Note:
The airborne data-link system is available on A/C Post SB 700-1A11-23-005 for Global 5000 and on A/C Post SB 700-23-005 for Global Express/XRS.

The airborne data-link system (ADLS) uses the telelink ACARS airborne data-link unit (ADLU) manufactured by Teledyne Controls. The ADLU provides digital messaging between the aircraft and ground networks.

ARINC, SITA, AVICOM, and Air Canada are data-link service providers. There are also satellite networks that supply air-to-ground, ground-to-air and air-to-air data communications.

The ADLS is a two-way data-link system and allows connection to any number of conveniences such as: pre-departure clearances, fully automated out/off/on/in (OOOI) functions, real-time weather (including graphics options), digital automatic terminal information system (ATIS), terminal weather information for pilots (TWIP) and messaging.

The ADLU interfaces with VHF 3, the SATCOM, the MAGNASTAR, the CAIMS, the flight management system (FMS) and the cockpit printer. The ADLU uses the FMS control display unit (CDU) to provide control and display of ADLS functions. The airborne data-link system lets maintenance messages, dispatch, and weather go to a computer, FAX machine, or modem.

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The airborne data-link unit (ADLU) is the digital communication router of the airborne data link system (ADLS). It provides the capability to exchange messages between the aircraft and a ground stations service provider or host computer. The ADLU supports full duplex communication via VHF voice/data, airborne telephone, or SATCOM. The ADLU unit typically requires less than 10 watts of electrical power, and needs no external cooling.

The airborne data-link system uses the ARINC Aircraft Communications Addressing and Reporting System (ACARS). ACARS is a data-link system which supplies communications of character-oriented data between the aircraft and ground systems. The data-link system connects the airborne data-link system and the aircraft operator ground control center through a ground station network of service providers that use ACARS. The airborne data-link system supplies a data communications path to receive and transmit data such as flight plans, maintenance, weather, aircraft conditions, and messages. Data sent to the aircraft is known as uplink and data sent to the ground station is known as downlink.

The primary component is the airborne data-link unit. The airborne data-link unit gets 28 VDC power from DC BUS 1. The data-link unit connects with many other systems to receive and supply data. It also connects with the FMS CDUs. The airborne data-link system operates in combination with the FMS and navigation computer units.

The airborne data-link unit is installed on the right hand side at FS 415.00 in the avionics compartment for Gobal Express/XRS and in the avionics rack, on the right side of the aircraft and aft of the forward bulkhead for Global 5000. The airborne data-link unit does the functions that follow: 

• Collects data from other aircraft systems and formats the data for downlink in the ACARS message format
• Monitors the data-link frequency through the different radio systems for activity
• Encodes the downlink messages for transmission when there is no traffic on the data frequency
• Controls the tuning and keying of the VHF 3 transceiver to transmit ACARS messages
• Receives uplink messages and acknowledges only those that have the registration number (address) of the aircraft
• Does error check on received messages and transmits a non-acknowledgment (NAK) when a message is in error
• Processes all uplink messages, starts a downlink message in response, or tells the pilots that their action or attention is necessary
• Monitors its condition and sends the reports of failure to the central aircraft information and maintenance system (CAIMS)
• Does built-in-tests (BIT)

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The configuration module is a four-wire module (clock, power, data, and ground) which is installed on the airframe’s mating connector to the ADLU. The configuration module records and stores system connections, connection protocols, and other aircraft-specific parameters for the particular installation. This allows the system interfaces to be customized based on the information contained in the configuration module to minimize changing the system software for different aircraft configurations.

Once programmed, the configuration module contains the aircraft configuration in memory. Any airborne data-link unit with like part number can then be installed on the mounting tray and operated correctly for that particular installation and aircraft.

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• Future Air Navigation Systems (FANS)
• ACARS Message Processing
• FMS CDU
• CDU Control Handshaking
• Messages
• ADLU FMS CDU Pages
• Modes of Operation
• VHF COM Control
• VHF Network
• SATCOM Network

The ADLU is a data communication system that provides two way air-to- ground communication and permits access to a wide variety of flight information services. Data may be transmitted through the VHF (ACARS) using the third VHF radio (optional installation), the cabin communication system for telephony communications or the SATCOM system. All communication is routed to a data service provider (DSP) selected by the user. The DSP provides 24/7 data management, message handling, flight planning and other flight related products and services.

The services provided by the ADLS include the following:

• Digital Automatic Terminal Information Service (ATIS)
• Flight plan upload to the FMS
• Messages
• Oceanic clearances
• Pre-departure clearances
• SIGnificant METeorlogical information (SIGMETS)
• Takeoff and landing times
• Terminal weather
• Terminal Weather Information For Pilots (TWIP)
• Winds aloft

The ADLS uses VHF COM 3 to link to the ACARS network. ACARS, which stands for aircraft communication and reporting system, is a network that consists of three VHF data-link networks, which is used by most scheduled airlines. The ACARS networks are:

• ARINC – covering North America, Hawaii and Mexico
• AVICOM – covering Japan
• SITA – covering Africa, Europe, South America and the South Pacific

ACARS VHF stations are stand-alone facilities and are usually not related to ATC voice communication or navigation facilities.

Future Air Navigation Systems (FANS)

For Global Express/XRS airplanes incorporating SB 700-34-053 and for Global 5000 airplanes incorporating 700-1A11-34-027, Modification - Flight Management System (FMS) - Introduction of Future Air Navigation Systems (FANS)-1/A+ and RNP-4 30/30 Functionality:

The RNP 4 30/30 is a combination of navigation performance and communication performance and allows 30 nautical mile lateral and/or longitudinal separation.

Future Air Navigation System (FANS) 1/A+ option provides air-ground data-link communication between the Air Traffic Services (ATS) and FANS-equipped aircraft.

ATC controller can send instructions and clearances without repeating them and the pilots can read and acknowledge instructions and clearances in text format.

Data link messages are sent via VHF or SATCOM networks, reducing the need for routine voice communication and alleviating voice channel congestion.

The current FANS-1/A standard uses the FMS CDU and aircraft communication and reporting system (ACARS) to exchange datalink messages with ATC facilities and to exchange data between aircraft and ground stations. The ACARS network can be accessed through VHF or SATCOM data links. Various ground networks such as ARINC and SITA are inter-connected to provide ATC/ATM services to all FANS-1/A equipped aircraft.

Downlink Message Priority

For FANS supported Telelink – Downlink messages are assigned a priority that determinesthe order that the messages are sent (ATC messages have the highest priority, otherTelelink screen generated messages have the next lower priority, and all other peripheralmessages have the lowest priority).

For non-FANS supported Telelink – Downlink messages are sent the order that they are queued up.

Message Transfer between Media

For FANS supported Telelink – ATC downlink messages are sent via SATCOM if the VHF link is busy (link is being utilized or is in voice mode).

For non-FANS supported Telelink – Downlink messages are sent via SATCOM only if the VHF link is in a NOCOMM state.

Multi-block Interruption

For FANS supported Telelink – Multi-block downlink messages can be interrupted by a single block ATC downlink message if the multi-block message has a lower priority than the ATC message.

For non-FANS supported Telelink – Downlink messages in progress are not interrupted by another downlink message.

Allow FMS to Print through Telelink

With Batch 3, the FMS can send a text message with a destination code P (printer) which the Telelink will forward to the existing printer.

Functionality

The FANS-1/A has three main functions:

• Air traffic services facilities notification (AFN)
• Controller/pilot datalink communications (CPDLC)
• Automatic dependant surveillance-contract (ADS-C)

AFN Functionality

For a ground initiated ATS transaction to start, the ATS facility must know the existence of the aircraft, as well as the identification of the end-system which contains the ATS application(s). To do this, a notification / log-on from the aircraft is necessary. The pilot must log-in to ATS on-ground before departure.

The AFN function provides the necessary information to the ground end-system such that the ground can establish CPDLC and ADS communications with the aircraft FMS. The AFN provides the ground system with the datalink applications and capability supported by the aircraft and also aircraft addressing information. The flight identification information and aircraft registration included in the AFN provides positive identification of the aircraft.

The AFN provides addressing information needed by ground applications so that they can communicate with their airborne peers. Once the addressing information is passed to the ground successfully, the AFN steps out of the way. The two applications decide when to start communications, and when to terminate communications by themselves. Once in-air, the communication link is updated automatically.

CPDLC Functionality

CPDLC provides a means of direct communication between an ATC controller and a pilot using preformatted text based messages transmitted via data link (ACARS). ATC Comm provides the aircraft with air-ground data communications for ATC service. The messages defined in RTCA DO-258A include a set of clearance/information/request message elements which correspond to existing phraseology employed by current ATC procedures. These message elements encompass altitude assignments, crossing constraints, lateral deviations, route changes and clearances, speed assignments, radio frequency assignments, and various requests for information. The pilot is provided with the capability to respond to messages, to request clearances and information, to report information, and to declare/rescind an emergency. A "free text" capability is also provided to exchange information not available in the defined formats. The intent of ATC Comm is to reduce voice frequency congestion.

ATC Comm application provides the capability to accept, manage, and terminate connections with ATC ground system peers. Once a connection is established, ATC Comm provides the means for a pilot to exchange messages with the established ATC Authority (Controller). The CD-820 provides a dedicated ATC push button to access the ATC (FANS) pages.

This function allows tactical communication between the flight crew and air traffic controller, allowing the flight crew to request deviations to, or replacements of, the filed flight plan. The air traffic controller also has the ability to directly request tactical changes to the airplane flight plan.

When a message is received, the ATC Comm function decodes the incoming data units and determines pilot alerting and response requirements. These requirements then direct ATC Comm concerning message handling, pilot alerting, message display, and response choices. ATC Comm also provides the capability to encode an outgoing message into data units for transmission. Other features include message recall, control capabilities, and status indications. Put simply, the ATC Comm application process provides the data communication functions necessary to mimic current verbal pilot and controller dialogue. Integration of the ATC Comm application into the FMS provides the ability for uplink clearance messages to be automatically stored in the FMC flight plan (with flight crew acceptance).

An ATC Comm connection is initiated by the Ground-Based ATC Comm (GBATC Comm) application. The avionics ATC Comm application will not accept a connection unless a successful AFN transaction has taken place with that ATC authority. Once a connection is established, ATC Comm messages may be exchanged between the ATC Comm application and the GBATC Comm application.

The ATC Comm application is able to maintain two simultaneous connections: one to the current ATC authority, and one to the next ATC authority. Only messages from the current ATC authority are presented to the flight crew. The next ATC authority connection is in a stand-by mode until the "End Service" message is received from the current ATC authority. Transfer of communications occurs when an aircraft traverses ATC authority or facility controlled airspace (Referred to in the oceanic realm as Flight Information Regions (FIRs).). During a transfer of communications, there will be two connections to the aircraft, but one will be established from the original controlling ground authority GBATC Comm application, and the second transport connection will be established from the new controlling ground authority GBATC Comm application.

The ATC Comm connection termination is originated by the GBATC Comm peer. The service is terminated by that GBATC Comm whenever the aircraft passes out of that ATC authority's control domain.

ADS Functionality

ADS-C is a surveillance technique that reports aircraft GNSS based position and other information allowing the aircraft to be tracked in airspace where ATS RADAR is not available. The ADS function reports current aircraft flight parameters via satellite or VHF data link to the air traffic controller, to improve the surveillance of en route aircraft.

The ADS reports may be used by ATS authorities to allow position determination outside of the range of radar. ADS reporting, coupled with improved pilot-controller communication by voice and/or data link facilitates increased safety and air space utilization. The ADS reports may also be used by Airline Operational Control (AOC) and meteorological service applications.

The airborne ADS Function (ADSF) obtains navigational and meteorological data from the FMS and processes the information into reports for ADS ground-based peer applications (ADSP). Information required by the ADSF includes latitude, longitude, altitude, time, identification, waypoint information, track or heading, airspeed, wind speed, wind direction and static air temperature.

The ADSF has the capability of communicating with one or more ground ADSP simultaneously. The dialogue on each association is unique, and is not dependent on the dialogue on any of the other associations. The ADSF can simultaneously communicate with up to 5 ground based ATC facilities. The ADSF provides the aircraft the capability of transmitting various types of information to a ground user, as requested from ground facilities.

The ADS connection termination is initiated by the ADSP based on ground information that indicates that the aircraft has left the FIR. When the ADSF receives this request, it terminates the connection, and clears all information associated with that specific connection.

Typically, there is no pilot interaction with ADS. However, the pilot may review current contracts or turn ADS off.

Refer to Flight Crew Operating Manual, Volume 2, Section 17-10 page 114 for details.

ACARS Message Processing

The two types of ACARS data communications are ground-to-air communications via uplink messages and air-to-ground communications via downlink messages. Data Link Service Providers (DSP), generate uplink messages. When not generated by a DSP, messages are passed to a DSP to uplink to a designated ADLU system on the aircraft. The ADLU then processes the message.

Downlink messages, generated by ADLU or passed on to the ADLU by an airborne peripheral, are sent to a DSP. The DSP then forwards the downlink message, when appropriate, to the designated AOC or ATC.

FMS CDU

Control of the ADLS is achieved by the flight crew via the FMS CDU’s menu-guided format. For the data-link function, the FMS CDU can be controlled either by the FMS or the ADLS. The data-link operations are therefore selected via FMS generated pages or data-link generated pages. However the first CDU to access a page type keeps control of those pages. The other CDUs cannot get access to those pages until the first CDU lets go control of that page type. The primary page types are as follows:

• DATALINK INDEX
• PREFLIGHT
• TEXT WX
• INFLIGHT
• CREATE MSG
• RCVD MSGS
• COMM CONTROL
• OOOI
• MAINTENANCE

The FMS CDU also displays advisories, “send” status messages, and scratchpad messages to communicate ADLS information to the user. Advisories generally denote system status. “Send” status messages appear only on screens from which a downlink message can be initiated. Scratchpad messages advise of invalid data entry and the inability of the system to perform a function. The following is a list of FMS scratchpad messages posted on the CDU:

• ACARS DMU FAILED (Note: The data management unit (DMU) term usage is for commonality with other ACARS-type systems)
• UNABLE TO SEND DOWNLINK
• FLT PLAN RECEIVED
• NEW WINDS AVAIL

FMS Pages

The DATALINK prompt is on the FMS NAV INDEX page 1/2. This provides access to the DATALINK INDEX page. The DATALINK INDEX page provides prompts to FMS functions that utilize uplink information from the ADLS (FLT PLAN, REPORTS, and WINDS). Each FMS-generated page is denoted “DATALINK” at the top of the page.

In “Single-FMS mode”, each FMS communicates independently with the ADLU from the FMS pages (e.g. a flight plan request must be sent separately from each FMS CDU). In “Dual-FMS mode”, communications occur between the master FMS and the ADLU, and the slave FMS is updated by the master FMS. If an optional third FMS is installed, the non-paired FMS will always communicate with the ADLU independently.

Airborne Data Link Pages

Aside from the FMS prompts noted in the previous section, all other DATALINK INDEX page prompts lead to pages generated and controlled by the ADLS. Each ADLS page is denoted with "ACARS" in the upper left-hand corner.

CDU Control Handshaking

Transfer of CDU control from the FMS to the airborne data-link unit, and vice versa, is initiated manually by the flight crew via the menu line select keys on the CDU. While the airborne datalink unit has control of the CDU, an RS 422 operational status message is sent to the FMS indicating that the data link is operational. In the event that the FMS does not receive operational status from the data link within 10 seconds, the FMS then reassumes control of the CDU and displays the NAV IDENT page. Thus, upon cold start power recovery, the data link starts operation in the idle state and does not send any page displays to the CDU until it has been given control of the CDU by the flight crew.

Transfer of CDU control from the airborne datalink unit to the FMS starts when the CDU is returned to a FMS page via menu line key selections or if a CDU mode select key, other than the PREV and NEXT page keys, is selected.

Messages

Downlink Messages

Downlink messages originate onboard the aircraft and are transmitted to the ground. The messages are generated by either the flight crew, a peripheral unit (FMS, FMS CDU), or are transmitted automatically when an appropriate system event has been detected. For messages generated by a peripheral unit, a sublabel is sent within the message defining the message originator. The airborne data-link unit encodes a downlink message, or receives a message/data from the FMS or FMS CDU, and stores it in a downlink queue until it is successfully transmitted.

Automatic Downlinks

ADLS automatic downlinks are generated by either the airborne data-link unit or by the FMS. Automatic downlinks are not annunciated on the FMS CDUs.

Data-Link Automatic Downlinks

• Out, off, on, in (OOOI) events

Each of these events is triggered by a corresponding off and on trigger. The OOOI state transitions as well as the OOOI triggers govern OOOI events. An OOOI report is generated in response to a transition to a new OOOI state. For example, a weight-on-wheels to a weight-off-wheels transition will trigger the transmission of an OOOI to the host computer or ground service provider.

Media Advisory (MA) Events

Upon detection of the MA trigger, the airborne data-link unit encodes and downlinks the MA message if at least one transmission medium is available for use. If the message was triggered by a medium becoming available, then the message is transmitted over that media.

Other Items

TRIGGER	TRIGGER CONDITIONS
OOOI Off	Five seconds have elapsed since the aircraft transitioned from on-ground to in-air (requires >50 knots in-air)
OOOI On	Five seconds have elapsed since the aircraft transitioned from in-air to on-ground (requires <50 knots on-ground)
Media Advisory	The status of a non-telephony transmission media link has changed (transition from available to non-available or from non-available to available) and at least one non-telephony transmission link is available

FMS Automatic Downlink

Initially, the service provider transmits a position report uplink to the aircraft, which automatically tags specified waypoints in the FMS. When the aircraft sequences one of these tagged waypoints en route, the FMS automatically downlinks a position report to the service provider. The link selected is based on transmission media priority.

Flight Complete

Upon the detection of the flight complete trigger, ADLU performs any or all of the following events as specified by the user:

1. Delete all messages in the downlink queue that are specified as being deleted at flight complete
2. Clear all Initialization data that is flight specific (flight number, origin, and destination)
3. Originate transmission of a user-defined downlink

The ADLU also generates and downlinks Media Advisory and Auto Position Reports as required.

VHF NOCOMM

Upon detection of the VHF NOCOMM trigger, ADLU performs any of all of the following events as specified by the user:

1. Generate a VHF NOCOMM user interface message
2. Inhibit the origination of the automatic position report messages, if enabled
3. Delete any queued media advisory downlink messages from the downlink queue

Queued Messages

Queued messages are transmitted in order of priority. The queuing routine takes into account the priorities of the messages in the queue and the priority of the media over which the messages can be transmitted. Any downlink messages generated during a NOCOMM state (when communication links with ground systems cannot be established using VHF, Telephony or SATCOM) will be stored in the queue buffer for downlink when communications have been re-established.

Uplink Messages

Uplink messages originate on the ground and are transmitted to the ADLU. The ADLU accepts messages directed to the ADLU or to a connected peripheral unit (FMS CDU or printer).

When the message is received, the ADLU first validates the data content and compares the aircraft address within the message to the address programmed in the configuration module. If the addresses match, the ADLS then transmits an ACK or negative acknowledgment (NACK) of receipt to the ground (via the same media that transmitted the original message). The ground station will retransmit the message if an ACK is not received within a specified amount of time or if a NACK is received. The ADLU does not process the message until the entire contents have been received and validated.

The ADLU determines which avionic system is targeted to receive the message. If the ADLU is the target, any combination of the following actions can occur: (1) the message can be printed, (2) the message can be viewed, or (3) the message data can be decoded and stored. Uplinked messages pertaining to the operation of the aircraft are displayed on each FMS CDU. If the message is targeted for processing by a peripheral unit, the ADLU transfers the message to the appropriate peripheral. A sublabel is included in the message, which addresses the message to the appropriate end-item peripheral.

ADLU FMS CDU Pages

ADLU generates most of its own control and display pages and passes these to the FMS CDU via the RS 422 interfaces. However, the FMS retains ultimate control of the FMS CDUs and can always override the ADLU displays for higher priority FMS functions.

Selecting DATALINK on the NAV INDEX menu generated by the FMS transfers control of the FMS CDU to ADLU and displays the ADLU-generated DATALINK INDEX. ADLU functions are then accessed according to the following menu structure

Typical ADLS FMS CDU Pages

The following are generic examples of ADLS pages on the FMS CDUs.

INFLIGHT Page

The inflight page is an index page that collects all in-flight ADLS functionality under one menu.

TEXT WX Request Page

The text WX request page is accessible from the main, preflight, or inflight menus. It is used to request the text weather products.

Modes of Operation

Transmission Media Priority

There are three possible types of transmission media: VHF, Telephony, and SATCOM. Each message has a defined media priority list; only the media contained in that list can be used to transmit the message to the ground (e.g. use VHF first, followed by telephony). Media priority is set by the ADLU’s software program based on the message’s data content. Typically, media priority is VHF first, Telephony second, and SATCOM last.

VHF Communications

VHF ground networks are responsible for transporting VHF messages from the aircraft to the data link service provider. VHF ground network providers are dependent upon location; therefore, ADLS operation via VHF is only possible if the aircraft is within range of a VHF ground station.

When VHF COM 3 is in data mode the airborne data-link unit (ADLU) tunes the radio to a frequency entered via the CDU or by a ground station uplink frequency message command. Data mode can be selected only by manual input using the radio management unit (RMU) or via the datalink pages on the CDU. Voice mode can be selected via the CDU or by a ground station VOICE MODE command. When in voice mode, the radio is tuned by the ADLU to a frequency entered on the CDU or by the radio management unit (RMU).

When the aircraft moves from one network coverage area to another, the ADLS automatically searches for the appropriate frequency by scanning an internal frequency table. While the data link is searching for a usable frequency, a “VHF NOCOMM” advisory is shown on the CDU display. The advisory disappears whenever the ADLS achieves communication with a VHF ground station.

The ADLU uses a discrete output for the push to talk (PTT) switch. ADLU is not be affected by any radio status data that may be provided by the radio. The type of radio and method used for tuning the radio are stored in the configuration module.

The COM 3 page on the RMU provides a selection for VOICE or DATA transmission. When DATA transmission is selected, the ADLU unit controls the radio. A Voice/Data mode discrete input allows the ADLU to determine whether the radio is in the voice or the data communication mode. The ADLU communicates with the VHF radio via an Audio Modem for the data communication, and through ARINC 429 to the radio for frequency selection.

The ADLU VHF management function performs the following, to manage the VHF air-ground link:

• Acquiring a frequency
• Establishing a frequency or channel
• Maintaining the frequency or channel

VHF COM Control

The ADLU communication control page is accessed by selecting 1L from the second page of the DATALINK INDEX. This page is used to configure the system communication preferences, and includes provisions for turning on or off the VHF, SAT, and telephony systems. ACARS VHF frequency setting should be left in automatic.

Voice is used to select the telephony communications link and should be left on the "DATA" selection.

VHF Network

The VHF network page is accessed by selecting 1L from the COM CONTROL page. This page is used to configure the system VHF settings. The following are optimized VHF settings for the widest VHF coverage.

It is desirable not to transmit via any network, use the right line select keys and turn off the particular network on these pages. Air Canada should always be turned off because the network has been decommissioned.

Telephony Communications

When the ADLU establishes a telephony link to an airfone ground, the ground station routes the message to the data link service provider or host computer.

If telephony is unavailable, the CDU display indicates “TEL NOCOMM”, unless an advisory with a higher priority (like “VHF NOCOMM”) takes precedence. The advisory is cleared when telephony becomes available. Telephony is provided by the Magnastar C-2000 system only in North America.

Note:
Not all data-link service providers (DSP) have the compatibility to interface to the telephony link.

SATCOM Communications

SATCOM provides more continuous coverage, especially in areas where VHF and telephony coverage is unavailable (i.e. oceanic). When communicating via SATCOM, the ADLU sends packet mode data to the SATCOM SDU, which uses a data channel to transmit the message to a SATCOM ground station. At the ground station, the message is directed to the data link service provider.

If SATCOM is unavailable, the CDU display indicates “SAT NOCOMM”, unless an advisory with a higher priority takes precedence. The advisory is cleared when SATCOM becomes available.

SATCOM Network

The SATCOM network page is accessed by selecting 3L from the COM control page. This page is used to configure the SATCOM system settings.

Select tracker timer to enable to ready the SATCOM system for data-link transmissions If it is desirable to transmit via SAT and not to transmit via the VHF network, turn off all VHF networks and leave the SATCOM tracker timer enabled.

The AUTO RETURN TO COMM setting is used to switch the SATCOM system back to the voice setting. This should be left in the enabled setting unless the SATCOM system is to be dedicated to data transmission.

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Configuration

All of the data link and digital processing components of the ADLU are installed in the DLU.

VHF Modem

The ADLU contains a VHF modem that provides an interface to a VHF radio. The VHF modem connects to the VHF radio through audio input and audio output interface connections. The modem can communicate with the VHF radio at a rate of 2,400 baud. The VHF modem has a self-test mode that is entered upon command from the unit processor.

Airborne Telephone Modem

The ADLU contains a dedicated airborne telephone modem that provides an interface to the aircraft airborne telephone system. The modem conforms to the V.34 standard, allowing it to communicate at a rate of up to 28.8 kilobaud.

ARINC 429 Channels

The ADLU uses a multi-channel ARINC 429 controller that is used to provide the ARINC 429 interfaces. It provides eight ARINC 429 receivers and three ARINC 429 transmitters.

RS 232/422 Serial Ports

The ADLU provides eight general-purpose RS 232/RS 422 transmitters and eight general-purpose RS 232/RS 422 receivers.

• COM 3 for tuning when the receiver is in the DATA mode
• DAU for system status information
• PRINTER to output uplink messages
• FMS computers to receive pre-departure clearances (PDC) or flight plans and to send ACARS information
• Satellite data unit (SDU) for SATCOM operation

The ADLU interfaces to two or three FMS CDUs through RS 422 buses. It sends ADLU screens and input message notices for display and accepts command inputs in return. A modem output is sent to the airborne telephone system through a cabin distribution bus repeater (CDBS-2) for control and data transmission.

ARINC 429 buses connect to the following units:

A data key discrete and audio lines interface to the COM 3 unit.

Power

Power is from a 2.5A 28 VDC bus 1 circuit breaker from SPDA 4.

Discrete Inputs/Outputs

ADLU provides 16 general-purpose discrete input connections and 16 discrete output connections. These discretes are able to drive relays and accept high-power inputs. One output discrete is reserved and is used to drive the push-to-talk switch for the VHF radio.

Configuration Module

ADLU supports an interface to the configuration module that is used to read or write data to the module. The configuration module stores system configuration for ADLS operation.

FMS

The ADLU communicates independently with three FMSs in the integrated avionics computers (IAC) (including the optional third FMS). The communication links between the FMS and the ADLS allow transfer of uplinked flight plans, weather patterns and other flight-related information from the ADLS to the FMS, and transfer of FMS-generated messages from the FMS to the ADLS for downlinking.

FMS CDU

The FMS CDUs serve as the control heads and pilot interface for the ADLS. The ADLU communicates directly with each CDU (the third being optional) via an RS 422 interface. These connections are initialized to operate at 312K baud using synchronous data link control (SDLC) with cyclic redundancy check (CRC) enabled. Each CDU is independently wired to the LADLU and is a separate end-item peripheral which can be specifically addressed.

DAU

The ADLU communicates with DAU 1 via an ARINC 429 interface to receive the aircraft’s time as well as output the ADLU’s maintenance label.

Printer

The ADLU provides uplinked data (e.g., weather reports and general flight/ground-related messages) to the printer via an ARINC 429 interface. Some uplinks may be sent directly to the printer (as an end-item peripheral); other messages or information may be manually selected to print via the appropriate line select key on an associated FMS CDU menu.

Communication Links

Third VHF COM: The ADLU communicates with VHF COM 3 using ARINC 429, audio signals, and a discrete. The ADLU monitors the ARINC 429 input bus for normal and extended status from the radio interface, indicating the radio’s current operation mode (DATA or VOICE), the radio’s currently tuned frequency, as well as other status information. The ADLU tunes VHF COM 3 to the necessary ACARS data frequencies. The discrete (“DATA KEY”) keys the transmitter during VHF COM 3 ADLU communications.

Airborne Telephone

The ADLU establishes an airborne telephone (telephony) link by interfacing with the CCS airborne telephone using an analog modem.

SATCOM

The ADLU communicates with the SATCOM satellite data unit (SDU) using packet mode data via an A429 interface.

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Built-In Test Equipment (BITE)

The ADLU incorporates built-in test (BIT) circuitry which monitors the internal operational status of the ADLU circuitry for faults or failures. In the event of a failure, a message will be posted in the FMS CDU’s scratchpad area. The ADLU BIT also monitors the following external interfaces:

• ARINC 429 bus inputs
• VHF radio modem (used for communication with VHF COM 3)
• Airborne telephone analog modem (used for communication with CCS)

No interface within the BITE will interfere with the normal operation of the system. The BITE provides loopback circuitry to feedback signals for the purpose of fault monitoring. Nondestructive BITE operates continuously. Monitoring of results is automatic and is intended to test and isolate failures to the functional component on the ADLU circuit board. The ADLU provides a digital discrete output signal as a system fail indicator. This digital discrete is coded in an ARINC 429 word and sent to the CAIMS through the DAU.

Advisories

Note:
For maintenance operation on the ADLS with the SATCOM system, the aircraft must be in open area outside the hanger with a direct view of the satellite.

The ADLS provides the following system advisories on the FMS CDU. The Advisories are displayed based on which advisory has the highest priority. The highest active priority advisory is displayed at the advisory field. The advisories are listed above in descending priority level.

FMS CDU Advisories

STATUS	MESSAGE
FAIL	The FAIL advisory is displayed when a ADLS failure is detected.
	SET: When a fault record that has not viewed exists in the fault log
	WHEN SELECTED: Displays DETAILED FAULT page associated with the most recently stored fault record
	CLEARED: When the last unread fault record is displayed
VOICE	SET: WHEN ADLS is in voice mode
	CLEARED: When ADLS is in data mode
ACKNOWLEDGE	The ACKNOWLEDGE advisory is displayed when the uplink message being displayed on the CDU requires flight crew acknowledgment.
	SET: When a ATC message is received but is not yet acknowledged
	WHEN SELECTED: Generates an acknowledgement downlink message related to the displayed uplink message
	CLEARED: When message is acknowledged
SELCAL	An unread ACARS Frequency Uplink or Voice Go-Ahead message exists in ADLS.
	SET: When a Voice Go-Ahead uplink message is received
	WHEN SELECTED: Displays the SELCAL page
	CLEARED: When SELCAL page is displayed
NEW MSG	The NEW MSG advisory is displayed when any unread uplink message exists in the message log.
	SET: When an unviewed uplink message exists in the received uplink message log
	WHEN SELECTED: Displays DETAILED MSG page associated with most recently received uplink message
	CLEARED: When no more unviewed uplink message, or graphics, exist in the received uplink message log
NEW WXMAP	SET: When a new weather map image arrives in the Received Graphics Log
	CLEARED: When there are no unviewed graphic images in the Received Graphics Log
INIT	The INIT advisory is displayed at the start-of-flight if any field requiring initialization has not yet been initialized.
DELAY	20-minute delay expired between Out and Off event.
NOCOMM	The NOCOMM advisory is displayed when ADLS is in the NOCOMM situation.
	SET: When none of the three air/ground links are available
	CLEARED: When any communication link becomes available
VHF NOCOMM	SET: When the VHF is configured and the link is not available
	CLEARED: When VHF link becomes available
SAT NOCOMM	SET: When SATCOM is configured and not available
	CLEARED: When SATCOM becomes available
TEL NOCOMM	SET: When telephony is configured and not available
	CLEARED: When telephony becomes available

Status Messages

The ADLS provides status messages to alert the flight crew of system events or data entry errors. Examples of crew alerts are MESSAGE PRINTING and VHF COMM AVAILABLE. Examples of data entry errors are INVALID ENTRY and INVALID FORMAT.

CAIMS

The ADLS is a CAIMS-compliant system. The ARINC 429 maintenance word is sent to DAU 1 and is available for viewing on the PMAT. The corrective actions for all CAIMS messages are in the FIM.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
A239	AIRBORNE DATA-LINK UNIT	ZONE(S) 140	23-23-01 [ GX ] [ GXRS ]
		ZONE(S) 232	23-23-01 [ G5000 ]

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