| Tutorials home | Decreasing risk exposure | Safety tour | Emergencies | Meteorology | Flight Theory | Communications | Builders guide |


Fly safe! home page

ADS-B surveillance technology
in Australia


Rev. 11a — page content was last updated 22 February 2013
Flight Planning and Navigation
  
Google logo



Automatic Dependent Surveillance – Broadcast (ADS-B) is an air traffic surveillance technology. A first stage ADS-B system ('ADS-B OUT' ) is operational, over most of Australia, for suitably equipped transport aircraft, as part of the RADAR/ADS-B 'Surveillance Information Service'. ADS-B will contribute substantially to air traffic management (ATM) surveillance and separation capabilities — at a comparatively low cost for Airservices Australia (AsA). It enables aircraft to be accurately tracked by air traffic services (ATS), without the need for secondary surveillance radar (SSR) except as a back-up system.




      Content



13.1 ADS-B navigation and surveillance technology system

The concept
The concept for the full ADS-B system is that all, or most, airborne aircraft operating in Class A, B, C and E airspace and Class G above 10 000 feet, automatically and continually (i.e. once or twice per second) squitter (i.e. broadcast automatically) several digital data packets which together contain the aircraft's ICAO 24-bit Aircraft Address code (the unique airframe identification assigned by CASA), flight identification (aircraft call sign), GNSS-derived position – latitude and longitude plus the integrity/accuracy of that position, its three-dimensional velocity; i.e. rate of climb/descent, direction in azimuth and speed. Pressure (or Mode C) altitude is provided by an altitude encoding device.

The data packets broadcast from aircraft are received by Airservices Australia [AsA] ground stations, which feed the data to air traffic management [ATM] systems, providing more precise tracking than primary or secondary surveillance radars. The broadcast ADS-B packets are also received by all aircraft equipped with an ADS-B data receiver that are within range. The derived data provides a real-time cockpit display of traffic information, similar to the ground ATC systems except that the traffic is shown in relation to the receiving aircraft's intended track.

The Mode S transponder, currently used for response to AsA's secondary surveillance radar network and as the standard air-air datalink in Traffic Collision Avoidance Systems [TCAS], is also used in ADS-B — with some enhancements. ADS-B broadcasts are via a Mode S 1090 MHz Extended Squitter [1090ES] transponder link. The term 'extended squitter' refers to the additional [112-bit] ADS-B data packet, which is part of the enhanced Mode S transponder data link standards for ADS-B.

However ADS-B, even in full operation, will not alter the VFR pilot's responsibility to 'see and avoid' other aircraft; ADS-B is seen as an aid to visual acquisition for VFR operations.
Airborne avionics
To achieve the full Airservices Australia ADS-B system concept, the onboard ADS-B avionics for general aviation and recreational aviation aircraft would have to include several functions or modes:

  • data transmission. This provides data broadcast capability so that positional data, provided by a GNSS system plus an altitude encoding altimeter or a pressure altitude blind encoder, is continually broadcast. This is known as 'ADS-B OUT' capability and all aircraft ADS-B units must have this minimum function. The accuracy of the broadcast data is dependent on the positional/navigational data from the GNSS receiver which, in turn, is dependent on the availability of signals and the capability of the GNSS. A high-performance TSO* GNSS receiver is part of the system.

    *Note: a 'TSO' or technical standard order is a 'minimum performance standard issued by the FAA (CASA issues ATSOs) for specified materials, parts, processes, and appliances used on civil aircraft'.

  • data reception. This refers to the capability to receive all data packets broadcast by all ADS-B OUT units within an appropriate range

  • data processing. This entails using the received data to provide a real-time plot of own and other aircrafts' tracks, speeds and altitudes; it is also known as a 'cockpit display of traffic information' [CDTI]. Data reception plus CDTI is known as 'ADS-B IN' capability, providing a pilot's own airborne surveillance and traffic alerting system — much the same as air traffic controllers may be viewing on their displays but completely independent of ATC.

    There are no regulatory proposals requiring use of ADS-B IN by any sector of aviation but it is the function that could benefit VFR recreational pilots, through enhanced situation awareness information.
ADS-B implementation in the USA
The United States Federal Aviation Administration [FAA] has decided that ADS-B transmission/data links in the USA will be via the Mode S 1090 MHz Extended Squitter [1090ES] surveillance link for aircraft that may operate above FL 180. For aircraft that only operate below FL 180 FAA has specified a Universal Access Transceiver [UAT] surveillance link using 978 MHz rather than use the 1090ES; mainly in order to reduce congestion on 1090 MHz.

UAT is a bi-directional data link system developed in the USA, specifically for ADS-B operation, so that aircraft with a UAT transceiver can also receive the freely available Flight Information Service data broadcasts [FIS-B] from the FAA-maintained 978 MHz uplink network, in addition to an ADS-B traffic information service broadcast TIS-B]. FIS-B includes METARs, TAFs, SPECI, winds and temperatures aloft, pilot reports [PIREPs], restricted area status and NOTAMs. In Australia similar products are available in flight from Airservices NAIPS Internet Service via mobile broadband, see EFB software suppliers. The FIS-B facility also provides an animated NEXRAD weather radar service — similar to the Australian BoM weather radar network. UAT is not a transponder so UAT equipped aircraft also need a Mode S transponder for the secondary surveillance radars.

Garmin released their portable GDL 39 ADS-B 1090 MHz/978 Mhz receiver and GPS receiver in June 2012, it can connect via Bluetooth to an iPad or iPhone to display the traffic information on a moving map. See the user guide. This particular device is built for the United State's ADS-B dual frequency environment and has no application in Australia. The current (November 2012) selling price in the US is $800.

13.2 The Australian ADS-B implementation program

AsA has opted for 1090ES for all aircraft, except those operating under the VFR in Class D airspace or in Class G below 10 000 feet. CASA amended CAO 20-18 December 20, 2012 to reflect the following ADS-B OUT implementation time table:

9B Directions relating to carriage and use of automatic dependent surveillance — broadcast equipment

9B.8 On and after 12 December 2013, any aircraft that is operated at or above FL 290 must carry serviceable ADS-B transmitting equipment that complies with an approved equipment configuration by meeting the conditions for approval set out in Appendix XI.

9B.9 An aircraft:
(a) that is first registered on or after 6 February 2014; and
(b) that is operated under the IFR; must carry serviceable ADS-B transmitting equipment that complies with an approved equipment configuration by meeting the conditions for approval set out in Appendix XI.

9B.10 On and after 2 February 2017, an aircraft:
(a) that is first registered before 6 February 2014; and
(b) that is operated under the IFR; must carry serviceable ADS-B transmitting equipment that complies with an approved equipment configuration by meeting the conditions for approval set out in Appendix XI.

9B.11 On and after 4 February 2016, an aircraft that is operated under the IFR in airspace:
(a) that is Class A, B, C or E; and
(b) that is within the arc of a circle that starts 500 NM true north from Perth aerodrome and finishes 500 NM true east from Perth aerodrome; must carry serviceable ADS-B transmitting equipment that complies with an approved equipment configuration by meeting the conditions for approval set out in Appendix XI.


None of the above ADS-B OUT legislation affects aircraft registered with a Recreational Aviation Administration Organisation as no RAAO aircraft may operate under the IFR or will operate in class A or above FL 285 except perhaps an officially sanctioned altitude attempt.

However, the following subsection of CAO 20-18 will apply from 6 February 2014 to any newly registered RA-Aus aircraft operating under the VFR that chooses to operate in any controlled airspace other than Class D. Such aircraft must be fitted with a serviceable Mode S transponder that meets the Australian standards for 1090 ES transponder equipment and for ADS-B OUT capability. This may create problems with imported aircraft.

9E Carriage of Mode S transponder equipment
9E.1 This subsection applies to an aircraft engaged in private, aerial work, charter or RPT operations.
9E.2 Subject to paragraph 9E.3, an aircraft:
(a) that is:
(i) first registered on or after 6 February 2014; or
(ii) modified by having its transponder installation replaced on or after 6 February 2014; and
(b) that is operated:
(i) in Class A, B, C or E airspace; or
(ii) above 10 000 feet amsl in Class G airspace; must carry a serviceable Mode S transponder that meets the standards:
(c) for Mode S transponder equipment — in subsection 9C; and
(d) for ADS-B transmission — in a clause or clauses of Appendix XI as follows:
(i) clauses 2 and 5 of Part B; or
(ii) clause 7 of Part C; or
(iii) clause 8 of Part C.

Note: The requirement is for aircraft to be fitted with a Mode S transponder with ADS-B OUT capability. That does not mean that ADS-B OUT transmission is also required under this paragraph. It means that, with the later connection of compatible GNSS position source equipment, ADS-B OUT can be transmitted as well as Mode S SSR responses.

Note: Paragraph 9E.2 does not apply to an aircraft operating in Class E airspace or above 10 000 feet in Class G airspace, if the aircraft does not have an engine or sufficient engine-driven electrical power generation capacity to power a Mode S transponder.


Otherwise, Australian sport and recreational aircraft that always operate under the visual flight rules below 10 000 feet and outside Class A, B, C and E airspace (the Class D areas are excluded) will not be affected by the ADS-B surveillance and separation service implementation, at least not before 2020.

13.3 Airservices Australia's ADS-B system

The upper airspace program
AsA states that ADS-B "is an air traffic surveillance technology that enables aircraft to be accurately tracked by air traffic controllers and other pilots without the need for conventional radar."

To date AsA has deployed 58 ADS-B ground stations at 29 sites across Australia which, combined with SSR, provide ATC surveillance capability over the entire continent above FL290 (29 000 feet ISA).

These first 29 locations established an Australian ADS-B network for ground-based air traffic management; i.e. an ADS-B OUT system. These stations, each with a range up to 200 nm, are co-located at existing VHF communication relay sites and linked to surveillance displays at ATC centres, which allows Airservices Australia to provide an SSR-like traffic separation service across the current non-radar airways above FL290. Of course these same ground stations also have the capacity for air traffic management at altitudes below 10 000 feet — but reduced range, being line-of-sight dependent.

Currently in Australia the main Mode S transponder function is to allow aircraft equipped with Traffic Alert and Collision Avoidance Systems to 'talk' directly with each other, thereby enabling mutual resolution of potential traffic conflicts. Mode S can also provide faster, more accurate ATC surveillance, provided the ground radars are of the fast single pulse interrogation type such as those Mode S Terminal Area Radar equipment with solid-state primary surveillance radar and Mode A/C and S capable SSR systems at Coolangatta, Melbourne, Adelaide, Sydney, Cairns, Brisbane, Canberra, Darwin and Perth.

The ADS-B OUT function is accomplished by upgrading an aircraft's existing Mode S transponder to 1090ES, and linking the GNSS system and the transponder. The upper air space program doesn't affect recreational aviation.
The lower airspace program
"A major, longer term program designed to make ADS-B the primary means of ground to air and air to air surveillance in Australian enroute airspace. Includes installation of additional ADS-B ground stations to provide air traffic surveillance in airspace currently covered by enroute radar facilities. Intended to lead to the eventual decommissioning of a number of radar sites."

Initially an accelerated introduction of ADS-B surveillance into lower airspace was planned, but in the last quarter of 2008 it was agreed that a more gradual transition to satellite-based systems, harmonised with the North American and European transition plans, would be wiser. Airservices Australia is "proceeding with the replacement of its enroute radars and navaids as necessary to ensure the integrity of Australia's air traffic control system." (CASA's Notice of Final Rule Making – Transition to Satellite Technology for Navigation and Surveillance).

"The timing and scope of future steps will be progressed through normal regulatory processes and will take into account ... outcomes of the Government's Aviation Policy Green Paper consultation."

The Australian land area is about 7.5 million km² and the airspace included from ground level to 10 000 feet agl is about 21 million km³. Probably no more than 10% of the 15 000 registered aircraft are airborne at any time. So it is not surprising that the Australian history of recreational day VFR aircraft 'mid-airs' or 'near-misses' appears to be confined to the circuit area, to aircraft flying formation or to gliders sharing a lift source. Certainly a CDTI traffic display will alert a pilot in the vicinity of an airfield to the direction to look to avoid collision with another aircraft but the likelihood of collision with the ground in a stall/spin incident would seem to be increased if the VFR pilot's eyes remain in the cockpit checking a CDTI traffic display.

CASA have published a 28 page ADS-B booklet dated November 12, 2012. There is also an 18 page Frequently Asked Questions pdf document.




This concludes the Flight Planning and Navigation Guide which I hope you have found useful. There are also two supplementary documents which should be read: "Operations at non-controlled airfields" and "Safety during take-off & landing".

If you have corrections or suggestions for improvement or expansion — please contact the author.



Groundschool – Flight Planning & Navigation Guide

| Guide content | 1. Australian airspace regulations | 2. Charts & compass | 3. Route planning | 4. Effect of wind |

| 5. Flight plan completion | 6.Pre-flight safety and legality check | 7. Airmanship & flight discipline | 8. En route adjustments |

| 9. Supplementary navigation techniques | 10. En route navigation using the GNSS | 11. Using the ADF |

| 12. Electronic planning & the EFB | 13. ADS-B surveillance technology |


Supplementary documents

| Operations at non-controlled airfields | Safety during take-off & landing |



John Brandon   2004–2013   [contact information]