Flight interphone system Purpose

The flight crew uses the flight interphone system to speak with each other and the ground crew.

Flight and maintenance crews use the flight interphone system to get access to the communication systems. You can also use the flight interphone system to monitor the navigation receivers.

Abbreviations and Acronyms

• AAU - audio accessory unit

• ACP - audio control panel

• ADF - automatic direction finder

• ALT - alternate

• CAPT - captain

• COMM - communication

• DFCS - digital flight control system

• DME - distance measuring equipment

• FCC - flight control computer

• F/O - first officer

• GPWC - ground proximity warning computer

• HF - high frequency

• I/C - intercommunication

• ILS - instrument landing system

• INT - interphone

• MD&T - master dim and test

• MIC - microphone

• MKR - marker

• NORM - normal

• OBS - observer

• PA - passenger address

• PLA - programmed logic array

• PTT - push to talk

• REU - remote electronics unit

• R/T - receive/transmit

• STA - station

• TCAS - traffic alert and collision avoidance system

• VHF - very high frequency

• VOR - very high frequency omni-range system

• XCVR - transceiver

General

The remote electronics unit (REU) and the audio control panel (ACP) control the audio signals to and from the flight crew. The REU also controls the communication with the service interphone and related electronics equipment. During a system failure, emergency operation bypasses all active system circuitry and maintains airplane-to-ground station communication.

Flight Crew Interfaces

This system description shows the captain system. Interfaces and components for other flight crew stations are similar.

The flight crew uses microphone (mic) switches on these components to send audio to the REU:

• Remote mic switch

• Control wheel

• ACP

• Hand microphone.

A microphone on these components lets the flight crew speak on the flight interphone system:

• Oxygen mask

• Headset boom mic

• Hand mic.

The flight crew uses the audio control panels for these functions:

• Listen to the communication and navigation receivers

• Adjust the volume of the received audio

• Select a transmitter and microphone

• Key the microphone.

The REU sends audio signals to the headsets and to the flight interphone speakers.

Other Component and System Interfaces

The REU connects to these other components:

• Communications radios - the REU sends push-to-talk (PTT) and microphone audio to the transceivers and receives audio back from them

• Navigation receivers - the REU receives voice and Morse code identification tones.

The flight interphone system also has an interface with these other systems:

• Passenger address system - lets the flight crew make announcements to passengers

• Service interphone system - lets the flight crew speak with attendants and service personnel

• Voice recorder - records the flight crew microphone and receive audio

• Ground proximity warning computer (GPWC) - lets flight crew monitor warning signals

• Weather radar (WXR) - lets the flight crew monitor WXR windshear warnings

• Traffic alert and collision avoidance system (TCAS) - lets the flight crew monitor TCAS signals

• Flight control computer (FCC) - gives discrete signals to the REU. This signal activates an altitude alert tone generator.

Aural alerts for TCAS, weather radar, ground proximity, and altitude are heard at the captain, first officer, or observer headphones and at the flight interphone speakers.

Flight Compartment Component Locations

These are the captain and first officer flight interphone system components:

• Remote mic switch

• Control wheel mic switch

• Flight interphone speaker

• Hand mic jack

• Oxygen mask mic jack

• Boom mic jack

• Headphone jack

• Audio control panel.

The observer has these flight interphone components:

• Hand mic jack

• Oxygen mask mic jack

• Headphone jack

• Audio control panel.

Flight Interphone Component Locations

There are flight interphone system components in these locations:

• Electronic equipment compartment

• Flight compartment.

Electronic Equipment Compartment

The REU is on the E4-1 rack.

Flight Compartment

These are the flight interphone system components in the aft portion of the flight compartment:

• Observer headphone jack

• Observer mask microphone

• Observer hand microphone.

• Flight Interphone Jack

There is a flight interphone jack on the P19 external power panel.

General

Power for the flight interphone system comes through circuit breakers in the P6-2 circuit breaker panel.

The REU has three station cards and an audio accessory unit (AAU) card. Each card has a power supply for internal operation. The station cards supply 15v dc to the audio

control panels (ACP).

CAPT AUDIO Circuit Breaker

The CAPT AUDIO circuit breaker supplies 28v dc to the captain station card in the remote electronics unit. The captain station card supplies 15v dc to the captain ACP.

F/O AUDIO Circuit Breaker

The F/O AUDIO circuit breaker supplies 28v dc to the first officer station card in the remote electronics unit. The F/O station card supplies 15v dc to the first officer ACP.

OBS AUDIO Circuit Breaker

The OBS AUDIO circuit breaker supplies 28v dc to the observer station card (плата) in the remote electronics unit. The observer station card supplies 15v dc to the observer ACP.

INPH AND WARN Circuit Breaker

The INPH AND WARN circuit breaker supplies power to the audio accessory unit card in the remote electronics unit.

Master Dim and Test

Each ACP gets 28v dc from the master dim(тусклый) and test (MD&T) system when the BRT/DIM/TEST switch on the captains main instrument panel is in the BRT position, and 16v dc when the switch is in the DIM position. This voltage supplies power for the lamps in the mic selector switches.

Panel Lighting

Each ACP gets 5v ac from the airplane electrical system to supply power for the edgelit panel lighting.