About ADS-B:

Standards for Automatic Dependent Surveillance - Broadcast (ADS-B) are currently being developed jointly by the FAA and industry through RTCA Inc. Special Committee 186 (SC-186). The concept is simple: Aircraft (or other vehicles or obstacles) will broadcast a message on a regular basis, which includes their position (such as latitude, longitude and altitude), velocity, and possibly other information. Other aircraft or systems can receive this information for use in a wide variety of applications. Current surveillance systems must measure vehicle position, while ADS-B based systems will simply receive accurate position reports broadcast by the vehicles.

Discussions of the use of ADS-B in the national (or international) airspace often involve the words "epoch" and "paradigm", which should give some idea of the revolutionary changes to the airspace that are envisioned using this system.  

As an simplified example, consider an air-traffic control secondary radar.  The radar measures the range and bearing of an aircraft.  The bearing is measured by the position of the rotating radar antenna when it receives a reply to its interrogation from the aircraft, and the range by the time it takes for the radar to receive the reply.  The beam of the antenna gets wider as the aircraft get farther from the antenna, thus making the measured position information less accurate.  An ADS-B based system, on the other hand, would listen for position reports broadcast by the aircraft.  These position reports are based on accurate navigation systems, such as satellite navigation systems (e.g. GPS).  The accuracy of the system is now determined by the accuracy of the navigation system, not measurement errors.  The accuracy is unaffected by the range to the aircraft.  With the radar, detecting aircraft velocity changes requires tracking the received data.  Changes can only be detected over a period of several position updates.  With ADS-B, velocity changes are broadcast almost instantaneously as part of the State Vector report.  These improvements in surveillance accuracy can be used to support a wide variety of applications and increase airport and airspace capacity while also improving safety.     

ADS-B Group Support:

The Research and Technology Division provides a wide variety of support to ADS-B and SF-21 programs.  Personnel are active participants in many of the RTCA, Inc. Special Committees and Working Group meetings, providing technical expertise to help define system standards and application concepts and requirements.  Personnel have significantly contributed to the ADS-B MASPS, MOPS and International SARPs documents for both the 1090 MHz ADS-B and UAT ADS-B data links, STP and CDTI requirements, and the concept of operations for Airborne Conflict Management.  Personnel are also supporting the Airborne Surveillance Applications (ASA) and TIS-B standards development activity.

The Division personnel provide data collection and analysis to support ADS-B and ADS-B applications.  The Division personnel perform flight testing and simulation work to test and evaluate commercially manufactured ADS-B and CDTI equipment.  Flight tests have been conducted to analyze various ADS-B data links in low and high-density environments.  The Division continues to support the SF-21/CAA operational evaluation of CDTI equipment and procedures.  The Division personnel are providing support for SF-21/Capstone project work to improve safety and operations in the Alaska region.  The Division also supports runway incursion projects as part of its SF-21 activities.

About RTCA SC-186:

Perhaps the best evidence of the sweeping changes and improvements envisioned to be enabled by ADS-B is the complex structure of the RTCA Special Committee for ADS-B, SC-186.  The structure and focus of the Special Committee changes as applications are defined, and regulatory challenges are addressed.  Currently, RTCA SC-186 has six working groups, with some working groups supported by a number of sub-groups, and some of the sub-groups divided into even more subgroups. 

RTCA SC-186 ADS-B Special Committee Structure, Descriptions and Contacts: 

Special Committee 186 (ADS-B) 

Co-chairs:  Rocky Stone (United Airlines) and Vincent Capezzuto (FAA ADS-B Program Office)

RTCA SC-186 is responsible for the defining ADS-B and other airborne surveillance system standards.  This charter includes developing system standards for ADS-B, ASA, and TIS-B, and developing requirements for the actual ADS-B broadcast data links, and defining and developing requirements for applications using these technologies.  The plenary sessions review and approve all documents produced by the six working groups. 

Working Group 1 – Operations and Implementation Working Group 

Co-chairs:  Randy Bone (MITRE) and Brian Townsend (US Airways)

This Working Group is responsible for developing application descriptions and providing the operational data required to prepare application requirements documents, as well as to work toward implementation of these applications.  WG-1 worked with WG-4 during development of the ASA MASPS and contributed the operational concepts and descriptions for all of the surveillance applications contained in the document.  WG-1 defines new applications for future revisions to the ASAS MOPS.  In addition, WG-1 members are supporting the two other SC-186 working groups: The RFG, which is working to harmonize applications for worldwide compatibility, and the CDTI subgroup of WG-4B, which developed the CDTI standards section for the ASAS MOPS.

Working Group 2 – Traffic Information Services – Broadcast  (TIS-B)

Co-chairs:  Ken Staub (Trios Assoc.)

This Working Group is tasked with developing and maintaining the standards for TIS-B.  Revision B of the TIS-B Minimum Aviation System Performance Specifications (MASPS) was published by RTCA, Inc. as DO-286B in October 2007.  This update to the TIS-B system standards clarified the ADS-B Rebroadcast (ADS-R) function as a means to receive ADS-B Messages at a Ground Station via one ADS-B link (e.g., 1090ES) and broadcast the data on another ADS-B link (e.g., UAT) to enable ADS-B aircraft using different ADS-B data links (1090MHz, UAT, or VDL-4) to see each other. 

Working Group 3 - ADS-B 1090 MHz Extended Squitter MOPS

Co-chairs:  Thomas Pagano (FAA Technical Center), Bob Semar (United Airlines)

This Working Group is responsible for the Minimum Operational Performance Standards (MOPS) for ADS-B systems using the 1090 MHz Extended Squitter (1090ES) data link.   Revision B of the 1090ES MOPS was approved and published by RTCA, Inc. in December 2009 as DO-260B.  The changes that went in to DO-260B were coordinated and developed jointly with EUROCAE Working Group 51, Subgroup 1, which was published by EUROCAE in December 2009 as ED-102A.  Transmitting and receiving subsystems compliant with DO-260B/ED-102A will use an ADS-B Version Number equal to two (2).  In DO-260B/ED-102A the integrity level of the ADS-B source has been redefined and changes made to the definitions of the NIC and NAC parameters.  Version 2 1090ES formats now include the transmission of selected altitude, selected heading, and barometric pressure setting in the target state and status messages. Version 2 1090ES formats also include the transmission of the Mode A (4096) code and the Register 30₁₆ content of the TCAS/ACAS resolution advisory data.  This working group works closely with the FAA to publish and maintain revisions to Technical Standard Order, TSO C166.

Working Group 4 - Aircraft Separation Assistance Systems

Co-chairs:  Don Walker (FAA), Tom Eich (L-3/ACSS) and Sethu Rathinam (Rockwell Collins)

This Working Group is tasked with developing and maintaining the requirements documents for ADS-B applications.  The Working Group completed work on the ASA MASPS with its publication of DO-289 in December 2003, which defined the end-to-end system performance standards for Airborne Surveillance Applications.  A revised version of the ASA MASPS is expected to be produced through WG-6 with the cooperation of EUROCAE WG-51, while the work focus of this Working Group has currently shifted to supporting the development and maintenance of the ASAS MOPS (DO-317), which specifically defines the operational requirements of a Aircraft Separation Assistance Systems. 

Working Group 5 - ADS-B UAT MOPS

Co-chairs: George Ligler (PMEI), Richard Jennings (FAA)

This Working Group is responsible for the Minimum Operational Performance Standards (MOPS) for ADS-B systems using the Universal Access Transceiver (UAT) data link.  The initial UAT MOPS was approved and published by RTCA, Inc. in June 2002 as DO-282.   Revision A of the UAT MOPS was approved and published by RTCA on 29 July 2004 as DO-282A.  Revision B of the UAT MOPS was approved and published by RTCA in December 2009 as DO-282B.  Transmitting and receiving subsystems compliant with DO-282B will use an ADS-B Version Number equal to two (2).  In DO-282B the integrity level of the ADS-B source has been redefined and changes made to the definitions of the NIC and NAC parameters.  Version 2 UAT formats now include the transmission of selected altitude, selected heading, and barometric pressure setting in the target state element.  This working group works closely with the FAA to publish and maintain revisions to Technical Standard Order, TSO C154. 

Working Group 6 - ADS-B MASPS

Co-chairs: J. Stuart Searight (FAA) and Dean Miller (Boeing)

This working group is responsible for defining the system standards of ADS-B systems.  These Minimum Avionic System Performance Standards (MASPS) are published in RTCA document DO-242.  Revision A of the ADS-B MASPS was published by RTCA as DO-242A.  WG-6 is coordinating with Eurocontrol and EUROCAE in an attempt to have the next revision of the MASPS be a joint US/European document.  Because of the nature of the need to revised and publish the ADS-B MOPS updates prior to the end of 2009, WG-6 worked closely with WG-3 and WG-5 to maintain a set of proposed revisions to DO-242A, which will be the basis for Revision B of the ADS-B MASPS as scheduled by the SC-186 Plenary. 

Requirements Focus Group (RFG) Working Group

Co-chairs: J. Stuart Searight (FAA) and Jorg Steinleitner (Eurocontrol)

The ADS-B Requirements Focus Group (RFG) is a international group consisting of members from the FAA, RTCA, Eurocontrol, EUROCAE, and other interested parties.  The primary object of the RFG is to internationally harmonize operational concepts and minimum safety and performance requirements for ground surveillance (GS) and aircraft surveillance (AS) applications.  These GS and AS applications are originally defined in Package 1 which lists initial applications to be implemented based on the Principles of Operation for Airborne Separation Assistance Systems (PO-ASAS).  

Documents Available through RTCA, Inc.:

Documents completed and approved by RTCA SC-186: