Notice
On Tuesday, 19 November, two aircraft came closer to each other than the separation minima stipulate, approaching Schiphol's Aalsmeerbaan (36R) and Zwanenburglaan (36C), respectively.
Air Traffic Control Netherlands (Luchtverkeersleiding Nederland, LVNL) is investigating this incident and, in accordance with the investigation process, has reported it to the Dutch Safety Board (Onderzoeksraad voor Veiligheid), the Human Environment and Transport Inspectorate (Inspectie voor Leefomgeving en Transport) and the Public Prosecution Service (Openbaar Ministerie).
Description of the incident
During stormy weather, inbound aircraft land on Schiphol's Kaagbaan (06) and Aalsmeerbaan (36R), while outbound aircraft depart from the Polderbaan (36L). A Boeing 737-800 (B738) approaching from the east is being routed to the Aalsmeerbaan (36R). A Boeing 767-300 (B763) approaching from the west is being routed to the Kaagbaan. Due to weather conditions, the B763 is high on its approach and the pilot reports to the air controller during the final approach that they will perform a go-around. Shortly afterwards, the tower controller relays the wind direction and speed to the pilot of the B738, who subsequently reports also initiating a go-around due to crosswind conditions.
Meanwhile, the landing runway configuration is changed to the Zwanenburgbaan (36C) and Aalsmeerbaan (36R) due to the cloud base. Both aircraft are scheduled for an approach on the Aalsmeerbaan (36R) after the go-around. The tower controller instructs the B763 and B738 to climb to 3000ft and 2000ft respectively and hands over both aircraft to the approach controller for the Aalsmeerbaan (36R). At the request of the pilot of the B738, the B738 is routed to the Zwanenburgbaan (36C) after which the flight is handed over to the approach controller for the Zwanenburgbaan (36C). The B763 is still scheduled to land on the Aalsmeerbaan (36R), but the controller inadvertently fails to pass on the runway to the pilot.
Following a series of heading instructions, the B738 then intercepts the Instrument Landing System (ILS) for its final approach to the Zwanenburgbaan (36C). The approach controller for the Aalsmeerbaan (36R) issues the B763 a series of heading instructions, followed by a clearance for a right turn to intercept the ILS of the Aalsmeerbaan (36R) and to descend to 2000 feet. The crew of the B763, however, assumes that they are being routed to the Kaagbaan (06) again and are confused by the instructions. They abort the left turn and inquire with the approach controller. This causes the B763 to cross the extended centreline of the Aalsmeerbaan (36R), coming within the separation criteria with the B738 on its final approach to the Zwanenburgbaan (36C). The approach controller issues the B763 a corrective heading instruction involving a right turn towards the northeast and instructs the aircraft to climb to 3000 feet. Additionally, the controller provides information concerning the position of the B738. After the B763 initially makes a left turn, the approach controller repeats the previous instruction to make a right turn. At the same time, the approach controller for the Zwanenburglaan instructs the B738 to turn left immediately to a westerly heading, with information about the position of the B763. As a result of these actions, the aircraft diverge from each other and are subsequently routed for an approach and landing without any irregularities.
Separation
The minimum horizontal separation between the two aircraft is about 1.6 nautical miles (3.0 kilometres) at the same altitude. The separation criteria are 3 nautical miles (about 5.5 kilometres) horizontally or 1000 feet (over 300 metres) vertically. After breeching the separation minima, the aircraft diverge and restore the necessary separation.
Investigation findings and follow-up action
The incident has been investigated by LVNL in coordination with the airline of the B763. The incident was the direct result of air traffic control scheduling the B763 to land on the Aalsmeerbaan (36R) after its go-around without informing the pilot. The various air traffic controllers involved were under the assumption that the other air traffic controller involved had informed the pilot of the B763 of the runway change. The crew of the B763 assumed they were approaching the Kaagbaan again and only verified this with air traffic following the uncertainty that arose after they intercepted the ILS. The stormy weather, causing two go-arounds and a runway configuration change, was a contributing factor. Lessons learned from the investigation include:
- The approach controller must always assign a runway to pilots after a go-around;
- Pilots should inquire with air traffic control if no runway is assigned;
- Approach controllers must monitor vertical separation during parallel approaches until both flights have intercepted the ILS heading guidance.
The lessons learned have been communicated to Schiphol air traffic controllers and pilots of the B767 fleet of the airline concerned.
Classification: major incident
