CS-Communication System

The ELT message includes always the aircraft GPS position.

The ELT cannot be manually activated by the pilots.

The unique identification of each ELT is represented as a string of 15 HEX characters.

The ELT transmits coded message on 243 MHz for location via satellite.

The COSPAS-SARSAT Low Earth Orbiting satellites provide immediate transmission 
detection.

The COSPAS-SARSAT system uses only one frequency for ELT transmissions.

LEOSAR provides global but non-continuous coverage meanwhile GEOSAR provides continuous but non-global coverage.

The CVR records the crew’s microphone audio signals even if the corresponding PTT switches are not activated.

The CVR records a time reference for synchronization with the FDR data.

The CVR records a time reference for synchronization with the represented as a string of 15 Hex characters.

The CVR installation is mandatory for all aircraft.

The CVR installation includes an automatic means to stop the recorder and prevent the erasure feature from functioning within 10 minutes after crash impact.

The RIPS can provide electrical power to the CVR during all flight duration in case of power loss from aircraft electrical system.

The Passenger Address system power is immediately disconnected after the shutdown or failure of all engines and auxiliary power units.

The Passenger Address transmission can be activated only through the Audio Management System.

The Passenger Address can be activated either from Audio Management System or from headsets.

The PA system must be powerable when the aircraft is in flight or stopped on the ground, after the shutdown or failure of all engines and auxiliary power units, or the disconnection or failure of all power sources dependent on their continued operation, for a time duration of at least 10 minutes, including an aggregate time duration of at least 5 minutes of announcements made by flight and cabin crew members.

The AMS audio bandwidth must be maintained between 300 and 3000Hz.

The interphone transmission can be activated using only the PTT switch.


The VOX function can be used for radio transmission.

The switches for loudspeaker and mask microphone connection are located outside the Audio Control Panels in some implementations.

The binaural capability is available for the pilots in many A/C

The modern a/c includes a wireless Intercom system for interphone communications between cockpit crew members

The aural alert reception must be activated by the operators using their Audio Control Panels

The Mask microphone can be used for one operator at the same time as the integral headset microphone

HF communication system provides short-distance (up to the line of sight) communications, complementary to satellite communications providing long-distance (over the horizon) communications.

Frequencies for a Major Work Air Route Area (MWARA) are chosen over adjacent channels, in order to provide a worldwide optimal division of the available HF bandwidth.

Availability of radio channels is semi-random, which makes the use of automated HF systems (ACS, ALE, ALM) highly recommended to reduce pilot/user interface requirements.

The HFDL system, which follows a layered protocol with the OSI reference model, is still in process for standardization at ICAO.

Simultaneous operation (SIMOP) makes reference to the simultaneous civil/military use of HF channels.

Considering spectral efficiency and energy efficiency, the modulation used for the HF system is a double sideband (DSB) full carrier amplitude modulation.

K index, solar flux F10.7 index and ionospheric maps allow to know the state of ionosphere and are useful for link performance prediction (by means of prediction models).

Iridium coverage does not include the polar regions.

The antenna system has to provide for any aircraft a minimum value for the G/T figure of 
merit, being this minimum value -19 dB/K over the 85% of coverage. 



The AMSS service in the L-band has priority over non AMSS services and the capability of pre-emption in this band.

ICAO approved safety services are currently supported worldwide by inmarsat and Iridium and in North America by the American Mobile Satellite Consortium (AMSC) and Telesat Mobile Inc (TIM)

In military SATCOM systems, airborne terminals usually follow an standardization process before integration.

In current civil SATCOM systems, terminals and antennas are not standardized, and each service provider has its own terminals, which has been identified as a potential problem for interoperability in the development of future communication services.

Geostationary satellite systems are preferred for aeronautical communications because of the worldwide coverage they provide.

Doppler effect is more important in geostationary satellite systems than in Low Earth Orbit (LEO) satellite systems.

Provision of broadband high speed data solutions in SatCom is typically supported by means of communication in the L-band.

Current Satcom systems provide enough communication capacity to the operational concept defined in the context ofthe Future Communications Infrastructure (FCI), as proved by different studies performed by EUROCONTROL and FAA in the joint Action plan 17 (AP17) and therefore development of new services is not a priority in the medium term.

MC increases the channel capacity.

MC is more robust to synchronization errors.

MC provides more effective ways of combating channel distortions.

MC allows more flexible and adaptive modulations.

Link-16 can provide non-secure communications.

A fighter can participate in any NPG in a Link-16 network.

A Link-16 terminal can use 51 different frequencies in the UHF band for the transmissions.

A Link-16 terminal transmits in the complete pulse of 13 microseconds of duration.

A Link-16 terminal can transmit at a data rate up to 1kbps.

A Link-16 terminal can modify its transmission parameters during operation.

Directional antennas (ECCM).

Encryption (ECCM).

Intercept (ESM)

Also valid as ECCM: Sitting, shielding, emission control, alternate means, frequency management, Identical equipment.

Also valid as ESM: Search, Direction finding, analysis

One V/UHF transponder qualified for SINCGARS operation and one antenna.

One V/UHF radio qualified for HAVE QUICK.

One V/UHF transponder qualified for PR4G standard with embedded COMSEC device.

One V/UHF radio and an external SELCAL cryptographic device.

One V/UHF radio qualified for SATURN.

It would be wise to check if Torrejon provides a listening watch on 317.275 MHz.

Link distance is likely to be the cause of this communication loss.

It would be wise to investigate possible faults on the antenna or RF wiring.

It would be wise to ensure what radio modulation type (AM/FM) was in use by the copilot.

The VHF radio should be OK, since the pilot could hear the copilot's call sidetone.

Data terminal interfaces

Radio cooling.

Antenna sitting.

Squelch control.

BW of the radio output.

PTT circuitry.

BW of the radio input.

The new airport surface communication system will make use of IEEE 802.16e (Mobile WIMAX) in the C-band.

Universal Access Transceiver (UAT) has been worldwide accepted as the final solution to support the Automatic Dependent Surveillance-Broadcast (ADS-B) system.

EUROCONTROL has identified the civil/military CNS/ATM interoperability as an important issue to maximize the use of airspace and has created the Directorate of civil-military ATM coordination (DCMAC).

The new (medium term) terrestrial datalink will be designed and developed in the UHF band.

The usual position for HF antenna in commercial airline aircrafts is in the vertical stabilizer at the tail

Wireline antennas have the advantage of having good aerodynamic properties.

Probe antennas are horizonatal conductors (aprox 2, 3 m long), typically placed on the far-forward edge of a wing or a tail and provide a reasonably economical solution for aircrafts where a long antenna is not suitable.

The typical number of HF antennas in commercial aircraft is 3, the same for VHF/UHF antennas.

The ATN/OSI model became the standard solution because this solution was highly supported by the industry.

Context Management (CM), Flight Information Services (FIS) and Controller Pilot Data Link Communications (CPDLC) are three examples of ATN applications.

Integrated COMM controls are intended to alleviate the crew’s workload.

Automated EMCON Plan management functions are intended to ensure communications 
Confidentiality.

The development of an integrated COMM control for military equipment is based on the use of ARINC standard interfaces.

Automated Management for COMM Plans should allow for in-flight edition.

The strength of an encryption method relies on the secrecy of the algorithms rather than on the keys’ secrecy.

Keys stored into a cryptographic device are, by definition, not erasable.

Protected radio modes always rely on the availability of precise time data from a GPS receiver.

COMSEC keys cannot be edited in flight by the Pilot Non-Flying.

Communication in the civil ATC band (118-137 MHz) provides secure authentication of the calling party.

Communications system for airport surface (AeroMACS) is based on optical fiber connections because of the high bandwidth that this kind of connections is able to provide.

Air forces of all countries in the European Union signed a cooperative agreement in March 2012 to use for ATC communications the Shared ATC System (SAS) with the virtual military ATC center created in the Maastricht Up.

The New ATM concept of operation (trajectory based concept) is Performance Based Navigation but cannot be fulfilled with current communication infrastructure

The New ATM will increase capacity by multiple channel communications, data communications and management by planning.

Level 1 and level 2 systems can be used for establishing circuit-mode connections.

Level 3 and level 4 systems can be used for establishing circuit-mode connections.

Both T and C channels can be used to support circuit-mode connections.

Circuit mode is used mainly for safety continuous voice but also for data communications.

The SDU is responsible for the voice digitalization necessary for voice communications.

The SDU provides the Beam Steering Unit (BSU) with information of inertial reference systems to help estimating the aircraft position.

SDU module is typically located at the cockpit of the aircraft

Integration of the SDU is independent of the Audio Management System (AMS).

The range for HF communications is mainly due to the ability of radio signals at these frequencies of having reflections at the ionized levels of the atmosphere.

Lowest usable frequency (LUF) is higher at night.

Maximum usable frequency (MUF) is highly dependence on the cycle of solar activity.

Maximum Usable Frequency (MUF) is higher at day.

Antenna system are highly efficient.

The range for HF communications is mainly due to the low attenuation of the ground wave at these frequencies.