On 29 March 2018, a Boeing 737-700 (PH-BGK) being operated by KLM on an international passenger flight from Manchester to Amsterdam as KL1080 was on approach to runway 18C at destination in day VMC and had been cleared to land. It was close to touchdown when its crew transmitted that they were commencing a go-around. At this point a Boeing 737-800 (PH-HXF) being operated by Transavia on an international passenger flight from Amsterdam to Paris Orly as HV5193 had already been cleared for takeoff from runway 24 by the same TWR controller who then instructed it to stop but when it did not, they then instructed the aircraft on go around to turn right and the one departing from runway 24 to turn left which resulted in the minimum separation achieved being 0.5 nm laterally and 300 feet vertically.
The conflicting runway centrelines and the aircraft ground tracks after avoiding action. [Reproduced from the Official Report]
An Investigation into the reduced separation event was carried out by the Dutch Safety Board using recorded ATC data. It was established that at the time of the event, runways in use included 18C for landing and 24 for takeoff. The Boeing 737-700 was on approach to land on runway 18C when the crew advised shortly before touchdown that they were going around. The controller had already issued a takeoff clearance to the Boeing 737-800 on runway 24 and in view of the intersecting centrelines of these two runways was immediately aware of the potential conflict and instructed the aircraft taking off from runway 24 to stop. However, because this call was inadvertently prefaced with the wrong callsign, the aircraft continued its takeoff and so the controller issued turn instructions to both aircraft to increase separation.
It was found that the flight crew of both aircraft had already recognised the potential conflict and therefore promptly responded to the turn instructions given. Minimum separation was assessed as having been 960 metres (a little over half a mile) laterally and 300 feet vertically.
It was noted that the simultaneous use of the two converging runways involved was in accordance with the Operations Manual of the ANSP LVNL. The rules for this working practice were noted to be that normally, a takeoff clearance is only issued once the controller has confirmed that a potentially conflicting dependent runway landing has actually occurred. However, a ‘reduced separation’ procedure is available and may be used subject to “certain conditions” (unspecified) so that a takeoff clearance may be given before it has been confirmed that the arriving aircraft has actually landed. The Investigation noted that “if immediate measures are not taken”, the two aircraft involved can “find themselves undesirably close together”, a situation it was noted has previously arisen twice.
It was recognised that the purpose of the ‘reduced separation’ procedure used at Amsterdam by Air Traffic Control the Netherlands (LVNL) was to increase capacity at the airport during the use of dependent takeoff and landing runways. However, it was considered that “the use of dependent runways can create an undesirable and potentially dangerous situation under certain circumstances”.
It was found this conditional procedure for reduced separation had not been explicitly approved by the Human Environment and Transport Inspectorate (ILT). Although it was included in a previous LVNL Operations Manual, when this Manual was “converted” into the current Operations Manual, the new manual was approved by the ILT in its entirety and this implicitly permitted. However, the ILT was unable to provide any record of how its approval of the Operations Manual “conversion” had been managed and the reduced separation procedure had not been considered during subsequent amendments to the new Operations Manual approved by the ILT. The Investigation considered that “it is not clear whether all procedures in the (LVNL) Operations Manual regarding dependent runway use are compliant”.
The formally documented Conclusions of the Investigation were as follows:
The runway controller observed the aircraft taking off from runway 24, and was confronted with a potential conflict when the crew of the landing aircraft on runway 18C announced their go-around. Runway 24 and 18C are converging runways. Attempts to cause the aircraft to abort its takeoff failed, resulting in a potential hazardous situation. Thanks to the almost simultaneous intervention by the runway controller and the response from the two crews, no actual collision hazard occurred.
Allowing reduced separation during the use of dependent takeoff and landing runways is a procedure which can result in the occurrence of undesirable and potentially hazardous situations. Aside from the uncertainty about the legitimacy of this procedure, the question is whether the advantage gained - namely increased capacity - outweighs the potential hazard that can arise. With that in mind, LVNL (the ANSP) should maintain the basic rule that takeoff clearance will only be issued after the landing on the dependent runway has actually been confirmed by the runway controller or if the landing aircraft is still at least 2 NM from the runway threshold.
Two Safety Recommendations were made as a result of the Investigation as follows:
- that Air Traffic Control the Netherlands (LVNL) remove the procedure “Reduced separation between takeoff and landing traffic” from the Operations Manual and adhere to the standard procedure for using dependent runways.
- That the Minister of Infrastructure and Water Management has Air Traffic Control the Netherlands’ (LVNL) procedures regarding the use of dependent runways assessed against current legislation and regulations.
The Final Report was published on 24 September 2020.