On Sunday 1 December, during parallel approaches to the Zwanenburgbaan runway (36C) and the Aalsmeerbaan runway (36R) at Amsterdam Airport Schiphol, two aircraft flew closer together than is permitted by the separation minima.
LVNL (Air Traffic Control the Netherlands) is conducting an investigation into this occurrence itself and reported the occurrence to the Onderzoeksraad voor Veiligheid (Dutch Safety Board).
Description of occurrence
An Airbus A320 (A320) aircraft was approaching to land on runway 36R (Aalsmeerbaan) from the east. The aircraft descended to 3,000 feet (900 meters). Coming in from the west, an Airbus A321 (A321) aircraft was on approach to land on runway 36C (Zwanenburgbaan). This aircraft descended to 4,000 feet (1,200 meters), in accordance with the procedure for this runway combination.
There were two approach controllers on duty at the time, one assigned to the Aalsmeerbaan and another to the Zwanenburgbaan.
The approach controller for the Zwanenburgbaan runway instructed the A321 to turn to pick up the Instrument Landing System (ILS), and gave permission for the final approach. At that time, the A321 commences its descent. The approach controller for the Aalsmeerbaan runway instructed the A320 to turn to pick up the Instrument Landing System (ILS), and then descend to 2,000 feet (600 meters). The vertical separation between the two aircraft was less than the standard of 1,000 feet (300 meters).
Both approach controllers, who were sitting side by side, saw the situation, and the approach controller for the Zwanenburgbaan runway instructed the A321 to stop its descent at 3,000 feet (900 meters). The approach controller for the Aalsmeerbaan runway instructed the A320 to descend faster to an altitude of 2,000 feet (600 meters). There was no danger of collision. Both aircraft landed safely.
Minimum distance
The minimum distance between the two aircraft was 1.6 nautical miles (nearly 3 kilometers) on the horizontal axis and 600 feet (180 meters) on the vertical axis. The separation standard for the phase of the final approach in which the flights were at that moment is 1,000 feet (300 meters) vertically.
Conclusions
The occurrence resulted from the fact that both aircraft received instructions to pick up final approach at a distance shorter than usual from the runway threshold. The A321 received permission for final approach and therefore started its descent while the A320 was also still descending. The corrective instructions provided by both approach controllers were unable to prevent a situation from occurring in which the minimal distance between the two aircraft was less than the standard of 1,000 feet (300 meters).
Based on this occurrence and a number of comparable occurrences, Air Traffic Control the Netherlands (LVNL) has conducted an internal investigation to thoroughly analyze all underlying causes of occurrences with parallel approaches at Schiphol Airport. The results of the investigation have led to the implementation of a number of improvements, such as paying extra attention to the specific procedures for parallel approaches among air traffic controllers as well as pilots, researching technological options for providing further support to air traffic controllers, and better monitoring of the parallel operation to learn from the resulting observations.
Classification: major occurrence