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Chapter 2 Communication
Voice and data communication
Airborne radio has been used in Australia for nearly 100 years, and voice communication on VHF and HF remains a vital part of air-to-ground and air-to-air communication. UHF voice is used by the military.
However, there is an increasing emphasis in both civil and military on the transfer of messages via digital codes. These screen-based messages use services such as the controller-pilot data link communication (CPDLC), a technology which emerged in the late 1990s.
As Australian aviation transitions from ground- to satellite-based navigation, communication and surveillance will be transformed by the introduction of four dimensional (4D) trajectories. When fully implemented, air traffic controllers (ATCs) will be able to plot the precise flight path an aircraft will take before an aircraft takes off. This will allow them to map out the projected trajectories of all flights in Australian airspace.
OneSKY Australia program
By 2021, Australia is aiming to provide air traffic control services using one of the most advanced and integrated air traffic control systems in the world. In collaboration with the Department of Defence, Airservices Australia aims to provide a single flight information region for Australian skies under an intergrated air traffic management system. The current civilian system, known as The Australian Advanced Air Traffic System (TAAATS) built in the 1990s and commissioned in 2000, will be retired.
One of the key operational and safety benefits from the new system is that an air traffic controller (ATC) at any of the 200 consoles across Australia will be able to access the same flight information simultaneously, reducing the risk of sharing incorrect information. It will place Airservices and the Department of Defence in a position to manage the forecast growth of air traffic movement in Australia.
Operations with controller-pilot data link communications (CPDLC)
CPDLC has been used in Australia since 1998. It uses a two-way data link, instead of voice, to transmit non-urgent information between air traffic control (ATC) and pilots. CPDLC can be used to issue clearances, such as weather deviations, altitude clearances, amended route clearances, speed instructions, as well as secondary surveillance radar (SSR) codes and frequency transfers.
CPDLC is used in a range of operations, including:
- oceanic airspace—instead of the unreliable and interference-prone high frequency (HF) radio
- other airspace at the discretion of the controller.
CPDLC functionality is integrated with the flight data record (FDR). When a CPDLC clearance is uplinked to an aircraft, the FDR is updated on receipt of the ‘will comply’ (WILCO) response from the flight crew. The controller accesses CPDLC message elements via the CPDLC editor.
In the 1990s, ICAO determined that future primary long-range communications with aircraft would be by HF or SATCOM data link, and at the time made no provision for satellite voice (SATVOICE). Under ICAO Standards and Recommended Practices (SARPs), SATVOICE is not recognised as an acceptable means of communication for air traffic services (ATS) purposes.
However, the transition to data link communications has not happened as envisioned, and HF voice communication remains a primary means of long-range communication.
Some countries have allowed SATVOICE to be used in lieu of a second HF communications system, providing the aircraft installation and ground segments of the system meet performance standards.
Status in Australia
SATVOICE is not authorised for ATS use in Australia because the Airservices Australia communications infrastructure does not support SATVOICE operations.
However, SATVOICE in North Atlantic high level airspace (NAT HLA) is permitted when authorised by CASA. About 3000 aircraft fly across the North Atlantic airspace daily, with approvals to operate in the ICAO NAT region airspace based on ICAO NAT DOC 007.
For unrestricted operations in the NAT region, operators must have fully functioning HF communications equipment. While SATVOICE and datalink communications are gradually being introduced into NAT operations, operators may still need HF datalink as back-up.
Operators who can demonstrate compliance with the ICAO satellite voice guidance material (SVGM) requirements may be authorised by CASA to use SATVOICE in the NAT HLA region. Aircraft must meet installation requirements and operational procedures must be appropriate.
In transitioning to performance-based navigation (PBN) requirements in this airspace by 30 January 2020, North Atlantic minimum navigation performance specification (NAT MNPS) was redesignated as the North Atlantic high level airspace (NAT HLA).
Aircraft operating in North Atlantic high level airspace require a CASA issued navigation authorisation until 30 January 2020, to coincide with the transition to PBN.
- Communication and surveillance are being transformed by the introduction of four dimensional trajectories which allow air traffic controllers (ATCs) to plot the precise flight path an aircraft will take before an aircraft takes off, allowing them to map out the projected trajectories of all flights in Australian airspace.
- CPDLC, used in Australia since 1998, is a means of communication between ATC and pilot, using a data link instead of voice. Its main advantages include reduced congestion of voice channels, fewer communication errors and reduced workload for pilots and controllers.
- Aircraft operating in North Atlantic high level airspace require a CASA issued navigation authorisation until 30 January 2020, to coincide with the transition to PBN.
Airservices Australia (2016). OneSKY Australia program. Retrieved April 2017.
Airservices Australia (2013). The Importance of Accurate Position Estimates. Safety Bulletin, 12 March. Retrieved April 2017.
CASA (2016). North Atlantic high level airspace operations Retrieved April 2017.
CASA (2016). SATCOM voice Retrieved April 2017.
ICAO (2013). Review of ADS-C/CPDLC Operations. The 2nd Meeting of the Future Air Navigation Systems Interoperability Team-Asia (FIT-Asia/2). 28-29 March. Retrieved April 2017.
Skybrary (2016). Navigation by Radio Aids Retrieved April 2017.
Australians have been early adopters of satellite navigation, using it for many activities and applications including aviation. The global nature of the technology is suited to Australia’s large land mass and low population density.
Many charter operators operating under visual flight rules (VFR), especially in remote areas, use panel-mounted or portable GNSS units.
Satellite-guided tracking and approach guidance are commonplace in instrument flight rules (IFR) operations.
This chapter will look at how GNSS works, what augmentation systems are in place and how to use these systems in aircraft operations.
It’s important to remember that the use of GNSS is no substitute for thorough flight planning—you can read up on this in Chapter 7.