NAT ATMG/40
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Dd/mm/2012
NORTH ATLANTIC AIR TRAFFIC MANAGEMENT GROUP
FORTIETH MEETING
(Brest, France, 10 to 14 September 2012)
Agenda Item 4:
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c):
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Flight Plan Definition of NAT Tracks Using Latitude/Longitude Coordinates to Support Auto
Loadable Clearances
(Presented by the United States)
1.
Introduction
1.1.
This paper proposes discussion and amendment of the Guidance Concerning Air
Navigation In and Above the North Atlantic MNPS Airspace (NAT Doc 007), Chapter 4, Sections
4.2.1. and 4.2.2. which currently state:
4.2.1 If (and only if) the flight is planned to operate along the entire length of one
of the organised tracks, from oceanic entry point to oceanic exit point, as detailed in the
NAT Track Message, should the intended organised track be defined in Item 15 of the
flight plan using the abbreviation 'NAT' followed by the code letter assigned to the track.
4.2.2 Flights wishing to join or leave an organised track at some intermediate point are
considered to be random route aircraft and full route details must be specified in the flight
plan. The track letter must not be used to abbreviate any portion of the route in these
circumstances.
1.2.
These paragraphs encourage the use of NAT Track contractions (i.e. NATU) for
flight planning on the Organized Track System (OTS). This routing abbreviation is problematic for
delivering fully loadable clearances via Controller Pilot Data Link Communications (CPDLC) to
aircraft flying in oceanic airspace and participating in the initial Departure Clearance Request
(DCL) program in US airspace.
2.
Discussion
2.1.
The FAA is currently implementing plans to upgrade the Tower Data Link Services
(TDLS) system to offer initial and revised departure clearances to CPDLC equipped aircraft. These
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aircraft will log on, request and receive their clearances on the ground via the standard FANS
CPDLC message set.
2.2.
As a precursor to upgrading the TDLS production system, the FAA Data
Communications Program Office will conduct DCL Trials. These trials are scheduled to start
November 2012 in Memphis, Tennessee, and continuing to Newark, New Jersey and Atlanta,
Georgia.
2.3.
The goals of the DCL Trials are to mitigate risk to the TDLS production system by
validating requirements, proving the Concept of Operations (CONOPS) and demonstrating benefits.
2.4.
During the process of developing requirements and selecting compatible CPDLC
messages across multiple airframe and avionics suites, it was quickly determined that FAA flight
plans containing NAT Track contractions i.e. NATU, would not be eligible for a loadable revised
departure clearance. Flight management computers reject a NAT Track contraction as a loadable
route element and will not process any CPDLC uplink messages (UM) that contain them.
2.5.
Airline Operations Center (AOC) flight dispatchers send fully loadable initial
clearances using ARINC 702 format to aircraft by providing latitude/longitude (lat/long)
coordinates to describe the NAT Tracks, yet when the official flight plan is filed for that same
flight, the NAT Track contraction is used as set forth in NAT Doc 007.
2.6.
AOC systems have been programmed to support the NAT Doc 007 guidance and
after years of use this guidance is perceived as mandate. AOCs have communicated a need for
guidance material changes that implicitly state that filing lat/long coordinates for OTS elements is
the preferred method.
2.7.
There are three distinct areas of concern and reasoning to justify a change to NAT
Doc 007: technical, operational, and safety.
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a)
Technical: Boeing and Airbus aircraft flight management systems, regardless of
avionics manufacturer, are unable to load NAT Track contractions into their
systems. Lat/long coordinates are required for all route elements composing a
valid NAT Track. Continued use of NAT Track contractions will inhibit use of
current/future advanced avionics with SESAR and NextGen capabilities.
b)
Operational: DCL Clearances containing routes with NAT Track contractions
will be ineligible for UM messaging, forcing controllers to revert to voice
communications to deliver the clearance. FAA controllers using the Ocean 21
automation system to send CPDLC route messages to aircraft with NAT Track
contractions contained in flight plans are required to cut and paste the coordinates
of that track from an approved source into the message composition window and
then send to the aircraft to enable a fully loadable clearance. This cumbersome
manual process is prone to error.
c)
Safety: The current procedure of encouraging users to file the NAT Track
identifier as part of the defined route in Item 15 of an FPL introduces significant
risk. The manual manipulation described in b) above often leads to problems
such as the inadvertent deletion of significant waypoints. Additionally, since an
abbreviation is used to define a route rather than the actual route itself, errors are
made when the Track Message Identifier (TMI) is confirmed. This is especially
true when revisions to an already published track have occurred. It is also very
common for an aircraft to file part of the track and then break off at some point.
This causes confusion and has led to verbal coordination errors due to the fact
that it appears as though an aircraft is flying the entire track when in fact it is not.
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For example, if Track Yankee is defined as JOBOC 40N060W 41N050W
45N040W 46N030W 47N020W BEDRA NERTU it is not uncommon for an
aircraft to file JOBOC NATY 46N030W NATY 47N020W SOMAX ATSUR.
Allowing the NAT Track identifier in Item 15 may result in the controller
overlooking the fact that an aircraft in not flying the entire track. Although NAT
Doc 007 specifically states that the abbreviation “NAT” followed by the code
letter assigned to the track should only be used if the flight is planned to operate
along the whole length of one of the organized tracks as detailed in the NAT
track message, the fact remains that this is a common occurrence.
3.
Summary
3.1.
The FAA recognizes that the NAT OTS is a well-organized and useful system and is
not recommending changes to the intent of its operation. The FAA does encourage that a change be
made to NAT Doc 007 to allow aircraft with advanced avionics to participate in data
communication transactions. Automation between air navigation service providers and aircraft has
advanced to levels making updates to guidance material necessary to take advantage of their full
capabilities.
3.2.
Due to the technical, operational and safety considerations explained in this paper, the
FAA recommends that NAT Doc 007 be amended to provide guidance for AOC Flight Planners to
file latitude/longitude coordinates for route elements composing both eastbound and westbound
NAT Tracks. The following new wording for paragraph 4.2.1 is proposed for consideration by the
meeting:
4.2.1 (NEW) For flights planning to operate on the Organised Track System (OTS), Flight
Planners should file the most current Latitude/longitude definition of the OTS track from an
approved source (instead of NAT followed by the code letter assigned to the track). This will
fully enable ANSP automation and allow loadable route elements to be sent to qualified aircraft
via CPDLC
3.3.
4.
Section 4.2.2 should be deleted.
Action by the Meeting
4.1
The NAT ATMG is invited to:
a)
Note the information provided in this paper;
b)
Determine whether the wording in NAT Doc 007, Chapter 4 should be amended as
proposed in paragraph 3.2; and
c)
Provide a recommendation to NAT IMG if deemed appropriate.
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