How to Understand the ADS-B Out Essentials (Part 1)

With the mandate drawing ever closer, Ken Elliott discusses all the need-to-know aspects of ADS-B. Specifically, what are the ADS-B Out requirements and operations?

Ken Elliott  |  22nd March 2019
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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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Understanding the ADS-B Out essentials

With the mandate drawing ever closer, Ken Elliott discusses all the need-to-know aspects of ADS-B. Specifically, what are the ADS-B Out requirements and operations?
As of December 2018, there were 49,000 US-registered General Aviation aircraft equipped with ADS-B (not including the light sport and experimental categories). In 2016, the total number of GA and Part 135 aircraft in-service was 166,167, of which 142,638 were piston-powered. Within that number, there were also 13,751 turbojets.
Regardless of how you shuffle the numbers, in the US all of the different aircraft groups are behind the curve to meet the January 1, 2020 ADS-B Out deadline.
Focusing on the roughly 24,000 turbojet and turboprop fixed-wing aircraft, most of the larger shops are completing ADS-B Out installations at a rate of between three and five aircraft per month.
Apart from the normal inspections and routine maintenance requirements, shops must deal with non-recurrent service, paint, interior, FANS and Wi-Fi upgrades, all of which will not just go away to accommodate the ADS-B deadline requirements.
MROs need to keep their other trades busy, which means keeping hangars full of other work. Of course, if ADS-B can be scheduled to coincide with calendar requirements, then great! But as 2019 progresses, it will be much harder to arrange an ADS-B upgrade if your aircraft is not already penciled in at your preferred maintenance facility.
Word-by-Word ADS-B Definition

  • Automatic: A system that works independently of pilot or controller initiation.
  • Dependent: A system that is dependent upon the use of the aircraft’s position.
  • Surveillance: A traffic awareness system collaborating data between aircraft and ATC and between the aircraft themselves.
  • Broadcast: A system relying upon wide area broadcast for any user to receive and display (if their aircraft is equipped with ADS-B In).
ADS-B Overview Essentials

What is ADS-B? Automatic Dependent Surveillance Broadcast (ADS-B) is a next generation air traffic surveillance technology supporting radar-like separation standards. It does not replace radar but provides a service where radar coverage is deficient.
What does ADS-B enable? Equipped with ADS-B Out each aircraft broadcasts its own highly accurate aircraft position, speed, direction and other data.
What is ADS-B In? If installed, ADS-B In allows an aircraft to receive and display ADS-B information providing a display of surrounding traffic, rather like your own on-board air traffic controller display. ADS-B In also provides the flight crew with a no-charge FAA TIS-B (Traffic Information Service-Broadcast) feature.
What is ADS-B Out? Each ADS-B Out equipped aircraft automatically transmits accurate position reports, with integrity, every second, to Air Traffic Control (ATC) and to other aircraft. This may result in a reduced separation minimum for equipped aircraft and allows more aircraft to follow the most efficient flight trajectory.
The Elements of ADS-B

Actual ADS-B data to be broadcast are defined in the relevant standards and certification documents. They include (amongst others) the following:
  • Aircraft horizontal position (latitude/longitude)
  • Aircraft air data and heading (including barometric altitude)
  • Various data quality indicators
  • Aircraft identification:

    - Unique 24-bit aircraft address
    - Aircraft identification
    - Mode A code
  • Emergency status
  • SPI (special position indicator) when selected by the crew.
ADS-B Coverage and Mandate Essentials

Table A and Figure A address the requirement to operate with a fully functional ADS-B system by classification of US airspace.
ADS-B Out Requirement by US Airspace
From a worldwide perspective, two other regions have a mature program in place; Australia (the first to embrace ADS-B) and Europe. Both regions are scheduled for full implementation in 2020 and have partial implementation to date.
Other nations with restricted ADS-B coverage, based on geographical region, altitudes above FL290, or requirements above FL100 and FL180, include: Canada, Mexico, China, Indonesia, India, Sri-Lanka, Vietnam, Thailand, Fiji, UAE, Sweden, Iceland, Hong Kong, New Zealand and Taiwan.
Note: Europe’s blanket requirement includes aircraft weighing >12,566lbs or with a speed >250ktas.
ADS-B Out Requirement by US Airspace, FAA
What is Space-Based ADS-B?

Many nations have date-based, partial implementations either in place or planned, and are waiting upon the implementation of space-based ADS-B. In place of ground-based continental broadcast and rebroadcast stations, space-based ADS-B has the advantage of using low earth orbit (LEO) satellites.
Aireon, using Iridium Next conventional satellites, and others using CubeSat standards will create the future environment for mandates. These will flow from endeavors that allow for worldwide tracking of aircraft, for added safety and recovery.
What’s the Stated Requirement?

For the US: Any airspace that requires the use of a transponder today will (on January 1, 2020) also require aircraft to be equipped with a Version 2 ADS-B Out system. This can be either a 1090ES (DO-260B) ADS-B system or a UAT (DO-282B) ADS-B system.
For aircraft operating at or above FL180 (18,000 ft) or needing to comply with ADS-B mandates outside the US, a Mode-S transponder-based ADS-B transmitter is required.
Aircraft operating below FL180 and within US airspace must be equipped with either a Mode-S transponder-based ADS-B transmitter or with UAT equipment.
For Europe: Aircraft operating IFR/GAT in Europe and with a maximum certified take-off mass exceeding 12,566lbs or having a maximum cruising true airspeed capability greater than 250ktas are required to carry and operate ‘Mode S Level 2s’ transponder(s) with Mode S Elementary Surveillance (ELS), Enhanced Surveillance (EHS) (for fixed wing aircraft) and ADS-B 1090MHz Extended Squitter (ES) capabilities. The applicability date for this requirement is June 7, 2020.
Note: aircraft operating under a civilian registration that do not meet specific criteria, may be granted an exemption against the Mode S EHS requirements.
The Different Aspects of ADS-B

As mentioned, ADS-B has an Out and an In component. The current focus is on ADS-B Out and most operators are not adding the equipment necessary for ADS-B In, partially because a proper requirement standard is still in the works.
ADS-C: This refers to ADS services, under a contract, between an aircraft operator, their service provider and mostly oceanic air traffic. It is envisaged ADS-C will evolve, transition or fall away when spaced-based ADS-B services emerge as the leading international means of aircraft surveillance.
ADS-R: ADS-B Rebroadcast exists because the ADS-B system operates on two separate frequencies (1090 MHz and 978 MHz) in the US and not worldwide. Because of the different frequencies there is a need to translate, reformat and rebroadcast the information from each frequency to enable aircraft operating on the alternate frequency to process and use the other’s information.
TIS-B: The broadcast of transponder-based traffic information derived from ATC surveillance systems, TIS-B provides the mostly smaller ADS-B In-equipped aircraft with a more complete picture of surrounding traffic in situations where not all aircraft are equipped with ADS-B.
FIS-B: This only operates on the 978 MHz (UAT) frequency used in America and provides ADS-B In equipped aircraft with a suite of advisory-only aeronautical and weather information products to enhance the user’s flight experience and safety.
Cessna Citation Business Jet
ADS-B Out V0, 1 and 2: Does it Matter?

Operators who fly internationally and brokers who are looking to trade aircraft from exotic locations, beware! ADS-B Out comes in three versions and the requirement for these versions varies by operating location.
For the US, Europe and Australia Version 2 is needed. Elsewhere the requirements are less, varying between Version 0 to 1 and it will not matter if you happen to have Version 2.
The problems arise when you want to operate a legacy Version 0 or 1 ADS-B equipped aircraft in a region that requires Version 2. Hence the warning to brokers trading aircraft between regions.
Here are the primary features of Version 2 that make it different and, therefore, a more advanced ADS-B configuration.
  • ADS-B Out DO-260B (Version 2):

    - Supports ADS-B In capability;
    - Provides higher navigation integrity; and
    - Crew alerting failure messaging.
Compliance Reporting

The airworthiness authorities need to ensure installed systems are operating correctly in flight. While flights are regularly monitored, as a complimentary service operators may request a compliance report. In the US, there are two types of compliance report:
i) For the certification of new hardware; and

ii) Post-installation compliance report for ADS-B Out-equipped aircraft.

Understand the ICAO 24-bit Address and Flight ID

The version of transponder required for ADS-B Out using 1090 MHz frequency, must be 1090ES (Extended Squitter). These transponders are required to have a Mode S Address that conforms to an ICAO 24-bit address standard. The address will be unique for each aircraft dual transponder system.
The Mode S address must decode to the aircraft’s current registration, and aircraft changing ownership must include this step as part of the transaction process.
Separately, each aircraft has a pilot enterable call sign (or Flight ID) which is also tied to the aircraft call sign (registration number), or to the operator code and flight number for commercial operators where the code is not tied to the airframe itself.
Issues with either the ICAO Mode S address and the Flight ID are common, and operators should ensure they comply.
Revision for Applications to Operate in RVSM Airspace

Effective January 22, 2019 the FAA revised its requirements for applications to operate in RVSM airspace. The new rule eliminates the requirement for operators to apply for an RVSM authorization when their aircraft are equipped with qualified ADS–B Out systems.
The new rule recognizes the enhancements in aircraft monitoring resulting from the use of ADS–B Out systems. (Reference: FAA–2017–0782; Amendment. No. 91–354.)
Having discussed the need-to-know elements of ADS-B above, next time we will address the equipage elements of ADS-B Out, including its installation in the aircraft and how operators should manage the upgrade. Stay tuned…

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