Countdown to ADS-B (Out) Compliance – Part 1

Over 3 Parts, Ken Elliott addresses ADS-B , less than three years before the equipage requirement comes into effect. Are you ready...?

Ken Elliott  |  26th May 2017
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    Ken Elliott
    Ken Elliott

    Ken Elliott is a veteran with 52 years of aviation experience, focussed on avionics in General and Business...

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    Over three articles, Ken Elliott addresses Automatic Dependent Surveillance - Broadcast (ADS-B) mode, less than three years before the equipage requirement comes due…

    We begin this series addressing equipage rates, summarizing the technology, data sources and operational requirements before diving deeper in Part 2 to explore the technical aspects of ADS of interest to operator flight departments. There we will provide insight into future space-based ADS services.

    We will conclude the series with a close look at worldwide implementation and operational differences in greater detail.

    Equipage Rates

    The storm clouds are forming as the ADS-B Out ‘mandate front’ draws near, bringing torrents of ADS-B Out installs. The more bunched together the installs, the greater the turbulence will be. Weather watchers and storm chasers are providing ample notice to all, but a reluctance to heed warnings of a bumpy ride to compliance may make matters worse.

    The number of aircraft needing to comply with ADS-B Out becomes murky as you begin counting the Single Engine category, and murkier still when the Light Sport and Experimental crowd are included. The FAA measures equipage statistics against a range of between 100,000 and 160,000 aircraft. This makes sense, because ADS-B Out is not required everywhere, as Table A demonstrates:

    It is notable that Class D and G Airspace is not mentioned within Table A, so to clarify…

    Class D Airspace: A defined cylinder of airspace centered on a Class D airport that needs an Air Traffic Control Tower to coordinate airport operations. Unlike Class B and C airports, however, Class D airports don't require a mandatory approach and departure control (though many do have approach/departure). Class D airspace extends upward to 2,500ft AGL. Surrounding airspace is Class E. ADS-B Out is not required in Class E airspace below 2,500ft AGL anywhere and only above 10,000ft MSL otherwise, (except for the Gulf of Mexico). So a blanket of ADS-B Out ‘free-airspace’ exists everywhere below 2,500ft AGL and outside of Class B or C airspaces. This by implication includes Class D airspace also.

    Class G Airspace: A blanket of narrow airspace following the contour of the ground and up to either 700 or 1,200ft AGL. Because this airspace also exists below 2,500ft AGL it is also free from the requirement for ADS-B Out.

    Doing the ADS-B Math

    As of February 1, 2017, between 12.9% and 20.7% of all US-based GA aircraft were equipped for ADS-B Out, with 22,609 installations scheduled or completed by March 1, 2017. GAMA approximates the population of US General Aviation aircraft is greater than 210,000, so the roughly 10% equipage rate is a pretty grim situation, given there are only 34 months until the ADS-B Out US mandate demands compliance by January 1, 2020 (counting from March 1, 2017).

    Note the GA aircraft population includes rotorcraft and all fixed-wing outside of air carriers, military and government operations. If you assume 20% of the aircraft will elect not to operate where ADS-B Out is required, that would leave 168,000 still to complete, less those already compliant (by equipage and not necessarily fully operational), leaving around 140,000 yet to comply.

    Repair Station membership of the Aircraft Electronics Association, a worldwide group representing the interests of the Avionics community, is an adequate indication of the number of ‘shops’ capable of performing ADS-B installations, albeit in many cases light GA. US based Repair Station membership of the AEA sits at around 723 shops. So, assuming 140,000 installs over 34 months across 723 avionic shops, there would need to be 5.7 installs a month, on average, for each shop. It’s doable, but only if all the stars are aligned.

    To keep things in perspective, the spread of aircraft between single-engine and turbine is heavily weighted toward single engine, and many of those will upgrade with novel, low-cost and (critically) shorter downtime solutions.

    Types of ADS-B Service

    Unique to the US there are two types of ADS-B Out service, one being based on the Universal Access Transmitter (UAT) and the other 1090ES. UAT operates at 978 MHz frequency and will allow for additional traffic and flight service information being provided to the aircraft.

    The 1090ES service, as the title suggests, operates at 1090 MHz frequency and uses Extended Squitter (ES). This latter service is mostly utilized by turboprops and business jets that are equipped with the more expensive and elaborate transponders required.

    Of those, there were 18,828 ADS-B Out equipped aircraft that are using the 1090ES and 5,074 using the UAT service, as of February 1, 2017. It is not possible to correlate the 22,152 turbine GA aircraft to the 1090ES count because a number of piston-powered GA aircraft have the same capability.

    One measuring stick for understanding the crowding likely to occur in scheduling and subsequent installation, is to show a best-case scenario of turbine aircraft potential upgrade rates based on a start date of 2012, roughly when operators and OEMs began to actively install ADS-B Out.

    There are 96 months between January 2012 and January 2020. This required, in 2012, a start-up rate of 230 aircraft per month being delivered with ADS-B Out. If one assumes each turbine aircraft upgrade takes an average of five work days (or four aircraft per month), compliance requires, in the US alone, 57 avionics facilities working at full-steam to complete all the aircraft in time.

    A Summary of ADS-B Out & ADS-C

    ADS-B Out is a surveillance tool for both aircraft and air traffic control, mitigating the need for existing ground radar, while providing virtual ground radar in places such as mountainous terrain where traditional ground radar would never have worked. In fact, aircraft equipped with both ADS-B Out and In have, in essence, an onboard virtual ground radar.

    ADS-B provides an additional layer of surveillance and situational awareness to the existing Traffic Alert and Collision Avoidance System (TCAS) as well as Enhanced Ground Proximity Warning System (EGPWS), both of which complete the toolkit to see and avoid. ADS-B enhances the existing transponders by adding further data for broadcasting precise aircraft position.

    The precision of the aircraft’s position is critical for beneficial performance of ADS-B, hence why the original GPS receivers often require an update. In simplistic terms, you may see overall surveillance/positional awareness as a four-legged stool; TCAS, EGPWS, ADS-B and the existing aircraft weather radar. Now you have surveillance protection from other aircraft, obstacles, terrain and weather. For aircraft, the protection extends to both pre-emptive tracking and the avoidance of collision with other traffic.

    Critically, as with TCAS, all aircraft are monitoring each other, somewhat in the manner of air traffic control (ATC). While ATC will have its own area of surveillance, each aircraft has a specific localized display of other aircraft activity within its vicinity, providing the operator elects to include the ‘ADS-B In’ feature as part of the upgrade.

    ADS-B Out is a continental based technology, requiring all aircraft to be within range of the prescribed ground stations (see Figure A).

    For remote areas and ocean regions, the coverage is not via broadcast (i.e., not via ADS-B). Instead the surveillance is contracted through the operator’s satellite service provider, assuming the operator is equipped with some form of compatible satellite communications system. This alternate surveillance service is contracted between the operator and ATC monitoring centers.

    Because it is contracted, the term for this automatic dependent surveillance is ADS-C (Contract). The contract permits the handshake to approve the transfer of the necessary data. It is common to see the ADS-C term alongside FANS (Future Air Navigation System). This is because FANS, an architecture incorporating Controller Pilot Data Link Communication (CPDLC) also uses satellites, is enabled by your satellite service provider, and communicates with ATC.

    For those operators that elect to connect UAT to their aircraft, there is the advantage of additional FAA-provided data in the form of weather, NOTAMS, traffic and more. This is not to be confused with ADS-B In, a separate non-mandated capability where each aircraft operator may view the nearby surveillance activity on their cockpit displays (termed CDTI, but may be integrated into existing displays), or on an approved iPad or similar device. It is with ADS-B In that ATC monitoring is somewhat replicated on board each equipped aircraft.

    Noticeably, pilot action is minimal at best with ADS-B or -C. As with many functions available on aircraft today, there is a greater reliance on automation. This process allows the pilot flying to focus on the core task of flight management. Of course, automation needs to be limited until such a time as its integration into the flight regime is natural and inevitable.

    As an indication of the complexity for an ADS-B upgrade on larger aircraft, Table B lists the possible equipment required. These items may need to be added, upgraded or amended via software, to provide ADS-B capability.

    Navigating useful ADS-B Data Sources

    Depending upon your regional location throughout the world, the requirements for ADS-B Out and resources available for guidance will vary. The major regions are those covered by the International Civil Aviation Organization (ICAO), as the governing body for aviation standards and operations across the world, North America and Europe, and (operating somewhat autonomously and in the case of ADS-B specifically) Australia, which was ahead of the pack in embracing this technology.

    ICAO has a working group that has held 12 meetings, as of end of 2016, covering ADS-B and many related sub-topics spanning technical issues involving individual nation or regional implementation.

    In 2015 ICAO issued a significant paper (ADS-B SITF/14 – IP/11) outlining differences, primarily between the US and everywhere else, but providing an informative chart depicting what is required (versus what is optional across the four main geographical ADS-B regions: Australia, US, Europe and everywhere else).

    ICAO has very detailed material for mandates in its Asia-Pacific (APAC) region, relating to implementation, and altitude and phase-in date requirements. Furthermore, ICAO has issued a helpful ADS-B guide. The APAC-released document, Appendix H to APANPIRG/26 – WP/9, covers the topic of ADS-B Out within the regional context.

    Europe: SKYbrary, issued by ‘European Organisation for the Safety of Air Navigation’ EUROCONTROL, is a good general source of material for all things Europe. This body provides the equipage and operational requirements, as well as the aircraft ADS-B monitoring service.

    On the other hand, the ‘European Organisation for Civil Aviation Equipment’ (EUROCAE) provides the equipage standards themselves and publishes those via a series of documents under the ED designation.

    United States: The FAA’s Equip ADS-B website is very useful to flight departments. The website is a central place for finding approved equipment monitoring ADS-B performance. It also covers capability and all aspects of installation.

    The FAA has another site for ADS-B ( which offers a more formal approach to the overall requirement. The FAA’s ‘Equipadsb’ site was a response to the primary concern of motivating operators to accomplish the upgrade. For example, the site includes the FAA Rebate Program for fixed-wing, single-engine, piston-powered GA. This program is running for one year from September 19, 2016 or until all 20,000 rebates have been claimed.

    Australia: Of note is the early adoption of ADS-B by Australia. Their Civil Aviation Safety Authority (CASA) provides a very useful and easy to read guidance booklet on ADS-B. This is particularly helpful for those intending to perform flight operations in that region.

    DO 260B/ADS-B Out Version 2

    Worth special mention is the term ‘ADS-B Out Version 2’. This refers specifically to the latest format of ADS-B adopted by the US; if not yet universally required, it may soon be. For sure, the primary flight areas and routes worldwide will require it.

    In some ways, the ADS-B Out Version 2 criteria is more an issue for newer aircraft manufactured and delivered within the last several years, but not for those most recently delivered. Aircraft manufacturers like to deliver current version products and will often deliver provisions for, or versions of, newly required or desired equipment.

    Unfortunately, while well-intended, they sometimes inadvertently deliver aircraft with equipment that is quickly supplanted by a later version. This is the case with ADS-B. The technology is now in its 3rd iterations, Version 0, 1 then 2.

    Version 2 is based on the RTCA special committee recommendations documented under DO 260B. For those seeking to wait, based on a further version forthcoming, it is advisable not to abide, as Version 2 is it. When ADS-B In is fully defined as a standard and then as a requirement, you can expect to see some fine tuning, but only after the current mandate has expired.

    Operational Requirement

    Table C outlines upcoming ADS-B operational requirements. (Also, refer to ICAO’s APAC material for detailed implementation in the Asia-Pacific Region.)

    From a global perspective, outside of North America and Europe, ADS-B implementation-related work is also being undertaken within all other continents, including:

    • Africa (Congo, Ethiopia, Guinea, Sierra Leone, Liberia, Namibia, South Africa);
    • South & Central America (Brazil, Peru, Trinidad and Tobago);
    • Asia (Afghanistan, China, Hong Kong, Fiji, India, Indonesia, Japan, Kuwait, Kyrgyzstan, Malaysia, Philippines, Qatar, Saudi Arabia, Singapore, Taiwan, Tajikistan, Thailand, UAE, Vietnam);
    • Oceania (New Zealand).

    Advantages of ADS Services

    Aside from the obvious operational advantages for each aircraft, ADS-B or C serves a plethora of other purposes. Below, (courtesy of EU’s SKYbrary) most of the advantages are listed.

    • Full “Network-wide” Surveillance coverage:
      - Surveillance “everywhere” (i.e. no gaps from gate-to-gate);
      - Air-to-air Surveillance possible (i.e. traffic situational awareness picture available on board);
      - The aircraft is an integral part of the Network;
      - Surveillance data provided directly from on-board systems.
    • High performance
    • Improved safety
    • Increased capacity
    • Cost-efficiency, including:
      - Reduced cost of the Surveillance infrastructure (ADS-B is less expensive than radar)
      - More efficient flight profiles (in areas where previously surveillance was not cost-effective)
      - Fuel savings etc.
    • Environmental sustainability (CO2 reduction)
    • Reduced Radio Frequency pollution (leading to an increased viability of the 1090 MHz datalink)
    • Global Interoperability
    • Foundation for future ATC applications (spacing, separation, self-separation).

    When you add in the remote and oceanic space-based coverage, the advantages of ADS-B expand further, particularly in its ability to provide worldwide, real-time, aircraft tracking.

    In Summary

    Despite the widespread availability of ADS-B (and -C) information, operators and those who advise them, are often uncertain of the requirements. For example, ADS-B Out Version 2 is a US requirement and operators who want to continue using earlier versions of ADS-B Out in other regions may do so.

    However, this arrangement would preclude operating in the US. If you are going to use ADS-B within the US, even prior to the 2020 deadline, you must operate with ADS-B Out Version 2.

    There are many aspects to consider when operating, transacting or maintaining an aircraft today. ADS-B Out is just one of them, and yet it has so many nuances, particularly for those who operate internationally. These articles are designed to assist operators in an overall understanding and sourcing of further guidance to assist ADS-B Out implementation.

    Next time, we will focus on technical aspects to assist flight departments and those that support them, in understanding the deeper layers of ADS-B - especially where there is applicability to overall operations.


    This article features in AvBuyer's 2018 Yearbook. Read the full edition here.


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