Communications - Aircraft Communications Addressing and Reporting System (ACARS)

As Installed.

Note : The ACARS system descriptions presented are general in scope and represent typical installations.

ACARS functionality and menu configuration is defined by the airline, and airline configurations of Buyer Furnished Equipment (BFE) can make significant changes in operational menus which are not presented here.

The Aircraft Communications Addressing and Reporting System (ACARS) is a digital data link system designed to automatically communicate flight data, performance data, and routine reports between the aircraft and a network of ground stations.

The airborne subsystem consists of an ACARS control panel, two Control Display Units (CDUs) and one (or two) ACARS Management Units (MU).

The MU provides the central clock, memory and data processor for ACARS. For airborne event sensing and flight crew alerting, the MU interfaces with:

 

The MU collects, controls, and processes incoming and outgoing data and messages through a dedicated VHF radio. The center VHF radio is normally dedicated to ACARS.

The dedicated ACARS radio is normally operated in data mode for automatic transmission of data and message traffic.

Additional ACARS Functionality

The ACARS interface provides for company specific data link operations through the Airline Operation Communication (AOC) Data Link system. AOC data link provides for the automatic programming of FMC data, such as performance parameters and flight plan routes. In addition, AOC data link provides for the automatic downlink of FMC data to the company.

ACARS Control

Flight crew access to ACARS control is through:

There are two management units (MU) installed in the airplane. Both CDUs can use either MU (one active, one standby). The MUs in turn can use either the center or right VHF radio to transmit and receive data. An ACARS control panel allows switching between the two MUs, between the center or right VHF radio, and between ACARS data or voice mode.

ACARS installations include airline modifiable buyer furnished equipment (BFE). The ACARS system descriptions and menu page illustrations presented represent typical installations. Airline configuration of BFE equipment can make significant changes in operational menus which are not presented here.

ACARS Control Through a CDU

Selecting the line select key adjacent to the < ACARS prompt will call up the ACARS Main Menu Page. From this page all ACARS functions may be accessed, such as pre-flight initialization, systems status checks, ACARS radio control, message status or display, printer functions and ACARS configuration.

ACARS Control Through Multipurpose Interactive Display Units (MIDU)

Pilot access to ACARS is through a multipurpose interactive display unit (MIDU). Access to ACARS functions and message displays is provided by depressing the appropriate function or line select key on the MIDU. The MIDU also provides access to other airplane data or communication functions, such as SATCOM.

Depressing the MENU key provides the < ACARS prompt on the display. Selecting the line select key adjacent to the < ACARS prompt will call up the ACARS Main Menu Page. From this page all ACARS functions may be accessed, such as pre-flight initialization, systems status checks, ACARS radio control, message status or display, printer functions, and ACARS configuration.

The specific software providing ACARS functionality is defined by the airline and is not covered in this manual.

ACARS Data Mode

ACARS is operated in the DATA mode, allowing automatic transmission of routine reports and engine and performance data. The flight crew should ensure that the VHF radio dedicated to ACARS is tuned to a data frequency and is set to DATA mode. A voice mode is also available for voice communications.

The system monitors and stores the times of the following events:

On some aircraft the out and in messages also detect closure and opening of cargo doors.

In the DATA mode, OOOI events are automatically transmitted at occurrence. In the DATA mode, the MU automatically tunes the ACARS dedicated VHF radio to a standard link frequency. ACARS monitors this frequency for messages addressed to that aircraft as well as sending messages to the ground.

In addition to transmitting routine data automatically, ACARS allows manual data entry into a CDU for subsequent transmission to ground stations. Engine parameters, fuel status and other information can be conveyed to a ground station by entering values on the appropriate page and pressing the SEND key.

Pre-flight data such as flight number, fuel on board, and departure/destination station are either entered manually at the gate, or may be received by data uplink.

The printer allows data, such as flight plans, to be transmitted by ground stations and printed automatically in flight.

ACARS Message Display

ACARS messages can be displayed on the CDU through the STORED MESSAGES pages. Message titles appear in large characters until displayed. Messages can be sent to the printer by pressing the PRINT line select key.

In addition, an ACARS MSG or ACARS CALL message is displayed in the status field on the CDU ACARS pages when an incoming call is received

The EICAS message •ACARS is displayed to indicate that a call has been received.

ACARS Voice Mode

The ACARS system provides a voice mode to facilitate voice communications between the airplane and ground stations.

Online ACARS Voice Mode

Online voice mode provides an ARINC compatible communication link to ground based telephone systems. ACARS voice mode communications are initiated either from the airplane of the ground. When online voice mode is initiated the ACARS MU will continue to compile, but not transmit data and message traffic. The MU will notify the crew whenever voice mode operations exceed two minutes.

ACARS Air-to-Ground Voice Calls (Typical)

To initiate an ACARS voice call, use the ACARS menu pages and request the call. The applicable phone number is automatically dialled with the downlink request and voice mode is automatically selected when the call is connected. When the call is connected, the ACARS system will annunciate the call with an aural chime and the appropriate SELCAL switch light on the PCP or ACP (VHF C or VHR R) will illuminate.

To complete the call, push the applicable microphone selector switch on the ACP and adjust the volume (if required). Push a Push-to-Talk (PTT) switch for microphone operation. Use a boom microphone headset or other flight interphone system to speak and listen tot he call. When the call is stopped, the MU will automatically return to data mode.

ACARS Ground-to-Air Voice Calls (Typical)

When and ACARS voice radio communication is received, the corresponding SELCAL light illuminates and an aural chime sounds on the flight deck. Received calls are automatically connected. ACARS voice mode is automatically selected and does not require flight crew action from the ACARS menu pages. To receive a call, push the illuminated VHF C or VHF R microphone selector switch on the ACP, push a PTT switch and begin the call.

The flight crew may also respond to a ground initiated voice call by selecting the appropriate responses on the ACARS menu pages and pushing the illuminated CALL microphone selector switch on the ACP.

Manual ACARS Override

Manual tuning the ACARS dedicated radio to the normal voice frequency or de-selecting data mode places that VHF or HF radio into voice mode.

The ACARS voice/data switch provides manual override of the ACARS system. In VOICE mode tuning of the ACARS dedicated VHF radio is given to the flight crew.

Data Link Communications Messages

When the system receives a medium-level communications message, an aural chime sounds and the message is presented on EICAS in white letters preceded by a white bullet symbol (•). A low-level communications message is displayed on EICAS but without the chime. During the routine operation of ACARS, several messages may be generated to keep the pilots aware of the status and functioning of the data link. These messages include:

Message Level Condition Crew Action
•ACARS Medium/
low
A company data link message has been received. Select ACARS from the CDU Menu Page and respond to the message.
•PRINTER Medium/
low
A company data link message has been received and sent to the printer. Review the printed message and press the reset button on the printer.
•DATALINK AVAIL Medium A lost data link connection has been re-established. Resume use of data link communication.
•VHF DATA OFF Medium VHF radio is in voice mode-Data cannot be sent. Switch radio to DATA to transmit data.

EICAS Messages