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Automatic Dependent Surveillance Broadcast (ADS-B)

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Category: Air Ground Communication Air Ground Communication
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Automatic Dependent Surveillance Broadcast


ADS-B is a Surveillance technique that relies on aircraft or airport vehicles broadcasting their identity, position and other information derived from on board systems (GNSS etc.). This signal can be captured for surveillance purposes on the ground (ADS-B Out) or on board other aircraft (ADS-B In). The latter will enable airborne traffic situational awareness (ATSAW), spacing, separation and self-separation applications.

ADS-B is automatic because no external stimulus is required; it is dependent because it relies on on-board systems to provide surveillance information to other parties. Finally, the data is broadcast, the originating source has no knowledge of who receives the data and there is no interrogation or two-way contract.

ADS-B is a key enabler of the future ATM Network, contributing to the achievement of the Single European Sky (SES) performance objectives, including safety, capacity, efficiency and environmental sustainability.

The vision for ground Surveillance foresees in en-route and terminal areas the combination of ADS-B with independent Surveillance, the latter provided by MSSR or Mode S or Wide Area Multilateration (WAM). It is noted that WAM system receivers generally include ADS-B functionality.

Airborne ADS-B systems will be available as enablers of the new separation modes. These airborne applications will require changes in the avionics to process and display the air situation picture to the pilot.

For airports, a locally optimised mix of the available technologies, i.e. airport Multilateration, Surface Movement Radars and ADS-B, will enable A-SMGCS systems and integrated airport operations. This could include the availability of Surveillance information on a moving map, using an HMI in the cockpit and in surface vehicles.

The introduction of ADS-B in the Surveillance infrastructure provides important features which can be exploited by the ATM Network:

  • 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 integral part of the Network
    • Surveillance data provided directly from on-board systems
  • High performance
  • Improved safety
  • Increased capacity
  • Cost-efficiency
    • Reduced cost of the Surveillance infrastructure (ADS-B is cheaper than radar)
    • More efficient flight profiles (in areas where previously surveillance was not cost-effective)
    • Fuel savings etc.
  • Environmental sustainability (CO2 reduction)
  • Reduced RF pollution (leading to an increased viability of the 1090 MHz datalink)
  • Global Interoperability
  • Foundation for future SESAR ATC applications (spacing, separation, self-separation)

ADS-B is currently being implemented in Europe and other areas worldwide (Asia, Australia, Canada, USA).

Global interoperability is ensured at application level and system level. The standards for ADS-B are being jointly developed by EUROCAE and RTCA. Relevant ICAO documentation is also produced.

The 1090 MHz Mode S Extended Squitter technology is used worldwide to ensure global interoperability. At local or regional level other datalink technologies could be used (such as Universal Access Tranceiver UAT in the USA or possibly VDL Mode 4).

The Single European Sky Surveillance Performance and Interoperability Implementing Rule (SPI IR) was approved in July 2011 and will be published in the Official Journal of the European Union in the course of 2011. The SPI IR will require all aircraft operating IFR/GAT in Europe will have to be compliant with Mode S Elementary Surveillance, whilst aircraft with maximum Take-Off Mass greater than 5700kg or maximum cruising True Air Speed greater than 250kts463 km/h
128.5 m/s
will have to be compliant with Mode S Enhanced Surveillance and “ADS-B out”. The mandate dates are January 2015 for forward fit and December 2017 for retrofit, with further provisions for State aircraft.

The SPI IR will accelerate both the aircraft ADS-B equipage and the ADS-B ground system deployment.

Initial ADS-B Applications

The ADS-B standardisation work is now completed for the initial ADS-B applications, namely all “ADS-B out” and ATSAW applications. It has delivered the Safety, Performance and Interoperability Requirements for:

  • ADS-B in Non Radar Airspace (ADS-B NRA)
  • ADS-B in Radar Airspace (ADS-B RAD)
  • ADS-B for Airport Surface Surveillance (ADS-B APT)
  • ATSAW In-Trail Procedure in oceanic airspace (ATSAW ITP)
  • ATSAW Visual Separation in Approach (ATSAW VSA)
  • ATSAW during Flight Operations (ATSAW AIRB)
  • ATSAW on the Airport Surface (ATSAW SURF)

In addition, the standardisation of the first spacing application has also been completed with the delivery of the Safety, Performance and Interoperability Requirements for:

  • Flight Deck Interval Management (ASPA-FIM)

Furthermore, work on the future ADS-B applications (spacing, separation and self-separation) is ongoing or planned by SESAR (Europe) and NEXTGEN (USA). The standards of future applications will be developed also by EUROCAE/RTCA joint work.

Aircraft Equipment

The “ADS-B Out” capability on board is enabled by transponders interfaced with the relevant avionics systems (such as GNSS, pressure altimeters etc.). Many aircraft have ADS-B Extended Squitter capability already available packaged with the Mode S Enhanced Surveillance installations already mandated for core-European airspace.

The “ADS-B In” capability requires a receiver, a processing system (traffic computer) and an HMI unit (often called Cockpit Display of Traffic Information - CDTI). The “ADS-B in” system could be integrated in the Forward Field of view or be in the form of the so-called Electronic Flight Bag (EFB).

The operational use of ADS-B requires certification and operational approval by the regulatory authorities.

Ground Equipment

The ADS-B data transmitted by the aircraft or airport vehicles are received by the ADS-B Ground stations.

In most of the cases, the output of the ADS-B Ground stations will be sent to Surveillance Data Processing and Distribution systems where they are fused with inputs from other possible Surveillance sensors (e.g radars, Multilateration) to create a Traffic Situation Picture for the Users.

ADS-B Data

The ADS-B data transmitted are defined in the relevant standards and certification documents (e.g. EASA AMC 20-24 for ADS-B in Non-Radar Airspace or CS-ACNS for “ADS-B out”). They include (amongst others) the following:

  • Aircraft horizontal position (latitude/longitude)
  • Aircraft barometric altitude (will be the same as for the SSR)
  • Quality indicators
  • Aircraft identification:
    • Unique 24-bit aircraft address
    • Aircraft identification
    • Mode A code (in the case of CS ACNS for “ADS-B Out”)
  • Emergency status
  • SPI (special position indicator) when selected

ADS-B Deployment

ADS-B Deployment in Europe

The deployment of initial ADS-B applications and WAM in Europe is co-ordinated by the EUROCONTROL CASCADE Programme. The ADS-B deployment in Europe is now ongoing in conjunction with WAM deployment and follows three paths:

  • Voluntary implementation of ADS-B sole means or with WAM in local Non Radar airspace of Europe (“pocket areas”), using currently existing (certified) equipment, from 2011 onwards
  • Deployment of WAM and ADS-B systems in Radar Airspace, in which WAM is used first, followed by the use of “ADS-B out”. The latter requires enhanced avionics and is, therefore, driven by the Implementing Rule (SPI IR).
  • Voluntary implementation of Airborne Traffic Situational Awareness (ATSAW) applications in oceanic areas, starting in the course of 2011.

WAM is already implemented in Armenia, Austria, Czech Republic, Spain and UK (N. Sea). It is noted that due to the integrated ADS-B functionality of WAM systems, the deployment of WAM by ANSPs will enable ADS-B ground station technical functionality.

In addition, WAM and ADS-B deployment is currently ongoing in Germany (WAM by 2012 in Frankfurt, expected to be followed by Munich and Berlin), Portugal (Azores by 2011, WAM/ADS-B), Latvia (WAM by 2011), the Netherlands (N. Sea by 2011, WAM/ADS-B) and Romania (WAM by 2011).

Other ANSPs have implementation plans with target dates of deployment from 2012-13 onwards: Bulgaria (WAM/ADS-B) Cyprus (ADS-B), France (overseas territory, ADS-B), Iceland (ADS-B), Italy (ADS-B), Greece (WAM/ADS-B), Norway (N. Sea, ADS-B), Portugal (WAM/ADS-B), Sweden (WAM/ADS-B) and UK (Scotland, WAM). In addition, UK NATS has included ADS-B with WAM in their Strategy (target date for ADS-B implementation is from 2018).

Airlines have started their certification and operational approval process for ADS-B. Several hundreds of aircraft are already certified for ADS-B operations in Non-Radar Airspace. More than 500 aircraft have received their EASA airworthiness certification, in the context of the CASCADE ADS-B Pioneer airline project.

Implementation based on the SPI Implementing Rule (mandate) covers SSR, Mode S and ADS-B Extended Squitter. This will make airborne installations “future proof”, i.e. supporting all surveillance techniques currently used or planned to be used. The rulemaking will require full compliance with all “ADS-B out” requirements in support of the initial Ground and Airborne Surveillance applications.

In terms of the future ADS-B avionics requirements, the SPI IR will necessitate a transponder upgrade to ED102A/DO260B and a direct GNSS receiver-transponder wiring.

The first aircraft with certified avionics, compliant with the European Commission Implementing Rule, will be available already from late 2011 onwards. The number of aircraft which will be compliant with the Rule will be increased in the next years driven by the mandate dates.

In parallel, “ADS-B in” will be introduced operationally on a voluntary basis from 2011 onwards (in the context of the CASCADE ATSAW Pioneer project) by the ATSAW pioneer airlines (Swiss International Airlines, Virgin Atlantic, Delta, US Airways and British Airways) supported by ISAVIA and UK NATS, driven by the benefits to be acquired. The first applications are the ATSAW during Flight Operations (ATSAW AIRB) and the ATSAW In-Trail Procedure (ITP) over N. Atlantic (Shanwick FIR and Reykjavik FIR). ITP trials are also foreseen in Pacific through a co-operation of FAA with United Airlines.

The issue of establishment and use of a list of aircraft that are approved to receive an operational ADS-B service within Europe will be investigated. The work will actively explore synergies with similar activities worldwide and any needs/opportunities for wider co-ordination.

ADS-B Deployment Outside Europe

In December 2009, Air Services Australia commissioned the ADS-B Upper Airspace Project (UAP), providing ADS-B coverage across the whole continent. Since then, 29 duplicated ADS-B sites have been added, plus a further 14 sites in Tasmania which are associated with the now fully operational Tasman wide area multilateration (WAM) system. Aircraft avionics are being assessed and approved for operational use. ADS-B data from non-approved aircraft is filtered out at each site. Currently, over 1200 airframes are approved and receiving the operational and safety benefits of ADS-B services in Australia. Australia has also made ADS-B equipage mandatory for all aircraft (domestic and foreign) operating at or above FL290 as from December 2013.

Automatic Dependent Surveillance-Broadcast (ADS-B) brought surveillance coverage for the first time to 250,000 square nautical miles of airspace over Hudson Bay in Northern Canada. The majority of the flights in this airspace link Europe and North America, while many transit to Asia, including those using polar tracks. Service commenced in January 2009. Controllers currently use ADS-B tactically by applying reduced separation between equipped aircraft on an opportunity basis. This means each aircraft will have the appropriate protected airspace around it applied based on its capability. The subsequent step for NAV CANADA is to segregate airspace vertically, ADS-B deployment is also ongoing by the US FAA, enabled by two datalinks, i.e. 1090 MHz ES and UAT. The U.S. ADS-B Final Rule will require aircraft that operate above FL180 to broadcast on the 1090ES link The FAA is not prescribing the choice of link for aircraft flying below FL180; both links are supported and operators are free to choose whichever link meets their needs. Aircraft broadcasts go to other aircraft and to ground radio stations, where the information is processed and displayed to controllers. Where available, information from FAA radars is combined with ADS-B data to support ATC separation services. In May 2010, the U.S. ADS-B Final Rule was published, requiring ADS-B Out equipage in U.S. airspace where a transponder is currently required, with compliance by 1 Jan 2020.

ADS-B deployment is also being undertaken in other regions worldwide (such as Indonesia).

Further Reading

  • Safety Performance and Interoperability Requirements for ADS-B in Non Radar Airspace (ADS-B NRA), EUROCAE ED-126 / RTCA DO-303, 2006
  • Safety Performance and Interoperability Requirements for ADS-B in Radar Airspace (ADS-B RAD), EUROCAE ED-161 / RTCA DO-318, 2009
  • Safety Performance and Interoperability Requirements for ADS-B for Airport Surface Surveillance (ADS-B APT), EUROCAE ED-163 / DO-321, 2010
  • Safety Performance and Interoperability Requirements for ATSAW In-Trail procedure in oceanic airspace (ATSAW ITP), EUROCAE ED-159 / RTCA DO-312, 2008
  • Safety Performance and Interoperability Requirements for ATSAW Visual Separation in Approach (ATSAW VSA), EUROCAE ED-160 / RTCA DO-314, 2008
  • Safety Performance and Interoperability Requirements for ATSAW during flight operations (ATSAW AIRB), EUROCAE ED-164 / DO-319, 2010
  • Safety Performance and Interoperability Requirements for ATSAW on the Airport Surface (ATSAW SURF), EUROCAE ED-165 / RTCA DO-322, 2010
  • Safety Performance and Interoperability Requirements for Flight Deck Interval Management (ASPA-FIM), EUROCAE ED-195, 2011
  • Acceptable Means of Compliance for ADS-B NRA (AMC 20-24), EASA, 2008
  • Technical Specification for the ADS-B Ground Station, ED-129, EUROCAE, 2010
  • Implementing Rule on Surveillance Performance and Interoperability Requirements (SPI-IR), 2011
  • Minimum Operational Performance Standards for 1090 MHz ADS-B and TIS-B, EUROCAE ED-102A / RTCA DO260B, 2009
  • Preliminary Safety Case for ADS-B NRA, EUROCONTROL, 2008
  • Preliminary Safety Case for ADS-B RAD, EUROCONTROL, 2011
  • ICAO Doc 9871 ‘Technical Provisions for Mode S Services and Extended Squitter’ First Edition 2008
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