Description

On 29 February 2004, a B732 being operated by Ryanair and taxiing in after landing across an intermediate point on runway 06L did not notice a MyTravel Airways AIRBUS A-321 accelerating along the same runway on its take off roll in normal day visibility. However, the A321 saw the potential conflict and made a high speed rejected take off as the 737 continued across the runway ahead, thereby eliminating any risk of collision.

Investigation

An Investigation was carried out by the UK AAIB. It was noted that the visibility was good and that the crossing point involved was at about the mid point of the 3048 metre long runway.

It was established that both aircraft had been operating in accordance with their respective ATC clearances and calculated from recorded data that the 737 had been taxiing at an average speed of 33 knots between clearing runway 06R after landing and entering runway 06L. The rejected take off carried out by the A321 had been commenced from above 100 knots and when the 737 had entered the runway, the A321 was away from the crossing point 873 metres. By the time the 737 vacated the runway, the A321 was, as a result of the rejected take off action, still 600 metres from the crossing point.

It was found that the A321 had been cleared for take off immediately before the 737 had checked in on the same frequency with a current clearance to hold short of the runway. A crossing clearance was then given and repeated because of another transmission from a non involved aircraft over the first attempt. Although the first transmission of the crossing clearance was not heard by the A321 crew, it was noted that it had coincided with the completion of standard flight crew calls related to their take off. The repeat of the clearance was heard and, as its significance was being assimilated, the 737 was seen entering the runway at what was perceived as a very rapid speed and initiation of the rejected take off, shortly after the standard airspeed crosscheck at 100 knots had been completed, followed, accompanied by the call ‘Stopping’ on frequency.

The 737 commander recollected looking left as his aircraft was about to enter runway 06L, but he had not seen the A321 and since it was evident that the position of his aircraft at that time would have allowed him to see the other aircraft, it was concluded that this reported check “was not effective”. It was noted that the Ryanair maximum permitted taxi speed was 30 knots, less than the average speed being maintained.

The runway controller had qualified eight years previously, had been at Manchester for four years and was also a current OJTI. He stated that he remembered giving a line-up clearance to the A321 but did not remember giving the subsequent take-off clearance. His recollection was that be had given the inbound aircraft priority across runway 06L. He advised that he thought he had placed the Flight Progress Strip (FPS) for the 737 in the corresponding position and that when he had seen the A321 coming into view and accelerating, his initial thought was that it had begun take off without clearance. The controller did not remember seeing the Runway Incursion Monitor (RIM), which produced only visual alerts, activate as the conflict occurred.

It was noted that the RIM function in place at the time was only applicable to the incident runway and was set up to generate a conflict alert when:

• An aircraft approaching the runway is within 1000 metres of the threshold and the

runway is not clear in 'normal' visibility.

• An aircraft approaching the runway is within 2 nm of the threshold and the runway is not

clear in LVP only.

• The speed of a departing aircraft' exceeds 40 knots and the runway ahead is not clear.

The Investigation found via discussions with ATC personnel at Manchester that the RIM system was susceptible to ‘spurious’ alerts, but nevertheless had been enabled during the incident and despite neither runway controller noticing, had activated under the third of the listed criteria.

It was considered “highly likely” that the controller involved had “lost situational awareness at a critical time”. Once this had happened, it was noted that the first line of defence was procedures which would highlight to the controller that he had made a mistake. Since in this Case, these procedures “were not effective” it was concluded that “a review of the procedures and RTF phraseology/discipline would therefore be sensible” and noted that such a review was already in hand. It was also found that prior to the incident, NATS had recognised an increase in the number of runway incursions at Manchester and were undertaking a review of their local FPS procedures. Following the occurrence under investigation, it was noted that it had been decided to extend this review to all NATS airports so as to facilitate the establishment of a common NATS standard.

In summary, the Investigation noted that the incident had occurred following a human error by a controller and accepted that even when procedures are continually evaluated to minimise the opportunities for such errors, they will still occur at times. It was observed that defence against this incident becoming an accident was the effective situational awareness displayed by the A321 flight crew, which had demonstrated the important of such awareness.

It was decided that as the ANSP NATS had already taken appropriate measures to review, standardise and improve their procedures, no Safety Recommendations were necessary. The Final Report of the Investigation was published in November 2004

Related Articles

• Runway Incursion
• Taxi-in Runway Incursions
• Situational Awareness