W DOC AIRBUS | AMM A320F

VHF MVDR SYSTEM - DESCRIPTION AND OPERATION

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1. General
F VHF System - Communication Principle ** ON A/C NOT FOR ALL
The Very High Frequency (VHF) system is used for all short-range voice communications between:
  • Different aircraft (in flight or on the ground) in voice mode
  • The aircraft and one or many ground stations in voice or data mode.
The VHF system operates within the frequency range defined by ARINC 716 (i.e. 118 to 136.975 MHz with 8.33 kHZ (VOICE)/25 kHZ (VOICE or DATA) spacing between channels).
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2. Component Location
F VHF System - Component Location ** ON A/C NOT FOR ALL
F VHF System - Component Location ** ON A/C NOT FOR ALL
FIN FUNCTIONAL
DESIGNATION		 PANEL ZONE ACCESS
DOOR		 ATA REF
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10RC1 XCVR-MVDR, 1 81 VU 127 23-12-00
10RC2 XCVR-MVDR, 2 81 VU 127 23-12-00
4RC1 ANTENNA-VHF, 1 220 23-12-11
4RC2 ANTENNA-VHF, 2 152 23-12-11
4RC3 ANTENNA-VHF, 3 250 23-12-11
3CA1 MCDU-1 11VU 210 22-82-12
3CA2 MCDU-2 11VU 210 22-82-12
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1RG3 RMP-COM FREQ SEL, 3 20VU 210 23-13-13
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1RG1 RMP-COM/NAV FREQ SEL, 1 11VU 210 23-13-13
1RG2 RMP-COM/NAV FREQ SEL, 2 11VU 210 23-13-13
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3. System Description
F MVDR Block Diagram - Dual LRU Configuration ** ON A/C NOT FOR ALL
The VHF system operates for short-range communications:
  • In voice mode between different aircraft, and between the aircraft and the ground stations
  • In data mode between the aircraft and the ground stations only (Air Traffic Control (ATC) and/or Airline Operational Control (AOC)).
To do this, the VHF system has:
  • Two Multiple VHF Data Radio (MVDR) transceivers (10RC1 and 10RC2) installed with dual LRU configuration.
    F MVDR in Dual LRU Configuration ** ON A/C NOT FOR ALL
  • Three VHF Data Radio (VDR) antennas (4RC1, 4RC2 and 4RC3).
The MVDR transceivers send/receive a Radio Frequency (RF) signal to/from the VDR antennas.
In dual LRU configuration, each MVDR has two channels:
  • COM (Communication) A: COM A channel of MVDR transceiver 1 hosts VHF1 and COM A channel of MVDR transceiver 2 hosts VHF2.
  • COM B: COM B channel of MVDR transceiver 1 hosts VHF3 and COM B channel of MVDR transceiver 2 is a spare channel.
VHF1, VHF2 and VHF3 channels can operate at the same time in voice and data modes.
MVDR transceiver 2 has a channel reconfiguration function (with three RF relays and a combiner/splitter) to keep VHF2 available on COM B spare channel if there is COM A channel failure.
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4. Power Supply
F MVDR Power Supply - Dual LRU Configuration ** ON A/C NOT FOR ALL
The electrical power generation and distribution system supplies the 2 MVDR as mentioned below:
  • The MVDR1 COM A that hosts the VHF1 transceiver is supplied by the 28VDC ESS BUS (sub bus bar 401PP). In case of emergency, this system is supplied by the DC emergency generation.
  • The MVDR1 COM B that hosts the VHF3 transceiver is supplied by the 28VDC1 BUS (sub bus bar 101PP).
  • The MVDR2 COM A that hosts the VHF2 transceiver and COM B that hosts its warm spare are both supplied by the 28VDC2 BUS (sub bus bar 204PP).
These components are supplied by the subsequent circuit breakers:
A. Circuit Breaker(s) Table
PANELDESIGNATIONFINLOCATION
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49VUCOM/VHF/12RC1G09
121VUCOM NAV/VHF/22RC2L04
121VUCOM NAV/VHF/32RC3L05
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5. Interface
F VHF System Interface Architecture - Dual LRU Configuration ** ON A/C NOT FOR ALL
In the dual LRU configuration, the MVDR transceivers are interfaced with:
  • Two Radio Management Panels (RMP1 and RMP2) (Ref. 23-13)
  • One Audio Management Unit (AMU) (Ref. 23-51)
  • One Centralized Fault Display Interface Unit (CFDIU) (Ref. 31-32)
  • One Data Loading Routing Box (DLRB) (Ref. 31-38) to get access to the configuration of the component and data loading. Only MVDR1 is interfaced with the DLRB.
  • Two System Data Acquisition Concentrator (SDAC1 and SDAC2) (Ref. 31-54)
  • Two Landing Gear Control Interface Units (LGCIU1 and LGCIU2) (Ref. 32-31)
  • One Air Traffic Services Unit (ATSU) for the MVDR1 COM B (Ref. 46-20).
A. Interface with the Radio Management Panel (RMP)
(1) The COM/NAV RMP subsystem centralizes radio communication control (VHF). It controls the frequencies (118 to 136.975 MHz) and the mode of the VHF transceivers through an ARINC 429 bus. The channel width (8.33 KHz or 25 KHz) is selected according to the pin programming of the RMP.
It is also used to control the frequency of the navigation equipments (VOR-DME, ILS, ADF) in case of failure of the Flight Management System (FMS). The RMP subsystem consists of 3 RMPs (RMP1, RMP2 and RMP3) which are identical and interchangeable (the RMP3 is optional).
The RMP displays and selections are synchronized using ARINC 429 buses to enable the control of all radio communication via any RMP. The synchronization of the RMPs also enables a reconfiguration in the case of a failure of one or more RMPs.
Each MVDR system is interfaced with RMPs through 2 ARINC 429 input low speed buses and one input discrete.
F MVDR/RMP Interface - Dual LRU Configuration ** ON A/C NOT FOR ALL
(2) The labels exchanged between MVDR and RMP are:
-------------------------------------------------------------------------------
| LABEL ID | DIRECTION |
-------------------------------------------------------------------------------
! 30 - Frequency command ! !
! (25 kHZ channel spacing) ! MVDR <--- RMP !
! ! !
-------------------------------------------------------------------------------
! 47 - Frequency command ! MVDR <--- RMP !
! (8.33 kHz channel spacing) ! !
-------------------------------------------------------------------------------

(3) MVDR/RMP Input Discrete
-------------------------------------------------------------------------------
| DISCRETE | ELECTRICAL LEVEL | DIRECTION | SIGNAL STATUS |
-------------------------------------------------------------------------------
! Port A/B select ! GROUND/O.C. ! MVDR <--- RMP ! GND = Port A !
-------------------------------------------------------------------------------

B. Interface with Audio Management Unit (AMU)
(1) The AMU centralizes the audio signals used by the crew:
  • In transmission mode, it collects the audio signals from the microphone input signal of the crew stations and routes them to the VHF communication system.
  • In reception mode, it collects audio output signals from the VHF transceivers and routes them to the crew stations.
It also monitors and decodes the selective calling audio output of the 3 transceivers. When one equipment receives a tone which matches the programmed code, the AMU activates an annunciating light and chime in the cockpit.
Each MVDR is connected with the AMU through 1 analog input, 2 analog outputs and 1 input discrete.
F MVDR/AMU - Interface ** ON A/C NOT FOR ALL
(2) MVDR/AMU Input Discrete
-------------------------------------------------------------------------------
| DISCRETE | ELECTRICAL LEVEL | DIRECTION | SIGNAL STATUS |
-------------------------------------------------------------------------------
! PTT ! GROUND/O.C. ! MVDR <--- AMU ! GND = Transmit !
-------------------------------------------------------------------------------

C. Interface with Centralized Fault Display Interface Unit (CFDIU)
(1) The CFDIU communicates with each VHF transceiver through 3 independent, bi-directional ARINC 429 buses (2 with MVDR1 for VHF1 and VHF3 and 1 with MVDR 2 for VHF2) to obtain their health status and identification via the "Built-In Test Equipment (BITE)" embedded maintenance software.
Each VHF has a low speed bus ARINC 429 input from the CFDIU and a low speed bus ARINC 429 output.
This system is thus capable of two-way communication with the CFDIU.
(2) The labels exchanged between the CFDIU and the MVDR are:
-------------------------------------------------------------------------------
| LABEL ID | DIRECTION |
-------------------------------------------------------------------------------
! 125 - UTC ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 126 - Flight phases ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 155 - Aircraft configuration 1 ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 156 - Aircraft configuration 2 ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 157 - Aircraft configuration 3 ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 227 - Command ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
!233 to 237 - Flight number ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 260 - Date ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
!301 to 304 - Aircraft Identification ! MVDR <--- CFDIU !
-------------------------------------------------------------------------------
! 354 - LRU Identification ! MVDR ---> CFDIU !
-------------------------------------------------------------------------------
! 356 - Fault message ! MVDR ---> CFDIU !
-------------------------------------------------------------------------------
! 377 - Equipment Identification ! MVDR ---> CFDIU !
-------------------------------------------------------------------------------

D. Interface with Data Loading Routing Box (DLRB) (Only for DUAL LRU Configuration)
(1) In the dual LRU configuration only MVDR1 is connected to the DLRB. Thus, MVDR software is data loadable per module via the DLRB. This function allows updating the operational software of the MVDR in case of upgrades.
The dataloading procedure must be performed twice since only MVDR1 is connected to the DLRB.
F MVDR/DLRB Interface - Dual LRU Configuration ** ON A/C NOT FOR ALL
Thus, once dataloading of the first LRU is performed, the physical positions of MVDR1 and MVDR2 must be switched in the electronic bay. Then, the second LRU can be dataloaded.
E. Interface with System Data Acquisition Concentrator (SDAC)/Flight Warning Computer (FWC)
(1) The SDAC 1 or 2 collects transmission information from the VHF system and allows the transmit mode of the VHF system to be recorded. The connection is obtained through the KEY EVENT discrete output information of the VHF transceiver. Each SDAC receives 3 discrete links, one for each VHF channel.
F VHF System - Key Event Data ** ON A/C NOT FOR ALL
When the VHF system is transmitting (PTT switch on) for 30 seconds, an aural warning starts and sounds every second for five seconds (i.e. five times in five seconds). After these 35 seconds of continuous transmission, the transmission is automatically cut off. 25 seconds later, if the Push-to-Talk (PTT) switch is still on (i.e. PTT lasting more than 1 minute), the following warnings are generated:
  • Level 1: VHF-X EMITTING message displayed on the Electronic Centralized Aircraft Monitoring (ECAM) Display Unit (DU)
  • Level 2: single chime + master caution.
The PTT has to be released, then activated again for a new transmission to be allowed.
NOTE: This behavior may be different depending on the Flight Warning System (FWS) standard installed on the aircraft.
(2) MVDR/DLRB Output Discrete
-------------------------------------------------------------------------------
| DISCRETE | ELECTRICAL LEVEL | DIRECTION | SIGNAL STATUS |
-------------------------------------------------------------------------------
! Key Event ! GROUND/O.C. ! MVDR ---> SDAC ! GND = Emission !
-------------------------------------------------------------------------------

F. Interface with Landing Gear Control and Interface Unit (LGCIU)
(1) The LGCIU provides leg information (flight/ground) through discrete signals to each VHF transceiver in order to disable the "interactive" mode of the BITE function during a flight.

Each MVDR system is interfaced with the LGCIU through 1 input discrete cable.
(2) MVDR/LGCIU Input Discrete
--------------------------------------------------------------------------------
| DISCRETE | ELECTRICAL LEVEL | DIRECTION | SIGNAL STATUS |
--------------------------------------------------------------------------------
! Landing Gear Extended ! GROUND/O.C. ! MVDR <--- LGCIU ! GND = Flight !
--------------------------------------------------------------------------------

G. Interface with Air Traffic Service Unit (ATSU)
(1) The ATSU sends and receives data with VHF3 through a bidirectional high speed ARINC 429 bus.
The ATSU is a modular hosting platform which centralizes all data communications.
ATSU hosts 3 main software components:
  • Aircraft Communication Addressing and Reporting System (ACARS) and Air Traffic Network (ATN) (depending on the Future Air Navigation System (FANS) product)
  • Airline Operational Control (AOC) applications
  • Air Traffic Control (ATC) datalink applications.

(a) ACARS and ATN routers (depending on the FANS product)
They route received messages from the ground to appropriate end-systems on-board the aircraft (Flight Management Computer (FMC), Aircraft Condition Monitoring System (ACMS), cabin terminal, airshow and cabin printer). They also route to the ground reports automatically generated by aircraft systems or by the pilots.

(b) AOC applications
They provide operational data communications between the aircraft and the airline facilities on the ground (departure/arrival time reports, delay/estimated time of arrival, gate assignment, etc.).

(c) ATC datalink applications
They warn the crew of any upcoming ATC message and also send the appropriate data to the peripherals to sustain the communication tasks (e.g. selection of the appropriate ATC center for datalinks all along the flight).

(2) The ATSU uses the services provided by the VHF3 to communicate with the ground in DATA mode.
Two output discrete signals from the ATSU are used to control:
  • VHF3 switching between voice and data mode: voice/data select discrete
  • VHF3 frequency selection (Port A for ATSU, Port B for RMP): port select discrete.
    Broadcast data are sent on output bus SYS5 of the ATSU to the VDR3 port A for VHF3 frequency selection.
    The ATSU COM2 and VHF/3 buses support:
  • VHF3 status transmission to the ATSU (voice/data mode, failure...)
  • ATSU status transmission to the VHF3 (primary source/destination, failure...)
  • VHF3 configuration and control by the ATSU
  • ARINC 618 downlink and uplink block exchanges.
(a) Functional split
The functional split between ATSU and VHF3 is the following:
1 In Voice mode:
a The ATSU controls the VHF3 switching between data and voice mode.
b The ATSU controls VHF3 port select.
c The ATSU provides the VHF3 voice frequency on port A.
2 In Data mode:
a The ATSU configures the VHF3 in the appropriate protocol.
b The ATSU sends ARINC 618 messages in digital format to the VHF3.
c The VHF3 adds the VHF protocol overhead and performs the modulation operation on the VHF signal.
d The VHF3 demodulates the received VHF signal, eliminates the VHF overhead and sends the received messages to the ATSU in digital format.
e The ATSU controls the VHF operational parameters of the VHF3 (frequency...).

When the ATSU transmits ARINC 618 blocks to the VHF3, it waits for the effective transmission to the ground before transmitting other ones.
In case where the transmission is not completed by the VHF3, the ATSU sends a'purge down-link' command, in order to clear the failed VHF3 downlink transmission.
(3) The labels exchanged between the MVDR1 Com B and the ATSU are:
-------------------------------------------------------------------------------
| LABEL ID | DIRECTION |
-------------------------------------------------------------------------------
! 172 - ARINC 429 protocol determination ! VHF3 <---> ATSU !
-------------------------------------------------------------------------------
! 270 - ATSU status indication, ARINC 750 ! !
! protocol determination, VHF3 status ! VHF3 <---> ATSU !
! indication, Voice/Data mode indication ! !
-------------------------------------------------------------------------------
! 377 - MVDR Equipment ID ! VHF3 ---> ATSU !
-------------------------------------------------------------------------------
! 030 - Voice frequency port A ! VHF3 <--- ATSU !
-------------------------------------------------------------------------------
! 047 - Voice frequency port A ! VHF3 <--- ATSU !
-------------------------------------------------------------------------------
! 253 - SAL MVDR1 Destination address for ! VHF3 <--- ATSU !
! ARINC 429 williamsburg word) ! !
-------------------------------------------------------------------------------
! 304 - SAL ATSU (Destination address for ! VHF3 ---> ATSU !
! ARINC 429 Williamsburg word) ! !
-------------------------------------------------------------------------------

NOTE: The label 172 is also used to transmit the MVDR configuration installation to the ATSU. If the bit 25 of the label 172 is set to "0", then the MVDR is in legacy configuration. If the bit 25 is set to "1", then the MVDR is set to the dual LRU configuration. This way, the ATSU can determine the maintenance message format to be used in adequacy with the configuration.
(4) MVDR/ATSU Input Dicrete
-------------------------------------------------------------------------------
| DISCRETE | ELECTRICAL LEVEL | DIRECTION | SIGNAL STATUS |
-------------------------------------------------------------------------------
! Voice/Data mode ! GROUND/O.C. ! VHF3 <--- ATSU ! GND = DATA !
! selection !
-------------------------------------------------------------------------------
! Port Select ! GROUND/O.C. ! VHF3 <--- ATSU ! GND = PORT A !
-------------------------------------------------------------------------------

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6. Component Description
A. MVDR Transceiver - Description FIN: 10-RC-1 FIN: 10-RC-2
The MVDR transceiver conforms to ARINC 600 specifications. Its case size is 3MCU and its nominal weight is 4.61kg.
(1) MVDR transceiver face
The face features:
F MVDR Transceiver ** ON A/C NOT FOR ALL
  • A self-test switch
  • Three LED indicators
  • A serial bus monitor jack
  • A fold-away carrying handle
  • An Airbus proprietary standalone identification system connector
  • An equipment identification plate.
(2) MVDR transceiver back
The back side is composed by an ARINC 600 connector size 1 to enable connection with:
F MVDR Transceiver - Rear Connector 1/2 ** ON A/C NOT FOR ALL
F MVDR Transceiver - Rear Connector 2/2 ** ON A/C NOT FOR ALL
  • Top Plug (TP): 60 pin arrangement with contact size 22
  • Middle Plug (MP): 60 pin arrangement with contact size 22
  • Bottom Plug (BP): pin/coax arrangement with 2 coax size 5, 2 contact size 16 and 1 contact size 12.
NOTE: In dual LRU configuration, since there are not enough plugs to connect COM A and COM B power supplies to the BP, COM B power supply had to be connected to the TP.
B. MVDR Characteristics
The MVDR transceiver houses all the components and electronic circuitry incidents for frequency/channel selection, receiving and transmitting functions of VHF air-ground-air communications.
(1) Electrical characteristics
(a) Transmitter
  • Antenna impedance: 50 ohms
1 Transmitter - AM-MSK voice & data mode A
  • Output power: 25 watts minimum into a 50 ohms resistive load.
  • Modulation: AM-MSK.
  • Bit rate in data mode: 2.4 KB/s.
2 Transmitter - mode 2 data - D8PSK
  • Output power: 15 watts minimum into a 50 ohms resistive load.
  • Modulation: D8PSK.
  • Bit rate: average of 31.5 KB/s.
(b) Receiver
1 Receiver - AM-MSK voice & data mode A
a Sensitivity (voice and analog data):
  • -107 dBm for 6 dB signal to noise ratio.
b Selectivity:
  • 25 kHz: 6 dB maximum attenuation at -8 kHz/+8 kHz and 60 dB minimum attenuation at -17 kHz/+17 kHz
  • 8.33 kHz: 6 dB maximum attenuation at -2.8 kHz/+2.8 kHz and 60 dB minimum attenuation at -7.3 kHz/+7.3 kHz.
2 Receiver - mode 2 data - D8PSK
a Sensitivity:
  • -98 dBm for 0.001 bit error rate.
b Selectivity (25 kHz channel):
  • 6 dB maximum attenuation at -8 kHz/+8 kHz and 60 dB minimum attenuation at -17 kHz/+17 kHz.
(c) Power Supply
1 Voltage requirement:
  • +27.5 (-0.5 VDC/+0.5 VDC).
2 Maximum input current at 27.5 VDC for a single transceiver:
  • 0.8 A in receive mode
  • 6.0 A in transmit mode.
(d) FM immunity filter
1 General operation
a The MVDR transceiver makes sure its primary functions through:
  • The FM immunity filter, which is a high-pass filter with a stop band attenuation at 108 MHz more than 10 dB. This filter prevents interference with the high-power FM broadcast-stations.
C. VHF antenna description FIN: 4-RC-1 FIN: 4-RC-2 FIN: 4-RC-3
The VHF antenna is a vertically polarized antenna and provides omni-directional azimuth radiation pattern coverage. The antenna impedance is 50 ohms.
This antenna is composed of:
F VHF Antenna ** ON A/C NOT FOR ALL
  • An aluminum base plate
  • A laminated radome
  • A duralinox leading edge
  • A C-type coaxial connector surrounded by a seal.

The maximum size of the VHF antenna is 74mm x 405mm x 423 mm, in compliance with ARINC 716.
The antenna is connected to the transceiver by means of a coaxial cable.
VHF antennas 1 and 3 are installed on the top of the aircraft fuselage, on the longitudinal center axis.
VHF antenna 2 is installed at the bottom of the aircraft fuselage, on the longitudinal center axis.
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7. Operation/Control and Indicating
A. Operation
The MVDR contains two independent VHF communication transceivers. Each transceiver within the MVDR operates in a frequency range defined by ARINC 716 (118.000 to 136.975 MHz).
It can operate in the following modes:
  • Voice mode
  • Data mode.

The VHF system operates in voice mode on the three VHF channels, and the data mode is active on the VHF3 channel only.
Thus the VHF system can use three channels at the same time:
  • Three VHF voice channels, or
  • Two VHF voice channels and one VHF data channel.

(1) Voice mode
When operating in voice mode, the MVDR transmits/receives voice signals in one-way mode with 8.33 kHz or 25 kHz channel spacing using amplitude modulation to fulfill European airspace requirements.
(a) Transmit function
In voice mode, the Audio Frequency (AF) signals from the microphones are transmitted to the VHF transceiver through the AMU.
The VHF transceiver tuned on the frequency selected on one RMP modulates the AF signals into VHF signals. These VHF signals are sent to the antenna by a coaxial cable. Then, they are transmitted to the various stations.
A connection between the VHF transceiver and the SDAC enables to record the use of the VHF system in transmit mode. The connection is obtained through the KEY EVENT output information of the VHF Transceiver.
(b) Receive function
The antenna picks up the VHF radio-communication signals from the stations. These signals are transmitted to the transceiver by a coaxial cable.
In voice mode, the transceiver, tuned on the frequency selected on one RMP, demodulates the VHF received signals into AF signals. The AF signals are transmitted via the AMU to the audio equipment.
(2) Data mode
Two different forms of VHF data link mode (mode A and mode 2) are defined by ARINC 750:
  • Mode A:
    Transmits/receives data signals in one-way mode through an Amplitude-Minimum Shift Keying (AM-MSK) modulation. The signal rate is 2.4 KB/s. This mode has been especially designed to use ACARS modulation equipment and radio. ACARS and VDL mode A is a low speed bit oriented data transfer system. It uses Carrier Sense Multiple Access methodology.
  • Mode 2:
    It is an improved version of the VDL mode A to transmit/receive data signals in one-way mode through D8PSK modulation. The signal rate is 31.5 KB/s. VDL mode 2 can be used over both ACARS and ATN networks.

(a) Transmit function
In data mode, the digital information is transmitted from the ATSU to VHF3 (tuned on the frequency selected on one MCDU and transmitted to the transceiver through an ARINC 429 HS bus) which modulates it. The VHF signals are sent to the antenna by a coaxial cable. Then, they are transmitted to the various stations.
(b) Receive function
The antenna picks up the VHF radio-communication signals from the stations. These signals are transmitted to the transceiver by a coaxial cable.
In data mode, the transceiver is tuned on the frequency corresponding to the DSP providers (selected on one MCDU).
The VHF received signals are transmitted to the transceiver through an ARINC 429 HS bus. The transceiver demodulates the VHF received signals into digital information. This information is transmitted to the ATSU through an ARINC 429 HS bus (only the messages addressed to the aircraft are transmitted to the ATSU, the others are filtered by the VHF).
B. Control and Indicating
(1) MVDR voice/data mode selection
The system has direct control over the VHF3 switching between voice and data modes.
A voice/data switching can be requested by:
(2) Self-test selection
The purpose of the self-test is to determine the functional health and integrity of the MVDR by testing certain portions of its hardware functions and elements to determine whether they are functioning within nominal performance specifications.
It is launched on power-up, and it can also be user-initiated by pushing the self-test pushbutton on the front panel. Self-test is only possible when the air/ground discrete from the LGCIU indicates ON GROUND.

The front panel LEDs (LRU, CONTROL and ANTENNA) show the self-test progress and status. These LEDs indicate the following information:
F MVDR Transceiver ** ON A/C NOT FOR ALL
  • LRU STATUS indicates the health of the Line Replaceable Unit (LRU).
  • CONTROL FAIL indicates if tuning data is received or not.
  • ANTENNA FAIL indicates if a Voltage Standing Wave Ratio (VSWR) fault is correct or not.

In response to an initiated self-test mode running as a result of the front panel self-test pushbutton being asserted, the following LED display operations sequence shall occur:
  • All indicators are set to RED for at least two (2) seconds.
  • The LRU indicator is set to GREEN and all other indicators are set to RED for at least two (2) seconds.
  • All indicators are set to OFF for at least five (5) seconds.
  • The LRU STATUS, CONTROL FAIL and ANTENNA FAIL indicators display the test results for at least 30 seconds.
  • If no faults are present, the LRU STATUS indicator is set to GREEN while the CONTROL FAIL and ANTENNA FAIL indicators are set to OFF.
** ON A/C NOT FOR ALL
8. BITE
The BITE facilitates maintenance on in-service aircraft. It detects and determines a failure related to the MVDR system.
The BITE of the MVDR transceiver is connected to the CFDIU.

The BITE:
  • Transmits permanently the MVDR system status and an identification message to the CFDIU
  • Memorizes the failures occurred during the last 63 flight legs
  • Monitors data input from the various peripherals (e.g. RMP and CFDIU)
  • Transmits to the CFDIU the result of the tests and self-tests performed
  • Can communicate with the CFDIU by the menus in the interactive mode.
A. BITE Architecture and Perimeter
System BITE is standard A, type 1. BITE architecture and MVDR FIN depend on the MVDR configuration. To determine the correct maintenance message format, the MVDR installation configuration is transmitted to the ATSU through the bit 25 of the label 172 ( "0" = legacy, "1"= dual LRU).
(1) BITE architecture and perimeter in dual LRU configuration
F BITE Architecture - Dual LRU Configuration ** ON A/C NOT FOR ALL
In this configuration, the MVDR1 FIN is 10RC1 and the MVDR2 FIN is 10RC2. The standard A maintenance message formatting for accusing MVDR is:
  • 23-12-33 VHF1-MVDR1 (10RC1)
  • 23-12-33 VHF3-MVDR1 (10RC1)
  • 23-12-33 VHF2-MVDR2 (10RC2).
Each VHF side system BITE has a dedicated ARINC 429 low speed bus.
B. Operational Modes
The BITE has 2 operational modes:
  • The normal mode
  • The interactive mode.
(1) Normal mode
During the normal mode, the BITE monitors cyclically the instantaneous status of the MVDR system. It transmits these information signals to the CFDIU during the flight concerned.
In case of fault detection, the BITE stores the information signals in the fault memories.
These information signals are transmitted to the CFDIU every 250 ms by an ARINC 429 message with label 356.
(2) Interactive mode
The interactive mode can only be activated on the ground.
This mode enables communication between the CFDIU and the MVDR transceiver BITE. This is by means of the MCDU.
F VHF System - REPORT/MAIN MENU ** ON A/C NOT FOR ALL

The MVDR transceiver interactive mode is composed of:
(a) LAST LEG REPORT
F VHF System - LAST LEG REPORT ** ON A/C NOT FOR ALL
This report contains the class 1 and 2 internal and external faults recorded during the last flight.

(b) PREVIOUS LEGS REPORT
F VHF System - PREVIOUS LEGS REPORT ** ON A/C NOT FOR ALL
The messages are identical to those given in the paragraph above, but concern the faults occurred during the last 63 flights.

(c) LRU IDENT
F VHF System - LRU Identification ** ON A/C NOT FOR ALL
This report displays all the LRU identification data for digital units such as the Part Number (P/N), the Serial Number (S/N) and the Software Part Number.

(d) GND SCANNING
F VHF System - Ground Scanning ** ON A/C NOT FOR ALL
This function is used to monitor and detect anomalies on ground. It presents all faults detected in real time.
The Universal Time Coordinated (UTC) displayed in the ground scanning corresponds to:
  • The time when the menu was accessed, if the fault was present before launching the ground scanning.
  • The time when the fault appears, if the fault appears while the ground scanning is activated.

After leaving the test, if a ground scanning is performed again and if a fault was detected during previous ground scanning, the UTC of this fault will be updated with the start time of the new ground scanning.

(e) TROUBLE SHOOT DATA
F VHF System - Trouble Shoot Data ** ON A/C NOT FOR ALL
This function permits to analyze the snapshot of the recorded fault to detect any software bug. Two types of data are displayed on the MCDU:
  • Correlation parameters which are the date and the UTC
  • Snapshot data.

(f) CLASS 3 FAULTS
F VHF System - Class 3 Faults ** ON A/C NOT FOR ALL
This report contains the class 3 internal and external faults recorded during the last flight.

(g) TEST
F VHF System - Test (System Test) ** ON A/C NOT FOR ALL
F VHF System - Test (Audio Tone Test - VHF1, 2) ** ON A/C NOT FOR ALL
F VHF System - Test (Audio Tone Test - VHF3) ** ON A/C NOT FOR ALL
A VHF built-in functional test can be initiated by pushing on the MCDU the line key adjacent to the TEST indication on the VHF maintenance sub-menu.

(h) GROUND REPORT
F VHF System - Ground Report ** ON A/C NOT FOR ALL
This function is used to display all system-internal faults only detected when the aircraft is on ground by results of:
  • Power On Test
  • Continuous monitoring
  • BITE manual test and BITE specific function
  • Ground scanning.

(i) SPECIFIC DATA (Information on discrete status)
F VHF System - Specific Data (LRU Status, Hardware Pin Programming) ** ON A/C NOT FOR ALL
F VHF System - Specific Data (LRU Status, Discrete/Status Page) ** ON A/C NOT FOR ALL
This function provides information about the discrete status, the ARINC 429 status and the A/C configuration.

[Rev.10 from 2021] 2026.04.02 06:11:58 UTC
"WTRUIB" 2025