NATS CPDLC Operations Guidance for Flight Crews and Airline Operators

NATS CPDLC Operations Guidance

for Flight Crews and Airline
Operators

DRAFT Version 1.00

28 January 2013
NATS CPDLC Operations Guidance for Flight Crews and Airline Operators

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NATS CPDLC Operations Guidance for Flight Crews and Airline Operators

NATS CPDLC Operations Guidance for Flight Crews

and Airline Operators

Table of Contents:

1. Introduction ..................................................................................... 2
2. CPDLC Airspace ................................................................................ 2
3. NATS CPDLC Service ......................................................................... 5
3.1. Aircraft LOG-ON .......................................................................... 5
3.2. Required Aircraft LOG-ON parameters ........................................... 5
3.3. Establishing CPDLC Connection ..................................................... 6
4. CPDLC MESSAGE SET (Valid from 2013) .............................................. 6
4.1. Downlink Messages (London and Scottish) ..................................... 6
4.2. Additional Downlink Messages (London Only) ................................. 7
4.3. Uplink Messages (London and Scottish) ......................................... 7
4.4. Additional Uplink Messages (London Only) ..................................... 7
5. Error Messages................................................................................. 8
6. Important Notes ............................................................................... 8
7. CPDLC R/T Phraseology ..................................................................... 9
8. Appendix 1: Message set developments ............................................ 10

Glossary:
ACC Area Control Centre
ATN Air Traffic Network
ATSU Air Traffic Service Unit
CDA Current Data Authority
CM Context Management
CPDLC Controller Pilot Datalink Communications
DA Data Authority
DLIC Data Link Initiation Capability
FANS Future Air Navigation System
FIR Flight Information Region
HMI Human Machine Interface
ICAO International Civil Aviation Organisation
NDA Next Data Authority
OACC Oceanic Area Control Centre
R-ATSU Receiving Air Traffic Service Unit
SID Standard Instrument Departure
TMA Terminal Manoeuvring Area

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1. Introduction
This is an information guide for flight crews and operators intending to
conduct Controller Pilot Datalink Communications (CPDLC) operations within the
London and Scottish FIRs. It contains information relating to the initial CPDLC
message set for ATN and FANS equipped aircraft, ATC procedures, CPDLC log-
on and connection information and details relating to UK continental airspace
where a CPDLC service is available.

This document also contains a small subset of what are expected to be the most
common datalink procedures, and new procedures developed to provide a
datalink service to ATN and FANS equipped aircraft. Appendix A contains details
of messages that will be introduced as part of a phased series of service
enhancements.

The areas of responsibility for the NATS participating ACCs (London Area Control
and Scottish Area Control) are referred to as Data Authorities. A data authority
is a defined area where a CPDLC service is provided. The NATS data authorities
are defined in Section 3.

2. CPDLC Airspace
Within the London (EGTT) and Scottish (EGPX) Data Authorities a CPDLC
service will be provided at FL285 and above, the service may be available
FL195 and above where possible. This excludes the London and Manchester
TMAs, where a CPDLC service is not provided.

Aircraft transiting the Manchester TMA below FL285 will maintain a log-on with
EGPX.

Upon entering airspace where a logon is maintained but CPDLC is not available,
the flight will receive the following CPDLC message:

"CPDLC NOT IN USE. VOICE ONLY UNTIL NOTIFIED."

If the flight crew initiates a downlink message the following response will be
received to indicate that no CPDLC service is available:

“CPDLC NOT AVAILABLE AT THIS TIME – USE VOICE.”

Upon entering CPDLC designated airspace the following CPDLC message will be
received:

"CPDLC IN USE."

Flight Crews should refer to the map of NATS CPDLC Data Authorities (see
Figures 1 & 2).

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Figure 1

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Figure 2

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3. NATS CPDLC Service

A LOG-ON address refers to the ICAO designator for a given Data Authority. In
the case of the United Kingdom the areas of responsibility are defined within the
London and the Scottish FIRs.

The CPDLC LOG-ON address for London Data Authority is EGTT

The CPDLC LOG-ON address for Scottish Data Authority is EGPX

An aircraft may only receive a CPDLC service from a single Data Authority e.g.
EGTT or EGPX.

3.1. Aircraft LOG-ON

LOG-ON can be established at any time prior to the entry time for the relevant
FIR boundary (EGTT or EGPX). For flights departing aerodromes in the United
Kingdom LOG-ON may also be conducted by aircraft on the ground where
coverage exists.

NATS is working with Airfield Operators to update Standard Instrument

Departure plates. This will advise flight crews of the appropriate CPDLC Data
Authority to select prior to departure.

Flight crews are requested to check the UK AIP regarding logging on to the
correct CPDLC Data Authority prior to departure. Additional information is
contained within the Eurocontrol Flight Crew Guidance document.
http://www.eurocontrol.int/services/link-2000-programme

3.2. Required Aircraft LOG-ON parameters

A CPDLC service is only established when all the required LOG-ON parameters
match those contained in the ICAO flight plan:

For an ATN LOG-ON

Mode-S Aircraft-ID i.e. ICAO [Flight plan item 7] callsign
Aircraft ID – 24bit address
ICAO Flight plan departure and destination airfields (not IATA codes)

For a FANS LOG-ON

Mode-S Aircraft-ID i.e. ICAO [Flight plan item 7] callsign
Aircraft registration
ICAO Flight plan departure and destination airfields (not IATA codes)

Notes:
 Using IATA flight ID, inserting additional leading zeros or spaces will
result in a failed LOG-ON.
 Incorrectly filed flight plans or late change of aircraft frame may result in
a failed LOG-ON unless the flight plan is updated.
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 Aircraft must be set to LOG-ON to the correct Data Authority.

3.3. Establishing CPDLC Connection

Although an aircraft (ATN or FANS equipped) may be logged-on to a Data
Authority, no CPDLC service will be available until a CPDLC connection has been
established. The previous Data Authority is required to send a CPDLC END
SERVICE message to the aircraft. A CPDLC START request must then be sent by
the receiving ground system and acknowledged by the airborne system.

On transfer from another CPDLC capable unit, for example Maastricht or

Shannon to London or Scottish Data Authority it is essential for the ground
system to establish that CPDLC instructions may be used with an individual
aircraft, and preferably prior to initial voice contact. This is referred to as
establishing Current Data Authority (CDA).

For an ATN Connection

Aircraft equipped with ATN automatically establish CDA with ground systems.

For a FANS connection

Aircraft equipped with FANS must receive and respond to a CPDLC welcome
message for CDA to be established. The format of the welcome message is as
follows:

“BAW123 WELCOME TO LONDON – RESPOND ROGER/ACCEPT”

On receipt of a response from the aircraft CDA will be established. Flight crews
are requested to respond promptly when a welcome message is received.

For more information on this process, refer to PANS ATM section 14, the
ICAO GOLD version 2.0, or Eurocontrol guidance material for ATC and
Flight Crews V6.0 for additional information.

4. CPDLC MESSAGE SET (Valid from 2013)

NATS is introducing CPDLC in a phased manner. Initially, only the following
messages will be supported:

4.1. Downlink Messages (London and Scottish)

Message Number Message
DM0 WILCO
DM1 UNABLE
DM2 STANDBY
DM3 ROGER (FANS ONLY)
DM4 AFFIRM (FANS ONLY)
DM5 NEGATIVE (FANS ONLY)

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DM22 REQUEST DIRECT TO [POSITION]

DM62 ERROR [ERROR INFORMATION]
DM63 NOT CURRENT DATA AUTHORITY
DM64 [FACILITY DESIGNATION] FANS ONLY
DM65 DUE TO WEATHER*
DM66 DUE TO AIRCRAFT PERFORMANCE*
DM67 [FREETEXT] FANS ONLY
DM98 FREETEXT [FOR ADDITIONAL ERROR INFO]
DM99 CURRENT DATA AUTHORITY
DM100 LOGICAL ACKNOWLEDGMENT
DM107 NOT AUTHORISED NEXT DATA AUTHORITY

* DM65 and DM66 can be concatenated with other Downlinked messages. See
ICAO documentation for a complete list of messages that may be concatenated.

4.2. Additional Downlink Messages (London Only)

Message Number Message
DM6 REQUEST [LEVEL]
DM9 REQUEST CLIMB TO [LEVEL]
DM10 REQUEST DESCENT TO [LEVEL]
DM106 PREFERRED LEVEL [LEVEL]

4.3. Uplink Messages (London and Scottish)

Message Number Message
UM0 UNABLE
UM1 STANDBY
UM74 PROCEED DIRECT TO [POSITION]
UM117 CONTACT [UNIT NAME] [FREQUENCY]
UM157 CHECK STUCK MICROPHONE [FREQUENCY]
UM159 ERROR [ERROR INFORMATION]
UM160 NEXT DATA AUTHORITY
UM162 SERVICE UNAVAILABLE
UM169 [FREETEXT] FANS ONLY
UM183 [FREETEXT] for additional error information
UM196 [FREETEXT]
UM203 [FREETEXT]
UM227 LOGICAL ACKNOWLEDGMENT
UM237 REQUEST AGAIN WITH NEXT UNIT

4.4. Additional Uplink Messages (London Only)

Message Number Message
UM79 CLEARED TO [POSITION] VIA [ROUTE CLEARANCE]
UM231 STATE PREFERRED LEVEL

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5. Error Messages
If a flight crew receives an ‘ERROR’ response to a downlink message it should
not be re-sent as this may generate another ‘ERROR’, and a possible time-out.

Crews should refrain from making technical enquiries on frequency as

controllers will not have any further information available.

6. Important Notes

IF A FLIGHT CREW HAS ANY DOUBT REGARDING THE CONTENT,

VALIDITY OR EXECUTION OF A CPDLC MESSAGE THEY MUST REVERT TO
VOICE IMMEDIATELY TO CLARIFY THE SITUATION.

 Within UK continental airspace CPDLC is a supplementary means of

communication. Voice over R/T remains the primary means of
communication.

 Flight crews are reminded that following a change of frequency, there is a

requirement to check in by voice prior to the use of CPDLC.

 Flight crews should ensure on receiving a UM79 CLEARED TO [position]

VIA [route clearance] that the position element is part of the original
flight plan to ensure that the onward route is not deleted from the FMS.

 Initially NATS controllers will be using a subset of the available CPDLC

messages. Controllers may be required to respond to a downlink request
with ‘UNABLE’ to close the dialogue, but may subsequently respond to the
initial request by voice.

 Pilots of FANS equipped aircraft are requested to respond promptly to

uplinked CPDLC messages due to known network latency issues.

 If a CPDLC instruction is superseded by a voice instruction, the flight crew

are requested to respond ‘UNABLE’ to close the dialog and avoid a time-
out.

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7. CPDLC R/T Phraseology

Operational Phraseology Pilot Action

Circumstance
Controller uses a voice “[Aircraft Callsign] Crew to disregard a CPDLC
instruction to correct a DISREGARD CPDLC message (of that type) that
CPDLC message [message type] MESSAGE, has arrived on the flight
BREAK [followed by the deck within the preceding
correct clearance, 120 secs or one that arrives
instruction information or within the next 120 secs. If
request]” not already responded, crew
to respond UNABLE to
avoid message time out and
unnecessary disconnects.

If not already responded, “[Aircraft Callsign] Crew to disregard a CPDLC

pilot to respond UNABLE to DISREGARD CPDLC message that has arrived
avoid message time out and [climb/route/clearance, on the flight deck within the
unnecessary disconnects. followed by executive previous 120 seconds and
instruction to clarify disconnect the CPDLC
clearance] connection with the Current
DISCONNECT CPDLC AND Data Authority.
REVERT TO VOICE”
A ‘commanded termination’
message is sent to the
aircraft.

Crew will be required to

LOG-ON manually with the
next Data Authority

CPDLC Failure “CALLSIGN/ALL STATIONS Crew shall revert to voice.

CPDLC FAILURE AT [Unit] ATC may require to clarify
[followed by the clearances.
appropriate clearance,
instruction information or
request]”

Discontinuation of the use of “ALL STATIONS STOP

CPDLC SENDING CPDLC
REQUESTS UNTIL
ADVISED [reason]”

Resumption of the normal “ALL STATIONS RESUME

use of CPDLC NORMAL CPDLC
OPERATIONS”

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8. Appendix 1: Message set developments

NATS is introducing CPDLC in a phased manner. The original message set as
stated in section 4 will be extended to include the following additional
messages:

Phase 2 uplinked Messages (London and Scottish)

Message Number Message

UM020 CLIMB TO [LEVEL]
UM023 DESCEND TO [LEVEL]
UM027 CLIMB TO REACH [LEVEL] BY [POSITON]
UM029 DESCEND TO REACH [LEVEL] BY [POSITION]
UM096 CONTINUE PRESENT HEADING
UM106 MAINTAIN [SPEED]
UM108 MAINTAIN [SPEED] OR GREATER
UM109 MAINTAIN [SPEED] OR LESS
UM116 RESUME NORMAL SPEED
UM190 FLY HEADING [DEGREES]

Phase 2 uplinked Messages (London only)

Message Number Message

UM092 HOLD AT [POSITION] AS PUBLISHED MAINTAIN [LEVEL]
UM94 TURN [DIRECTION] HEADING [DEGREES] (FANS only)
UM215 TURN [DIRECTION] [DEGREES] DEGREES (ATN only)

Phase 2 uplinked Messages (Scottish only)

Message Number Message

UM053 CROSS [POSITION] AT OR AFTER [TIME]
UM079 CLEARED TO [POSITION] VIA [ROUTE CLEARANCE]

Phase 2 downlink Messages (Scottish only)

Message Number Message

DM6 REQUEST LEVEL [LEVEL]
DM9 REQUEST CLIMB TO [LEVEL]
DM10 REQUEST DESCENT TO [LEVEL]

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