On Monday 27 June, two aircraft flew closer together than is permitted by the separation minima. The aircraft took off consecutively from the Kaagbaan (24) at Amsterdam Airport Schiphol. LVNL (Air Traffic Control the Netherlands) is conducting an investigation into this occurrence itself and reported the occurrence to the Onderzoeksraad voor Veiligheid (Dutch Safety Board).
Description of occurrence
A Boeing 737 MAX 8 (B38M) aircraft took off from the beginning of runway 24 (Kaagbaan). One minute later, an Embraer 175 aircraft (E75L) took off from the same runway. Both aircraft initially flew the same route eastward after taking off. After take-off, the E75L caught up with the B38M in both altitude and speed, bringing the aircraft within the applicable separation minima.
The radar controller observed the E75L overtaking the B38M . At that time, the B38M and E75L were both flying at Flight Level 40 (approximately 1.3 kilometres altitude). The radar controller instructed the E75L to stop climbing at Flight Level 50 (1.5 kilometres altitude).The radar controller subsequently gave heading instructions to both the B38M and the E75L to resolve the situation.
During this occurrence, the minimum distance between the two aircraft was approximately 1.6 nautical miles (3 kilometres) horizontally and 200 feet (60 metres) vertically. The minimum separation is 3 nautical miles (5.5 kilometres) horizontally or 1,000 feet (300 metres) vertically. At the time when the minimum distance was reached, the E75L and the B38M were already flying away from each other, thus resolving the loss of separation.
Conclusions of the investigation
The speed of the E75L after take-off was higher than that of the B38M, which reduced the distance between the aircraft. In addition, the B38M’s climb was less steady than that of the E75L, which also reduced the difference in altitude between them. The investigation showed that the B38M had – without reporting this to ATC – followed a different climb procedure (the ‘NADP1 procedure’) than the NADP2 procedure prescribed since 8 June 2022 for outbound traffic at Schiphol. The NADP2 procedure results in a higher vertical and horizontal speed, achieved faster after take-off than in NADP1, and is prescribed specifically to avoid significant speed differences between aircraft after take-off. Airlines and pilots were notified of this procedure through a NOTAM (Notice To Airmen). The E75L did fly according to this prescribed procedure.
Finally, there was a difference in the lateral flight path of the two aircraft. The B38M took a wider flight path in the first curve than the E75L, which flew its departure route very precisely.
LVNL has informed air traffic controllers about this and asked them to remain alert for such speed differences after take-off. The airline concerned has also been informed of the mandatory requirement to fly according to the NADP2 procedure and to report any deviations from it. By means of a temporary additional message via ATIS (Automatic Terminal Information Service: a system that provides pilots with information about the airport in question), pilots have been once again reminded of the importance of flying the correct procedure (NADP2). The lateral flight path after take-off is also being subjected to additional internal investigation.
Classification: major incident