FMC and NATS

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I am curious about how NATS are programmed into the FMC. If I am on NAT-F, for example, (where the entry point is BURAK and exit CYMON) do you list each point in the NAT as DCT or do you put NAT-F into the airway line and get the points like you program any other airway?

I appreciate any insight you can all offer me.

Cheers!

[Thunderbug]

xFeed

For NAT tracks it is DCT waypoint to waypoint - sort of join the dots! The tracks change every day and the number of possible routes are too numerous.

One feature of the FMC (Honeywell in my case) is that the waypoints do have short codes. rather than type in N5400.0W03000.0 you type 5430N and FMC knows where you mean.

The North Canadian tracks do stay the same, so NCAB in the route page will give you the correct waypoint for track B.

Clever stuff.....

T'bug
:ok:

[PPRuNe Radar]

If you find NAT Track B starting in Canada, you've really got some big nav problems :)

Are the NCA Tracks numbered as opposed to lettered ??

[xfeed]

Thunderbug,

Thanks very much, mate! I appreciate your response. I didn't realise that the tracks changed as often as every day.

Thanks again!

Cheers

[Notso Fantastic]

The NATs change every day after being planned by meteorologists to avoid or use jetstream winds.
https://www.notams.jcs.mil/common/nat.html

[PPRuNe Radar]

Notso .... accurate :)

The met data is fed to both the Oceanic Centres and the major airline operators.

From that information, these airlines calculate their desired routes between major city pairs and then send the Oceanic Centres their PRMs (Preferred Route Messages). In addition, the minimum time path between New York and London (and vice versa) will also be calculated. This then gives the Oceanic Centre a good idea of where the majority of the traffic wants to fly.

The Oceanic Planner will then look at any other activity such as adverse weather (thunderstorms, etc) plus any other aerial activity such as airspace reservations and then propose a track structure. Users can then add their comments online before the final structure is then agreed with all concerned and published.

Shanwick do this for the Westbound tracks and Gander do it for the Eastbounds.

So, apart from supplying the met data at the beginning of the process, there's no planning of the tracks done by meteorologists I am afraid. I wouldn't expect them to know all the ins and outs of legal separation standards or airspace in any case ;)

[Notso Fantastic]

I see. So you're saying every day, twice a day, 50 different airlines are sending their preferred tracks to Oceanic? I would have thought the only input required is for the Oceanic Planner to look at where the jetstreams are as well as rocket firing etc and use that to set eastbounds and westbounds. So sometimes the tracks go right up over Greenland to get/avoid the winds. Whatever the mechanism, winds are the driving force in track allocation. I'm sure airline input is minimal.

[PPRuNe Radar]

You should have a look around an OACC one day Notso .. might be educational.

No where near 50 airlines in the PRM scheme, nearer a dozen who account for about 80% of the traffic. Majority rules in the OCA !!

PS Ask BA Ops how it is done, sure they'll be pleased to let you know the real story and also maybe give you an insight in to PRMs :ok:

Failing that, you could read the NAT MNPSA Ops Manual

NAT MNPSA Manual (http://www.nat-pco.org/nat/MNPSA9/mnps9.pdf)

Pages 18 and 31 are the relevant ones.

[xfeed]

This is some very interesting information you have all provided. Can you explain how you plan step climbs within the NATS? For example, if your flight plan reads thus:

CPT UL9 BURAK/N0465F360 UL9 MALOT DCT 5420N 5430N 5340N 5150N/N0461F380 DENDU CYMON...

how do you know that you will be able to climb to FL380 within the NAT region or at the waypoint? How do you plan ahead for this if ATC can not give you what you request AND how do you know that it will be 5150N that will be ready to climb FL380?

I've always been curious when looking at flight plans how the step climbs are planned. Do they know what the pay load is in advance? Also, does the "5150N/" mean that you climb AFTER 5150N or while you are still travelling to that way point?

Thanks in advance.

Cheers!

[Notso Fantastic]

The ATC Flight Plan is (usually) generated by the Dispatch Section who are aware of approximate aircraft weights and capabilities, and also the winds en route, therefore it has best climb points. After take-off when Atlantic entry point ETA is known, or closer to Gander Oceanic entry point, accurate ETAs can be sent and an Oceanic Clearance at a single level is issued. No enroute climbs are involved at that stage. It is then up to the crew during the Oceanic phase to request reclearance at any time to whatever level they deem appropriate, which does not necessarily correspond to whatever level was in the preflight clearance. Proximity to another aircraft just above you can keep you down. Sometimes it is worth climbing earlier than optimum to get out of cloud tops.