FAQ Inmarsat aircraft safety and communications’ services

Inmarsat aircraft safety and communications services are transmitted to and from aircraft globally via 10 wholly-owned satellites located in geosynchronous orbit 35,786km (22,236 miles) above the Earth.

Together they deliver voice and data communications to the aircraft cockpit, aircraft systems, and passenger cabin.

Other users of Inmarsat services include ships at sea and mobile users on land working in remote locations outside the range of terrestrial networks across the major landmasses of the world.

What aviation safety services does Inmarsat provide?

Satellite-aided Air Traffic Control (ATC) Communications

When an aircraft is out of range of VHF/UHF radio, such as in oceanic airspace, Inmarsat enables air traffic controllers to stay in touch with the aircraft. The ability to have reliable communications with ground-based controllers at all times, on all major oceanic routes, is an important safety feature.

Automatic dependent surveillance (ADS)

Inmarsat facilitates the automatic reporting of an aircraft’s real-time position to ATC centres, including altitude, speed and heading, via satellite to air traffic control centres, helping controllers know where an aircraft is at all times.

Voice services

Our satellite services support air traffic control and critical airline voice communications when the aircraft is out of VHF radio range. The aircraft systems are set up so that the cockpit communications have priority over any of the passenger communications, maximising safety and reliability.

Controller/pilot datalink communications (CPDLC)

The Aircraft Communications Addressing and Reporting System (ACARS) enables route instructions, clearances and other messages to be sent directly to the cockpit via Inmarsat as electronic data messages.

ACARS is used for sending text messages between an aircraft, aviation authorities and the airline, and is the standard non-voice communications method for aviation operations.

Messages and data can include those sent from pilots to air traffic control, or automatically generated data on how the aircraft’s systems are performing, or other vital information such as weather reports.

When an aircraft flies over land, ACARS messages are sent via VHF radio. But when an aircraft is in remote regions, or over water and out of range of VHF radio, the signal automatically switches to satellite.

How do Inmarsat communications work?

To use Inmarsat the aircraft needs to be installed with appropriate equipment comprising an antenna – typically installed on the top of the aircraft fuselage – and ‘avionics’ (aircraft electronics installed within the fuselage), normally in the aircraft electronics bay or similar.

The system automatically logs on to the Inmarsat network when the aircraft powers up.

The Inmarsat system will automatically send or receive voice, ACARS or other communications to or from the aircraft as required, wherever the aircraft flies.

If no communications activity is registered, the relevant Inmarsat ground earth station then periodically sends ‘polling signals’ or ‘handshakes’ to the satellite, which relays them to the aircraft. If the aircraft is still operating, an acknowledgement signal, containing basic system information, is sent back to the ground earth station from the aircraft. This includes its unique identification code, and confirmation the aircraft satcom is still operating and available for communications, if required.

How does Inmarsat identify one aircraft from another?

All aircraft are given a unique code confirming its identity, linked to the tail number of the aircraft. The signal sent from an aircraft carries this unique code and cannot get confused with another aircraft.

How are Inmarsat’s services delivered?

Inmarsat’s suite of aviation services includes SwiftBroadband, Swift64 and Classic Aero, which are used by most of the world’s leading airlines, business jet operators, general aviation and government agencies.

Classic Aero services are accessible over both the Inmarsat-3 and Inmarsat-4 satellite constellations, which offer global coverage. Classic Aero currently carries Inmarsat’s aviation safety voice and data services, as well as voice and data services for passengers, crew, telemedicine etc.

Inmarsat is implementing voice and data safety services using our SwiftBroadband services, via our Inmarsat-4 satellites, which also support more efficient, prioritised IP data services, enabling SwiftBroadband to carry Flight Data Recorder data.

What kind of services does Inmarsat provide for passenger communications?

Inmarsat Classic Aero services enable passengers to make phone calls from their in-seat phone, which often doubles up as the in-flight entertainment controller.

Where Inmarsat’s SwiftBroadband service is available and a cabin Wi-Fi network is installed, passengers can stay connected to the internet throughout the flight using personal smartphones, tablets or laptops to send emails and texts.

Where an aircraft is installed with a cabin GSM/GPRS pico cell system, SwiftBroadband is also used to allow passengers to use their own cellular mobile phones for both incoming and outgoing calls.