NAT HLA Procedure Guide
NAT HLA Procedure Guide
NAT HLA Procedure Guide
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
Content
1. General
1.1 The Airspace
1.2 Navigation Requirements
1.3 Route Structure
2. Planning Phase
2.1 Determining Your Route Across The Atlantic
2.2 SELCAL
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
1. General
1.1 The Airspace
According to the NAT HLA Document 2020, the North Atlantic is the busiest
oceanic airspace in the world. It is considered a remote area without radar
coverage and limited VHF coverage. Most conversation is done via HF and
datalink. This guide will familiarize you with the standard operating procedures
and phraseology used.
The North Atlantic High Level Airspace (NAT HLA) consists of the following
Oceanic Control Areas (OCA) between FL285 and FL420:
REYKJAVIK (BIRD)
SHANWICK (EGGX)
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
The most southerly nighttime track gets the letter “Z” and next most southerly
track the letter “Y”. The most northerly daytime track gets the letter “A”.
Information about available levels and domestic routings like the North
American Routing (NAR) belonging to these tracks are also included in the
Track Message. Each Track Message is identified by a Track Message
Identification Number (TMI) according the Julian calendar (simple progression
of numbered days without reference to month, with numbering from the first
day of the year). Amendments will get the letter “A”, then “B”, etc. added to
the end of the TMI number (e.g. TMI 032A). The latest track message can be
obtained here and should be part of your OFP.
The hours of validity of the two Organized Track Systems (OTS) are normally as
follows:
The tracks utilizes even and odd levels to enable as much traffic as possible.
The usable levels are indicated on the Track Message.
In general the OTS is not compulsory, flight plans may be filed along the tracks
or join/leave the outer tracks at any waypoint. These Random Routes must use
published Oceanic Entry and Exit points and only have to cross a full degree of
longitude each 10° of latitude (20° north 70°N and every 30 minutes when
north of 80°N) when flying east-west bound. When flying north-south bound,
every 5° of longitude must cross a full degree of latitude. However, flying
across the track system and through an opposite OTS (also one hour before
and after the validity) should be avoided.
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2. Planning Phase
2.1 Determining Your Route Across The Atlantic
If flying along a track, the ATC flight plan between the NAT Entry- and Exit
point contains the proper Track Identifier in this form: “NATU” stands for Track
“U”, “NATB” for “B”, etc. A route via NAT Track Z at FL350 and Mach .85
would look like this:
If flying along a random routing, the ATC flight plan between the NAT Entry-
and Exit point contains the full routing with all coordinates in between (as
explained in 1.3 Route Structure). A random routing at FL350 and Mach .85
would look like this:
2.2 SELCAL
SELCAL is a signaling method which can alert an individual aircraft that a
ground station wishes to communicate with it. It consists of two pairs of
letters, each of which represents a unique tone. The higher the letter, the
higher also the tone. In each pair, the first tone must be lower than the second
tone.
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
3.1 VHF
The VATSIM controller will operate a VHF frequency, where clearances can be
requested via voice. Your clearance request shall contain your entry point, the
estimated time at the entry point, your requested flight level, your requested
mach number, the maximum flight level you are able to accept and any other
information which might be of interest for the controller. A typical conversation
would look like this.
The radio operator will then read back your clearance request and state
„standby for clearance“.
After you have received your clearance, read it back and make sure to state
the current TMI from the track message (see 1.3 Route Structure). Return to
domestic frequency and expect to be handed over to the oceanic controller
again when reaching your NAT entry point.
3.2 nattrak.vatsim.net
Your oceanic clearance can also be requested on nattrak.vatsim.net. The
website is self-explanatory, you just need to enter all the information specified
in 3.1 VHF and wait for the controller to issue your clearance.
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
3.3 ACARS
If your controller offers datalink services, you can also request the clearance
via ACARS. A log on via CPDLC is not necessary in this case, as the oceanic
clearance request is processed in a similar way as a Pre-Departure Clearance
(PDC) via the ACARS network. Enter all the information specified in 3.1 VHF
and wait for the controller to issue your clearance.
NAT HLA Guide DO NOT USE FOR REAL WORLD NAVIGATION V 1.0
4.3 HF Communications
Important to know: When talking to Shanwick/Gander Radio, you are not
talking to the oceanic controller. Instead, a radio operator is relaying messages
between you and the control center. It is therefore important to use standard
phraseology, especially on noisy HF frequencies and include the frequency
you are transmitting on, as the radio operator often simultaneously monitors
multiple frequencies. Communication example:
The pilot has the option to fly centerline, 1 NM or 2 NM right of track. Flying
left of track is not permitted. There is no ATC clearance required nor is ATC
being informed about this procedure. It is important that aircraft return to
centerline before exiting NAT HLA airspace.
4.6 CPDLC
Whereas CPDLC is mandatory in NAT HLA airspace in reality, this has not been
yet implemented for VATSIM controllers and pilots. If your oceanic controller
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decides to offer CPDLC, you can log on to the appropriate facility (e.g. EGGX,
CZQX).
The radio operator will then read back your position report.