What happened
On the morning of November 13, 2012, during a period of heavy inbound traffic at Amsterdam Airport Schiphol, two aircraft flying at the same altitude came within unsafe proximity to one another. The first aircraft, a Boeing 737-800 approaching runway 18R from the west, and the second, an Airbus A330-200 approaching runway 18C from the east, experienced a reduction in separation below the required minimums.
To increase efficiency during a temporary lull in western traffic, the air traffic controller managing the eastern approach had instructed aircraft to descend to 2,000 feet rather than the standard 3,000 feet. As the Airbus descended to this lower altitude, the Boeing 737-800 was also established on the 2,000-foot level. The two aircraft eventually reached a minimum distance of just 0.6 NM with no vertical separation between them.
The investigation
The Dutch Safety Board (OVV) examined the actions of Air Traffic Control Netherlands (LVNL) and the operational procedures in place during the morning peak. The investigation focused on how the separation minima were breached and whether the established safety nets functioned correctly. The inquiry reviewed the flight paths, the instructions provided by the controllers for both runways, and the decision-making process regarding altitude changes during parallel approaches.
Findings
- The controller for runway 18C authorized the Airbus to descend to 2,000 feet to expedite traffic flow, which eliminated the vertical buffer between the two arrival streams.
- The deviation from standard approach altitudes directly contributed to the loss of separation, as the two aircraft were now flying at the same level.
- While the controllers recognized the potential conflict and issued heading changes to maneuver the aircraft away from each other, the margin of safety was significantly compromised.
- The Airbus crew maintained visual contact with the Boeing, which helped prevent a collision, but the separation breach had already occurred.