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Bruce
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Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 7:09 am

What is an Atlantic Crossing Track? How many are there? How far apart are they? Are they only over the north Atlantic? What about a flight going from JFK to South Africa - do they have to use the same track?

Does this mean that every jet going to or from Europe must cross the Atlantic at a certain location?
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Purdue Arrow
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 12:13 pm

The North Atlantic uses a variable track system for getting aircraft across the pond. Basically, there are a series of routes across the Atlantic that change every twelve hours based on winds and weather. In the morning, the tracks point predominantly west, for flights travelling from Europe to North America. Later in the afternoon, they are flipped to allow flights in the other direction. At either time, there are also one or two that point in the other direction for "abnormal" traffic. The tracks, spaced at about 60 miles, are defined by a set of latitude/longitude coordinates. They are used only for North Atlantic operations, so planes going to South Africa would take a different route. The system is set up this way because the Atlantic airspace is extremely busy and has no radar or anything like that. Instead, pilots give position reports to ATC.

As an aside, the much less busy airspace over the Pacific uses a fixed track system, in which there are always tracks going in both directions that don't change.
 
Boeing727
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 12:37 pm

In addition,
the tracks across the Atlantic are in a 6*6 grid, meaning when you look from a profile view onto the tracks there are six of them next to each other and again six on top of each other. The North Atlantic routes (as mentioned by Purdue Arrow) change on a daily basis, dependent on the winds. This grid of tracks crosses the Atlantic from Gander, NewFoundland, all the way to Northern Scottland.

Boeing727
 
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 12:44 pm

There can be more than 6 tracks stacked... A copy of 3 of the tracks was given to us in one of my classes here at Purdue, at it shows tracks A-C (the only three given to us) as being stacked 9 deep. The extra layers are allowed because of the RSVM (Reduced Vertical Seperation Minima) that MNPS (Minimum Navigation Performance Standards) allow between Flight Levels 320-390. The flight levels available with RVSM are 310, 320, 330, 340, 350, 360, 370, 380, 390. For clarification, aircraft at each of these altitudes would be going the same direction, as each track allows traffic to flow only one way.
 
Boeing727
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 1:04 pm

That is very true; I was referring to an article from 1992, when the reduced vertical seperation minimum standards were still in the making...

Boeing727
 
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Bruce
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 1:06 pm

So when they change each day they are not really a major change, probably just a few degrees either way to compensate for the winds, right?

Those flight tracks only apply to cross-ocean flights, not domestic flights across land?
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
Boeing727
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 1:13 pm

The Atlantic routes are unique, where they change daily (unlike domestically). These routes can actually change quite drastically, more than just a couple of degrees. I have flown from Europe many times, and on some flights it will leave us slightly south of Greenland and then others were I flew right over the heart of it. But the concept is pretty much the same, flying as close to the great circle as possible.

Boeing727
 
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Bruce
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 1:17 pm

Thats interesting. I never realized that flights were stacked in neat orderly tracks like that, because over land here, they're all over the place.

So flying on an Atlantic Track you're probably more likely to see another plane above you or next to you (but far enough away) as opposed to crossing over or under you.
Bruce Leibowitz - Jackson, MS (KJAN) - Canon 50D/100-400L IS lens
 
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RE: Question About Atlantic Crossing Tracks

Sun Mar 26, 2000 2:04 pm

The Atlantic tracks are set up differently than land routes due to the different methods of ATC surveillance. Over land, ATC has radar pictures of airplanes, and controllers can see what's going on. Should the need arise, they can issue commands to aircraft and resolve situations very quickly. Ove the Atlantic, however, the lack of radar requires a more orderly navigational routing system. ATC only knows the position of aircraft based on pilot position reports made every 5 degrees. Due to the radio system used for long range communication (HF as opposed to the VHF used over land), it can take up to 20 minutes from the time a pilot makes a position report, it is received by ATC, ATC issues a command, and the pilot receives the instruction. Needless to say, if two aircraft are converging, 20 minutes is not quick enough. Therefore, the aircraft need to be in neat, orderly tracks rather than flying however they want to. The tracks can, as Boeing727 said, be changed drastically from day to day. The changes are especially drastic if there is severe weather over the ocean that must be circumnavigated.

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