On Friday 6 September 2019, an aircraft at Amsterdam Airport Schiphol took off from a taxiway instead of using runway 18C (Zwanenburgbaan) southwards. By order of air traffic control, the crew aborted the take-off. There was no conflicting traffic nearby at that time. The occurrence was jointly investigated by the parties involved. This investigation took place based on the Joint Sector Integral Safety Management System (ISMS). The sector parties involved reported the incident to the Onderzoeksraad voor Veiligheid (Dutch Safety Board).
A Boeing 737 aircraft taxied towards runway 18C via taxiway C around 06.00 hours (local time). It was dark, weather and visibility were good, and there was relatively little traffic at the airport. While taxiing on taxiway C, the Boeing reported it was ready for departure. The air traffic controller gave the pilot take-off clearance to depart from runway 18C. The crew of the Boeing requested the air traffic controller if they could use an intersection, but given the position of the Boeing, it was decided in mutual consultation to take off from the beginning of the runway (W1). To get there, they had to take a turn at the end of taxiway C (at point C1) and go straight on to W1. After point C1, the Boeing continued its turn and ended up on taxiway D. After this turn, the Boeing started its rolling take-off without stopping. A colleague in the tower alerted the air traffic controller to the situation. That air traffic controller then intervened by instructing the Boeing to come to an immediate halt. The Boeing aborted its take-off and came to a standstill on taxiway D. There was no other traffic on taxiway D during the occurrence, so there was no risk of collision. The Boeing taxied back to the beginning of runway 18C and took off without any problems.
Results of the investigation
This occurrence was investigated jointly with the sector parties involved based on the ISMS. The investigation yielded the following results:
The investigation revealed that the turn at point C1 could lead to confusion for aircraft crews regarding the taxiing direction. When taking off from runway 18C southwards, aircraft taxi to that runway via taxiway D or taxiway C. Both taxiways are equipped with centreline lighting. The lighting along taxiway C in the direction of runway 18C (point C1) is not equipped with centreline lighting, because that area is not designed for conditions that involve reduced visibility (such as fog) This creates a dark location at point C1. Moreover, the yellow centreline marking from taxiway C to runway 18C is interrupted at C1. This is to prevent potential runway incursions. As soon as the Boeing’s lights, which are used for take-off and landing, are switched on at C1 while it is dark, the yellow centreline marking will be visible, guiding the aircraft crew from taxiway C to taxiway D.
Some of the features of taxiway D differ from taxiway C, such as the width, the colour of the concrete and the taxiway edge lights, which might have given the crew the impression that taxiway D was the take-off runway.
It is unusual to use runway 18C as a take-off runway during the night. When taking off southwards at night, it is customary to use runway 24 (Kaagbaan), but that runway was under maintenance at the time of the occurrence. Aircraft usually taxi via taxiway D to the take-off point of runway 18C (W1). The reason for having the aircraft taxi via taxiway C was that taxiway D was in use for landing traffic to taxi from runway 18R (Polderbaan) to the gates.
The Boeing reported it was ready for take-off, and the air traffic controller then issued take-off clearance to the Boeing while it was taxiing on taxiway C. An air traffic controller may issue take-off clearance as soon as an aircraft reports that it is ready for take-off, is approaching the take-off runway, and there is no conflict with other traffic. Those conditions were met. On that night, eleven other aircraft taxied in the same way via taxiway C and took off from runway 18C without any problems. Air traffic control was not aware of the fact that the centreline lighting and markings on the taxiway did not provide a continuous line between taxiway C and runway 18C. In the perception of the air traffic controller, there was nothing that could go wrong while the aircraft was taxiing. After issuing take-off clearance, the air traffic controller proceeded to other work activities in the tower, with the intention of actively observing the departing Boeing again as soon as it started its take-off on runway 18C.
The Boeing crew had reported that they were ready for take-off, the air traffic controller’s take-off clearance had been received, and the crew were preparing for take-off during the turn from taxiway C to C1. At that moment, the attention was divided between inside and outside the cockpit. Preparations for take-off were being carried out inside the cockpit, and at the same time the crew was looking outside to navigate and manoeuvre. These preparations were carried out in a timely manner so the aircraft would be able to perform a rolling take-off. A rolling take-off means that the Boeing would turn onto the runway and start its take-off without stopping. That is the policy of the airline based on Boeing’s advice.
In most cases, the operational situation allows the air traffic controller to route an aircraft via the directly adjacent taxiway to the take-off runway, after which the crew turns onto the take-off runway with a single turn. During the occurrence, the aircraft was taxiing via the outermost taxiway C to runway 18C, which would have involved taxiing straight ahead after the first turn before turning onto the take-off runway. Partly due to the infrastructural situation at point C1, an error occurred, as a result of which the Boeing entered taxiway D in a single turn and started its rolling take-off.
This occurrence happened due to a combination of circumstances. The infrastructure between taxiway C and taxiway D, at point C1, gave the crew of the Boeing the impression that they had turned onto runway 18C, whereas in reality they were on taxiway D. The crew received take-off clearance from the air traffic controller and were directed to the take-off runway via the outermost taxiway. After their turn at C1, they did not end up on runway 18C, but on taxiway D. At that time, the crew was preparing for a rolling take-off, which meant that they had to divide their attention between operations in the cockpit as well as navigating and manoeuvring by looking outside. The air traffic controller was focused on other work in the tower and did not initially notice the Boeing’s turn to taxiway D. Once the Boeing was on taxiway D, the deviating characteristics of the taxiway compared to the take-off runway (lines, colour of the lighting, etc.) were no longer distinctive enough to catch the crew’s attention and notify them that they were preparing to take off from a taxiway.
During the rolling take-off, the air traffic control detected that the Boeing was on the taxiway instead of on runway 18C. The air traffic controller intervened and the Boeing crew aborted the take-off.
Follow-up action based on the investigation
As a result of the investigation, the ISMS set up a Task Force with participants from the airlines, air traffic control and the airport. The Task Force introduced a number of short-term measures to mitigate the risk of an aircraft taking off from taxiway D instead of from runway 18C. Important measures included changes to the lines at C1 and placement of extra markings. The hotspot map (map that indicates potentially risky locations at Schiphol for pilots) was also expanded to include the location around C1, and a NOTAM (message for all pilots) was issued that requires extra attention from the pilots. In addition, aircraft that take off from Runway 18C after dark will for the time being be guided by air traffic control via taxiway D by default. These measures will prevent the occurrence from happening again. Over the coming year, the Task Force will work on additional structural measures to mitigate the risk of a taxiway take-off for all relevant take-off runways at Amsterdam Airport Schiphol: runway 18C, runway 24 and runway 27 (Buitenveldertbaan).
Classification: Significant occurrence