Overview of VHF Transceivers and Communication Systems

  • ATA 23 VHF transceivers deal with short-distance communication.
  • Can be tested through:
    • CFDS (Centralized Fault Display System) using the MCDU (Multi-Function Control Display Unit).
    • A test switch on the front of the unit.

Director Failover and RMP Functionality

  • If Director 1 fails during self-test:
    • Director 2 activates and takes control of the system.
  • When an RMP (Radio Management Panel) tunes to a radio (VHF/HF) not connected:
    • The SEL (Select) light illuminates on both the indicated RMP and the one allocated for the radio tuning.
  • Purpose of RMPS:
    • Selection of frequencies for all communication radios.

Ground Maintenance Warnings and Cockpit Alerts

  • Ground maintenance technician calls are indicated in the cockpit by:
    • Flashing 'MECH' key on the Audio Control Panels (ACPs) and audible warning.

Cockpit Voice Recorder (CVR) Functions

  • CVR Purpose:
    • Record communications and crew conversations.
  • Operational Details:
    • VHF systems utilize individual antennas.
    • CVR operation during flight: always on.
    • In-flight CVR is always connected to 115 VAC.
    • Ambient microphone connected to CVR features autonomous amplification.
    • Cockpit cabin interphone system communicates from cockpit to cabin via AMU/CIDS.

Communication Interphone Systems

  • Service interphone is supplied by the CIDS (Configuration and Information Distribution System).
  • Inactive director testing can be done on the ground via:
    • MCDU.
  • DEU (Data Electronics Unit) addressing codes are situated:
    • On DEU mounting racks.

Communication Signals and System Integration

  • In CIDS, the TOP LINE/MID LINE buses communicate between:
    • Directors and DEUs.
  • A SELCAL (Selective Calling) indication occurs in the cockpit via:
    • Audible and visual signals on all ACPs.

Programming and Testing Panels

  • The PROGRAMMING and TEST PANEL PTT allows:
    • Testing CIDS and obtaining relevant Built-In Test Equipment (BITE) information.
  • Communication between ACPs and AMU occurs through:
    • 32-bit A-series digital communication of ARINC 429 type.

Audio Control Panels (ACPs) Specifics

  • "AUDIO SWITCHING CONTROL" in CAPT ON 3 allows:
    • The captain to utilize the ACP in the 3rd position.

Powering Conditions and Failures

  • CIDS when the essential bus fails while maintaining the service bus:
    • Operates without limitations.
  • DEU-B in emergency mode maintains:
    • Essential circuits to ensure communications.
  • Muting circuit purpose:
    • Activates when any microphone is in transmission.
  • Service interphone operation is activated via an override switch when:
    • The landing gear is uncompressed or when the Ground Power plug isn’t connected.

Cockpit Voice Recorder (CVR) Erasure Process

  • To erase CVR on the ground:
    • Confirm parking brake is engaged,
    • Ensure that main landing gear (LF and RH) is compressed,
    • Press ERASE for 2 seconds.

Communication and Public Address Functions

  • Flight interphone provided by:
    • AMU.
  • HF transceivers recognize transmission states exceeding one minute, generating warning messages via:
    • SDAC (Signal Data Acquisition Computer).

Public Address (PA) System Functionality

  • To make a PA from the cockpit via AMU:
    • Press the PA key on one of the ACPs and use dedicated microphone.
  • Following a SELCAL via ‘VHF2’, the CALL legend:
    • Flashes amber on the VHF2 key.

RMP Failures and Control

  • If RMP2 fails, communication frequencies can still be controlled.
  • Functionality of AMU includes:
    • Integration of all communication functions.
  • The RESET key cancels pending calls on ACPs.

SELCAL Call Indication and Acknowledgment

  • SELCAL CALL lamp is reset by:
    • Pressing the Reset key on any ACP.
  • If “VHF2” is selected on “RMP3”:
    • SEL light illuminates on both RMP2 and RMP3.

Audio Control Panel Functions

  • Pressing the “ON VOICE” key on ACP affects:
    • Attenuation of signals from certain navigation receivers.
  • Audible warnings from cockpit loudspeakers are produced by:
    • Flight Warning Computers (FWCs).

Communication and Data Buses

  • Selected options on ACPs transmit to AMU via:
    • ARINC 429 communication protocol.
  • Signaling a SELCAL call via HF1 involves:
    • Illuminating the Call Light on HF1, flashing for 60 seconds, along with an audible warning through cockpit loudspeakers.

Cockpit Voice Recorder (CVR) Summary

  • CVR maintains recording of crew conversations and communications continuously
  • When VHF1 is selected on RMP2, the SEL light:
    • Illuminates on both RMP1 and RMP2.