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System Description
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RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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Overview

Note: 
VHF communication system No. 3 installation is available via optional SB 350-23-003.

The very high frequency (VHF) communication system supplies short range air-to-air and air-to-ground communications, with amplitude modulation (AM) signals. The VHF communication system has two VHF communication units (VHF transceivers) and two VHF antennas. Installation of a third VHF communication unit and antenna system is optional. Each VHF communication system operates independently. The VHF transceivers can be tuned in 8.33 kHz or 25 kHz increments in the 118.000 MHz to 136.975 MHz range. A control display unit (CDU), or the multi-function displays (MFD), tune the VHF transceivers.

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VHF Communication Unit

The VHF communication units are installed in the LH and RH equipment racks. The VHF communication unit No. 1 and the optional VHF communication unit No. 3 (option) are in the LH equipment rack. The VHF communication unit No. 2 is in the RH equipment rack. Each VHF communication unit is installed in a mounting tray (VHF communication-unit tray) that is attached to the equipment rack.

At the front, The VHF communication unit has one hold-down hook that attaches to the hold-down clamp of the mounting tray. Also, at the front, the VHF communication unit has a swivel-handle to help remove the unit from the mounting tray.

At the rear, the VHF communication unit has an electrical connector that supplies the interface with the other aircraft systems.

The VHF communication units can be tuned in 8.33 kHz increments in the 118.000 MHz to 136.990 MHz range.

The units can also be tuned in 25 kHz increments in the 118.000 MHz to 136.975 MHz range. The extended range option (137.000 MHz to 151.975 ). The optional extended range is strapped in the configuration strapping unit (CSU).

The VHF communication unit No. 1 is a multichannel VHF voice-transceiver. The pilot MFD usually tunes this VHF transceiver. The copilot MFD, the pilot control display unit, or the copilot control display unit can also tune it.

The VHF communication unit No. 2 is a multichannel VHF voice-transceiver. The copilot MFD usually tunes this VHF transceiver. The pilot MFD, the pilot control display unit, or the copilot control display unit can also tune it.

The VHF communication unit No. 3 (option) is a multichannel VHF voice/data-transceiver. The VHF communication unit No. 3 (option) is operated as the VHF communication unit No. 1.

The pilot MFD usually tunes the VHF transceiver No. 3. The copilot MFD, the pilot control display unit, or the copilot control display unit can also tune it.

The VHF transceivers get power from a 28 VDC electrical source as follows:

  • The VHF transceiver No. 1 gets 28 VDC power from the L ESS BUS, through circuit breaker B2 on the left circuit-breaker panel (CBP1)

  • The VHF transceiver No. 2 gets 28 VDC power from the R MAIN BUS, through circuit breaker B2 on the right circuit-breaker panel (CBP2)

  • The VHF transceiver No. 3 gets 28 VDC power from the L MAIN BUS, through circuit breaker E2 on the left secondary power-center (LSPC)

Datalink

The VHF communication unit No. 3 (option) provides datalink functionality (Link 2000+ (Europe only), aircraft communication addressing and reporting system (ACARS), future air navigation system (FANS).

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VHF Communication-Unit Mounting Tray

The VHF communication-unit mounting tray holds the communication unit in the equipment rack. The VHF communication-unit mounting tray is attached to the equipment rack with screws.

There is one VHF communication-unit mounting tray for the VHF communication unit No. 1 and one VHF communication-unit mounting tray for the VHF communication unit No. 2. There is also a third VHF communication-unit mounting tray for the VHF communication unit No. 3, when the third VHF-communication system (option) is installed.

Each mounting tray has a hold-down clamp that engages in the hold-down hook of the applicable VHF communication unit. The VHF communication-unit mounting tray has an electrical connector at the rear that connects to the interface connector of the VHF transceiver.

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VHF Antenna

The VHF antennas are omni-directional blade-type antennas. They are 52Ω impedance-type antennas. They can transmit in the 118.00 MHz to 136.975 MHz frequency range.

VHF antenna No. 1 is connected to VHF transceiver No. 1. VHF antenna No. 2 is connected to VHF transceiver No. 2. In the optional installation (third VHF option), VHF antenna No. 3 is connected to VHF transceiver No. 3.

The VHF antennas are located as follows:

  • VHF antenna No. 1 is in the top area of the forward fuselage at FS430.00
  • VHF antenna No. 2 is in the bottom area of the forward fuselage at FS382.00
  • VHF antenna No. 3 is in the top area of the center fuselage at FS610.00

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Operation

Transceiver Functions

The VHF transceiver supplies the primary functions of the VHF communication system. The VHF transceiver includes the three different parts that follow:

  • A radio frequency (RF) module that supplies signal amplification, demodulation, filtering, and conversion functions
  • A circuit unit that supplies memory and processor functions, control signals, modulation functions, and internal power-supply functions
  • A rear connector unit (with no active components) that supplies interface functions and also interference protection.

Frequency and other control selections are kept in the non-volatile memory (NVM) of the VHF transceiver so that the radio does not change status or frequency if there is a power fail condition.

The VHF communication system has different tune and control command routes. Radio tune reversion and display reversion give different modes to tune the VHF communication units.

Tune Modes

Normal Operation

When a radio tuner (MFD or CDU) sends a tune or control command to its target radio, it also sends that signal to all radio tuners. It does this so that the radio tuners are all synchronized. A radio tuner sends a tune and control command when the frequency or channel is set.

The radio tuners each monitor correct radio tune signals and controls, as much as possible. The radio tuner compares its tune command with its radio echo. It does this when a radio tuner does a local tune or receives a tune command from a different radio. It compares them for no longer than 3 seconds. If the radio echo is not the same as the tune command in less than 3 seconds, the active frequency display changes color.

A local tune command overrides a remote tune command. The radio interface units each give two channels of data concentration to and from the VHF transceivers. Each channel in each radio interface unit is isolated and operates independently. The data from the VHF transceivers must go through the radio interface units to the tuners, the PFDs and the MFDs. The VHF transceivers give their frequency, status, and data to the radio interface unit. The radio interface unit sends this data to the on-side input/output concentrator unit (IOC). The radio interface unit also sends this data directly to each MFD and to the CDUs.

Tune Reversion

The TUNE reversion switch on the reversion select panel (RSP) is a switch that makes specified tuners serviceable.

In normal operation mode (TUNE reversion switch on the RSP set to NORM position), each MFD tunes its on-side VHF communication radios through the radio interface unit (RIU). Tune commands from the opposite-side MFD or CDU are received by the on-side MFD and transmitted to the applicable radio through the RIU. A fail condition of the same-side MFD, makes the opposite-side MFD the primary tuner.

In MFD ONLY mode (TUNE reversion switch on the RSP set to MFD ONLY position), the CDUs do not tune the VHF transceivers. The MFDs ignore signals from the CDU, if it tries to tune the VHF transceivers. In MFD ONLY mode, the MFD tunes the VHF transceivers as in normal operation.

In CDU ONLY mode (TUNE reversion switch on the RSP set to CDU ONLY position), the MFDs cannot tune the VHF transceivers, and the CDUs tune the VHF transceivers directly. When the CDU tunes the VHF transceivers in CDU ONLY mode, the CDU tune signal goes directly to the VHF transceivers. The CDU ONLY mode is usually for pre-departure clearance, if the full avionics system is not energized. CDU ONLY is also the usual reversion mode because the signal bypasses much of the equipment to make sure the operation is as basic as possible.

In COM1 121.50 mode (TUNE reversion switch on RSP set to COM1 121.50 position), the VHF transceiver No. 1 (COM1 radio) frequency is tuned to the 121.50 MHz emergency frequency.

Display Reversion

The LEFT DISPLAYS and RIGHT DISPLAYS reversion switches on the RSP are switches that make the MFDs send selections and commands along different routes. This lets the serviceable tuner continue to operate.

Emergency Modes

The radio interface unit (RIU) is the primary interface between the VHF communication radios and the audio inputs/outputs. In normal operation mode, audio, tune, control, and maintenance data is transmitted between the VHF transceivers and the audio system through the RIUs in digital format.

However, if there is a fail condition in the digital interface, the VHF communication system can operate through an analog interface. The analog interface can be enabled by the flight crew with the EMER/NORM (emergency/normal) toggle switch, on the audio control panel (ACP). The analog signals and the selection discretes transmitted between the ACPs and the VHF communication units are routed through the CPEs.

Also, the flight crew can automatically set VHF COM1 radio to the emergency frequency 121.50 MHz. To do the selection of this emergency frequency, the pilot/copilot sets the RSP TUNE reversion switch to the COM1 121.50 position.

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System Interfaces

The VHF communication system has interfaces with the other aircraft systems that follow:

  • Audio Integrating System
  • Electronic Flight-Instrument System (EFIS)
  • Flight Management System

The control, monitor, and display functions for the VHF communication system operate through interfaces with the following:

  • Two components of the audio integrating system (Radio interface units and control panel electronics (CPE) units)
  • Control display units (CDUs)
  • Reversion select panel (RSP)

Radio Interface Unit

The radio interface units (RIU) send and receive data to/from the VHF communications units on ARINC 429 high-speed (HS) data buses, as follows:

  • For the VHF communication unit No. 1

    • RIU No. 1 receives frequency and maintenance data from VHF communication No. 1 on the L-VHF-3 bus
    • RIU No. 1 sends frequency data to the VHF communication unit No. 1, on the LA-RIU-1 bus
    • RIU No. 1 sends digital audio and frequency data to the VHF communication unit No. 1, on the LB-RIU-1 bus.

  • For the VHF communication unit No. 2

    • RIU No. 2 receives frequency and maintenance data from VHF communication No. 2 on the R-VHF-3 bus
    • RIU No. 2 sends frequency data to the VHF communication unit No. 2, on the RA-RIU-1 bus
    • RIU No. 2 sends frequency data to the VHF communication unit No. 2. on the RB-RIU-1 bus.

  • For the VHF communication unit No. 3

    • RIU No. 1 receives frequency and maintenance data from the VHF communication No. 3 (option), on the T-VHF-3 bus
    • RIU No. 1 sends frequency data to the VHF communication No. 3 (option), on the LA-RIU-2 bus
    • RIU No. 1 sends digital audio and frequency data to the VHF communication unit No. 3 (option), on the LB-RIU-2 bus.

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Control Panel Electronics

The VHF communication units send and receive data and discrete inputs to/from the control panel electronics (CPEs) units as follows:

  • VHF communication unit No. 1 sends/receives EMER AUDIO data to/from CPE No. 1
  • CPE No. 1 sends push-to-talk (PTT) discrete input to VHF communication unit No. 1
  • VHF communication unit No. 2 sends/receives EMER AUDIO data to/from CPE No. 2
  • CPE No. 2 sends PTT discrete input to VHF communication unit No. 2.

Control Display Units

The CDUs send/receive communication and recall frequencies data to/from the VHF communication units, on ARINC 429 low-speed (LS) data buses, as follows:

  • CDU No. 1 gives the data to VHF communication unit No. 1 (and No. 2 if installed), on the L-CDU-6 bus
  • When optional CDU is not installed, VHF communication unit No. 2 receives the data from CDU No. 1 on the L-CDU-7 bus. When optional CDU No. 2 is installed, VHF communication unit No. 2 receives the data from CDU No. 2 on the R-CDU-6 bus.

Also, CDU No. 1 receives CDU TUNE and EMER 121.5 discrete outputs from the RSP. CDU No. 2 receives CDU TUNE discrete output from the RSP.

Reversion Select Panel

The VHF communication units receive discrete inputs from the reversion select panel (RSP) for the functions that follow:

  • Selection of CDU ONLY tune mode (CDU TUNE input)
  • Selection of emergency frequency mode (EMER 121.50 input, for VHF transceiver No. 1 only)
  • Selection of display reversion mode (MFD1/PFD1 REV and MFD2/PFD2 REV inputs)

Also, the RSP sends discrete outputs to the CDUs as follows:

  • The RSP sends CDU TUNE and EMER 121.5 discrete outputs to CDU No. 1
  • The RSP sends CDU TUNE discrete output to CDU No. 2.

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Controls and Displays

The pilots control the radio tune and display functions of the VHF communication system with two possible procedures:

  • With the multi-function display (MFD) radio displays and the display control panel (DCP) controls
  • With the display control unit (CDU).

The MFD/DCP radio tune method is the usual tune procedure. The CDU radio tune method is the secondary radio tune procedure.

MFD Radio Displays

With the MFD/DCP procedure, the pilots use the radio data that shows at the bottom area of each MFD, and the controls on the display control panel (DCP) to tune the VHF transceivers. Pilots also use the reversion select panel (RSP) controls to tune and display reversion functions.

MFD Radio Menu

The MFD shows all the necessary displays for the control of the radios. Each communication (COM), navigation (NAV), and high-frequency (HF) radio has a primary radio display that is a box approximately 1 in. (2.54 cm) square. These radio displays show active and recall frequencies.

The radio displays show in a row along the bottom of the MFD. All of these primary radio displays together are called the MFD radio menu. When the selection box is set in one of the MFD radio-menu columns, and the RADIO pushbutton on the DCP is pushed, an MFD radio sub-menu shows for the applicable radio.

MFD Radio Sub-menu

The MFD radio sub-menu supplies more items for the applicable radio. Most control of the radios, other than to tune the frequency or channel, is done on the radio sub-menu Some controls replace the MFD radio menu with an MFD radio sub-menu An MFD radio sub-menu, for a radio, replaces the row of radio displays in the MFD radio menu.

A radio shown in an MFD radio sub-menu is tuned as it is tuned in the MFD radio menu. An MFD radio sub-menu can fully control a radio. The MFD radio sub-menu for the VHF communication system (COM1 CONTROL, COM2 CONTROL, or COM3 CONTROL sub-menu) shows items for the SQUELCH mode control, frequency spacing selection (FREQ SEL), and self-test (TEST) operation.

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Selection Box

Some of the DCP controls are used to show menus on the PFDs and/or MFDs for different aircraft system functions. The selection box shows together with the applicable PFD and/or MFD menu to let the pilot/copilot do the selection of a specific menu item.

The DCP controls include the RADIO pushbutton which, when pushed, shows the MFD radio menu. The selection box is an important part of the MFD radio menu. The selection box is a movable box that shows in only one location on the PFD or MFD. Different controls move the selection box to different radio equipment in a radio menu display.

The selection box shows what radio equipment can be controlled or changed. When the MFD radio menu shows, the selection-box home-position can be in the bottom-left VHF or in the bottom-left HF COM radio-display. The COM radio that contains the home position is different for the pilot and copilot MFD. In the MFD radio menu or sub-menu, if no change is made for 20 seconds, the MFD radio menu shows. The selection box goes back to the radio menu home-position.

Active/Recall Frequencies

The active frequency shows in green at the top line, in the applicable radio column of the MFD radio menu and sub-menu.

Another important part of the MFD radio menu and sub-menu is the recall frequency. Each radio's recall frequency shows in smaller numbers below the active frequency of the radio. The recall frequency is a frequency that can be easily interchanged with the active frequency of the radio.

DCP Radio Controls

The display control panel (DCP) includes the radio tune controls that follow:

1/2 Pushbutton

If the MFD radio menu is shown, the 1/2 pushbutton on the DCP interchanges between the No. 1 and No. 2 systems of the shown radios.

If the NAV1, ADF1, and HF1 radios show, then the 1/2 pushbutton, when pushed, shows the NAV2, ADF2, and HF2 radios.

If the NAV2, ADF2, and HF2 radios show, then the 1/2 pushbutton, when pushed, shows the NAV1, ADF1, and HF1 radios.

If the MFD radio menu is not shown, then when the 1/2 pushbutton on the DCP is pushed, the MFD radio menu comes into view. The selection box then shows in the default home position.

DME H Pushbutton

The DME H pushbutton on the DCP sets the DME hold function on or off for the DME system. When the DME hold function is on, the DME radio stays tuned to the frequency it is tuned to. The VOR frequency is then tuned independently of the DME radio.

When the DME H pushbutton is pushed, the selection box shows around the NAV recall frequency of the NAV radio display. If the NAV sub-menu shows before the DME hold is set, the sub-menu stays. If a menu, sub-menu, or list (other than the NAV sub-menu) shows on the same-side MFD or PFD, it goes out of view when DME H is pushed.

TUNE Control

The TUNE control, on the DCP, includes:

  • Large outer button (coarse TUNE button)
  • Small inner button (fine TUNE button)
  • A Pushbutton in the center (transfer pushbutton)

The coarse TUNE button is for the coarse tune control of the radio frequencies. The fine TUNE button is for the fine tune control of the radio frequencies. The transfer pushbutton is used to interchange the active frequency or channel and the recall frequency or channel.

The coarse/fine TUNE buttons tune the applicable radio when the selection box is around a tune frequency or channel. The coarse/fine TUNE buttons adjust the recall frequency on the VHF COM radios, the NAV radios, and the HF communication transceivers in simplex mode. The coarse/fine TUNE buttons adjust the active frequency or channel on the air traffic control (ATC) transponders, the DME transceivers, and the HF communication transceivers in duplex mode.

For the VHF COM, DME, and NAV radios, the coarse TUNE button tunes the three most-significant digits and the fine TUNE button tunes the three least-significant digits. For the HF radio frequency and the ATC-transponder flight identification (FLT ID) number the coarse/fine TUNE buttons tune one digit at a time. One digit is set with the coarse TUNE button. The other digit is set with the fine TUNE button. A line shows under the selected digit. If the selection box is in an MFD radio menu, but not around a radio frequency, the fine or coarse TUNE button moves the selection box. The fine or coarse TUNE button moves it to the nearest frequency or channel that can be tuned.

If the selection box is not in an MFD radio menu or sub-menu, then the fine or coarse TUNE button, when moved, causes the MFD radio menu to come into view. The selection box then shows in default home position. If the selection box is in an MFD radio sub-menu, and the sub-menu is not changed for 20 seconds, the radio menu shows, and the selection box goes back to its radio menu home-position.

If a menu or list is shown, other than on the MFD radio menu or sub-menu, the first detent of the fine or coarse TUNE button can erase it. The first detent of the fine or coarse TUNE button moves the selection box if the first detent erases a menu or list. The radio menu shows, and the selection box goes back to its radio menu home-position.

The fine and coarse TUNE buttons can also change the frequency that is in the tune window, in steps. The coarse TUNE button changes the necessary frequency in 1 MHz steps. The fine TUNE button changes the frequency in 50 kHz steps or in 25 kHz steps. It does this for the first two steps, when the button is turned the other direction.

When the selection box is around a recall tune frequency or a channel, a two-direction arrow symbol shows to the right of the selection box. The arrow symbol shows that the transfer pushbutton on the DCP (center of the fine TUNE button), when pushed, will interchange two values. It will interchange the recall frequency or channel, and the active frequency in the selection box or channel in the selection box.

If the MFD radio menu or a sub-menu is shown, the transfer pushbutton can move the selection box. This only occurs when the selection box is not around a frequency or a channel. The transfer pushbutton moves the selection box to the tune frequency in the same primary radio display. If an MFD radio menu or sub-menu does not show, then the transfer pushbutton shows the MFD radio menu. It also moves the selection box to the home position.

RADIO Pushbutton

The RADIO pushbutton, on the DCP, when pushed, can have two different functions in relation to the radio-menu display condition. If the MFD radio menu is not shown, the RADIO pushbutton, when pushed, shows the MFD radio menu. The selection box goes back to the home position.

If there is not another menu or list, other than the MFD radio menu shown, and the RADIO pushbutton is pushed, the radio display that contains the selection box, expands to show the radio sub-menu

MENU/DATA Control

The MENU/DATA control on the DCP includes:

  • A Large outer button (MENU button)
  • A Small inner button (DATA button)
  • A Pushbutton in the center (PUSH SELECT pushbutton)

The MENU button is used to move the selection box through active menus. The MENU button moves the selection box right and down, if turned clockwise. The MENU button moves the selection box left and up, if turned counterclockwise. The MENU button has no end stops. The selection box moves to the left side of the MFD on the clockwise detent, after it shows in its farthest right position. The selection box moves to the right side of the MFD on the counterclockwise detent, after it shows in its farthest left position. The MENU button moves the selection box to the necessary radio tune frequency or channel. Other than to tune the frequency or the channel, radio control is done on a radio sub-menu If the selection box is not in the MFD radio menu, the MENU button moves the selection box to the necessary item.

The DATA button increases a numeric value or moves the selection box. If the selection box is around a numeric value, the DATA button increases that value, when turned clockwise. It decreases that value, when turned counterclockwise. If the selection box is around an item that is not numeric, each clockwise DATA button detent moves the selection box through the possible positions (right and down). Each counterclockwise detent goes though the possible selections to the left and up.

The PUSH SELECT pushbutton sets a value or changes an item selection. If the selection box is around a numeric value, and the numeric value is changed, then the PUSH SELECT pushbutton sets that value. The value is also set if the changed value is not adjusted for 3 seconds, or if the selection box moves. The selection box returns to its home position in the MFD radio menu after 20 seconds with no adjustments. If the selection box is around an item that is not numeric, the PUSH SELECT pushbutton changes the item through its possible selections.

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RSP Radio Controls

The reversion select panel (RSP) can change the operation of the MFD and the PFD with the controls that follow:

TUNE Reversion Switch

The TUNE reversion switch, on the RSP, lets the pilots do the selection of different radio tuning modes. In usual conditions, radio tuning is done in the normal (NORM) tune mode (TUNE reversion switch, on the RSP, set to NORM position).

When the TUNE reversion switch, on the RSP, is in the CDU ONLY position, the radio menu and radio sub-menus go out of view. Also, the RADIO, 1/2, or DME H pushbuttons on the DCP, when pushed, show SELECTION INACTIVE on the same-side PFD, for 5 seconds.

In the CDU ONLY mode, the MFDs cannot tune the VHF transceivers, and the CDUs tune the VHF transceivers directly. The CDU tunes the same-side radios only when the RSP TUNE reversion-switch is in the CDU ONLY position.

When the TUNE reversion switch, on the RSP, is in the MFD ONLY position, the CDUs do not tune the VHF transceiver. The MFDs ignore signals from the CDU, if it tries to tune the VHF transceivers. In this MFD ONLY mode, the MFD tunes the VHF transceivers as in the normal operation mode.

If the TUNE reversion switch, on the RSP, is in the COM1 121.50 position, then the MFD operates as usual, but the COM1 radio does not. The COM1 radio is automatically tuned to the emergency frequency 121.50 MHz.

LEFT DISPLAYS Reversion-Switch

The LEFT DISPLAYS reversion-switch, on the RSP, controls which pilot display shows what data.

When the pilot PFD and MFD are serviceable, the switch is in the NORM position. When the pilot PFD or right MFD has a fail condition, the LEFT DISPLAYS reversion switch is set to the applicable PFD REV or MFD REV position.

When the LEFT DISPLAYS reversion-switch is in the PFD REV position, the pilot PFD shows a compressed PFD display. When the LEFT DISPLAYS reversion switch is in the MFD REV position, the pilot MFD shows a compressed PFD display.

The compressed PFD display does not show the MFD radio menu and the MFD radio sub-menu Also, the selection box goes out of view when the MFD radio menu and MFD radio sub-menu go out of view and no other menu shows.

RIGHT DISPLAYS Reversion-Switch

The RIGHT DISPLAYS reversion-switch, on the RSP controls which copilot display shows what data. When the copilot PFD and MFD are serviceable, the switch is in the NORM position. When the copilot PFD or right MFD has a fail condition, the RIGHT DISPLAYS reversion switch is set to the applicable PFD REV or MFD REV position.

When the RIGHT DISPLAYS reversion switch is in the PFD REV position, the copilot PFD shows a compressed PFD display. When the RIGHT DISPLAYS reversion switch is in the MFD REV position, the copilot MFD shows a compressed PFD display.

The compressed PFD display does not show the MFD radio menu and the MFD radio sub-menu Also, the selection box goes out of view when the MFD radio menu and MFD radio sub-menu go out of view and no other menu shows

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VHF-COM Basic Operations

The basic operations of the VHF communication system are usually controlled with the MFD radio menu and the DCP controls.

If the MFD shows another menu or list, the pilot/copilot must first push the RADIO pushbutton, on the DCP, until the radio menu shows on the MFD.

The MFD radio menu shows the primary display and control functions for the different radio equipment. The pilot or the copilot can control the on-side or the cross-side VHF radios with the MFD radio menu and the DCP controls.

Radio Tuning

The VHF COM radios can be tuned with the MFD radio menu or the MFD radio sub-menu (COM1/COM2/COM3 (optional) CONTROL sub-menu).

To tune a VHF COM radio with the MFD radio menu, the MENU button, on the DCP, must be turned to move the selection box to the applicable frequency or channel that must be tuned. Then the frequency in the selection box is adjusted to the correct value with the fine TUNE button and the coarse TUNE buttons on the DCP.

The fine TUNE button and the coarse TUNE button are turned clockwise to increase the value and counterclockwise to decrease the value. When the correct value is obtained, the PUSH SELECT pushbutton, on the DCP, is pushed to set the new frequency value.

To tune a VHF COM radio with the radio sub-menu, the applicable COM1/COM2/COM3 (optional) CONTROL sub-menu is first shown. To show this sub-menu, the selection box must be located on the applicable item (COM1, COM2, or COM3) and the RADIO pushbutton, on the DCP, must be pushed. The MENU button, on the DCP, is used to move the selection box around the frequency or channel that must be tuned. Then, the frequency is tuned with the same procedure used to tune the frequency with the radio menu.

To replace the active frequency with the frequency value of the recall frequency, the selection box is first moved around the recall frequency adjacent to the transfer symbol. Then, the transfer pushbutton, on the DCP, is pushed to interchange the recall frequency and the active frequency.

Channel Spacing Selection

Channel spacing for VHF-COM radio tuning can be changed from 25 kHz to 8.33 kHz on the COM CONTROL sub-menu The MENU button, on the DCP, is turned to move the selection box to the FREQ SEL display. Then the DATA button or the PUSH SELECT pushbutton, on the DCP, is used to do the selection of 25 kHz or 8.33 kHz channel spacing.

Squelch Mode Selection

Squelch mode selection is done with the COM CONTROL sub-menu The MENU button, on the DCP, is turned to move the selection box to the SQUELCH display. Then the DATA button or the PUSH SELECT pushbutton, on the DCP, is used to do the selection of ON mode (to hear the background noise) or OFF mode (to not hear the background noise).

Transmit Operation

Selection of a VHF communication unit as the active transmitter is done when the applicable selection pushbutton (COM1, COM2, or COM3 (optional)), on the ACP, is pushed. The VHF communication unit is set to the transmit mode with the radio transmit (R/T) switch on the pilot/copilot control wheel (when a boom microphone is used) or with the microphone push-to-talk (PTT) switch (when the pilot/copilot hand microphone is used).

When a VHF COM transmitter is in the transmit mode, a TX transmit symbol shows adjacent to the active frequency on the MFDs.

Receive Operation

Selection of a VHF communication unit as the audio source is active when the applicable ACP audio selection/volume-control button (COM1, COM2, or COM3 (optional)), on the ACP, is in the pulled-out position. The same ACP control button also lets the pilot/copilot adjust the volume of the audio output from the VHF communication units.

Emergency Tuning Operation

To set automatically the VHF COM1 to the emergency frequency 121.51 MHz, the pilot/copilot sets the TUNE reversion switch, on the RSP, to the COM1 121.51 position.

Emergency Audio Operation

To bypass the digital interface between the VHF COM radio and the audio system, the pilot/copilot sets the EMER/NORM toggle switch, on the ACP, to the EMER position. In this emergency (EMER) mode, analog audio is transmitted between the audio system and the VHF COM radios.

Test Mode Operation

Self-test operation for the VHF COM radio can be initiated from the COM CONTROL sub-menu The MENU button, on the DCP, is turned to move the selection box to the TEST display. Then the DATA button or the PUSH SELECT pushbutton, on the DCP, is used to put the applicable VHF radio into a TEST mode operation. TEST operation results are shown to the flight crew on the MFD and/or the CDU.

CDU Controls and Displays

The control/display functions for the VHF communication system show on the CDU pages that follow:

TUNE Pages

The TUN key on the CDU, when pushed, shows the radio TUNE page 1/2. The NEXT function key on the CDU, when pushed, gives an access to the TUNE page 2/2.

The radio TUNE pages are used to tune the communication and navigation radios and to control their operation modes. They also give access to CDU pages that give more radio control/display functions.

The TUNE pages show COM1, COM2, and COM3 (optional) labels. These are for the control of the VHF communication radios.

A frequency or preset number recorded on the CDU scratch-pad line, tunes a COM radio. The COM1 or COM2 (or optional COM3) line-select key is pushed to move the entered data to a data field below the applicable label. If the frequency is correct, it shows in the data field and the radio immediately tunes to that frequency. The COM1, COM2, or COM3 (optional) line-select key, when pushed again, shows the applicable COM CONTROL page.

The TUNE pages have also a RECALL or PRESET frequency line-select key for each COM radio. The RECALL/PRESET frequency display shows the VHF COM frequency that the flight crew can move to the COM display. The flight crew can push the RECALL/PRESET frequency line-select key to interchange the RECALL/PRESET COM frequency and the COM frequency that is in operation. The COM radio tunes again to the new frequency, and the frequency that was in operation before, becomes the new RECALL frequency. The value that was used before is available. It can be put into operation again if the flight crew pushes the RECALL frequency line-select key.

The RECALL frequency can also be set with the entry of a frequency on the scratch-pad line. Then, the RECALL frequency line-select key is pushed to move this frequency to the RECALL/PRESET data field. If the frequency is correct, it shows in the data field.

300_2311_028

COM 1 (2) (3) CONTROL Pages

The COM1, COM2, or COM3 (option) line select key, on the applicable TUNE page, when pushed, shows the COM 1, COM 2, or COM 3 CONTROL page, respectively. The COM 1 CONTROL page is used as an example.

The COM 1 display shows that the CDU controls the No. 1 (left side) VHF COM radio. The COM active frequency display shows the active frequency of this VHF COM radio.

The flight crew records the frequency or preset number on the scratch-pad line. Then, the flight crew pushes the COM line-select key to move this frequency to the data field below the COM 1 label. If the frequency is correct, it shows in the data field, and the radio immediately tunes to the new frequency. The frequency used before is moved to the data field below the RECALL frequency display and is kept as a RECALL frequency.

The flight crew can also record a RECALL frequency or a preset number on the scratch-pad line. Then, the flight crew pushes the RECALL line-select key to move this frequency to the RECALL data field. If the frequency is correct, it shows in the data field. This RECALL VHF COM frequency is available to immediately tune the radio again. To tune to this RECALL frequency, the flight crew must push the RECALL line-select key to move the RECALL frequency to the data field of the active COM frequency.

The COM PRESETS frequencies display lines contain up to 20 COM frequencies and a number (four preset frequencies show at one time on the COM1 CONTROL page). The NEXT or PREV key on the CDU, if pushed, shows a preset page that was on the display before or a subsequent preset page. The flight crew pushes the related line select key to move the preset frequency to the data field for the COM active frequency.

To make or change a COM PRESETS frequency, the flight crew records the frequency and/or identification on the scratch-pad line. Then, the flight crew pushes the related line-select key to move this frequency to the preset frequency data field. If the frequency is correct, it shows in the data field. The preset default frequency is 118.00 MHz.

The flight crew pushes the SQUELCH line select key to first put the receiver squelch circuits on (ON) and then off (OFF). The larger annunciation shows the squelch selection. SQ OFF shows adjacent to the COM label when squelch is not in operation. TX shows when the radio transmits. The TEST line select key, when pushed, starts the self-test of the VHF communication system for 10 seconds. The TEST annunciation becomes larger and cyan in color while the self-test is on.

300_2311_029

System Test

The VHF communication system includes a self-test function. The test function operation can be started from the MFD radio menu or from a CDU control page.

MFD TEST Selection

When the self-test function is not on, the TEST indication, on the MFD radio menu, shows in white. To start the self-test, the selection box is first set around the TEST indication. Then, the PUSH SELECT pushbutton, on the DCP, is pushed to start the self-test operation.

When the test function is on, TEST indication dimension increases and becomes cyan. If the VHF communication system has a fault condition or is not serviceable, applicable indications and error messages show on the MFD radio menu. On the MFD radio menu, if the echo from the radio is not available or does not agree with the frequency selection, the applicable frequency indication changes from green to yellow.

CDU TEST Selection

On the CDU, test selection is made on the applicable COM CONTROL page, with the TEST select-line key. When the test function is not on, TEST indication shows in white. When the test function is on, TEST indication dimension increases and becomes cyan.

If the test is not satisfactory, COM tuning error-messages will show in white in the CDU scratch-pad line. If the VHF communication system has a fault condition or is not serviceable, applicable indications and error messages show on the CDU COM page.

10/14/20

Component Location Index

Component Location Index
IDENT DESCRIPTION LOCATION IPC REF
A7 VHF COMMUNICATION UNIT NO. 1 (LH) ZONE(S) 221 23-11-01
A8 VHF COMMUNICATION UNIT NO. 2 (RH) ZONE(S) 222 23-11-01
A10 VHF COMMUNICATION UNIT NO. 3 (LH) 
(OPTIONAL)		 ZONE(S) 221 23-11-01
       - VHF COMMUNICATION-UNIT MOUNTING 
TRAY NO. 1 (LH)		 ZONE(S) 221 23-11-05
       - VHF COMMUNICATION-UNIT MOUNTING 
TRAY NO. 2 (RH)		 ZONE(S) 222 23-11-05
       - VHF COMMUNICATION-UNIT MOUNTING 
TRAY NO. 3 (LH) (OPTIONAL)		 ZONE(S) 221 23-11-05
E13 VHF ANTENNA NO. 1 ZONE(S) 230 23-11-09
E12 VHF ANTENNA NO. 2 ZONE(S) 140 23-11-09
E14 VHF ANTENNA NO. 3 (OPTIONAL) ZONE(S) 230 23-11-09

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