Description

On 14 January 2010, two Ryanair Boeing 737-800 aircraft were operating scheduled passenger flights from Girona to Las Palmas and Turin respectively and had taxied from adjacent gates at Girona in normal day visibility in quick succession. The Turin-bound aircraft taxied first but because it was early at the holding point for its Calculated Take Off Time (CTOT), the other aircraft was designated first for take off and during the overtaking manoeuvre in the holding area, the wing tip of the moving Las Palmas aircraft hit the horizontal stabiliser of the Turin bound aircraft causing minor and substantial damage to the respective aircraft. None of the respective 81 and 77 occupants were injured and both aircraft taxied back to their gates.

Investigation

An Investigation into the collision was carried out by the CIAIAC. It was established that both aircraft were only fitted with steering tillers at the left hand pilot position, which meant that prior to sufficient speed being reached on the planned take off roll for directional control by use of the rudder to be effective, both aircraft were being controlled by their respective commanders.

It was noted that the stop bar had recently been moved further from the runway because of the planned introduction of Cat 2/3 ILS operations and that this action had reduced the minimum lateral clearance between an aircraft correctly parked at the stop bar and an overtaking aircraft maintaining the marked centreline.

It was found that the aerodrome map for ground movement shown in the AIP on the day of the collision had the stop bar for runway 20 in the old position, whereas the airport reported that the location of the stop bar had been changed in October 2009 and that, although the information for publication in the AIP was sent on 19 August 2009, no such publication had occurred or any Notice To Airmen been issued to that effect. It was noted that although AENA had conducted a ‘Functional Hazard Assessment’ of the modifications associated with moving the runway 20 threshold, this assessment had not analysed risks associated with the airport infrastructure.

It was noted that dimensions of the taxiway at Girona Airport were in compliance with the stipulations of ICAO Annex 14, as was the distance separating the runway and taxiway centrelines.

It was established that the fact that the new stop bar position favoured positioning the stopped aircraft on right hand side of the holding area was not considered by ATC and they did not give specific instructions to the aircraft which was instructed to wait to stop at either end of the stop bar and “whether the passing manoeuvre took place to the left or right was undoubtedly considered irrelevant to the safety of the operation (and) controllers (were not) aware of the existence of a collision risk”.

The absolute responsibility of the commander of a moving aircraft for the safety of that aircraft in respect of any fixed or stationary obstruction were note and it was concluded that the overtaking aircraft had “misjudged the distance separating both aircraft”.

The documented Findings of the Investigation included that:

• The stop bar at the runway 20 threshold had been moved without the new location being published in the AIP.

• As the Las Palmas-bound aircraft deviated to the right of the stationary Turin-bound aircraft in order to overtake it, the left wingtip of the former struck the trailing edge of the horizontal stabiliser of the latter.

• If both aircraft had been in the positions where, in theory, they should have been during the takeover manoeuvre, the distance between the right edge of the horizontal stabiliser on the stationary aircraft and the left wingtip of the overtaking aircraft would have been 4.7 m.

• The clearance when overtaking the stop bar involved in this collision would be greater if the stationary aircraft was positioned to the right of the stop bar and overtaken on the left whereas the reverse applied in this case.

• It could not be determined whether the stationary aircraft was positioned with its nose section over the stop bar and its longitudinal axis exactly atop the taxiway centreline (the position that, in theory, it should have had) or whether the overtaking aircraft was accurately following the marked taxiway line (which it should have been).

The Investigation determined that cause of the collision was a combination of two factors:

• the misjudgment on the part of the crew of (the overtaking) aircraft of the distance separating their left wingtip and the nearest part of the stationary aircraft (the right edge of the horizontal stabilizer).

• the decreased room available for overtaking in the transition zone between the taxiway and the holding area at the head of the runway as a consequence of having moved the stop bar backward.

Two Safety Recommendations were made:

• That AENA report changes to markings affecting airport operations, as well as of any possible consequences to aircraft operations, as soon as possible via the method deemed most suitable, such as the issuing of a NOTAM, whenever the publication of the AIP that details said changes is delayed. (REC 05/11)

• That AENA review the risk analysis methods of the safety studies it conducts so as to ensure that said analyses consider the risks to both air navigation activities and airport infrastructure. In particular, an additional margin shall be included before the stop bar or hold point for the pilot to stop and from which he can see the stop bar or hold point. For a 4-C category airplane, this distance shall be approximately 5 m. (REC 06/11)

The Final Report Report IN-001/2010 was approved on 21 February 2011.

Further Reading

• Ground Operations
• Wing Tip Clearance Hazard
• Ground Accident Prevention Program
• Situational Awareness