Faculty of air transport engineering the department of «air navigation systems»

Operating method.

The Point Merge operating method aims at integrating inbound flows, using a PMS route structure, and comprises two main phases:

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  Create the spacing through path stretching without ATC intervention – by leaving aircraft fly along the sequencing leg, followed by a “direct-to” instruction to the merge point, issued when the appropriate spacing is reached with the preceding aircraft in the sequence;
  
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  Maintain the spacing through speed control after leaving the legs.
  

The normal procedure only involves one ATC lateral intervention i.e. the direct-to instruction. As this is a closed loop intervention, aircraft remain under lateral guidance by the FMS all along the procedure. This “direct-to” instruction is key to the operation of Point Merge as it creates both the sequence order and the initial longitudinal inter-aircraft spacing in the sequence. This property makes it also pivotal when considering how Point Merge relates to phases in sequence management.
Nevertheless, alternate procedures in the frame of Point Merge may involve the use of open-loop vectors e.g. for non-equipped aircraft or to deal with unexpected events.
The normal procedure also only involves one ATC vertical intervention i.e. a descent clearance that may be given after the direct-to, when clear of traffic on the other leg(s). Subject to design options, this may happen at different stages in the procedure. The descent profile can be optimised accordingly, at least from the sequencing legs altitude/level, in the form of a Continuous Descent Approach – as the distance to go is known by the FMS.
Thanks to the iso/equidistance property in the route structure, during the path stretching phase the controller can easily and intuitively assess the spacing with the preceding aircraft in the sequence (already on course to the merge point), and therefore determine with sufficient accuracy the appropriate moment to issue the ‘direct-to’ instruction, without requiring the support of any new ground tool. Importantly, as stated above, this remains possible even with an approximation in equidistance; it is actually the case in the example shown here, where sequencing legs are designed 2nm apart.
Point Merge is normally not thought as an open-ended procedure, as it is by its own principle seeking to decrease tactical ATC interventions and enable extensive use of RNAV. It shall thus be designed as a closed STAR, so that if the aircraft reaches the end of the sequencing leg without receiving a ‘direct-to’ clearance, it turns automatically towards the merge point. In the remainder of this document, we will always consider Point Merge as being a closed procedure. Nevertheless, for the sake of readability, subsequent figures will generally not include the ‘closing part’.

2.