Notice
On Sunday 10 November two aircraft came closer to each other than the separation minimums stipulate. The incident occurred after departing consecutively from the Oostbaan (22) and the Aalsmeerbaan (18L) at Schiphol.
LVNL is conducting its own investigation into this incident and has reported this incident to the Dutch Safety Board, the Human Environment and Transport Inspectorate and the Public Prosecution Service in accordance with the investigation process.
Situation and investigation
Two take-off runways and one landing runway were being used in the morning, namely the Kaagbaan (24) for take-offs to the west and north, the Aalsmeerbaan (18L) for take-offs to the south and east and the Polderbaan (18R) for landings. In addition to this runway combination for commercial air traffic, the Oostbaan (22) was being used for occasional general aviation.
A Diamond Twin Star (general aviation) and an Airbus 220 were ready for depature. The Diamond Twin Star (general aviation) was going to depart from the Oostbaan and the Airbus A220 was going to depart from the Aalsmeerbaan to the east.
The Diamond Twin Star was the first to be granted permission to take off from the Oostbaan. To ensure that the Airbus A220 would also be able to take off from Aalsmeerbaan after that, the tower controller provided the Diamond Twin Star with additional departure instructions prior to take-off, which were correctly read back by the pilot. One of these additional departure instructions was not to depart according to the Standard Instrument Departure (SID) route, but to fly straight ahead (runway heading) and await the next instruction. After the Diamond Twin Star had taken off and passed the intended departure route of the Airbus A220, the tower controller gave the Airbus A220 take-off clearance.
After that the tower controller checked that both aircraft were flying in accordance with the correct departure route and instructions and instructed the pilots to switch to the radar controller's frequency. The tower controller also instructed the Diamond Twin Star pilot to report the current heading (runway heading) to the radar controller ('report your heading to departure'). The pilot then responded that the heading was being adjusted to the departure route ('adjust the heading for departure'). The tower controller did not notice that the pilot had read back a different instruction.
The pilot of the Diamond Twin Star interpreted the instruction as meaning that the aircraft should continue towards the standard departure route (SID) and then turned the aircraft left towards the flight path of the Airbus A220. Shortly afterwards the tower controller noticed this anomaly and called on the Diamond Twin Star pilot to steer immediately to the right.
The radar controller instructed the pilot of the Airbus A220 to steer further to the left. At that point the separation standard* was exceeded and the minimum separation between the aircraft was reached. The intervention of the air traffic controllers caused the aircraft to diverge and restored the necessary separation.
Minimum separation
*The aircraft were at 3,000 feet (900 metres) altitude and were no longer visually perceptible to air traffic control due to cloud cover. The separation standard which is then used is radar separation with a minimum of 3 nautical miles (5.5 kilometres) or 1,000 feet (300 metres). The minimum distance between the Diamond Twin Star and the Airbus A220 was 1.9NM/400ft.
Conclusion and follow-up
After the incident the tower controller was relieved by a colleague and the situation was immediately discussed with the supervisor. The pilot of the Diamond Twin Star was also contacted immediately after the flight to discuss the situation. The loss of distance occurred after the Diamond Twin Star pilot misinterpreted the instruction to inform the radar controller of the aircraft's current heading. The pilot interpreted this as meaning that the aircraft had to adjust the aircraft's heading to continue on the standard departure route. The tower controller did not notice that the pilot had read back the instruction wrongly, so the pilot was not corrected in time.
The Air Traffic Control Netherlands investigation department also contacted the pilot later to gather more information about this incident. The pilot was invited to Air Traffic Control Netherlands so that the incident could be discussed and so that the parties involved could take learnings from each other’s perspective.
In addition, more serious incidents are discussed with the relevant group of air traffic controllers on a recurring basis as examples to learn from and be alert to in this type of situation.
Classification: Major Incident
