air Accident Investigation Unit (AAIU), which made safety recommendations in light of the case.
The report found there had been no damage to either aircraft and no one was injured.
The incident took place on a “taxiway” lane, which planes use to travel onto the main runway, and neither aircraft was in the process of taking off or landing. The AAIU inquiry was ordered due to the small margin of clearance between the two aircraft.
The near-contact between the grounded planes took place at a designated “hot spot” along the airport taxiway system, the report says.
The area had been the site of two previous aircraft ground collisions, which were the subject of previous accident reports published in 2015 and 2016.
The October 2015 report recommended that the Dublin Airport Authority, now rebranded simply as DAA, "conduct a critical review of the taxiway system at Dublin Airport, to ensure that taxiway routes are as simple as possible in order to avoid pilot confusion and the need for complicated instructions".
Following the report, the DAA carried out significant work realigning the taxiway lane along the section in question.
In the incident last year, the commanding pilot in the stationary Airbus had “expected” the oncoming Boeing to stop, and transmitted a message for the aircraft to hold position when it did not, the report said.
However, the Boeing did not hear any of the transmission and proceeded to overtake the Airbus in the queue to the runway.
The Airbus pilot also contacted the air-traffic control tower, from which the Boeing pilot was contacted.
In a message to the air-traffic controller, the Airbus pilot said the Boeing “only just had wing-tip clearance to go in front of us there”.
In an interview with air-accident inspectors, the commanding pilot of the Airbus estimated “the wing tip of the [OTHER] aircraft missed our aircraft nose and cockpit by approx three meters”. The Boeing aircraft took off a short time later.
The Airbus pilot estimated the Boeing was travelling at around 24 km/h when it overtook their plane, according to the report.
Following the near miss, the Irish Aviation Authority (IAA) examined if it would be feasible to ensure all aircraft moving near each other were on the same radio frequency.
However the IAA concluded as different areas were managed by separate air-traffic controllers, it was “unavoidable” to have nearby aircraft on different frequencies while crossing between traffic-controller areas.
The report found that the Boeing aircraft had not been given “sequencing” instructions, on the order in which planes are to move from a taxiway queue onto the runway to begin takeoff.
The report’s main safety recommendation was that the IAA should amend its procedures at Dublin Airport “to include mandatory sequencing instructions where aircraft are in a queuing situation and are joining from more than one taxiway”.