North Atlantic Tracks

[dmwalker 601]

I have been noticing at FlightAware that, for transatlantic flights, such as Air Canada 872, the route is showing the North Atlantic Track as NATT, for example, instead of the individual waypoints.

 

Is this how it is shown on the official route documents used by the flight crew? If so, how could that be used, given the variability of the track waypoint co-ordinates from day to day?

[Jim Harnes 13]

Hi,

 

Each daily track has a designator.  In your case it's track "T".  The advisory messages list track specifics:  entry point, lat/long along the track and the exit point.

  

 

Best,

Jim Harnes

[dmwalker 601]

Thanks. So would the flight crew receive a document with the route showing NATT, plus a separate document with the latest advisory about the entry point, track waypoints and exit point, etc, for Track T?

[Jim Harnes 13]

It's all contained in the daily NAT advisory messages.   See https://www.notams.faa.gov/common/nat.html

 

 

 

Best,

Jim Harnes

[hopskip 253]

Flight crew get full briefings, which look remarkably similar to the output of PFPX.

Example (from PFPX) at https://drive.google.com/file/d/0B25GjWrn0HgrTElDUU9VN25OeUU/view?usp=sharing 

[dmwalker 601]

Jim Harnes: That is the one I am referring to. Thanks.

 

Hopskip: I think that is what I need to read. Thanks.

[dmwalker 601]

It seems that many of the entry and exit waypoints have changed within the last year. I wonder why "they" would do that. I suppose that PFPX does not yet reflect those changes.

[hopskip 253]

It seems that many of the entry and exit waypoints have changed within the last year. I wonder why "they" would do that. I suppose that PFPX does not yet reflect those changes.

 

PFPX updates it's AIRAC, like most FMC addons, via navigaph or similar.

 

It is possible to use Navigraph to update your AIRAC to the current AIRAC in use today.

 

http://www.navigraph.com/

 

For a look at every airway/waypoint etc on a visual representation, head over to http://skyvector.com/ and click "World Hi" (for high altitude airways).

Open the "Layers" tab and click "NAV" to select various daily tracks such as PACOTS, AUSOTS, NATS etc.

 

I believe PFPX originally came with a 2013 AIRAC, but that may be because I purchased it in 2013.

 

Updating the PFPX AIRAC using Navigraph turned out to be a little tricky for me, because the Navigraph installer seemed to place the updated files into the wrong directory, and I had to modify the directory Navigraph saved to for some reason.

[dmwalker 601]

I have AIRAC 1309 which came with the 777 and it has, for example, the eastbound entry points which are shown in the 2013 Edition of the North Atlantic Operations and Airspace Manual, e.g. DENDU, KOBEV, LOGSU, NOVEP and RONPO. All of these are documented at opennav.com and fallingrain.com.

 

At Skyvector, the new entry points are ALLRY, ELSIR, JOOPY, NICSO and PORTI. None of these are documented yet at opennav.com or fallingrain.com. I imagine they are in the AIRAC 1411.

 

I was wondering if the use of the identifiers NATV, NATW, etc. in the routes was connected to the introduction of the new entry points. For example, tonight's AC872 route is:

 

ADVIK Q907 ATENE MIILS N215A ELSIR NATW LIMRI NATW XETBO MORAG LAMSO REMBA UL607 SPI UT180 PESOV T180 RASVO T180 UNOKO UNOKO1L.

[hopskip 253]

The NATs (North Atlantic Track s) have always been identified by a letter.

 

NAT A B C D E F (G H J) going west

 

NAT U V W X Y Z going East.

 

They are published daily, and the actual waypoints inside them change daily.

Each NAT has a TMI (Track Message Identifier) which is a 3 digit number that depicts the "Day of the year" (ie January 1st is 001, December 31st is 365 or 366, Febuary 1st is 032 etc)

 

To save space, the "airway" known as NATW has been used.

instead of, say... NICSO N48W050 N48W040 N49W030 N49W030 BEDRA NERTU

 

NATW on the flightplan and "Request Clearance via NAT W TMI316" on the radio is much shorter than

NICSO N48W050 N48W040 N49W030 N49W030 BEDRA NERTU on the flight plan and

Request clearance via NICSO North 48 West 050 North 48 West 040 North 49 West 030 North 49 West 030 BEDRA NERTU on the radio.

 

New entry points, old entry points, entry points from 1995, the identifiers are still NATV NATW etc.

[dmwalker 601]

I was surprised to find that even the entry points and exit points can vary from day to day. Today's NATW is:

 

NICSO 48/50 48/40 49/30 49/20 BEDRA NERTU

 

but, within the last few days, it has also been:

 

NICSO 48/50 49/40 50/30 50/20 SOMAX ATSUR

 

and even:

 

ALLRY 51/50 52/40 52/30 52/20 LIMRI XETBO

 

Is this solely because of changes in the jetstream?

 

In your Flight Briefing, did it follow a North Atlantic Track? I can't find any reference to one even though there seemed to be an entry point, LIMLO, and an exit point, HECKK.

[hopskip 253]

Yep. The entire track moves for wind. Jetstream winds across the North Atlantic can easily exceed 100 knots, and generally pump in an easterly direction (from west to east), however of course they will wander north or south based on other weather influences, sometimes twist around into a kind of loop, and so on.

 

The track moves to accommodate the least headwind, and most tailwind, as possible for the most amount of traffic.

 

I do see NATA etc being used on flightaware (and filed plans) quite often, but just having NATA, NATB etc on the flight briefing for the crew doesn't help them put anything into the FMC. 

 

The FMC needs the entire input. (ie: ALLRY 51N050W etc) and so the briefing will have all of that info in it.

The NAT track shorthand only goes into the ATC flightplan notification, and is referenced when recieving oceanic clearance.

 

Here's a great video about some of the operations of the NATs 

 

[dmwalker 601]

Thanks. The video looks as if it will answer all of my questions.

[UAE77W 16]

Hi everyone,

 

What are you doing when you're currently on a Track, let's say NATA reaching 60N030W on "ERAKA 60N020W 60N030W 59N040W 57N050W HOIST", and it expires and NATA changes to

 

"GOMUP 59N020W 60N030W 60N040W 58N050W CUDDY"?

 

How is it done in real life, do you continue your actual Track or do you enter the next and then following appropriate coordinates?

 

 

 

*Edit: I see that the times are from 1130z to 1900z. Do you still continue on your Track or if you would reach the actual Track after 1900z are you even assigned to a Track?

 

 

Thanks in advance  B)

[hopskip 253]

The NAT expiry times tend to co-incide with airport curfew times with a fair bit of leeway. If an aircraft were to enter an expired track, it's arrival time is going to be 2am - 5am at the other end. In this case, the flight plan would be rejected by the system and a "non-nat" flex track would need to be filed.

 

When ATC receives the flight plan, it will receive the notification via computer, which would check Estimated departure against the requirements for NAT expiry and accept/reject based on this.

 

When an aircraft calls up for clearance, a slot time will be provided. A takeoff slot (Takeoff between time x and time y) and a NAT entry slot.

 

Aircraft that miss the slot times significantly (+- 10 mins at takeoff, +- 3 mins at NAT entry) may be required to adjust their flight plan. This may be mach number, altitude, or even an entire change of the NAT - "Recleared direct abc then NxxWxxx NxxWyyy etc")

 

Aircraft will sometimes even file off the NAT structure for other reasons while the NAT is valid, usually due to ETOPS restrictions or RVSM capability issues. In those cases the flex track requested is required to be clear of any NAT, not crossing the structure and keeping clear of it by a number of nm.

 

ATC can modify the cleared routing if required, and this procedure is covered in the video I linked above.