Chapter 2 Aircraft Communication System
Summary
Air-ground communication provides aircraft with flight command transmission,
flight status interaction, and flight decision management capabilities. Aircraft
communication capability is an important means of voice communication and
information exchange between pilots and ground air traffic control (ATC),
command centers, maintenance centers, or other stakeholders during flight.
1. Introduction
The aircraft communication system is used for speech (voice) communications
and for data communications. The communication system in aircraft is used for
communication between the crew members and between crew members and ground
personnel. It is also used to communicate with the passengers, other aircraft, and
ground stations (both speech and data). In the early avionics systems, radio stations
were set up to support pilot and airport communication with voice, enabling pilots
and command centers (or airports) to understand each other's conditions, mastering
the dynamic changes in air and ground, coordinating their intentions, and
implementing collaborative management during the whole flight process.
Figure 1
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2. Components and Operations
Aircraft communications systems comprise the following:
Radio Communication,
HF System – For long-distance voice communications,
VHF System – For short-range voice communications,
Radio Management Panels,
SELCAL System – For selective calling using HF and VHF,
SATCOM System – For satellite communication,
ACARS – For datalink communication,
Interphone Communication,
Flight Interphone System – For internal cockpit communication and also with
ground mechanics,
Cabin Interphone System – For cabin crew or cabin crew/pilots
communications.
Service Interphone System – On ground only, for maintenance personnel only.
Ground Crew Call System – To tell ground crew or flight crew there is a call.
Passenger Address System – For passenger announcement from cockpit and
cabin crew station.
Audio Management System.
Figure 2
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3. Radio Communication Basics
Aviation communication is accomplished through the use of radio waves.
3.1`Radio Waves
Radio waves are electromagnetic in nature and part of the electronic spectrum. The
atmosphere is filled with these waves. Each wave occurs at a specific frequency and
has a corresponding wavelength. The relationship between frequency and
wavelength is inversely proportional. A high-frequency wave has a short wavelength
and a low-frequency wave has a long wavelength.
3.2 Loading Information onto a Radio Wave
The production and broadcast of radio waves do not convey any significant
information. The basic radio wave is known as a carrier wave. To transmit and
receive useful information, this wave is altered or modulated by an information
signal. The information signal contains the unique voice or data information desired
to be conveyed. The modulated carrier wave then carries the information from the
transmitting radio to the receiving radio via their respective antennas. Two common
methods of modulating carrier waves are amplitude modulation and frequency
modulation.
4. Broad categorization of radio frequency bands
Band Name Abbreviation Frequency
Very low frequency VLF 3-30 kHz
Low frequency LF 30-300 kHz
Medium frequency MF 300-3000
kHz (3 Mhz)
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High frequency HF 3-30 MHz
Very high frequency VHF 30-300
MHz
Ultra high frequency UHF 300-3000
MHz (3 GHz)
Super high frequency SHF 3-30 GHz
Extremely high frequency EHF 30-300
GHz
Elements of Radio Communication: the elements of the radio communication are:
The Transmitters: consists of a precise oscillating circuit or oscillator that
creates an AC carrier wave frequency.
The Receivers: Antennas are simply conductors of lengths proportional to the
wavelength of the oscillated frequency put out by the transmitter.
The Transceivers: A transceiver is a communication radio that transmits and
receives.
The Antennas: Antennas As stated, antennas are conductors that are used to
transmit and receive radio frequency waves.
