Originally Posted by
CaptainMiles
W0X0F,
This thread, along with its sister thread on the poker site, are some of the most interesting reads ever. Thanks so much. You have been kind to answer some of my questions before, and now I have a new one.
I was flying MUC-IAD on UA the other day, and for a while listing to Channel 9 (pilot/ATC communications). Over Ireland, the last controller before Oceanic control would ask each aircraft if they had their oceanic crossing clearance already. Some did, some were still working on it, one pilot even asked for a frequency to talk to the oceanic controller in case they need to work out the clearance. What is this about? I thought all flights had a clearance to destination before departing. What is this oceanic clearance? And what happens if you don't get it? Land in Ireland, enter a hold, what?
One aircraft responded saying they had a clearance at FL320, which they did not like and asked for higher. That Irish controller worked with them, getting them a different track at FL380, and read to them a full route that started with "cleared to Orlando via...". So if that was the oceanic clearance and then some (the overland clearance in North America too), it means that this controller can handle clearances all the way to the destination, including the oceanic part. Then what is this business of asking aircraft if there have their clearance for the crossing, which apparently is obtained over some other channel?
Thanks for indulging my curiosity.
When we fly across the Atlantic, we use the NAT system (North Atlantic Tracks) which is a series of routes which vary from day to day and are identified by phonetic alphabet. Thus, today's tracks might be Alfa through Golf, which are usually (but not always) non-crossing tracks spaced with at least one degree of latitude separation. The tracks themselves might be more southerly one day, more northerly the next, depending on prevailing winds and weather. Most traffic in the morning is heading West and most of the traffic in the evening is headed East.
Our flight plan from, say, JFK to TXL (Berlin) will have a route of flight to the coast-out point for one of the tracks, followed by the NAT route, and then the route over Europe. Each NAT route comprises a set of LAT/LON points and we know what these are because we get a NAT Message with our flight plan and this shows the points for that day's tracks.
Here's an example of a NAT message for Westbound tracks (A through D):
A RESNO 56/20 57/30 57/40 56/50 SCROD VALIE
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR N242B N248C N250F N254A N258A N260A-
B DOGAL 55/20 56/30 56/40 55/50 OYSTR STEAM
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR N224E N228B N230E-
C MALOT 54/20 55/30 55/40 54/50 CARPE REDBY
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR N202B N206C-
D LIMRI 53/20 54/30 54/40 53/50 HECKK YAY
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR N184B N188B-
[For Track D, e.g., the entry point is LIMRI and then we see the LAT/LONs for the crossing, specified at each 10 degrees of longitude, exiting at HECKK and then proceeding to YAY. There are no valid eastbound flight levels for this route (sometimes there will be) and after crossing there are two valid North Atlantic Routes (N184B and N188B) to be used after YAY.]
On the ground at JFK we might get "cleared as filed", but that really only clears us to the coast-out point (which I'll also refer to as the "entry point"). Before entering the track, we have to get our Oceanic Clearance from the controlling agency – eastbound this would be either New York Oceanic, for southerly entries, or Gander Oceanic for the more common northerly routes; westbound it could be Bodo, Shanwick or Santa Maria depending on latitude.
To get the clearance, we send the request over ACARS when we are within 90 minutes of the entry point, and the message we send will contain the entry point, estimated time at the entry point, and the requested altitude and mach speed for the crossing. We don't have to specify the track because that's implied by the entry point (unique to the track). [Note: New York Oceanic is the only oceanic control facility that does
not have automated capability; if using NY Oceanic, you must get the clearance via radio. Since they handle southerly entries, this is usually only necessary when flying to Africa.]
When we get our clearance, we acknowledge via ACARS. If we don't get a clearance over ACARS within 30 minutes of coast-out, we will resort to voice procedures. Our maps show the clearance frequency associated with each entry point, so we call them up and get a voice clearance. In my 3 years of flying international, I think I've done this about 3 or 4 times, although I do remember one time where Gander was having problems with the automated clearances and just about everyone was calling on the radio for their oceanic clearance.
Whether the clearance comes via ACARS or by voice, it will contain the track name (e.g. NAT Z) and the altitude and mach speed for the crossing. Additionally, it will specify the points for the track, e.g. VALIE SCROD N56W050 N56W040 N54W030 N53W020 RESNO.
Once you've got your clearance, you can negotiate (via radio) for a different route or speed if you don't like what you've got, but often you're going to be stuck with what they issued. They try to accommodate our requested route, altitude and speed, so if they change it, it's usually for a good reason (traffic on the tracks).
Position reports are important when crossing because we will be out of radar contact or voice control. So they space us at least 10 minutes in trail at a given altitude (about 50-60 miles in trail).
If for some reason we don't get an oceanic clearance (I've never had this happen yet), we can't enter the NAT system and must divert to a landing.