Tranatlantic routing?

[Shaggy Sheep Driver]

Two weeks ago I travelled Manchester - Chicago on American flight 55. The outbound route was (off 06L) immediate turn onto approx westerly (LH downwind) heading, out across Irish sea north of Liverpool, and right across Ireland. We coasted in over St Johns, Newfoundland (all visible both out the window and on the occasional cabin displays). The return, a week later was the reciprocal - out over the great lakes, in over Ireland coasting into UK south of Southport for 24R at Manch.

I'd have though a great circle, Manchester to Chicago, would have routed much further north than that? Out of interest, I listened to todays AA55 departure from Manch. This was off 24L and the aeroplane turned right after take off onto pretty much a downwind (easterly) heading. In fact ATC gave him a radar heading of 040 which he was on for about 10 minutes, before giving him a heading of 350. That's a completely different routing to the day I flew on it, and seems more appropriate for a great circle.

Why the difference in deprture routings, and why was the routing on the day I flew so far south?

SSD

[PIGDOG]

Every twelve hours the routes are decided by Canadian and British ATC (they take it in turns) These routes will be decided mainly by weather, and the flights choice of route will be decided by destination etc.

Westerly routes are numbered A, B, C, etc from north to south, and are decided by british ATC. Easterly routes are numbered Z, Y, X, etc from south to north, and are decided by Gander (Canadian) ATC.

[as737700]

It just depends on the weather. On the JFK-IST route that I fly a lot, somedays we fly as far north as the middle of Greenland, and other days we're about 500 miles away from the tip of Greenland. The winds were probably more advantagous one day than it was the other.

[Captain Airclues]

SSD

The current tracks can be viewed here (www.natroutes.glideslope.de/html/nats.php3)

Airclues

[Shaggy Sheep Driver]

Thanks guys. I did wonder if it was related to upper winds, but I thought a more direct routing (great circle) would have been the first consideration. But I guess if the favorable wind results in a shorter journey time despite longer routing, thet's the one to choose. We did descend to 28,000 feet at one point to avoid the worst of some turbulence - even at that level the light chop was nearly enough to spill my Champagne. :cool:

I was talking to a fellow flyer at the weekend about this, and he reminded me of the old days of piston transatlantic airliners. They used to employ'pressure pattern' flying (following favorable isobars), being at low enough altitude to be affected by high and low pressure systems.

And Concorde, of course, was so damned quick that the upper winds at 60,000 feet were not of significance and they flew the same tracks every day. ;)

SSD

[Edited to thank Capt. Airclues for the link - but I'm afaraid those waypoints don't mean a lot to me. I recognise some (JFK, Merit) but is there a site that gives lat/long?]

[BALIX]

It is indeed down to the forecast winds - somebody with better knowledge than myself can go into the finer detail but the westbound tracks for a particular day are produced the previous evening by one of the Shanwick controllers based on the forecast and the prefered routes of the airlines. There are usually six tracks and the bulk of the transatlantic traffic will fly along one of these, though some will fly on random tracks. The main idea is to avoid the srong upper winds (jetstreams) that blow from west to east. Conversely, eastbound tracks will try and utilise these winds which is why it takes less time to fly from Chicago to Manchester than the other way round.

It does come as a suprise that there can be so much of a difference - many years ago I flew on AA55 to Chicago and we entered oceanic airspace at 51N 15W. At work I quite frequently see the same flight entering oceanic airspace at 57N 10W. That is 360nm further north!

[Captain Airclues]

SSD

That site does give the Lat and Longs. Scroll down until you get to the tracks (immediately after "PART ONE OF TWO PARTS"). For example, Track R, after CARPE routes via 54N50W, 55N40W, 56N30W etc.

Airclues

[Engine overtemp]

The Great Circle route can be found here (http://gc.kls2.com/cgi-bin/gc?PATH=man-ord&RANGE=&PATH-COLOR=&PATH-UNITS=mi&SPEED-GROUND=&SPEED-UNITS=kts&RANGE-STYLE=best&RANGE-COLOR=&MAP-STYLE=) :ok:

[as737700]

Captain Airclues

Do you know a site that gives the tracks on a map, rather than just giving longitude and latitude?

[enicalyth]

G'day Shaggy Sheep Driver

I'll widen the brackets from Chicago-Manchester a bit to expand on other aspects of pond crossing, namely that continental winds may provide more of an assist than you think. So now make your destination Heathrow but from two departures, the one Los Angeles and the other New York.

Jet stream affects the continental USA differently from the North Atlantic both in strength and compass direction. Continental USA routes tend to be aligned to benefit from this and yet traffic from the West Coast musn't be allowed to conflict too much with East Coast traffic when both are over the pond. They can and do overlap time-wise and other routes are reserved for the military to add to the confusion.

Flying LAX-LHR, say, your transcontinental portion is catered for mainly by airway J107 in the USA and Southern Control Area "Juliet" (SCAJ) in Canada to take you to N62 W60. The ideal landfall off Ireland is N56 W10.

The busy times off the West of Ireland are say 0500-1000GMT for JFK traffic and 0800-1500 for LAX traffic. Additionally for 2-engine aircraft no one likes to be more than 180 minutes flying time from the Azores on one engine if that is the nearest suitable and open airport.

So there is a lot of juggling and wind is an important issue but not the only one.

Ask on the day, giving this as an example, I'm sure you'll get a scribbled correction from the pilot to take account of pressures of the day.

LAX-J9/J107-NORRA-J107-VBI-SCAJ-N62 W60-N62 W40-N59 W20-N56 W10-UN561-BEL-UB3-WAL-B3-HON-EGLL.

This means you leave Los Angeles and take either J9 or J107 as directed until junction NORRA. Then J107 to VBI which is Sioux Narrows where you pick up SCA "Juliet". Then you cross the pond and pick up UN561 to BEL which is Belfast. The rest is good old Upper B3 and B3 to Wallasey and a Honiley arrival into Heathrow.

Meanwhile someone else that you have to keep out of the way of is flying from New York to Heathrow. Scribble again to the pilot and you might see something like this

JFK-MERIT-HFD-PUT-WITCH-ALLEX-DCT YQX-KOBEV-N50 W50-N52 W40-N53 W30-N53 W20-N53 W15-UG1/G1-CPT-EGLL.

This flight leaves JFK on a MERIT departure over Hartford, Putnam, WITCH and ALLEX. These bold type waypoints always have 5 letters and are not necessarily distinct places. DCT however means "Direct" otherwise 2- and 3-letter waypoints are navaids. Landfall this time includes Shannon (SHA) but it is not mentioned because the airway UG1 includes SHA but does not terminate there but continues on. Once in England a descent from Upper G1 to lower G1 takes place for a Compton arrival into Heathrow. I have written it UG1/G1 because neither the pilot nor air traffic control have sorted that out yet although the on-board computer is continuously calculating the optimum.

LAX-LHR typically 9.75 to 10.25 hours (better overall wind and fewer delays); JFK-LHR typically 6.00 to 6.75 hours (less jetstream and more delays).

Sometimes you might think looking at your wristwatch that your departure is late. Not so. All is well and the whole effort including expected delays is backtimed from your preferred arrival time. (Cue the announcement " L & G we're a little late leaving but we have favourable winds etc and shall be in Heathrow at the expected time etc").

If you want the tracks just cut and paste departure, the pond lat and long bits, and arrival into http://gc.kls2.com as a colleague advises. I don't know of any on-line system that can accommodate routes and waypoints.

Enjoy your flights!!

Best rgds

enicalyth

[selfin]

Here (http://ourworld.cs.com/bobraemer/ownnav/natplot.zip) for a programme which reads this (http://www.natroutes.glideslope.de/html/nats.php3) text file of the current tracks. Above programme was linked from here. (http://www.natroutes.glideslope.de/)

[PPRuNe Radar]

enicalyth

You need to get a new map mate ;)

The 15W and 10W waypoints were given 5 letter names 4 or 5 years ago and the route designators you gave as examples changed probably 3 or 4 years ago.

56/10 is now MIMKU. UN561 is replaced by UP6-MORAG-UL10. UB3 is now UL10. UG1 is now UL9. Etc, etc.

UK charts can be found here (you have to register which is free)

Upper Airspace Chart (South) (http://www.ais.org.uk/aes/pubs/aip/pdf/enr/26030201.PDF)

Upper Airspace Chart (North) (http://www.ais.org.uk/aes/pubs/aip/pdf/enr/26030202.PDF)

[tug3]

Try this:

http://www.jetplan.com/tda/

Rgds
T3

[enicalyth]

You are right pprune radar

But I kept away from MALOT, BURAK etc because I thought that I'd tone it down.

I left out MORAG because it is such a short leg from thence to thence and on balance since writing to SSD and trying to keep it brief etc.,,,

But you are right and nothing in my long career excuses me from carelessness.

It is nice to know people care enough to correct a sloppy article. I'll be more careful and less patronising in future.

Your good friend always

E

(BTW just retired! But not from Atlantic runs, that was 5-6 years ago! That'll teach an antipodean to teach a podean how to fly podean airspace too. I hope that these mistakes are forgiveable over a flying life of 1968-2005. I've managed to throw myself at the ground and miss up till now, just don't you dare miss my farewell barbie!!)

[justcoolen]

Eastbound and westbound tracks are developed to incorporate airlines preferential routings and the Jetstream. It has nothing to do with two engines on an aircraft. A great deal, if not the majority of Trans-Atlantic aircraft are only twins. Some aircraft, depending on the company, must get an ETOPS certification before being able to fly on whatever route they want. AN ETOPS route will take you closer to Greenland and Iceland than it will to the Azores.
The great circle route is the shortest distance route, but a 100mph tail or head wind is a pretty important piece of information.
When the Eastbound tracks are designed, minimum time tracks (MTT'S) the preferential routes, forecasted turbulence, and even radar holes are all deciding factors. Quite often when there is a very strong Jetstream the MTT from JFK to EGLL is the same as ORD to EGLL. KLAX to EGLL is almost always over Greenland.
A long story short, the Jetstream mainly decides where you are going to fly for either East or Westbound. The Jetstream changes on a daily basis, so do the routes.
Hope this helps.

[Shaggy Sheep Driver]

Thanks guys. Lots of interesting stuff here - there's more to this than I thought!

SSD

[PPRuNe Radar]

If you want chapter and verse (in great detail), then try this for a download:

North Atlantic Minimum Navigation Performance Specification Airspace Operations Manual (http://www.nat-pco.org/mnpsa.htm)