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On Friday, November 28, two aircraft approached each other closer than the separation minima require while approaching the Zwanenburg runway (18C) at Schiphol Airport.
LVNL is investigating this incident and has reported it to the Dutch Safety Board, the Human Environment and Transport Inspectorate, and the Public Prosecution Service in accordance with the investigation process.
A Boeing 737-800 is approaching from the east under reduced visibility conditions for an ILS approach to the Zwanenburg runway (18C), behind an Airbus A321neo on the same runway. Both aircraft are being guided by the approach controller into the final approach. The Boeing begins the final approach at a significantly higher speed than the Airbus, causing the distance to the Airbus ahead to decrease more rapidly.
The approach controller therefore instructs the Boeing to further reduce its speed to the landing speed, informs the tower controller of the speed difference, and hands the aircraft over.
The tower controller then instructs the Airbus to clear the runway as soon as possible after landing. Both controllers monitor the situation and determine shortly thereafter that, despite the measures taken, the operational margin will be insufficient. They therefore decide to abort the Boeing’s approach. The tower controller informs the Boeing’s crew that a new approach will follow and instructs them to fly an easterly course and climb to 2,000 feet.
When, after some time, the tower air traffic controller still sees no effect from these instructions, he asks the pilot whether the turn has already been initiated. The pilot replies that it is happening at that moment. Radar data shows that at that moment, the aircraft were closest to each other.
The Boeing then turns onto the instructed easterly course, after which sufficient separation from the Airbus is reestablished, and the aircraft is guided for a new approach on the same runway.
The minimum distance between the two aircraft is approximately 1.5 nautical miles (3.3 kilometers) horizontally and 500 feet (183 meters) vertically. The separation standard is 3 nautical miles (5.5 kilometers) horizontally or 1,000 feet (300 meters) vertically.
The analysis shows that the Boeing began the final approach at a relatively high speed. The approach controller recognized the aircraft’s speed trend later than usual.
Due to the speed difference, the Boeing closed in on the Airbus ahead. The approach controller and the tower controller coordinated the situation and took measures to resolve it. When these measures proved insufficient, the controllers decided to abort the Boeing’s approach.
The investigation revealed that the Boeing’s flight was part of a training exercise. Prior to aborting the approach, the captain spent time preparing the first officer for the procedure and the expected instructions. As a result, the instructions were carried out more slowly than usual, causing the separation to decrease further.
The findings of the investigation were communicated to the air traffic controllers involved and shared within the air traffic control group via a safety publication to draw lessons from the incident and raise awareness.
Despite the separation violation, the available procedures and safety barriers functioned properly. The investigation found no evidence of systemic deficiencies that would require additional risk management measures. LVNL therefore sees no reason to implement additional measures.
Classification: major incident