Oceanic Flight Plan Routes

The rules for filing routes overland where airways exist come easier to most. Filing flight plans for areas without designated routes are a bit of a mystery to many people. As already mentioned, the AIP Canada provides us with some direction for this task. The rule is put a fix in the route every 200 NM or 30 minutes of flying time. A pilot should consider the speed of the aircraft in the process, too. An aircraft expected to make a ground speed of 480 knots (8 miles per minute) would travel 240 NM in 30 minutes while one flying at 180 knots would only make 90 miles in that time frame. Thus, the pilot of the slower aircraft may wish to file more points. For an IFR flight, ATC will be interested in hearing from him more often outside of a radar environment to ensure the aircraft is still proceeding along as expected. In the event of a problem, ATC will initiate search and rescue services sooner if an overdue position report is expected sooner. That same aircraft flying 180 knots would take well over an hour to fly the 200 NM. If something happened in the meantime, ATC wouldn't be expecting a position report until the next fix, which would allow another 30+ minutes to elapse before they went looking for him.

So what fixes do you include if there are none published? For a flight that is generally in an east-west direction of travel between 70° N and 70° S latitudes, significant fixes may be defined by reference to half or whole degrees of latitude where they cross meridians (lines of longitude) spaced at 10°. Some areas require more, such as New York Oceanic who desires fixes every 5°. An example of a flight proceeding eastbound of the North Atlantic would be N48W050 N50W040 N51W030. Alternatively, the fixes may include half degrees, as follows: N4830W05000 N5030W04000 and so on. These formats, by the way, are the proper format for insertion of latitude and longitude points in a flight plan. They should be defined including the letter "N" or "S" as appropriate, followed by 2 digits for whole degrees, then "W" or "E" followed by 3 digits. For the fixes including more than just a whole degree of lat of long, it should be written with "N" or "S", then the four digits (2 for degrees and 2 for minutes), then "E" or "W" followed by five digits (3 for degrees and 2 for minutes). Zeros are filled in as necessary as place holders as in the examples above. Note that because of the definition of significant points as described above means that a flight will not be proceeding, in all likelihood, on a direct path. Rather, the flight will now fly directly to points, which makes the track less of a straight line between departure and destination. ATC needs these points both for alerting services, and for the application of separation standards between aircraft tracks.

For those doing north-south flight paths, the direction for flight planning is similar. We are told to define significant points in relation to whole degrees of longitude with specified degrees of latitude spaced at 5° intervals. The same note goes here, in that forcing an aircraft to travel over points of whole degrees will make the flight somewhat less direct to destination.

Other significant points must be included where an altitude or speed change is requested. This has been mentioned in a past topic so I won't go into detail again except to provide an example. If an altitude change were requested in the first route example above at the 40W coordinate, it would be written like this: N48W050 N50W040/N0440F350 N51W030. This would mean that the aircraft is requesting 420 knots true airspeed and a climb to FL350 commencing at that point. With any altitude or speed change, the speed and altitude must be stated whether both or only one change. Also note that in controlled airspace, the altitude or speed change can not be initiated without a clearance from ATC to allow it. The one thing that knowledgeable people will catch here is that a pilot may change speed within 5% of filed true airspeed (not applicable to Mach numbers) without approval from ATC. For use of Mach numbers in the cruise, the pilots have a leeway of 0.01 Mach either side. When a Mach number is included in a clearance from ATC, the pilot should also report Mach number with each position report.

Another method of defining a fix, instead of using a latitude/longitude pair, is to use a reference to a NAVAID with a bearing and distance. This should be used with some common sense, as a fix 700 NM from a NAVAID is hardly realistic. If a flight were to define a significant point in the flight plan as being the Yarmouth VOR's 180 radial at 125 DME, for example, the flight plan entry would be written as YQI180125.

All points defined in flight plans as mentioned above become compulsory reporting points and normal position reports must be made unless the magical phrase "radar identified" is heard. If the phrase "radar service terminated" is subsequently heard from ATC, the old position reports must resume from then until radar identified again.

Due to the regularity and volume of traffic crossing the North Atlantic Ocean, an Organized Track System (OTS) has been devised. The tracks in the real world change daily in relation to the jetstream. With an eastbound flow of traffic, the tracks are planned near the jetstream to give the additional "push" of the high speed winds aloft. I have seen aircraft cruising with the jetstream grounding in excess of 700 knots on rare occasions, but it's almost always 100 knots or more. Because of that, the westbound tracks are generally planned north or south of the jetstream to keep them out of the winds since it would be a strong penalty to take headwinds of that velocity.

With the flow of traffic being very highly oriented one way or the other, the OTS has defined times within which there are westbound tracks in effect, and then eastbound tracks instead. The normal times for OTS tracks are:

Day-time OTS: 1130z to1800z at 30°W
Night-time OTS: 0100z to 0800z at 30°W

The hours of validity are always specified within a track message. The most northerly track in a day OTS (westbound flow) is named NAT A (North Atlantic Track Alpha), the next track B and so forth. For a night OTS, the most southerly track is Z and each track north of that progresses back through the alphabet.

The OTS is generally restricted to an altitude range of FL290 up to and including FL400, which also includes MNPS airspace (Minimum Navigation Performance Specification). Flight levels are allocated for use in the track system and there are generally two levels reserved for traffic opposing the flow.

Flights that are planned within the OTS need not mention each individual point in the track as described in the track message. They simply need to flight plan up to the point of entry into the desired track, then use the track name, include the track exit point, and then pick up the route from there in the normal fashion.

Flights planned through OTS airspace outside of OTS times are a little more touchy. If the flight is expected to arrive at 30W at or very near the commencement of an OTS (the times indicated above can be used as a guideline but track messages should be consulted for current validity periods) the pilot should file a track appropriate to the OTS about to come into effect. If the flight is planned at such a time that opposes an OTS and the flight level is critical, pilots should plan to avoid the airspace affected by the OTS by flying north, south, above or below the OTS airspace.

One last note about North Atlantic Airspace involved the flight rule to be flown under while in the area. RAC 11.5 says that "over the high seas" the lower limit of all NAT Oceanic Control Areas is FL55 (5,500 feet ASL under standard pressure). Throughout the NAT OCA, the airspace is Class A and therefore only IFR flight is permitted between the floor (FL55) and the ceiling (FL600). No flight will be permitted with VFR restrictions, either, regardless of flight conditions. Below FL55, the airspace is Class G, or uncontrolled airspace.

There are more rules to flying Oceanic that weren't covered here. The above notes can get you through VatSim's world, but as always, refer to real world information for real world flights. Strangely, for all the information on Atlantic airspace, there is very little for oceanic airspace over the Pacific. While not being totally sure of the reasons for this, I believe it's because Canada isn't directly responsible for any oceanic control areas over the Pacific Ocean such as it is with the western portion of the North Atlantic. Any questions, comments, feedback or anecdotes? Send them to me through e-mail at moxner@nbnet.nb.ca. As always, thanks for visiting and taking the time to read!