Note: The datalink system installation is available via optional SB 350-23-004.

The datalink system (option) gives the flight crew data transmission capability. The controller/pilot datalink communication (CPDLC) system supplies a communications link between the aircraft and ground stations. The aircraft systems that use the datalink function are the VHF No. 3 communication and the satellite communication (SATCOM) system. The datalink system uses the aircraft communications addressing and reporting system (ACARS) format. There are satellite networks that provide air-to-ground, ground-to-air, and air-to-air data communications.

The CPDLC function allows ATC controllers on the ground to manage a large number of aircraft simultaneously, preventing multiple radio transmissions, communications disruption caused by multiple radio transmissions, communications disruptions caused by simultaneous transmissions, or misheard oral instructions or requests. The CPDLC function lets the flight crews to communication using a common set of pre-formatted messages.

The services offered through ACARS are as follows:

• Aeronautical operational control (AOC)
• Text messaging (receiving text messages/sending E-mail/contact/fax/air-to-air messages)
• Textual weather reports
• Requests for graphical weather images
• Route uplink/downlink messages
• Flight plan recall
• Flight plan winds updates
• Auto off/on and position reports
• Terminal weather information for pilots (TWIP) reports
• Automatic terminal information services (ATIS) reports
• Predeparture/oceanic clearances
• ATC flow reports.

The datalink system (option) functions through the primary use of the component that follows:

• VHF Communication Unit No. 3
• Satellite Communications (SATCOM)
• Radio Interface Unit
• External Compensation Unit

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The Link 2000+ datalink function provides traffic control/air/ground digital communications using the CPDLC system. The Link 2000+ datalink service is used by EUROCONTROL only.

The Link 2000+ datalink function provides an enhanced assessable set, in the form of reader shown text, of messages for communications between the flight crew and the controller. The European system provides VHF messaging capability for aircraft that operate above 28,500 feet MSL.

The Link 2000+ services requires the components
that follow:

• Radio interface unit
• External compensation unit
• VHF communication unit No. 3
• ATN electronic application key (ATN-6200)

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FANS capability provides flight crews with a method to uplink and downlink Air Traffic Control (ATC) messages between an airborne pilot and a ground controller. FANS messages are received and transmitted over the character orientated ACARS network. FANS functionality includes:

• ATS Facilities Notification (AFN)
• Automatic Dependent Surveillance – Contract (ADS-C)
• Controller-Pilot Data Link Communications (CPDLC).

The FANS 1/A+ function is performed by dual DLCAs, each hosted by FMC1 and FMC2 respectively. FANS capability provides the means to establish an AFN logon, CPDLC and ADS-C connection with an ATS provider system to send and receive FANS messages over a VHF data link radio or SATCOM system.

The FANS 1/A+ communication protocol is implemented in oceanic and in select continental airspace which are typically beyond the range of ground-based ATC radar and VHF communications. The FANS ADS-C function provides automatic position reporting to ATS. The FANS CPDLC function allows the crew to communicate with Air Traffic Control any time using a common set of preformatted messages. FANS CPDLC messages are displayed on up to two CDUs available in the cockpit. Data entry is done on the CDU.

Aircraft with the ADS-C (transponder) and FANS capability allow for preferred routes and for real-time flight plan updates. The flight management computer (FMC-6200) provides flight management data and functionality to the FANS and ADS-C options.

The FANS function is started at the FANS MAIN MENU page from the INDEX 1/2 page, not from the DATALINK MENU page.

All FANS exchanges between the aircraft and the ground control facilities (AFN, CPDLC and ADS-C) are recorded by the data-capable cockpit voice recorder (CVR), through its interface with the RIU-4000.

The FANS CPDLC services require the components that follow:

• Flight management computer (FMC-6200)
• Radio interface units (RIU No. 1 and RIU No. 2)
• Dual DLCA electronic application keys
• VHF communication unit No. 3 or SATCOM system
• FANS electronic application key

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The control display unit (CDU) is the primary CPDLC interface for the flight crew. The function keys and the pushbuttons give the flight crew functionality to move through the CDU pages for the datalink and FANS pages. The line select keys (LSKs) are used to transfer data from the scratchpad to the data line. The functions are assigned to each LSK. The CDU provides datalink communication interface with the VHF and SATCOM systems.

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The datalink function is done through the two radio interface units (RIUs) that are installed in the LH and RH equipment racks. Each RIU can support all the optional datalink functions.

The RIU is the datalink communications management unit for the datalink system. There are two different datalink versions available to support the datalink function. One datalink version with selective calling (SELCAL) and one version without SELCAL.

The RIU No. 1 supports ARINC 429 HS data busses that interface with the VHF communication unit No. 3. The RIU No. 1 sends an output signal to the VHF communication unit No. 3 on the LA-RIU-2 and LB-RIU-2 data busses. The RIU No. 1 receives an input signal from the VHF communication unit No. 3 on the T-VHF-3 data bus.

The RIU No. 1 interfaces with the SDU on ARINC 429 HS data busses. The RIU No. 1 sends an output signal on the L-RIU-10 bus to the SDU. The RIU No. 1 receives an input signal on the SDU-3 bus from the SDU.

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The external compensation unit (ECU) is the aircraft personality module to store aircraft specific data necessary for correct data link operation. The ECU stores the aircraft specific encrypted application keys (EAKs) to provide functionality to the datalink system. The ECU interfaces with the RIU No. 1 for EAK information.

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The VHF communication unit No. 3 provides datalink functionality for the data transmission communication. The VHF communication unit No. 3 provides datalink functions for the Universal graphical weather (option post SB 350-46-003) with the use the CDU No. 1 or the CDU No. 2.

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The satellite communications (SATCOM) system (option) provides datalink functionality for the data transmission communication. The satellite data unit (SDU) provides datalink function when the VHF communication unit No. 3 (option post SB 350-23-003) is out-of-range or if the VHF No. 3 communication unit is not installed.

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Datalink System Interfaces

The VHF communication unit No. 3 receives the datalink message in the VHF band and the satellite communication (SATCOM) satellite data unit (optional) receives the datalink message in the L band INMARSAT satellite constellation.

SELCAL Datalink

The RIU No. 1 controls the SELCAL code detection of the SATCOM satellite data unit (SDU). The RIU No. 1 supplies the selective calling (SELCAL) code to the SDU.

The RIU No. 1 tells the data concentrator unit (DCU) when a SELCAL coded pulse pair is received from a ground transceiver. Also, the RIU No. 1 sends related digital data to the CDU No. 1 and the CDU No. 2.

Universal Graphical Weather Datalink (Post SB 350-46-003)

The Universal graphical weather function (option) is enabled by the GWX-5000 electronic application key (EAK). The weather images are requested from the ground through the CDU. The requested images are sent through the VHF communication unit No. 3. The RIU No. 1 then sends and stores the images to the file server unit (FSU) No. 1 or FSU No. 2. The flight crew can request the image(s) on the CDU or the MFD one image at a time. The RIU No. 1 interfaces with the CDU No. 1, the FSU No. 1, and the integrated avionics processing system (IAPS) on the ARINC 429 HS L-RIU-11 data bus. The RIU No. 1 interfaces with the CDU No. 2, the FSU No. 2, and the IAPS on the ARINC HS L-RIU-12 data bus.

FANS (Post SB 350-23-011)

The RIU No. 1 tells the data concentrator unit (DCU) when a datalink message is received from a ground transceiver. Also, the RIU No. 1 sends related digital data to the CDU No. 1 and the CDU No. 2. The SDU sends an ARINC 429 LS output signal on the SDU-2 bus to the CDU No. 1 and CDU No. 2. The CDU No. 1 sends an input signal on the ARINC 429 LS L-CDU-2 bus to the SDU. The CDU No. 2 sends an input signal on the ARINC 429 LS R-CDU-2 bus to the SDU. An aural chime can be heard when a FANS CPDLC message is received. The DCU gives the EICAS message and visual alert to the flight crew on the multi-function display (MFD).

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When a CPDLC message is received, the CDU shows a message to alert the flight crew:

• a new message has been received
• an active advisory causes the initiation of a specific function
• the new message requires attention
• when more than one advisory is shown, the highest priority is activated first.

Selection of the datalink pages are done on the CDU pages that follow:

DATALINK MENU 1/2 Page

The IDX pushbutton on the CDU, when pushed, shows the INDEX 1/3 page. The datalink line select key (LSK) on the INDEX 1/3 page, when pushed, gives access to the DATALINK MENU 1/2 page. The DATALINK MENU 1/2 page consists of the subpages that follow:

• RCVD MSGS
• SEND MSGS
• WEATHER
• TWIP
• ATIS
• ATS LOG
• DEPART CLX - departure clearance request
• OCEANIC CLX - oceanic clearance request

DATALINK MENU 2/2 Page

The IDX pushbutton on the CDU, when pushed, shows the INDEX 1/3 page. The datalink line select key (LSK) on the INDEX 1/3 page, when pushed, gives access to the DATALINK MENU 1/2 page. When the NEXT pushbutton is pushed on the CDU, the DATALINK MENU 2/2 page is shown. The DATALINK MENU 2/2 page consists of the subpages that follow:

• ATC ADVISORY - ATC advisory request
• POS/TIME RPTS - position/time report
• LINK STATUS
• TECHNICAL - technical pages

FANS (Post SB 350-23-011)

The IDX pushbutton on the CDU, when pushed, shows the INDEX 1/3 page. The FANS LSK on the INDEX 1/3 page, when pushed, gives access to the FANS MAIN MENU page. The FANS MAIN MENU consists of the subpages that follow:

• LOGON/STATUS
• MSG LOG (message log)
• REQUESTS
• EMERGENCY
• POS REP (position report)
• REPORTS DUE
• FREE TEXT
• ADS

Datalink EICAS Messages

When the aircraft datalink system message is received, the DCU causes the message that follows to show on the EICAS:

• The DATALINK CPDLC ATN message annunciation is shown on the EICAS when a datalink ATC message is received
  
  
• The DATALINK FANS ATN message annunciation is shown on the EICAS when a FANS ATC message is received (Post SB 350-23-011)
  
  
• The DATALINK CPDLC FAIL message annunciation is shown on the EICAS when the system finds a datalink equipment failure and fault
  
  
• The DATALINK FANS FAIL message annunciation is shown on the EICAS when the system finds a FANS equipment failure and fault (Post SB 350-23-011)
  
  
• The SELCAL DATALINK advisory message, is shown when a SELCAL code is received by the SATCOM SDU or the VHF communication unit No. 3.

The EICAS messages that follow are related to the

EICAS MESSAGES	LEVEL (COLOR)
DATALINK CPDLC ATN	ADVISORY (cyan)
DATALINK CPDLC FAIL	ADVISORY (cyan)
SELCAL DATALINK	ADVISORY (cyan)

Additional messages Post SB 350-23-011:

EICAS MESSAGES	LEVEL (COLOR)
DATALINK FANS ATN	ADVISORY (cyan)
DATALINK FANS FAIL	ADVISORY (cyan)

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
A199	DATALINK EXTERNAL COMPENSATION - UNIT	ZONE(S) 221	23-23-01

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