Data link initiation capability (DLIC) .1 Purpose of the logon (flight plan correlation)

2.2.3.1.1 The logon is the first step in the data link process. A logon, initiated either by the flight crew or by another ATSU, is performed prior to the ATSU establishing a CPDLC and/or ADS-C connection. The purpose of the logon is to:

a) Provide the ATSU with the data link application “context” of the aircraft, namely:

1) The ATS data link applications supported by the aircraft system (e.g. CPDLC, ADS-C) and the associated version numbers of these applications; and

2) The unique identification of the aircraft;

b) Provide the ATSU with the relevant aircraft information required to allow the ATSU to correlate the logon information with the aircraft’s corresponding flight plan.

Note 1.— For FANS 1/A, the unique identification of the aircraft is the aircraft registration and/or aircraft address; for ATN B1 the unique identification of the aircraft is the aircraft address.

Note 2.— Under certain circumstances, it may be operationally desirable for an ATSU to set up an ADS-C connection (perhaps for a single demand contract) without a preceding logon. When this is done, correlation with the flight plan can be achieved by requesting the optional flight identification group and checking this against the aircraft registration in the flight plan. See also section 4.5.3 for guidelines on ADS-C connection management.

2.2.3.1.2 On receipt of a logon request, the ATSU correlates the logon information with the relevant information in the flight plan held by the ATSU. This ensures that messages are sent to the correct aircraft and that automation associated with ADS-C reports or CPDLC messages updates the correct flight plan.

2.2.3.1.3 When making this correlation, the ground system:

a) Ensures that the aircraft identification in the logon request matches that in Item 7 of the associated flight plan and at least one of the aircraft registration or aircraft address provided match the corresponding descriptors (following the REG and/or CODE indicators, respectively) in Item 18 of the flight plan; and

b) Only uses the information contained within the portion of the logon request message that is protected by the cyclic redundancy check (CRC).

Note 1.— The data used for correlation are:

a) For FANS-1/A, the aircraft identification, aircraft registration, and optionally, the aircraft’s current position (lat/long) and the aircraft address (if available);

b) For ATN B1, the aircraft identification, departure and destination airports, the aircraft address, and optionally estimated off-block time (EOBT), if available.

Note 2.— For FANS 1/A, the aircraft identification in the ACARS message header is not protected by the CRC and the flight crew does not use this information to verify aircraft identification. Additionally, the format for the aircraft identification in the ACARS message header is different from the format used by the ground system. For example, the ground system uses a three alpha character ICAO designator for the operating agency followed by up to four numeric characters for the flight identification.

FANS 1/A Example

The following example of an AFN logon indicates the appropriate information in the ACARS message to correlate the AFN logon with a flight plan.

QU <ACARS “TO” address>

. <ACARS “FROM” address> 010000 AFD

FI AB0123/AN ST-XYZ DT QXT POR1 010000 J59A

- AFN/FMHABC123,.ST-XYZ,DEF456,000002/FPOS30000E160000,0/FCOADS,01/

FCOATC,01<CRC>

The ATSU only uses the information in the CRC-protected portion of the ACARS message. In the example above, the CRC portion is highlighted, and contains the following information:

• aircraft identification is ABC123 (not the AB0123 contained in the ACARS header);

• aircraft registration is ST-XYZ (hyphen is removed by ATS automation per paragraph 3.1.2.1.2); and

• aircraft address is DEF456.

Note.— Some ATSUs may operate a ground system that does not integrate data link capability with a flight data processing system. Under these circumstances, the ATSU will need to ensure that the logon information is available for the controller to manually cross-check the information with the details in the flight plan.

ATN B1 Example

The following example of a CM logon indicates the appropriate information in the CM message to correlate the CM logon with a flight plan.

CMLogonRequest

aircraftFlightIdentification ABC123

cMLongTSAP ATN address of the aircraft CM application (string of 18 or 19 octets), including the aircraft address DEF456 (3 octets).

groundInitiatedApplications 1 (CMA) and 22 (PM-CPDLC) airOnlyInitiatedApplications 1 (CMA)

facilityDesignation None

airportDeparture LFBO

airportDestination ENGM

dateTimeDepartureETD None

The ATSU only uses the information in the CRC-protected portion of the message:

• aircraft identification is ABC123;

• aircraft address is DEF456 and is included in the cMLongTSAP; and

• departure airport is LFBO (Toulouse) and destination airport is ENGM (Oslo).

Note.— The facilityDesignation field would be used to require a logon to a facility different from the one to which the logon request will be addressed. Such capability (commonly referred to as DLIC server) is not implemented by ATN B1 systems.

2.2.3.2 Initial logon request

2.2.3.2.1 An initial logon request is needed when the aircraft does not already have an ADS-C or CPDLC connection, such as when:

a) The aircraft is preparing for departure; or

b) The aircraft will enter an area where data link services are available from an area where data link services are not available; or

c) Instructed by ATC (e.g. following a failed data link transfer).

2.2.3.2.2 To perform an initial logon request, the flight crew enters the four character ICAO identifier of the ATSU to which the logon request is to be sent and includes the following flight-specific information:

a) Aircraft identification (same as item 7 of the flight plan);

b) Aircraft registration and/or aircraft address (same as item 18, preceded by REG and/or CODE, of the flight plan); and

c) Departure and destination aerodromes, when required (same as items 13 and 16 of the flight plan).

Note 1.— In accordance with ICAO Doc 4444, the aircraft identification entered into the aircraft system is either the ICAO designator for the aircraft operating agency followed by the flight identification or the aircraft registration.

Note 2.— The aircraft identification and registration may have been loaded prior to departure.

Note 3.— When the aircraft identification includes a numeric component, this component matches exactly that included in the flight plan. In other words, “ABC3” does not match “ABC003.”

Note 4.— While the ATSU identifier is only 4-characters, ATN B1 is capable of supporting up to 8 characters.

2.2.3.2.3 To avoid an automatic rejection of the logon request, the flight crew ensures that the flight-specific information entered into the aircraft system is the same as the corresponding details filed in the flight plan.

2.2.3.2.4 When the flight crew performs the logon request, the aircraft system transmits the logon information in a logon request message (as per Table 2-6) to the specified ATSU.

Note.— The flight crew procedure for performing an initial logon request is provided in paragraph 5.2.

2.2.3.3 Logon response

2.2.3.3.1 As shown in Figure 2-7, the ground system automatically responds to a logon request with a logon response (as per Table 2-6). The logon response message provides information to the aircraft system concerning whether:

a) The logon request was successful (e.g. could be correlated with a flight plan); or

b) The logon request was unsuccessful (e.g. could not be correlated with a flight plan). Refer to paragraph 3.1.2.1.1 for conditions when an ATSU rejects a logon request.

2.2.3.3.2 The logon response message also provides information concerning the ATS data link applications the ATSU supports.

Logon Request Logon Response

ATSU

Figure 2-7. Initial logon exchanges

2.2.3.4 Logon request triggered by contact request

2.2.3.4.1 The air-ground address forwarding procedure is the process whereby one ATSU instructs the aircraft system to initiate a logon request to another ATSU (e.g. when the flight is leaving one ATSU where a logon had already been completed and the flight is transferred to another ATSU).

2.2.3.4.2 When triggered by a contact request, a logon request is initiated without flight crew input.

2.2.3.4.3 The CDA typically initiates address forwarding to permit a downstream or adjacent ATSU (NDA) to establish an inactive CPDLC connection and/or an ADS contract for monitoring purposes.

2.2.3.4.4 Any ATSU can initiate address forwarding by sending a contact request message to the aircraft. Upon receipt, the aircraft automatically transmits a logon request to the ATSU whose address was included in the contact request message.

Note.— Some aircraft will not accept a CPDLC connection with an ATSU to which they have been instructed to log on unless the ATSU issuing the instruction had itself established a CPDLC connection with the aircraft. Refer to Appendix F, paragraph F.3

2.2.3.4.5 The messages associated with address forwarding are listed in Table 2-6, and the sequence is depicted in Figure 2-8.

Note 1.— Only FANS 1/A aircraft will send a contact response message to the initiating ATSU.

Note 2.— For some ATN B1 aircraft, the contact complete message indicates a positive result even though the logon response from the receiving ATSU indicated failure.

2.2.3.4.6 The ATSU initiating the address forwarding procedure receives an indication of the status of the air-ground logon procedure with the specified ATSU upon receipt of the contact complete message.

ATSU 1 ATSU 2

Contact Request

Contact Response

Contact Complete

Logon Request

Logon Reponse

Figure 2-8. Air-ground address forwarding message sequence (Transfer between areas where data link is provided)

2.2.3.4.7 Where the functionality is available, an ATSU can imitate the air-ground address forwarding procedure with a ground-ground address forwarding procedure that uses messages listed in Table 2-7. The logon forwarding message contains the same information as a logon request, but is transmitted by one ATSU to another as depicted in Figure 2-9.

ATSU 1 ATSU 2

Logon Forwarding

Figure 2-9. Ground-ground address forwarding using logon forwarding message

2.2.4 CPDLC connection management