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:  Jim Walton (UPS) and Randy Bone (MITRE)

This 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, 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 RTCA and Eurocae Requirements Focus Group (RFG), which is working to harmonize applications for worldwide compatibility, and the CDTI subgroup of WG-4B, which is developing the CDTI standards section for the ASAS MOPS.

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

Co-chairs:  Ken Staub (Trios Assoc.), Andy Zeitlin (MITRE)

This working group is tasked with developing and maintaining standards for TIS-B.  Revision A of the TIS-B Minimum Aviation System Performance Specifications (MASPS) was published by RTCA, Inc. as DO-286A on April 7, 2005.  This update to the TIS-B system standards includes a means to uplink ADS-B-like information about non-ADS-B equipped aircraft and to serve as a multi-link gateway 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 data link.   Revision A of the 1090 MHz MOPS was approved and published by RTCA, Inc. in April 2003 as DO-260A.  Revision A included many changes from the original MOPS including harmonization with revision A of the ADS-B MASPS (DO-242A),  and suggested implementations of enhanced reception techniques, and TIS-B message definitions and management requirements for the 1090 MHz data link.  This working group works closely with the FAA to publish and maintain revisions to Technical Standard Order, TSO C166.  This working group has also published change documents for both DO-260 and DO-260A.

Working Group 4 - Aircraft Separation Assistance Systems

Co-chairs:  Jonathan Hammer (MITRE), Steve Koczo (Rockwell Collins)

This working group is tasked with developing requirements documents for ADS-B applications.  The group completed work on the ASA MASPS with its publication in December 2003, which defined the end-to-end system performance standards for an Airborne Surveillance Applications.  While a revised version of the ASA MASPS is expected to be produced in concert with EUROCAE WG-51, the work focus of this group has currently shifted to supporting the development of the ASAS MOPS, which will specifically define the operational requirements of a Aircraft Separation Assistance Systems.  Because of this shift in activity and expansion of interested parties, the group has officially been split into two different groups:

WG4A, the ASA MASPS working group.  This group is currently dormant.

WG4B, the ASAS MOPS working group.  This group consists of three subgroups, corresponding to the three major ASAS subsystems: Surveillance Transmit Processing (STP), Aircraft Surveillance Application Processing (ASAP), and the CDTI display, which was realigned from WG-1 to streamline the work.  This working group published the STP MOPS as RTCA/DO-302 on 13 December 2006.

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, Inc. on 29 July 2004 as DO-282A.  Revision A reflects additional operational experience with UAT, lessons learned in certification of UAT avionics equipment, and further inputs from the International aviation community during the development of ICAO SARPs for UAT, which are expected to become effective in November 2007.

Working Group 6 - ADS-B MASPS

Co-chairs: Tom Foster (Retired consultant), J. Stuart Searight (FAA Technical Center)

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 approved by the SC-186 plenary in April, 2002 and was published by RTCA, Inc. as DO-242A.  WG6 is coordinating with Eurocontrol and EUROCAE in an attempt to have the next revision of the MASPS be a joint US/European document.

Documents Available through RTCA, Inc.:

Documents completed and approved by RTCA SC-186:

ADS-B MASPS, Revision A: published June 25, 2002 as RTCA DO-242A
Change 1 to DO-242A, published December 13, 2006

Application Descriptions for Initial Cockpit Display of Traffic Information (CDTI) Applications: RTCA DO-259

1090 MHz ADS-B/TIS-B MOPS, Revision A:  published April 10, 2003 as RTCA DO-260A
Change 1 to DO-260,   published June 27, 2006
Change 1 to DO-260A, published June 27, 2006
Change 2 to DO-260A, published December 13, 2006
(Also see FAA TSO C166A, published December 21, 2006)

Concept of Operations for Airborne Conflict Management: RTCA DO-263

UAT MOPS, Revision A: published July 29, 2004 as RTCA DO-282A
Change 1 to DO-282A, published December 13, 2006
(Also see FAA TSO C154B, published December 21, 2006)

TIS-B MASPS, Revision A: published April 7, 2005 as RTCA DO-286A

Airborne Surveillance Applications (ASA) MASPS: published December 9, 2003 as RTCA DO-289
Change 1 to DO-289, published December 13, 2006

Surveillance Transmit Processing (STP) MOPS, published December 13, 2006 as RTCA DO-302

Documents currently under SC-186 development:

Aircraft Separation Assistance Systems (ASAS) MOPS: WG-4B
(will contain sections on CDTI and ASSAP)

TIS-B MASPS, Revision B: WG-2