User avatar
BALandorLivery
Topic Author
Posts: 313
Joined: Mon Jan 17, 2005 7:54 pm

Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 5:56 am

A few years back whilst traveling LGW to Puerto Plata on a Britannia 767 I visited the flight deck. When I asked which North Atlantic Track (NAT) we were on the captain said that we were not on one.

Instead the crew had suggested THEIR OWN route and that this had been approved. He said it was a GPS track.

I was under the impression that all north Atlantic crossings routed via the NAT tracks e.g. Track A, B, C, D etc westbound and Track U, V, W, X, Y, Z eastbound.

Any other pilots out there have any answers?
 
PhilSquares
Posts: 3371
Joined: Sun Mar 28, 2004 6:06 pm

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:01 am

There is no requirement to use the NAT system. During the winter months, it's not uncommon to go fairly far north, out of the NAT system. By doing that you are now on a random track. Some airlines use that system to minimize headwinds westbound during the winter months.

In addition, flights westbound to southern destinations don't have to follow the NATs either. In some cases it's quicker to just go on a random track.

However, there is no real thing such as a GPS track.
Fly fast, live slow
 
geoffm
Posts: 2082
Joined: Fri Feb 27, 2004 5:58 am

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tr

Tue Jan 18, 2005 6:11 am

Puerto Plata = Dominican Republic (ok, I had to look it up!). Isn't this too far south for the NAT tracks?

How do the planes keep apart if not flying NAT, and out of radar contact? I thought the whole purpose was to force separation of aircraft... TCAS hasn't always been around.

Geoff M.
 
PhilSquares
Posts: 3371
Joined: Sun Mar 28, 2004 6:06 pm

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:16 am

Separation is accomplished by two methods, first altitude and secondly by lateral spacing.

Aircraft on the same route and altitude are 15 minutes in trail, otherwise, they're separated by 1000' increments. No real big deal at all.
Fly fast, live slow
 
geoffm
Posts: 2082
Joined: Fri Feb 27, 2004 5:58 am

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tr

Tue Jan 18, 2005 6:18 am

Yeah, but who controls it - pilots, ATC? I know Gander and Shanwick do the NATS stuff - are there similar centres for non-NATS stuff?

Geoff M.
 
petazulu
Posts: 683
Joined: Fri Jan 31, 2003 3:32 am

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:23 am

On a recent flight in December on LH (FRA-JFK), there were really strong headwinds. The plane crossed the ocean farther south than I have ever seen. In fact, we can in straight off the tip of long island into JFK. Normally, we would have come down through Maine, VT, Newfoundland, etc. This time, we were never even close to those places the whole time. The flight was really long and bumpy (people were throwing up behind me and in front!). The pilot seemed to have a lot of vertical mobility in that he changed our altitude by many thousands of feet in an attempt to find clearer air (no luck btw!). My guess was that were on a unique track that day due to the unusual headwinds. It was clear that there were no other planes to tell us where the turbulance was or wasn't because the pilot seemed to have no clue.

We were probably outside of ETOPs range at times, but obviously, this was not a concern. Trailblazing across the Atlantic!
 
PhilSquares
Posts: 3371
Joined: Sun Mar 28, 2004 6:06 pm

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:24 am

Both Gander and Shanwick would cover northern random tracks. To the south Santa Maria and New York would provide oceanic atc.

Beleive me, it's no real big deal.
Fly fast, live slow
 
Lemmy
Posts: 243
Joined: Fri Dec 10, 2004 8:40 am

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:29 am

Probably a dumb question, but if you can choose your own route, what's the incentive to use NAT tracks? Also, roughly what percentage of transatlantic crossings actually use the published tracks?

I am a patient boy ...
 
User avatar
BALandorLivery
Topic Author
Posts: 313
Joined: Mon Jan 17, 2005 7:54 pm

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:33 am

That makes sense. Whilst in the cockpit the captain was communicating with Santa Maria. We did go a lot further south than the usual NAT tracks. Thanks for the help Philsquares.
 
PhilSquares
Posts: 3371
Joined: Sun Mar 28, 2004 6:06 pm

RE: Atlantic Crossings Using GPS Tracks NOT NAT Tracks

Tue Jan 18, 2005 6:38 am

In commercial aviation, the reality is Dispatch chooses the route. At most large carriers, the computer flight planning system looks for a minimum time track and goes with that. Theoretically, the NAT system should accomplish the same thing, but sometimes the data used by the airlines is a little more up to date than the NAT.

By far, the overwhelming majority of the traffic goes on the NAT system.
Fly fast, live slow