Communications

Question 1

What is the Com system

Answer 1

The purpose of the communications (COM) system is to supply the equipment necessary for communication in an aircraft, between different aircraft, and between aircraft and ground stations. It includes components used for voice and data communications. The COM system includes the following systems:

Question 2

What is audio integrating system

Answer 2

Audio Integrating System
The audio integrating system controls the audio functions of the communication and navigation radios, headphones, microphones, and loudspeakers.

Question 3

What is radio management system

Answer 3

Radio Management System
The radio management system provides tuning, control and system select capabilities to the aircraft communication and navigation radios via two radio management units (RMUs) and/or two flight management system (FMS) control display units (CDUs)

Question 4

What is VHF com system

Answer 4

VHF Communication System The very high frequency (VHF) communication system receives and transmits voice/data between different aircraft and between aircraft and ground stations. The VHF COM system is a remotecontrolled integrated COM radio system. It transmits and receives voice/data between 118.000 and 136.975 MHz. The VHF COM has selectable channel spacing of 8.33 kHz (2280 channels) or 25 kHz (760 channels)

Question 5

What is HF system

Answer 5

HF Communication System
The high frequency (HF) communication system is a long-range two-way communication system, which operates in the HF band from 2.0000 to 29.9999 MHz. It has 280,000 discrete operating frequencies in 100-Hz steps. The system can supply simplex and half-duplex operations.

Question 6

What is sella

Answer 6

SELCAL
System A single selective calling system (SELCAL) is installed. This ground-to-air calling system supplies an aural annunciation and an EICAS message when a preset four-letter code is received by one of the aircraft HF and VHF radios. The system can monitor three VHF and two HF radios at the same time. This removes the continuous monitoring of the communication frequencies by the flight crew.

Question 7

Who decides where aerials go

Answer 7

The purchaser !!

Question 8

How many ICU,s

Answer 8

3

Question 9

Is radio bus connected to IAC,s

Answer 9

Yes

Question 10

What is ARTU

Answer 10

Airborne radio telephone unit
Uses VHF2 antenna through duplexer

Question 11

What do Audio panels do

Answer 11

Audio Panels
Figure A3 The audio panel has manual controls that include pushbuttons, switches, and knobs. Each control operates as follows:
Microphone Selection
The top row of switches under the label TRANSMIT connect the MIC audio and PTT to the selected radio or PA (passenger address) amplifier when pushed in. The received audio is automatically enabled at the same time. An illuminated bar on the switch indicates that the function is active. Only one transmit pushbutton can be engaged at a time.

Question 12

What does emerg switch do on Audio Panel

Answer 12

EMER Switch
This switch is located in the upper right corner of the AP. When pushed in, it bypasses all internal electronic circuitry and connects the onside headset directly to the onside VHF COM unit, AP 1 and 3 to VHF COM 1 and AP 2 to VHF COM 2. This switch disables all other functions on the AP.

Question 13

What is VHF3

Answer 13

In normal mode is data only

Question 14

What is sidetone

Answer 14

ST Switch The ST (sidetone) switch is used to adjust the sidetone level on the speaker to prevent undesirable positive feedback into the transmitting microphone. The sidetone level is independent of the volume control. This switch is also used as a speaker ON/OFF switch. The speaker is OFF when the switch is latched (pushed in). The speaker audio cannot be disabled when the oxygen mask is selected. The aural warning audio from the IACs, TCAS and EGPWS audio also bypass the OFF position of the ST SPKR ON/OFF switch. The aural warning audio has a preset level in the APs that is not affected by the SPEAKER audio volume control.

Question 15

What is the system interface

Answer 15

Inputs
The APs receive analog audio inputs from the following sources: • Aural warnings from the integrated avionics computers (IACs) 1 and 2, TCAS and EGPWS • Flight interphone and service interphone audio • MIC audio from the hand mics, boom mics, and mask mics • The onside VHF COM to be used when the EMER switch is pushed Each AP receives inputs on two digital audio buses (DABs). These signals originate in the onside and cross-side integrated communication units (ICUs) and integrated navigation unit (INU). The received audio from the HF systems is sent to their onside ICU to be digitized and put on the DABs. The received audio from the VHF COM 3 is sent to INU 1 to be digitized and put on DAB 1.

Question 16

What are RMU controls

Answer 16

RMU Controls
Figure B2 Photosensor The photosensor detects ambient light and causes the display brightness to be automatically adjusted to compensate for varying levels of light. Transfer Key The transfer (flip flop) keys are the two top keys on each side of the display. When pushed, they interchange the active frequency (top line) and the preset frequency (second line) of the window. If both transfer keys are pushed at the same time, the RMU enters aircraft maintenance mode. Line Select Key The line select keys are the next five keys on each side of the RMU display. The first push of a line select key moves the yellow cursor to that data field. This electronically connects that data field to the tuning knobs so that field may be changed. The preset line select key, if held for 3 seconds, enables the direct tune mode for the COM and NAV.

Question 17

what is POC

Answer 17

Power on count

Question 18

What is VHF com system

Answer 18

INTRODUCTION
The VHF communication system is used for line of sight voice and data communication. It covers the frequency range of 118.000 to 136.975 MHz. with a selectable spacing of 8.33 kHz (2280 channels) or 25 kHz (760 channels). The VHF communication system includes two Honeywell model RCZ-833E and one RCZ-833 series integrated communication units (ICUs). The RCZ-833E ICUs contain a VHF COM transceiver module, an ATC transponder module and a cluster module and the RCZ-833 ICU contains a VHF COM transceiver module and a cluster module. The VHF COM radios are normally tuned from the RMUs. VHF COM emergency tuning is available from the flight management system control display units (FMS CDUs) via an ARINC 429 data bus. COMPONENTS Figure C1 The VHF communication system consists of the following components: • Integrated communication unit (ICU) 1 and 2, model RCZ-833E • Integrated communication unit (ICU) 3, model RCZ-833 • In-line filters • Antennas- VHF COM 1- Dual VHF COM 2/UHF- VHF COM 3

Question 19

Does VHF com 3 have transponder

Answer 19

No,send to other coms to transmit

As there are only two DABs on the aircraft, VHF COM 3 sends analog audio to INU 1 to be converted to digital audio and placed on DAB 1. The MIC audio (analog) and the PTT signals are sent directly from the audio panels to the ICUs.

When DATA mode is selected for VHF COM 3, the RMU sends status information to the DATA LINK unit. VHF COM 3 receives ARINC 429 tuning information, DATA KEY (PTT) and ACARS DATA for transmission from the DATA LINK unit.

Question 20

How does it transmit

Question 21

What does inline filter do

Answer 21

In-Line Filters
There are in-line, low pass filters installed between the VHF COM transceivers and their antennas. This filter is installed to prevent interference to GPS and SATCOM systems.

Question 22

What are basic and direct tuning

Answer 22

Direct Tuning
Figure C4 To direct tune the COM, press the line select key beside the preset COM frequency and hold for approximately 3 seconds. The cursor will move to the active frequency, allowing direct tuning of that frequency, and the preset window will blank. To exit from direct tuning, press the line select key beside the preset COM frequency window and hold until the preset frequency reappears. Any memory location displayed inside the cursor can be changed by tuning and storing a new frequency. When the new frequency is tuned, the identifier will change from MEMORY to TEMP. This frequency (121.70) may be stored in MEMORY-1 location by pressing the STO button.

Question 23

What is MIC STK

Answer 23

MIC STK
When the microphone is stuck for over 2 minutes, a beep will sound in the audio system, and this message will appear until the mic button is released. 10 seconds after the MIC STK annunciation appears, the transmitter automatically turns off.

Question 24

What is the HF

Answer 24

INTRODUCTION
The aircraft has dual high frequency (HF) communication (COM) systems. They provide amplitude modulated (AM) and single sideband (SSB) modes of operation for long distance air-toair and air-to-ground voice communications. The operating frequency of the HF system is from 2.0000 to 29.9999 MHz in 100-Hz increments. Transmit power is selectable up to 175 peak envelope power in SSB and up to 50 W average in AM mode. Communication range on HF frequencies is much greater but less reliable when compared to VHF and UHF frequencies. HF communication range varies substantially, depending on several factors such as frequency, season, time of day, atmospheric noise, and solar activity. Tuning for the HF COM system is normally done by the two radio management units (RMUs), and the FMS CDUs provide backup tuning.

Question 25

What is the HF coupler

Answer 25

Antenna Couplers
The HF antenna coupler tunes the HF transceiver to the antenna when different frequencies are selected for maximum power transfer. The unit front panel contains electrical and fiber optic connectors. The antenna coupler is pressurized to prevent highvoltage arcing and moisture ingress, and provides uniform cooling medium. The antenna coupler is pressurized with 5-7 psi of dry nitrogen. An air pressure valve on the front face provides a service and test point for the internal dry nitrogen charge. The two couplers are installed in a dual mounting rack on the front spar of the vertical stabilizer at FS 1007.00, behind the dorsal fairing. The mounting rack is attached by screws to the front spar of the vertical stabilizer. Each of the four mount isolators has a ground bonding strap between the rack and the structure. A flexible braided strap feedline (RF strap) connects the mounting rack and the couplers to the antenna.

Question 26

What is Burst tuning

Answer 26

Normal tuning occurs when the input from the onside RMU is received through ports A for HF 1 and B for HF 2. The receivers are strapped for BURST TUNING which means that they search for a burst input on all three ports sequentially.

Question 27

What type of antenna is used

Answer 27

A Shunt style antenna

Question 28

Does HF use fibre optics

Answer 28

The HF couplers interface with the HF receiver/ transmitters through fiber optic cables for control signals and coaxial cables for RF signals. There are status lines between the two units to prevent both units transmitting at the same time and to isolate the other receiver input when one is transmitting.

Question 29

What is Selcal

Answer 29

The selective calling system (SELCAL) is an aircraft paging system, capable of operating with existing ground-to-air radio systems. A decoder monitors audio inputs from up to five communication receivers for a code assigned to the aircraft. Upon receiving the correct code, the decoder triggers aural and visual annunciations in the cockpit. Selective calling eliminates the necessity of continuous monitoring of the radio frequencies by the flight crew.

Question 30

What’s in selcal

Answer 30

COMPONENTS
Figure E1 The SELCAL system consists of the following components: • Decoder • Terminal block
COMPONENT DESCRIPTION Decoder The SELCAL uses the communication receivers for inputs, and the EICAS display unit and audio system as outputs. The decoder has five channels and receives audio inputs from VHF 1, VHF 2, VHF 3, HF 1 and HF 2. Terminal Block The terminal block is used to program the decoder to respond to its assigned code.

Question 31

Selcal operation

Answer 31

OPERATION
Figure E2
When a ground station, equipped with SELCAL encoding equipment, wishes to call a specific aircraft, the SELCAL code assigned to that aircraft is entered into SELCAL encoder by the operator. This action causes two consecutive audio pulses to be transmitted. In the aircraft, one of the communication receivers is tuned to the assigned SELCAL frequency. The received audio is sent to the SELCAL decoder. The receiver audio volume may be turned down or off. When the aircraft code is detected by the SELCAL decoder, a discrete output is sent to data acquisition unit (DAU) 3 or 4. The DAUs convert the discrete signal to digital ASCB format and forward it to the integrated avionics computers (IACs). The symbol generators send a CAS message “SELCAL HF 1/2, VHF 1/2/3” to the EICAS display and the fault warning computers send an aural message “SELCAL, SELCAL” to the audio integrating system. The decoder and CAS message are reset by a momentary transmission on the selected radio.

Code Selection
The decoder is programmed by connecting program pins on the rear connector to ground via the terminal block. A SELCAL code is assigned to each aircraft by the Aeronautical Radio Incorporated (ARINC). The code is composed of four audio tones designated by letters, transmitted in two individual pulses. Each letter is associated with a group of strapping pins.

Question 32

Elt-what mhz

Answer 32

406 mhz

Question 33

What are static differences

Answer 33

Static Discharger
The static discharger is a resistive graphite-coated rod of aligned fibers, tapered towards the tip. This design allows flexibility and graded resistance, which has a noise-quieting quality. The discharger also has a heat-shrunk sheath for more protection. The discharger tip is a small brush of 700 nichrome wires to give high-current capability. The static discharger type 2-17SC-1 has external threads on its mounting end. The remaining types have internal threads on their mounting ends. Static Discharger Base
Two types of bases are installed, the standard type (Chelton 2-23), and the machined fitting type. All discharger bases are titanium materials except the ones at WS 530, which are aluminum. The dischargers are electrically bonded to the aircraft structure and sealed.

Question 34

Curser control panel

Answer 34

Enter switches on side

Question 35

What is utility password

Answer 35

COLLINS