[Beowulf] NAT Tracks (flying over iceland)
Lux, Jim (337C)
james.p.lux at jpl.nasa.gov
Wed Sep 5 16:45:16 PDT 2012
Over the North Atlantic, where radar and radio coverage is poor, airlines follow what are called the NAT Tracks, to enforce separation, etc. between FL285 and FL420 (28,500 and 42,000 ft pressure altitude)
They are not geodesics (great circle) paths, but are optimized for current forecast winds (and separation) for minimum time enroute. They change every day.. and are actually unidirectional (i.e. everyone is going the same direction along the tracks, depending on the time of day)
Think of it like a multilane highway in the air with a tightly enforced following distance. You are responsible for hitting your waypoints within a certain lateral deviation and at a particular time. Yeah, there's GPS and satellite phones these days, but not everyone has that, and the Air Traffic Control business is big into standard procedures, everyone following the procedure, and not making customized changes. That way, if communications fails, everything still works, and planes don't fall out of the sky after colliding. If the wind forecast is wrong, it's ok, because everyone is equally affected.
They were used as a target for over-the-horizon HF radar testing, as well.
It was a big deal back in the late 60s when the Carousel (?) Inertial Nav System was introduced for the 747, as well as worldwide nav systems like Omega. You didn't have to do star sights enroute any more, since the "black box" met the "Minimum Navigational Performance Standards". If you couldn't do the MNPS, you had to do island hopping across the north atlantic (what people in small planes did). North east Canada (Goose Bay?), Greenland, Iceland, Scotland, etc. airports and routes redolent of history. (heck, it's the same route followed by John Cabot in a boat, for all practical purposes). There were articles in flying magazines about doing the trip: I was thinking of it in the early 80s, just after I got my pilot's license. Load some 55 gallon drums of fuel in the back seat, etc.
http://en.wikipedia.org/wiki/North_Atlantic_Tracks has a good explanation.
From: beowulf-bounces at beowulf.org [mailto:beowulf-bounces at beowulf.org] On Behalf Of Prentice Bisbal
Sent: Wednesday, September 05, 2012 1:29 PM
To: beowulf at beowulf.org
Subject: Re: [Beowulf] Collocation in Iceland?
On 09/05/2012 04:22 PM, Joe Landman wrote:
> On 09/05/2012 04:03 PM, Prentice Bisbal wrote:
>> As someone who lives in the NYC area, I've flown between NYC and
>> London (and Europe) plenty of times. Airline routes are almost always
>> great circles, and I can assure you, every time I've flown between
>> NYC and London or continental europe, I flew over Iceland.
> From Chicago, the geodesic lies a few hundred km south of Iceland.
> Flying from NY to London should make the geodesic move further south.
> Unless I am missing something.
> When I've flown to the UK, we passed south of Iceland, but never over it.
> It would be fun to visit there some day though.
The little graphic cartoon of where the jet is on Continental flights might not be the most accurate depiction of our exact location. That's what I was working from, and I was pulling that from memory. Not sure of the margin of error of that display or my memory.
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