Regulation (EU) No 923/2012 SERA : Standardised European Rules of the Air
Revision from October
- EASA :
- FRANCE :
SECTION 15 Controller–pilot data link communication (CPDLC) procedures
SERA.15001 Data link initiation and data link initiation failure - Regulation (EU)
- The logon address associated with an air traffic services unit shall be published in the
national aeronautical information publications (AIPs).
- Upon receipt of a valid data link initiation request from an aircraft approaching or within
the data link service area, the air traffic services unit shall accept the request and, if
able to correlate it with a flight plan, shall establish a connection with the aircraft.
- The air traffic services provider shall establish procedures to resolve, as soon as
practicable, data link initiation failures.
- The aircraft operator shall establish procedures to resolve, as soon as practicable, data
link initiation failures.
SERA.15005 Establishment of CPDLC - Regulation (EU) 2023/1772
- CPDLC shall be established in sufficient time in advance to ensure that the aircraft
communicates with the appropriate air traffic control unit.
- Information concerning when and, if applicable, where the air or ground systems should
establish CPDLC shall be published in aeronautical information circulars or publications.
- The pilot shall be able to identify the air traffic control unit that provides the air
traffic control service at any time while the service is being provided.
SERA.15010 Transfer of CPDLC - Regulation (EU) 2023/1772
- When CPDLC is transferred, the transfer of voice communication and CPDLC shall commence
- When an aircraft is transferred from an air traffic control unit where CPDLC is available to
an air traffic control unit where CPDLC is not available, the termination of CPDLC shall
commence concurrently with the transfer of voice communication.
- The air traffic controller shall be informed when attempting a transfer of CPDLC resulting
in a change in data authority if there are data link messages for which a closure response
has not been received. When the air traffic controller decides to transfer the aircraft
without receiving pilot responses to the uplink message(s) outstanding, the air traffic
controller shall normally revert to voice communication to clarify any ambiguity associated
with the uplink message(s) outstanding.
SERA.15015 Construction of CPDLC messages - Regulation (EU) 2023/1772
- The text of CPDLC messages shall be composed in standard message format, in plain language,
or in abbreviations and codes. Plain language shall be avoided when the length of the text
can be reduced by using appropriate abbreviations and codes. Non-essential words and
phrases, such as expressions of politeness, shall not be used.
- The air traffic controller and the pilot shall construct CPDLC messages using standard
message elements, free text message elements, or a combination of both. The use of free text
message elements by air traffic controllers or pilots shall, be avoided.
- When the implemented CPDLC message set does not provide for specific circumstances, the
competent authority may determine, in consultation with operators and other air traffic
services providers, that it is acceptable to use free text message elements. In such cases,
the competent authority concerned shall define the display format, intended use and
attributes for each free text message element.
- The composition of a CPDLC message shall not exceed five message elements, only two of which
may contain the route clearance variable.
- Construction of multi-element CPDLC messages:
- When a multi-element CPDLC message requires a response, the response shall apply to
all message elements.
- When a single message element clearance or any part of a multi-element clearance
message cannot be complied with, the pilot shall send an “UNABLE” response for the
- The controller shall respond with an “UNABLE” message that applies to all elements
of the request when no element(s) of a single or multi-element clearance request can
be approved. The current clearance(s) shall not be restated.
- When a multi-element clearance request can only be partially accommodated, the
controller shall respond with an “UNABLE” message applying to all the message
elements of the request and, if appropriate, include a reason and/or information on
when clearance may be expected.
- When all elements of a single or multi-element clearance request can be
accommodated, the controller shall respond with clearances corresponding to each
element of the request. This response shall be a single uplink message.
- When a CPDLC message contains more than one message element and the response
attribute for the message is “Y”, when utilised, the single response message shall
contain the corresponding number of replies in the same order.
SERA.15020 Responding to CPDLC messages - Regulation (EU) 2023/1772
- Unless otherwise specified by the competent authority, voice read-back of CPDLC messages
shall not be required.
- Except when correction of the CPDLC message transmitted is needed, when a controller or a
pilot communicates via CPDLC, the response shall normally be via CPDLC. When a controller or
a pilot communicates via voice, the response shall normally be via voice.
SERA.15025 Correction to CPDLC messages - Regulation (EU) 2023/1772
- When a correction to a CPDLC message is deemed necessary or when the contents of such a
message need to be clarified, the air traffic controller and the pilot shall use the most
appropriate means available for issuing the correct details or for providing the necessary
- When voice communication is used to correct a CPDLC message for which no operational
response has yet been received, the controller’s or the pilot’s voice transmission shall be
prefaced by the phrase: “DISREGARD CPDLC (message type) MESSAGE, BREAK” – followed by the
correct clearance, instruction, information or request.
- When referring to and identifying the CPDLC message to be disregarded, caution shall be
exercised in its phrasing so as to avoid any ambiguity with the issue of the correction to
the clearance, instruction, information or request.
- If a CPDLC message that requires an operational response is subsequently negotiated via
voice, an appropriate CPDLC message closure response shall be sent to ensure proper
synchronisation of the CPDLC dialogue. This may be achieved either by explicitly instructing
the recipient of the message via voice to close the dialogue or by allowing the system to
automatically close the dialogue.
SERA.15030 Controller data link communication procedures for emergencies, hazards, and CPDLC
equipment failure - Regulation (EU) 2023/1772
- When an air traffic controller or a pilot is alerted that a single controller–pilot data
link communication message has failed, the air traffic controller or the pilot shall take
one of the following actions, as appropriate:
- via voice, confirm the actions that will be taken with respect to the related
dialogue, prefacing the information with the phrase: “CPDLC MESSAGE FAILURE”;
- via controller–pilot data link communication, reissue the controller–pilot data link
communication message that failed.
- Air traffic controllers that are required to transmit information concerning a complete
controller–pilot data link communication ground system failure to all stations likely to
intercept should preface such a transmission by the general call: “ALL STATIONS CPDLC
FAILURE” – followed by the identification of the calling station.
- When controller–pilot data link communication fail and the communication reverts to voice,
all CPDLC messages outstanding shall be considered not delivered and the entire dialogue
involving the messages outstanding shall be recommenced by voice.
- When controller–pilot data link communication fails but is restored prior to a need to
revert to voice communication, all messages outstanding shall be considered not delivered
and the entire dialogue involving the messages outstanding shall be recommenced via CPDLC.
SERA.15035 Intentional shutdown of CPDLC system - Regulation (EU) 2023/1772
- When a system shutdown of the communications network or the CPDLC ground system is planned,
a NOTAM shall be published to inform all affected parties of the shutdown period and, if
necessary, the details of the voice communication frequencies to be used.
- Aircraft in communication with the ATC units shall be informed by voice or CPDLC of any
imminent loss of the CPDLC service.
SERA.15040 Discontinuation of the use of CPDLC requests - Regulation (EU)
- When a controller requires all stations or a specific flight to avoid sending CPDLC requests
for a limited period of time, the following phrase shall be used: ((call sign) or ALL
STATIONS) STOP SENDING CPDLC REQUESTS [UNTIL ADVISED] [(reason)].
- The resumption of the normal use of CPDLC shall be advised by using the following phrase:
((call sign) or ALL STATIONS) RESUME NORMAL CPDLC OPERATIONS
SERA.15045 Use of CPDLC in the event of air–ground voice communication failure -
Regulation (EU) 2023/1772
The existence of a CPDLC connection between an air traffic services unit and an aircraft should
not prevent the pilot and the air traffic controller concerned from initiating and performing
all the required actions in the event of air–ground voice communication failure.
SERA.15050 Testing of CPDLC - Regulation (EU) 2023/1772
Where the testing of CPDLC with an aircraft could affect the air traffic services being provided
to the aircraft, coordination shall be effected prior to such testing.