What is N553D for?

[NorthSouth]

No particular axe to grind on this, but what is advisory route N553D for? It runs from MAC to FYNER and seems to have been created in about 1995-6, but has no obvious purpose - how many flights are there between Inverness/Kinloss/Lossiemouth and Ireland? Was it perhaps put there to try to give some predictability for schedules between Glasgow and the islands against Nimrod traffic routing from Kinloss to Ireland & the SW approaches?

Contrast that with the withdrawal of the Newcastle-Carlisle section of W911D which has several scheduled CAT flights a day and crosses an area busy with military traffic.

[Arran's view]

Trans Atlantic traffic to and from 55 north from Scottish TMA airports.

[NorthSouth]

I think you're looking at N552D. N553D runs NNE from MAC. There are no routes in the Standard Route Document which use it.

[10W]

N553D is to allow traffic from NIBOG and MIMKU (55N 10W and 56N 10W in old money) to get to the holding facility for Glasgow arrivals from the West ... which is at FYNER.

[NorthSouth]

Hmm. So how come the SRD says inbounds to EGPF from MIMKU and NIBOG should route MAC N552D TRN then into the TRN 1A STAR? Also, EGPF STARs via FYNER seem to be for inbounds off N573D and W958D only - they don't mention N553D. And inbounds to Scottish TMA from the FIR to the west are told to expect to route via ROBBO.

[10W]

The SRD is for Flight Planning purposes only. We do it slightly differently in the real world ;)

Traffic via MAC for Glasgow will of course flight plan via TRN and the TMA controller will normally provide an acceptance level at TRN for the flight to the West Coast controller tactically before the flight routes on to LANAK or is vectored for final approach.

However, if holding is taking place for Glasgow traffic then the holding fix and clearance limit point for the West Coast controller is FYNER. There is little point in feeding further traffic from the West into the already busy TMA airspace if there is holding in progress. By issuing a tactical reroute along N553D then it gets the aircraft out of the TMA traffic count freeing up a slot in each of the two TMA sectors involved, and West Coast sector can liaise the aircraft's approach direct with Glasgow Approach cutting down on co-ordination requirements with the already busy TMA controllers. This rarely happens, but it is the procedure available if ATC need it and hence the reason why N553D was put in place when the revised TMA airspace and procedures were drawn up in the early/mid 90s.

The FIR arrivals via ROBBO are for traffic not planned along the ADR structure, e.g from Islay or Eglinton perhaps. Normally their clearance will be at or below 6000' and issued by Glasgow Approach. There may be a wait if Glasgow are on Runway 23 and have a lot of departures since they have to ensure separation.

The use of N553D is not in the SRD because it is not the Standard Inbound Route, just one which exists primarily as an ATC tool .... though nothing to stop anyone filing it if it fits in to their plans ;)

[NorthSouth]

Fascinating. I guess it's not used very much though? Not that many transatlantics into Glasgow. I suppose if they have a radar failure or something and arrivals are all procedural then it might come into play.