What happened
On March 29, 2018, at approximately 19:56 local time, a loss of separation occurred in the airspace near Amsterdam Airport Schiphol involving two commercial passenger flights. A Boeing 737-700, registration PH-BGK, was performing a go-around on runway 18C. Simultaneously, a Boeing 737-800, registration PH-HXF, was initiating its takeoff from runway 24. Because these two runways converge, the flight paths of the two aircraft were set to intersect.
As the crew of the PH-BGK announced their intention to abort the landing and perform a go-around, the runway controller attempted to instruct the departing PH-HXF to abort its takeoff. However, the controller used the incorrect flight number during the instruction. Consequently, the crew of the departing aircraft did not respond to the command and continued the takeoff. To prevent a collision, the controller directed both aircraft to perform divergent turns. The two aircraft eventually achieved separation, with the minimum distance recorded at approximately 960 meters horizontally and 300 feet vertically.
The investigation
The Dutch Safety Board (OVV) examined the operational procedures used by Air Traffic Control the Netherlands (LVNL). The investigation revealed that the controller had already cleared the PH-HXF for takeoff before the landing of the PH-BGK was confirmed. This was possible because the LVNL Operations Manual contained a specific procedure allowing for reduced separation between aircraft on dependent, converging runways to increase airport capacity.
Furthermore, the investigation found that this specific reduced-separation procedure had not been explicitly approved by the Human Environment and Transport Inspectorate (ILT). The procedure had been carried over from a previous manual during a conversion process and had escaped scrutiny during subsequent manual updates and regulatory approvals.