[Federal Register: May 28, 2010 (Volume 75, Number 103)]
[Rules and Regulations]
[Page 30159-30195]
[DOCID:fr28my10-16]

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Part III

Department of Transportation

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Federal Aviation Administration

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14 CFR Part 91

Automatic Dependent Surveillance--Broadcast (ADS-B) Out Performance
Requirements To Support Air Traffic Control (ATC) Service; Final Rule

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 91

[Docket No. FAA-2007-29305; Amdt. No. 91-314]
RIN 2120-AI92

Automatic Dependent Surveillance--Broadcast (ADS-B) Out
Performance Requirements To Support Air Traffic Control (ATC) Service

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: This final rule amends FAA regulations by adding equipage
requirements and performance standards for Automatic Dependent
Surveillance--Broadcast (ADS-B) Out avionics on aircraft operating in
Classes A, B, and C airspace, as well as certain other specified
classes of airspace within the U.S. National Airspace System (NAS).
ADS-B Out broadcasts information about an aircraft through an onboard
transmitter to a ground receiver. Use of ADS-B Out will move air
traffic control from a radar-based system to a satellite-derived
aircraft location system. This action facilitates the use of ADS-B for
aircraft surveillance by FAA and Department of Defense (DOD) air
traffic controllers to safely and efficiently accommodate aircraft
operations and the expected increase in demand for air transportation.
This rule also provides aircraft operators with a platform for
additional flight applications and services.

DATES: This final rule is effective on August 11, 2010. The compliance
date for this final rule is January 1, 2020. Affected parties, however,
do not have to comply with the information collection requirement in
Sec.  91.225 until the FAA publishes in the Federal Register the
control number assigned by the Office of Management and Budget (OMB)
for this information collection requirement. Publication of the control
number notifies the public that OMB has approved this information
collection requirement under the Paperwork Reduction Act of 1995. The
incorporation by reference of certain publications listed in the rule
is approved by the Director of the Federal Register as of August 11,
2010.

FOR FURTHER INFORMATION CONTACT: For technical questions concerning
this final rule, contact Vincent Capezzuto, Surveillance and Broadcast
Services, AJE-6, Air Traffic Organization, Federal Aviation
Administration, 800 Independence Avenue, SW., Washington, DC 20591;
telephone<PHONE_NUMBER>; e-mail<EMAIL_ADDRESS>    For legal questions concerning this final rule, contact Lorelei
Peter, Office of the Chief Counsel, AGC-220, Federal Aviation
Administration, 800 Independence Avenue, SW., Washington, DC 20591;
telephone<PHONE_NUMBER>; e-mail<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Authority for This Rulemaking

    The FAA's authority to issue rules on aviation safety is found in
Title 49 of the United States Code (49 U.S.C.). Subtitle I, Section
106, describes the authority of the FAA Administrator. Subtitle VII,
Aviation Programs, describes in more detail the scope of the agency's
authority.
    This rulemaking is promulgated under the authority described in
Subtitle VII, Part A, Subpart I, Section 40103, Sovereignty and use of
airspace, and Subpart III, Section 44701, General requirements. Under
section 40103, the FAA is charged with prescribing regulations on the
flight of aircraft (including regulations on safe altitudes) for
navigating, protecting, and identifying aircraft, and the efficient use
of the navigable airspace. Under section 44701, the FAA is charged with
promoting safe flight of civil aircraft in air commerce by prescribing
regulations for practices, methods, and procedures the Administrator
finds necessary for safety in air commerce.
    This regulation is within the scope of sections 40103 and 44701
because it prescribes aircraft performance requirements to meet
advanced surveillance needs to accommodate increases in NAS operations.
As more aircraft operate within the U.S. airspace, improved
surveillance performance is necessary to continue to balance the growth
in air transportation with the agency's mandate for a safe and
efficient air transportation system.

Guide to Terms and Acronyms Frequently Used in This Document

ACI-NA--Airports Council International-North America
ACSS--Aviation Communication and Surveillance Systems
ADIZ--Air Defense Identification Zone
ADS-B--Automatic Dependent Surveillance-Broadcast
ADS-C--Automatic Dependent Surveillance-Contract
ADS-R--Automatic Dependent Surveillance-Rebroadcast
AGL--Above Ground Level
AIA--Aerospace Industries Association of America
ALPA--Air Line Pilots Association, International
AOPA--Aircraft Owners and Pilots Association
ARC--Aviation Rulemaking Committee
ASA--Aircraft Surveillance Applications
ASAS--Aircraft Surveillance Applications System
ASDE-X--Airport Surface Detection Equipment, Model X
ASSA--Airport Surface Situational Awareness
ATC--Air Traffic Control
CAA--Cargo Airline Association
CDTI--Cockpit Display of Traffic Information
CNS--Communication, Navigation, and Surveillance
EAA--Experimental Aircraft Association
ELT--Emergency Locator Transmitter
ES--Extended Squitter
EUROCAE--European Organisation for Civil Aviation Equipment
EUROCONTROL--European Organisation for the Safety of Air Navigation
FAROA--Final Approach Runway Occupancy Awareness
FedEx--Federal Express
FIS-B--Flight Information Service-Broadcast
FL--Flight Level
GA--General Aviation
GAMA--General Aviation Manufacturers Association
GNSS--Global Navigation Satellite System
GPS--Global Positioning System
HAI--Helicopter Association International
IATA--International Air Transport Association
ICAO--International Civil Aviation Organization
MHz--Megahertz
MOPS--Minimum Operational Performance Standards
MSL--Mean Sea Level
NACP--Navigation Accuracy Category For Position
NACV--Navigation Accuracy Category for Velocity
NAS--National Airspace System
NBAA--National Business Aviation Association
NextGen--Next Generation Air Transportation System
NIC--Navigation Integrity Category
NM--Nautical Mile
NPRM--Notice of Proposed Rulemaking
NTSB--National Transportation Safety Board
OPD--Optimized Profile Descent
OMB--Office of Management and Budget
RAA--Regional Airline Association
RAIM--Receiver Autonomous Integrity Monitoring
RFA--Regulatory Flexibility Act
RNP--Required Navigation Performance
SANDIA--Sandia National Laboratories
SARPs--Standards and Recommended Practices
SCAP--Security Certification and Accreditation Procedures
SDA--System Design Assurance
SIL--Source Integrity Level
SSR--Secondary Surveillance Radar
TCAS--Traffic Alert and Collision and Avoidance System
TIS-B--Traffic Information Service-Broadcast
TMA--Traffic Management Advisor

TSO--Technical Standard Order
UAT--Universal Access Transceiver
UPS--United Parcel Service
URET--User Request Evaluation Tool
VFR--Visual Flight Rules
WAAS--Wide Area Augmentation System

Table of Contents

I. Background
    A. Notice of Proposed Rulemaking
    B. ADS-B Aviation Rulemaking Committee
    C. Summary of the Final Rule
    1. Airspace
    2. Datalink Requirements
    3. System Performance Requirements
    4. Antenna Diversity and Transmit Power Requirements
    5. Latency of the ADS-B Out Message Elements
    6. Conforming Amendments and Editorial Changes
    D. Differences Between the Proposed Rule and The Final Rule
    E. Separation Standards Working Group
II. Discussion of the Final Rule
    A. Airspace
    1. 2,500 Feet Above Ground Level Exclusion in Class E Airspace
    2. Airspace for Which ADS-B is Required
    3. Requests for Deviations From ADS-B Out Requirements
    B. Dual-Link Strategy
    1. Altitude To Require the 1090 MHz ES Datalink
    2. Automatic Dependent Surveillance-Rebroadcast (ADS-R)
    3. 1090 MHz Frequency Congestion
    C. Performance Requirements--System
    1. Performance Requirements Tailored to Operator, Airspace, or
Procedure
    2. Navigation Accuracy Category for Position (NACP)
    3. Navigation Accuracy Category for Velocity (NACV)
    4. Navigation Integrity Category (NIC)
    5. Surveillance Integrity Level
    6. Source Integrity Level (SIL) and System Design Assurance
(SDA)
    7. Secondary Position Sources
    D. Performance Requirements--Antenna Diversity
    E. Performance Requirements--Transmit Power
    F. Performance Requirements--Total and Uncompensated Latency
    G. Performance Requirements--Time To Indicate Accuracy and
Integrity Changes
    H. Performance Requirements--Availability
    1. Preflight Determination of Availability
    2. System Availability
    I. Performance Requirements--Continuity
    J. Performance Requirements--Traffic Information Service--
Broadcast Integrity (TIS-B)
    K. Broadcast Message Elements
    1. NACP/NACV/NIC/SDA/SIL
    2. Receiving ATC Services
    3. Length and Width of the Aircraft
    4. Indication of the Aircraft's Barometric Pressure Altitude
    5. Indication of the Aircraft's Velocity
    6. Indication if Traffic Alert and Collision Avoidance System II
or Airborne Collision Avoidance System is Installed and Operating in
a Mode That May Generate Resolution Advisory Alerts
    7. For Aircraft With an Operable Traffic Alert and Collision
Avoidance System II or Airborne Collision Avoidance System,
Indication If a Resolution Advisory Is in Progress
    8. Indication of the Mode 3/A Transponder Code Specified by ATC
(Requires Flightcrew Entry)
    9. Indication of the Aircraft's Call Sign That Is Submitted on
the Flight Plan, or the Aircraft's Registration Number (Aircraft
Call Sign Requires Flight Crew Entry)
    10. Indication if the Flight Crew Has Identified an Emergency,
Radio Communication Failure, or Unlawful Interference (Requires
Flightcrew Entry)
    11. Indication of the Aircraft's ``IDENT'' to ATC (Requires
Flightcrew Entry)
    12. Indication of the Emitter Category
    13. Indication Whether an ADS-B in Capability Is Installed
    14. Indication of the Aircraft's Geometric Altitude
    L. Ability To Turn Off ADS-B Out Transmissions
    M. Existing Equipment Requirements
    1. Transponder Requirement
    2. Emergency Locator Transmitter Requirement
    N. Program Implementation
    1. Timeline
    2. Financial and Operational Incentives
    3. Decommissioning Traffic Information Service-Broadcast (TIS-B)
    O. Safety
    P. Efficiency
    1. Improved Position Reporting
    2. Optimized Profile Descents (OPDs)
    3. Reduced Aircraft Separation
    4. Expanded Surveillance Coverage
    Q. ADS-B In
    R. ADS-B In Applications
    1. Surface Situational Awareness With Indications and Alerting
    2. In-Trail Procedures
    3. Interval Management
    4. Airport Surface Situational Awareness and Final Approach
Runway Occupancy Awareness
    S. International Harmonization
    T. Backup ATC Surveillance
    U. Privacy
    V. Security
    W. Alternatives to ADS-B
    X. ADS-B Equipment Scheduled Maintenance
    Y. Specific Design Parameters
    Z. Economic Issues
    1. ADS-B Out Equipage Cost
    2. FAA Cost Savings With ADS-B Out Compared To Radar
    3. Business Case for ADS-B Out and In
    4. Improved En Route Conflict Probe Benefit Performance
    5. Capacity Enhancements, Airspace Efficiency, and Fuel Savings
Benefits
    6. Deriving Benefits From Capstone Implementation in Alaska
    7. Regional Airline Benefits
    8. General Aviation: High Equipage Costs With Little Benefit
    AA. Revisions to Other Regulations
III. Regulatory Notices and Analyses
    A. Paperwork Reduction Act
    B. International Compatibility
    C. Regulatory Impact Analysis, Regulatory Flexibility
Determination, International Trade Impact Analysis, and Unfunded
Mandates Assessment
VI. Executive Order 13132, Federalism
VII. Regulations Affecting Intrastate Aviation in Alaska
VIII. Environmental Analysis
IX. Regulations That Significantly Affect Energy Supply,
Distribution, or Use
X. Availability of Rulemaking Documents

I. Background

    While there is currently a drop in air travel due to a general
economic downturn, delay and congestion continue to build in the
nation's busiest airports and the surrounding airspace. The FAA must
not only address current congestion, but also be poised to handle
future demand that will surely return as the nation's economy improves.
The FAA has been developing the Next Generation Air Transportation
System (NextGen) for the purpose of changing the way the National
Airspace System (NAS) operates. NextGen will allow the NAS to expand to
meet future demand and support the economic viability of the system. In
addition, NextGen will improve safety and support environmental
initiatives such as reducing congestion, noise, emissions and fuel
consumption through increased energy efficiency. for more information
on NextGen, go to http://www.faa.gov/about/initiatives/nextgen/.
    As part of NextGen development, the FAA has determined that it is
essential to move from ground-based surveillance and navigation to more
dynamic and accurate airborne-based systems and procedures if the
agency is to enhance capacity, reduce delay, and improve environmental
performance. Automatic Dependent Surveillance-Broadcast (ADS-B)
equipment is an advanced surveillance technology that combines an
aircraft's positioning source, aircraft avionics, and a ground
infrastructure to create an accurate surveillance interface between
aircraft and ATC. It is a key component of NextGen that will move air
traffic control (ATC) from a radar-based system to a satellite-derived
aircraft location system. ADS-B is a performance-based surveillance
technology that is more precise than radar. ADS-B is expected to
provide air traffic controllers and pilots with more accurate
information to help keep aircraft safely separated in the sky and on
runways. The technology combines a positioning capability, aircraft
avionics, and ground infrastructure to enable more accurate
transmission of information from aircraft to ATC.
    ADS-B consists of two different services: ADS-B Out and ADS-B In.
ADS-B Out, which is the subject of this

rulemaking, periodically broadcasts information about each aircraft,
such as identification, current position, altitude, and velocity,
through an onboard transmitter. ADS-B Out provides air traffic
controllers with real-time position information that is, in most cases,
more accurate than the information available with current radar-based
systems. With more accurate information, ATC will be able to position
and separate aircraft with improved precision and timing.
    ADS-B In refers to an appropriately equipped aircraft's ability to
receive and display another aircraft's ADS-B Out information as well as
the ADS-B In services provided by ground systems, including Automatic
Dependent Surveillance-Rebroadcast (ADS-R),\1\ Traffic Information
Service-Broadcast (TIS-B),\2\ and, if so equipped, Flight Information
Service-Broadcast (FIS-B).\3\ When displayed in the cockpit, this
information greatly improves the pilot's situational awareness in
aircraft not equipped with a traffic alert and collision avoidance
system (TCAS)/airborne collision avoidance system (ACAS). Benefits from
universal equipage for ADS-B In currently are not substantiated, and
standards for ADS-B In air-to-air applications are still in their
infancy. Thus it is premature to require operators to equip with ADS-B
In at this time. This rule, however, imposes certain requirements that
will support some ADS-B In applications.
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    \1\ ADS-R collects traffic information from each broadcast link
and rebroadcasts it to ADS-B In-equipped operators on the other
broadcast link. This is further explained in section B.2., Automatic
Dependent Surveillance-Rebroadcast.
    \2\ TIS-B uses primary and secondary surveillance radars and
multilateration systems to provide proximate traffic situational
awareness, including position reports from aircraft not equipped
with ADS-B. TIS-B data may not provide as much information as could
be received directly from an aircraft's ADS-B Out broadcast, because
of the required data processing. The TIS-B signal is an advisory
service that is not designed for aircraft surveillance or
separation, and cannot be used for either purpose.
    \3\ With FIS-B, aircraft equipped with 978 megahertz (MHz)
Universal Access Transceiver (UAT) ADS-B In avionics can receive
weather information, notices to airmen, temporary flight
restrictions, and other relevant flight information, at no
additional cost.
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    As noted in the preamble of the Notice of Proposed Rulemaking
(NPRM) associated with this rule, published in the Federal Register on
October 5, 2007 (72 FR 56947), Congress enacted the ``Century of
Aviation Reauthorization Act'' in 2003. That Act mandated that the
Secretary of Transportation establish a Joint Planning and Development
Office (JPDO) to manage NextGen-related work, including coordinating
the development and use of new technologies for aircraft in the air
traffic control system. Since 2006, Congress has appropriated over $500
million to the FAA for implementing ADS-B and developing air-to-air
capabilities. The FAA remains committed to implementing NextGen and
adopts this final rule, with some modifications, as discussed in
further detail below.

A. Notice of Proposed Rulemaking

    The FAA published the NPRM for ADS-B Out in the Federal Register on
October 5, 2007 (72 FR 56947). The comment period for the NPRM was
scheduled to close on January 3, 2008. In response to several
commenters, the FAA subsequently extended the comment period to March
3, 2008 (72 FR 64966, Nov. 19, 2007). The FAA received approximately
190 comments to the docket on the NPRM. Commenters included air
carriers, manufacturers, associations, Government agencies, and
individuals.

B. ADS-B Aviation Rulemaking Committee

    As part of the rulemaking effort, the FAA chartered an aviation
rulemaking committee (ARC) on July 15, 2007, to provide a forum for the
U.S. aviation community to make recommendations on presenting and
structuring an ADS-B Out mandate, and to consider additional actions
that may be necessary to implement its recommendations. The ADS-B ARC
submitted its first report, ``Optimizing the Benefits of Automatic
Dependent Surveillance-Broadcast,'' \4\ on October 3, 2007.
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    \4\ A copy of this report is available from the Web site http://
www.regulations.gov. To find the report, enter FAA-2007-29305-0009.1
in the search field.
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    The FAA also tasked the ARC to make specific recommendations
concerning the proposed rule based on the comments submitted to the
docket. The ARC submitted its second report, ``Recommendations on
Federal Aviation Administration Notice No. 7-15, Automatic Dependent
Surveillance-Broadcast (ADS-B) Out Performance Requirements to Support
Air Traffic Control (ATC) Service; Notice of Proposed Rulemaking,'' \5\
to the FAA on September 26, 2008.
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    \5\ A copy of this report is available from the Web site http://
www.regulations.gov. To find the report, enter FAA-2007-29305-0221.1
in the search field
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    To give the public an opportunity to comment on the recommendations
received from the ARC, the FAA published a notice in the Federal
Register on October 2, 2008 (73 FR 57270), reopening the comment period
of the ADS-B Out NPRM docket for an additional 30 days. The purpose of
reopening the comment period was to receive public comments on the ARC
recommendations only. This comment period closed November 3, 2008, with
the FAA receiving approximately 50 comments to the ARC's
recommendations. Commenters included air carriers, manufacturers,
associations, and individuals.

C. Summary of the Final Rule

    This final rule will add equipage requirements and performance
standards for ADS-B Out avionics. ADS-B Out broadcasts information
about an aircraft through an onboard transmitter to a ground receiver.
Use of ADS-B Out will move air traffic control from a radar-based
system to a satellite-derived aircraft location system. As discussed
more fully in the sections of this preamble describing equipage
requirements and performance standards, operators will have two options
for equipage under this rule--the 1090 megahertz (MHz) extended
squitter \6\ (ES) broadcast link or the Universal Access Transceiver
(UAT) broadcast link. \7\ Generally, this equipment will be required
for aircraft operating in Classes A, B, and C airspace, certain Class E
airspace, and other specified airspace. See section C.1. ``Airspace''
below for additional details.
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    \6\ An extended squitter is a long message that Mode S
Transponders transmit automatically, without needing to be
interrogated by radar, to announce the own-ship aircraft's presence
to nearby ADS-B equipped aircraft or ground based Air Traffic
Control.
    \7\ The 1090 MHz ES broadcast link uses the 1090 MHz frequency.
The UAT broadcast link uses the 978 MHz frequency.
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    The NPRM proposed performance requirements for ADS-B Out to be used
for ATC surveillance. In addition, several aspects of the proposal
would be necessary for future ADS-B In applications. The comments to
the NPRM and the ARC recommendations raised significant concerns about
the operational needs and costs of the proposed performance
requirements, as well as the proposed antenna diversity requirement.
    The FAA specifically proposed higher ADS-B Out and antenna
diversity requirements than what is needed for ATC surveillance to
enable certain ADS-B In applications. As discussed in further detail in
this document, the FAA has reconsidered these elements in view of the
comments and has changed the implementation plan for ADS-B.
    The FAA has concluded that this rule will require only the
performance requirements necessary for ADS-B Out. While certain
requirements adopted in this rule will support some ADS-B In
applications, the agency is not adopting

the higher performance standards that would enable all of the initial
ADS-B In applications. The agency is mindful, and operators are
advised, that in accepting the commenters' and the ARC's positions
regarding antenna diversity and position source accuracy, compliance
with this rule alone may not enable operators to take full advantage of
certain ADS-B In applications. Operators may voluntarily choose
equipment that meets the higher performance standards in order to
enable the use of these applications.
    The following table provides an overview of the costs and benefits
of this final rule.

                      Summary of Costs and Benefits
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------------------------------------------------------------------------
3% Discount Rate:

  Low Costs.................................................      $2.74
  High Benefits.............................................       5.03
                                                             -----------
    Net Benefits-High Benefit/Low Cost......................       2.29
                                                             ===========
  High Costs................................................       5.47
  Low Benefits..............................................       3.98
                                                             -----------
    Net Benefits-Low Benefits/High Costs....................      (1.49)
                                                             ===========

7% Discount Rate:

  Low Costs.................................................       2.15
  High Benefits.............................................       2.74
                                                             -----------
    Net Benefits-High Benefit/Low Cost......................       0.59
                                                             ===========
  High Costs................................................       4.11
  Low Benefits..............................................       2.09
    Net Benefits-Low Benefits/High Costs....................      (2.02)
                                                             -----------
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1. Airspace
    This final rule prescribes ADS-B Out performance requirements for
all aircraft operating in Class A, B, and C airspace within the NAS;
above the ceiling and within the lateral boundaries of a Class B or
Class C airspace area up to 10,000 feet mean sea level (MSL); and Class
E airspace areas at or above 10,000 feet MSL over the 48 contiguous
United States and the District of Columbia, excluding the airspace at
and below 2,500 feet above the surface.
    The rule also requires that aircraft meet these performance
requirements in the airspace within 30 nautical miles (NM) of certain
identified airports \8\ that are among the nation's busiest (based on
annual passenger enplanements, annual airport operations count, and
operational complexity) from the surface up to 10,000 feet MSL. In
addition, the rule requires that aircraft meet ADS-B Out performance
requirements to operate in Class E airspace over the Gulf of Mexico at
and above 3,000 feet MSL within 12 NM of the coastline of the United
States.
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    \8\ These airports are listed in appendix D to part 91.
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2. Datalink Requirements
    ADS-B requires a broadcast link for aircraft surveillance and to
support ADS-B In applications. Operators have two options for equipage
under this rule-- the 1090 MHz ES broadcast link or the UAT broadcast
link. The 1090 MHz ES broadcast link is the internationally agreed upon
link for ADS-B and is intended to support ADS-B In applications used by
air carriers and other high-performance aircraft. The 1090 MHz ES
broadcast link does not support FIS-B (weather and related flight
information) because the bandwidth limitations of this link cannot
transmit the large message structures required by FIS-B. The UAT
broadcast link supports ADS-B In applications \9\ and FIS-B, which are
important for the general aviation (GA) community.
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    \9\ These applications include enhanced visual acquisition,
conflict detection, enhanced visual approach, Airport Surface
Situational Awareness (ASSA), and Final Approach Runway Occupancy
Awareness (FAROA).
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    This final rule requires aircraft flying at and above 18,000 feet
MSL (flight level (FL) 180) (Class A airspace) to have ADS-B Out
performance capabilities using the 1090 MHz ES broadcast link. This
rule also specifies that aircraft flying in the designated airspace
below 18,000 feet MSL may use either the 1090 MHz ES or UAT broadcast
link.
3. System Performance Requirements
    When activated, ADS-B Out continuously transmits aircraft
information through the 1090 MHz ES or UAT broadcast link. The accuracy
and integrity of the position information transmitted by ADS-B avionics
are represented by the navigation accuracy category for position
(NACP), the navigation accuracy category for velocity
(NACV), the navigation integrity category (NIC), the system
design assurance (SDA), and the source integrity level (SIL).
    In the proposed rule, the FAA referenced the accuracy and integrity
requirements to the appropriate NACP, NACV, NIC,
and SIL values defined in Technical Standard Order (TSO)-C166a \10\
(for operators using the 1090 MHz ES broadcast link), and TSO-C154b
\11\ (for operators using the UAT broadcast link) as the baseline
requirements for ADS-B Out equipment. TSO-C166a adopted the standards
in RTCA, Inc.\12\ (RTCA) DO-260A.\13\ TSO-C154b adopted the standards
in RTCA DO-282A.\14\
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    \10\ Extended Squitter Automatic Dependent Surveillance-
Broadcast (ADS-B) and Traffic Information Service--Broadcast (TIS-B)
Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz).
    \11\ Universal Access Transceiver (UAT) Automatic Dependent
Surveillance--Broadcast (ADS-B) Equipment Operating on the Frequency
of 978 MHz.
    \12\ RTCA, Inc. is a not-for-profit corporation formed to
advance the art and science of aviation and aviation electronic
systems for the benefit of the public. The organization functions as
a Federal Advisory Committee and develops consensus-based
recommendations on contemporary aviation issues. The organization's
recommendations are often used as the basis for government and
private sector decisions as well as the foundation for many FAA
TSOs. For more information, see http://www.rtca.org.
    \13\ Minimum Operational Performance Standards for 1090 MHz
Extended Squitter Automatic Dependent Surveillance--Broadcast (ADS-
B) and Traffic Information Services--Broadcast (TIS-B).
    \14\ Minimum Operational Performance Standards for Universal
Access Transceiver (UAT) Automatic Dependent Surveillance--
Broadcast.
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    After the NPRM was published, the ADS-B ARC issued numerous
recommendations in response to public comments on the TSOs referenced
in the proposal. Based on the ARC recommendations and broad industry
input, RTCA revised DO-260A to become DO-260B \15\ and revised DO-282A
to become DO-282B.\16\ The new RTCA revisions include: (1) An allowance
for transmitting a NIC of 7 on the surface, (2) procedures for
correctly setting the NACV, (3) clarifying the latency
requirements, (4) removing the vertical component of NACP,
NACV, NIC, and SIL, (5) revising the definition of SIL to
correspond to the definition in the FAA NPRM, (6) clarifying the
definition of SIL by dividing it into SIL and SDA message elements, (7)
creating a medium power single antenna class, and (8) redefining the
bit for the ``ADS-B In capability installed'' message element.\17\ DO-
260B and DO-282B are more mature standards and fully support domestic
and international ADS-B air traffic control surveillance. The updated
standards do not increase performance requirements.
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    \15\ Minimum Operational Performance Standards for 1090 MHz
Extended Squitter Automatic Dependent Surveillance-Broadcast (ADS-B)
and Traffic Information Services-Broadcast (TIS-B).
    \16\ Minimum Operational Performance Standards for Universal
Access Transceiver Automatic Dependent Surveillance-Broadcast.
    \17\ A number of these items address issues with the current
TSOs.
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    The FAA updated the TSOs in accordance with these new RTCA
standards. In addition, the FAA has

decided that it is necessary to require the new standards contained in
TSO-C166b \18\ (1090 MHz ES) and TSO-C154c \19\ (UAT) as the minimum
performance standards in this final rule.\20\ The updated standards
incorporate multiple changes that address public comments and the ARC's
recommendations on the proposal. On September 11, 2009, the FAA
announced in the Federal Register the availability of draft TSO-C166b
and TSO-C154c for comment (74 FR 46831). The FAA issued final versions
of the above TSOs on December 2, 2009. The FAA also added additional
language in Sec. Sec.  91.225 and 91.227 stating that equipment with an
approved deviation under Sec.  21.618 also meet the requirements of the
rule.
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    \18\ Extended Squitter Automatic Dependent Surveillance-
Broadcast (ADS-B) and Traffic Information Service-Broadcast (TIS-B)
Equipment Operating on the Radio Frequency of 1090 Megahertz (MHz).
    \19\ Universal Access Transceiver (UAT) Automatic Dependent
Surveillance-Broadcast (ADS-B) Equipment Operating on the Frequency
of 978 MHz.
    \20\ Operators with equipment installed that meets a later
version of TSO-C166b or TSO-C154c, as applicable, are in compliance
with this rule.
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    In addition, this final rule specifies the performance requirements
for accuracy and integrity (NACP, NACV, and NIC)
in meters and nautical miles rather than referencing the numerical
values used in DO-260B, DO-282B, or the NPRM. This change translates
the values but does not alter the actual performance requirements. The
FAA wants to avoid any misinterpretations of the performance
requirements for this rule, if in the future, RTCA revises
NACP, NACV, and NIC.
    Table 1 summarizes the NACP, NACV, NIC, and
SIL values proposed in the NPRM and their equivalent measurements, as
noted in DO-260A and DO-282A. Table 2 summarizes NACP,
NACV, NIC, SDA, and SIL values as defined in DO-260B and DO-
282B. These two tables contain only the values applicable to the NPRM
and the final rule. See DO-260B paragraph 2.2.3 or DO-282B paragraph
2.2.4 for complete information on all values.
[GRAPHIC] [TIFF OMITTED] TR28MY10.000

[GRAPHIC] [TIFF OMITTED] TR28MY10.001

    In this final rule, the NACP must be less than 0.05 NM.
The NACV and NIC values are adopted as proposed. The
NACV must be less than 10 meters per second. The NIC must be
less than 0.2 NM. The SIL parameter from the NPRM has been divided into
two separate parameters and is discussed in detail later in this
document.\21\ In this final rule, the SDA parameter must be less than
or equal to 1x10 -5 per hour, which is equivalent to an SDA
of 2, and the SIL parameter must be less than or equal to 1x10
-7 per hour or per sample, which is equivalent to a SIL of
3. Global navigation satellite system (GNSS) systems \22\ will set
their SILs based on a 1x10 -7 per-hour probability.
Operators must meet these performance requirements to operate in the
airspace where ADS-B is required. Any ADS-B position source that meets
the specified performance standards is acceptable and complies with the
requirements in the final rule.
---------------------------------------------------------------------------

    \21\ In the NPRM, SIL was defined as surveillance integrity
level and represented the maximum probability of exceeding the NIC
containment radius and a maximum probability of a failure causing
false or misleading data to be transmitted. In this final rule, SIL
is referred to as source integrity level and defines the probability
of exceeding the NIC containment radius; SDA represents the
probability of transmitting false or misleading position
information.
    \22\ Global navigation satellite system (GNSS) is a generic term
for a satellite navigation system, such as the Global Positioning
System (GPS), that provides autonomous worldwide geo-spatial
positioning and may include local or regional augmentations.
---------------------------------------------------------------------------

4. Antenna Diversity and Transmit Power Requirements
    The aircraft antenna is a major contributor to ADS-B system link
performance and an important part of the overall ADS-B Out system. In
the NPRM, the FAA proposed an antenna diversity requirement that would
support ADS-B In applications, such as Airport Surface Situational
Awareness (ASSA) and Final Approach Runway Occupancy Awareness (FAROA).
    The FAA has reconsidered the need for antenna diversity in view of
the comments submitted. The agency has determined that a single bottom-
mounted antenna is the minimum requirement for ATC surveillance.
Furthermore, the analysis of ASSA and FAROA does not conclude that
antenna diversity is required for these applications. As discussed
later, the FAA decision to require a NACP less than 0.05 NM
signifies that certain ADS-B In applications, including ASSA and FAROA,
will not be fully supported.
    If future analysis indicates that antenna diversity is required for
ASSA and FAROA, a higher NACP than that required in this
rule also would be necessary to support these applications. The FAA
does not adopt antenna diversity as a requirement for ADS-B Out under
this rule because it is not required to support ATC surveillance.
Operators must note that this rule does not remove or modify any
existing antenna diversity requirements for transponders or TCAS/ACAS.
    Aircraft must transmit signals at a certain level of power to
ensure ground stations and ADS-B In-equipped aircraft and vehicles can
receive the transmitted signals. As proposed, the final rule requires
UAT systems to broadcast at a 16-watt minimum-transmit power, and 1090
MHz ES systems to broadcast at a 125-watt minimum-transmit power.
5. Latency of the ADS-B Out Message Elements
    When using an ADS-B system, aircraft receive information from a
position source and process it with onboard avionics. The aircraft's
ADS-B system then transmits position and other information to the
ground stations through antenna(s) using either the UAT or 1090 MHz ES
broadcast link. Generally, latency is the time lag between the time
that position measurements are taken to determine the aircraft's
position, and the time that the position information is transmitted by
the aircraft's ADS-B transmitter. The latency requirements in this
final rule, although different from the proposal, represent a more
appropriate way to address latency. The proposal created ambiguities
that are addressed in these modifications and are supported by the
commenters. Under this rule, total

latency cannot exceed 2.0 seconds. Within those 2.0 seconds,
uncompensated latency cannot exceed 0.6 seconds. Total and
uncompensated latency are explained in further detail in section II F.
``Performance Requirements--Total And Uncompensated Latency.''
6. Conforming Amendments and Editorial Changes
    Section 91.225 requires ADS-B Out for operations in Class A, B, and
C airspace. In the NPRM, the FAA inadvertently left out the proposed
conforming amendments to Sec. Sec.  91.130, 91.131, and 91.135, which
address Class A, B, and C airspace. This rule amends these sections to
include the ADS-B Out performance requirements for the appropriate
airspace.
    In addition, the regulatory text for Sec.  91.225 has been
reorganized from the proposed rule language. The restructuring of the
text should make this section clearer and more reader-friendly.
    Lastly, the proposed regulatory text has been moved from Appendix H
to new Sec.  91.227.
    All substantive changes to this rule are fully discussed in Section
II, Discussion of the Final Rule.

D. Differences Between the Proposed Rule and the Final Rule

    Table 3 summarizes the substantive changes between the proposed
rule and this final rule. Editorial changes and clarifications are
explained elsewhere in this preamble.

  Table 3.-- Substantive Differences Between the Proposed Rule and the
                               Final Rule
------------------------------------------------------------------------
         Issue area                The NPRM--         The final rule--
------------------------------------------------------------------------
Technical Standard Order....  Proposed performance  Requires performance
                               standards as          standards as
                               defined in TSO-       defined in TSO-
                               C166a (1090 MHz ES)   C166b (1090 MHz ES)
                               or TSO-C154b (UAT).   or TSO-C154c (UAT).
Airspace....................  Proposed requiring    Requires all
                               all aircraft above    aircraft in Class A
                               FL 240 to transmit    airspace (FL 180
                               on the 1090 MHz ES    and above) to
                               broadcast link.       transmit on the
                                                     1090 MHz ES
                                                     broadcast link.
                              Proposed ADS-B        Requires ADS-B
                               performance           performance
                               standards for         standards for
                               operations in all     operations in Class
                               Class E airspace at   E airspace at and
                               and above 10,000      above 10,000 feet
                               feet MSL.             MSL, excluding the
                                                     airspace at and
                                                     below 2,500 feet
                                                     AGL.
NACP........................  Proposed a NACP >=    Requires NACP < 0.05
                               9, which provides     NM.
                               navigation accuracy   (NACP >= 8)
                               < 30 meters.
NIC.........................  Proposed changes in   Requires changes in
                               NIC be broadcast      NIC be broadcast
                               within 10 seconds.    within 12 seconds.
SIL.........................  Proposed a SIL of 2   Requires an SDA of
                               or 3.                 2.
                                                     Requires a SIL of
                                                     3.
Antenna Diversity...........  Proposed antenna      Does not require
                               diversity in all      antenna diversity.
                               airspace specified
                               in the rule.
Total Latency...............  Proposed latency in   Requires
                               the position source   uncompensated
                               < 0.5 seconds and     latency <= 0.6
                               latency in the ADS-   seconds and maximum
                               B source < 1 second.  total latency <=
                                                     2.0 seconds.
Message Elements............  Proposed a broadcast  Does not require a
                               message element for   broadcast message
                               ``receiving ATC       element for
                               services''.           ``receiving ATC
                                                     services.''
An ability to turn off ADS-B  Proposed that the     Does not require the
 Out.                          pilot be able to      pilot be able to
                               turn off ADS-B        disable or turn off
                               transmissions if      ADS-B
                               directed by ATC.      transmissions.
------------------------------------------------------------------------

E. Separation Standards Working Group

    The FAA established an internal Surveillance and Broadcast Systems
Separation Standards Working group (SSWG) to develop methodologies and
define metrics as appropriate that evaluate the end-to-end performance
of ADS-B and wide area multilateration surveillance systems. These
evaluations include investigating the integration of these technologies
in conjunction with legacy surveillance technologies, that is,
separation between target positions that are derived from ADS-B, radar,
and wide area multilateration on ATC displays.
    This SSWG was tasked to perform: (1) Analyses of performance using
system models and simulations, including the identification of key
performance drivers and the development of test scenarios; (2)
preliminary evaluations with prototype system components to enable
verification and validation of the models and as early evidence of
system performance; and (3) analyses of test results, operational
testing and dedicated separation standards flight tests for each key-
site with fully functional end-to-end systems. Also included is a test
period for each system where performance data is collected on aircraft
operating in the surveillance service volume.
    The SSWG analyses and evaluations are the basis for most of the
performance requirements specified in this rule.\23\
---------------------------------------------------------------------------

    \23\ The SSWG findings are available from the Web site http://
www.regulations.gov. The docket number for this rulemaking is FAA -
2007-29305.
---------------------------------------------------------------------------

II. Discussion of the Final Rule

    Below is a more detailed discussion of the final rule relative to
the comments received on the proposal:

A. Airspace

1. 2,500 Feet Above Ground Level Exclusion in Class E Airspace
    The NPRM proposed that aircraft meet ADS-B Out performance
requirements to operate in Class E airspace at and above 10,000 feet
MSL over the 48 contiguous states and the District of Columbia.
    Several commenters, including the DOD and the Experimental Aircraft
Association (EAA), stated that the proposed ceiling of 10,000 feet MSL
for aircraft without ADS-B would be a major hardship and safety issue
for aircraft operators flying in mountainous terrain. Commenters and
the ARC suggested that the final rule exclude Class E airspace at and
below 2,500 feet above ground level (AGL), similar to the exclusion in
Sec.  91.215, ATC Transponder and Altitude Reporting Equipment and Use.
    The FAA recognizes the benefit of excluding this airspace in the
rule, particularly for visual flight rules (VFR) pilots flying in
mountainous areas. This modification addresses airspace that is not
affected by the agency's efforts to maximize NAS efficiency and
capacity. Excluding this airspace from the rule minimizes any
unnecessary financial and operational burdens being placed on aircraft
operators who fly in mountainous areas that encroach on

Class E airspace at and above 10,000 feet MSL, but choose not to equip
for the ADS-B Out performance standards in this rule. Consequently, the
final rule does not require ADS-B performance standards for operations
2,500 feet AGL and below in Class E airspace at and above 10,000 feet
MSL.
2. Airspace for Which ADS-B Is Required
    The NPRM proposed requiring ADS-B performance standards for
operations in most classes of airspace where operators currently are
required to carry a transponder.
    Numerous commenters recommended that the FAA limit ADS-B
performance requirements to aircraft operating in Class A airspace
only, or Class A and B airspace only. Several commenters questioned the
proposed ADS-B performance requirements in Class E airspace above
10,000 feet MSL. Many of these commenters made varying requests to the
FAA concerning the proposed altitude for which ADS-B Out would be
required, including 12,000 feet MSL, 15,000 feet MSL, FL 180, and FL
250. The United States Parachute Association noted that skydiving
operations are typically conducted above 10,000 feet MSL and sometimes
conducted in Class A, B, and C airspace.
    ADS-B cannot be used for ATC surveillance if all aircraft are not
appropriately equipped. Moreover, it is unreasonable to set up a
regulatory framework and performance standards that are based on using
two primary systems for surveillance; nor is it feasible to fund and
maintain two such systems. The airspace requirements specified in this
rule for ADS-B Out meet ATC surveillance needs.
    Class B and C airspace have the highest volume of air carrier and
GA traffic. They also experience the most complex transitions of
aircraft from the en route environment to the terminal area. With the
intricate nature of the airspace, current regulations dictate more
stringent operational requirements to operate within Class B and C
airspace areas.
    In addition, ATC must have surveillance data for all aircraft
operating in these areas to ensure appropriate situational awareness
and to maximize the use of the NAS. ADS-B Out will enhance surveillance
in controlled airspace areas where secondary surveillance radar (SSR)
currently exists.
    One commenter stated that the FAA should expand the airspace in
which ADS-B is required and specifically recommended including Air
Defense Identification Zones (ADIZ) \24\ and Offshore Control Area
Extensions.
---------------------------------------------------------------------------

    \24\ An Air Defense Identification Zone (ADIZ) is an area of
airspace over land or water in which the ready identification,
location, and control of civil aircraft is required in the interest
of national security.
---------------------------------------------------------------------------

    This rule applies to aircraft operating within U.S. airspace, which
extends 12 NM from the U.S. coast. (The airspace also includes the
Washington, DC, Special Flight Rules Area (SFRA), referred to as an
``ADIZ'' prior to 2009.) Most of the airspace in the ADIZ falls outside
the 12 NM boundaries.
3. Requests for Deviations From ADS-B Out Requirements
    This rule requires operators to broadcast ADS-B Out information
when operating in specified airspace. If an aircraft is not capable of
meeting the performance requirements, the operator may request a
deviation from the ATC facility responsible for that airspace. However,
as noted in the NPRM, ATC authorizations may contain conditions
necessary to provide the appropriate level of safety for all operators
in the airspace. ATC may not be able to grant authorizations in all
cases for a variety of reasons, including workload, runway
configurations, air traffic flows, and weather conditions.

B. Dual-Link Strategy

    The NPRM proposed a dual-link strategy for ADS-B Out broadcasts.
Under the proposal, aircraft operating above FL 240 would be required
to use the 1090 MHz ES broadcast link. Aircraft operating below FL 240
and in airspace where ADS-B Out performance requirements were proposed
could use either the 1090 MHz ES or UAT broadcast link.
    Many commenters suggested that a single-link system would reduce
operational complexity. The commenters noted that the installation and
maintenance costs of a dual-link system exceed those of a single-link
system. Some of the commenters proposed a single-link solution but
disagreed over which link should be chosen. Commenters supporting a
single-link UAT system noted that 1090 MHz ES does not support FIS-B
and is at risk for frequency congestion in a future air traffic
management environment. Commenters supporting a single-link 1090 MHz ES
system explained that UAT is not internationally interoperable and
opposed a system that requires international operators to equip with
both links.
    Boeing noted that most of the NAS system delays are associated with
arrivals and departures. Therefore, Boeing recommended that the
airborne surveillance functions should provide benefits at all
altitudes and on the ground. Ultimately, Boeing commented that a single
1090 MHz ES broadcast link would advance future ADS-B In applications
at low altitudes.
    In mandating ADS-B, the FAA is mindful that some members of the
international air transport community and the GA community have already
purchased ADS-B Out equipment, which use either the 1090 MHz ES or UAT
broadcast link. The FAA finds that a dual-link system is necessary for
the United States to meet the operational needs of all NAS operators.
Moreover, if the FAA were to require one segment of the aviation
community to equip to meet the needs of another segment of the
community, this would present additional costs for some operators to
equip.
1. Altitude To Require the 1090 MHz ES Datalink
    Under the proposal, aircraft operating above FL 240 would be
required to use the 1090 MHz ES broadcast link. Operators using only
the UAT broadcast link would be limited to operations below FL 240.
    The Air Line Pilots Association, International (ALPA) recommended
that the FAA require operators to use 1090 MHz ES above 18,000 feet MSL
to be consistent with the Class A airspace lower boundary (rather than
introduce a new subclassification of established airspace). In
addition, several GA commenters requested limiting ADS-B performance
requirements to only Class A airspace. The EAA and some individuals
stated that UAT would work just as well as 1090 MHz ES above FL 240 and
that aircraft should be permitted to use exclusively UAT for operations
above FL 240.
    The final rule specifies FL 180 (the lower boundary of Class A
airspace) as the ceiling for operating an aircraft equipped only with
UAT. Using 1090 MHz ES at or above FL 180 provides a clear operational
boundary for controllers and pilots, and does not create conditions of
mixed equipage for existing or future applications. The FAA recognizes
that this modification will affect certain operators that want to
operate above FL 180 and equip only with UAT. However, the agency
concludes that requiring 1090 MHz ES performance standards for
operations in all of Class A airspace is not only reasonable for
surveillance, but also establishes a baseline for ADS-B In.
    The requirement to broadcast 1090 MHz ES at and above FL 180 does
not

preclude UAT reception of FIS-B services up to FL 240 for aircraft with
a dual-link reception capability.
2. Automatic Dependent Surveillance-Rebroadcast (ADS-R)
    Under a dual-link strategy, the FAA will use ADS-R to allow ADS-B
In-equipped aircraft using one type of broadcast link to receive
messages about aircraft transmitting on the other broadcast link.
    Various commenters, including the Air Transport Association of
America, Inc. (ATA), Airservices Australia, the Australia Civil
Aviation Safety Authority, the Aircraft Owners and Pilots Association
(AOPA), Boeing, British Airways, and the International Air Transport
Association (IATA), expressed concern about a dual-link system. Some of
these commenters asserted that the need for ADS-R introduces additional
system-wide latency into the ADS-B system and poses a single point of
failure for the degradation or loss of surveillance data. In their
view, this could limit potential separation and efficiency improvements
and affect the air-to-air surveillance element of future ADS-B In
applications. In addition, some commenters expressed concern about the
additional risk of faults or failures that could result from
translating, merging, and rebroadcasting data from the 1090 and 978 MHz
frequencies.
    Some commenters, including Boeing, contended that ADS-R may not
have sufficient growth capability to support future ADS-B In air-to-air
applications. Such applications include merging and spacing, self
separation, or using ADS-B data to supplement or replace TCAS because
of potential of latency or loop delays. Rockwell-Collins stated that
ADS-R should be able to support many ADS-B In air-to-air applications,
including closely spaced parallel approaches and enhanced visual
approach. It recommended developing ADS-R to support more demanding
aircraft surveillance applications (ASA).\25\
---------------------------------------------------------------------------

    \25\ ASA comprises a number of flight-deck-based aircraft
surveillance and separation assurance capabilities that may directly
provide flight crews with surveillance information and alerts.
---------------------------------------------------------------------------

    Several commenters, including AOPA, asserted that the dual-link
system presents a safety hazard because aircraft equipped with
different links cannot ``see'' each other on ADS-B In displays in areas
without ADS-R coverage. The commenters suggested providing ADS-R at all
public airports where a mix of both systems will be encountered.
    The FAA is deploying ADS-R in all areas where ADS-B ATC
surveillance exists.\26\ ADS-R collects traffic information broadcast
on the 978 MHz UAT broadcast link and rebroadcasts the information to
1090 MHz ES users. Similarly, ADS-R collects traffic information
provided on the 1090 MHz ES broadcast link and rebroadcasts the
information to UAT users. ADS-R permits aircraft equipped with either
1090 MHz ES or UAT to take advantage of ADS-B In applications.
---------------------------------------------------------------------------

    \26\ The service coverage volume for ADS-B In applications is
explained in greater detail at http://www.adsb.gov.
---------------------------------------------------------------------------

    The FAA disagrees with the comments suggesting that ADS-R
introduces safety issues because of the added latencies attributed to
ADS-R processing. ATC automation systems do not require or use ADS-R to
provide surveillance. The added latency in the rebroadcast of the
original ADS-B message are measurably small and do not degrade the
reported NACP, NACV, and NIC values. The ARC
agreed in its report that the latency in ADS-R processing does not
degrade the reporting of the position quality parameters.\27\ Latency
attributed to ADS-R does not compromise the safety of the initial ADS-B
In applications.
---------------------------------------------------------------------------

    \27\ ADS-B ARC Task II Report to the FAA Appendix N, ADS-R
Latency and Reliability Expectations (September 26, 2008), available
on the Web site, http:///www.regulations.gov, FAA-2007-29305-0221.1.
---------------------------------------------------------------------------

    The intended functions of ADS-B, as identified in the NPRM, are not
compromised by the latency introduced with rebroadcasting the messages.
However, future ADS-B In applications necessarily may be limited
becauseof the latency associated with ADS-R.\28\ The FAA has a strong
interest in providing the option for operators to equip with UAT, so
they may benefit from FIS-B service. In making the decision to use a
dual-link strategy, the FAA acknowledged and weighed the fact that
potential benefits of future applications may not be fully realized
based on this decision. In situations where an airport is not within
the planned ADS-B coverage area, the airport will not have ADS-R
coverage. Consequently, an aircraft with ADS-B In will not have the
benefit of ADS-R, and ADS-B In will not provide awareness of aircraft
that are broadcasting on a different broadcast link.
---------------------------------------------------------------------------

    \28\ To date, the requirements for using ADS-B for advanced
iterations of merging and spacing, and self separation have yet to
be defined.
---------------------------------------------------------------------------

    If an aircraft leaves the ADS-B coverage area, there will be an
indication to the pilot that the aircraft is no longer within range of
ADS-R service. In this case, the pilot needs to maintain separation in
the same manner done today, which is relying on visual scanning and
directions from ATC. The FAA will ensure that the dual-link strategy
does not impact safety as future applications are developed.
3. 1090 MHz Frequency Congestion
    Boeing, Federal Express (FedEx), and IATA suggested that the FAA
assess future 1090 MHz frequency congestion. The ARC supported the
dual-link strategy, but recommended that the FAA study the necessary
mitigations of 1090 MHz frequency congestion. The ARC specifically
recommended that these mitigations ensure 1090 MHz ES is interoperable
with ACAS and SSR, while providing sufficient air-to-air range to
support NextGen ADS-B In applications.
    Congestion on the 1090 MHz frequency is a risk shared by TCAS/ACAS
and SSR systems using the Mode S transponder. The FAA conducted a study
to assess 1090 MHz frequency congestion in the future air traffic
environment.\29\ The FAA is analyzing alternatives and will enact the
necessary mitigations to reduce the 1090 MHz frequency congestion risk
for ADS-B, TCAS, and SSR, while enabling ranges appropriate for many
ADS-B In applications through 2035.
---------------------------------------------------------------------------

    \29\ A copy of this report is available from the Web site http:/
/www.regulations.gov. The docket number for this rulemaking is FAA-
2007-29305.
---------------------------------------------------------------------------

C. Performance Requirements--System

    While some commenters supported the proposed performance
requirements, numerous organizations and individuals commented that the
performance requirements generally were too stringent, unnecessary, and
would entail an undue economic burden on operators.
1. Performance Requirements Tailored to Operator, Airspace, or
Procedure
    The NPRM proposed specific performance requirements for ADS-B Out.
Several commenters, including the Aerospace Industries Association of
America (AIA), Boeing, the DOD, EAA, Honeywell, Lockheed Martin, and
the ARC, asked the FAA to tailor the ADS-B performance requirements
based on specific application requirements or airspace.
    Lockheed Martin and the DOD noted that some military aircraft may
not meet the proposed equipage requirements and would need
accommodations to operate in ADS-B Out-designated airspace. One
commenter was concerned that the DOD was exempt from the proposed
requirements.

    The FAA has determined that it is not operationally feasible to
assign different performance requirements dependent on the nature of
the operation. It would not be effective to require both pilots and
controllers to verify specific performance parameters before any given
operation or change of airspace. Therefore, the FAA is specifying
minimum performance requirements for all ADS-B Out-equipped aircraft to
operate in certain designated airspace.
    No special allowance is made in this rule to relieve the military
from the same performance requirements as the civilian aviation
community. The FAA recognizes that the DOD and other Federal agencies
are NAS users, and need access to all areas of the NAS today and in the
future. This rule provides procedures for an aircraft that does not
meet the ADS-B Out performance requirements, i.e., to obtain an ATC
authorized deviation to operate in the airspace for which ADS-B is
required. The FAA will collaborate with the appropriate U.S. Government
departments or agencies (including but not limited to DOD, and the
Department of Homeland Security) to develop Memorandums of Agreement to
accommodate their National defense mission requirements while
supporting the needs of all other NAS users.
2. Navigation Accuracy Category for Position (NACP)
    The NPRM proposed requiring a NACP greater than or equal
to 9. This is equivalent to horizontal position accuracy of less than
30 meters and vertical position accuracy of less than 45 meters. A
NACP of less than 30 meters horizontal would support ATC
surveillance, ASSA, FAROA, and other future ADS-B In applications.
    Airbus, ATA, Aviation Communication and Surveillance Systems
(ACSS), Boeing, Rockwell-Collins, United Airlines, and United Parcel
Service (UPS) questioned the necessity of a NACP greater
than or equal to 9. The ARC recommended that the FAA institute
NACP requirements based on domains of airspace defined by
different types of operations, with minimum NACP values
ranging from 5 through 9.\30\ The ARC also recommended that when a
NACP greater than or equal to 9 is necessary, operators
should only be required to equip with a position source that could meet
a NACP greater than or equal to 9 for 95 percent of an hour
and meet a NACP greater than or equal to 8 for 99.9 percent
of an hour.
---------------------------------------------------------------------------

    \30\  ADS-B ARC Task II Report to the FAA 6 (September 26,
2008), available on the Web site, http://www.regulations.gov, FAA-
2007-29305-0221.1.
---------------------------------------------------------------------------

    Boeing commented that there is no need for vertical accuracy
because neither ATC nor any of the initial ADS-B In applications
require it. The ARC recommended that the FAA not apply the vertical
position accuracy requirement associated with a NACP of 9
for surface operations. The ARC also recommended that the FAA modify
the definition of a NACP of 9 in DO-260A and DO-282A. This
modification would remove the vertical accuracy requirement if the
aircraft is on the surface.
    The FAA reviewed these comments and the necessary requirements for
the ADS-B Out and ADS-B In applications that are contemplated today. A
NACP of less than 0.05 NM is required for ATC surveillance.
A NACP of less than 30 meters is required only for ASSA and
FAROA. Because surface surveillance benefits enabled by ADS-B will only
be fully available where Airport Surface Detection Equipment, Model X
(ASDE-X) systems,\31\ and ADS-R and TIS-B are in use, the FAA has
reconsidered the universal requirement of a NACP of less
than 30 meters.
---------------------------------------------------------------------------

    \31\ ASDE-X is a traffic management system for the airport
surface that provides seamless coverage and aircraft identification
to air traffic controllers. The system uses a combination of surface
movement radar and transponder multilateration sensors to display
aircraft position.
---------------------------------------------------------------------------

    While the higher NACP would support a limited number of
ADS-B In applications, it could also increase costs \32\ to all
operators required to meet the ADS-B performance standards. Therefore,
this final rule reduces the position accuracy reporting requirement and
adopts a NACP of less than 0.05 NM. This NACP
requirement applies to all aircraft operating in the airspace
identified in this rule.
---------------------------------------------------------------------------

    \32\ ADS-B ARC Report to the FAA Appendix P, Programmatic
Decision Analysis (September 26, 2008), available at http://
www.regulations.gov, FAA-2007-29305-0221.1.
---------------------------------------------------------------------------

    In addition, the FAA considered the comments regarding the vertical
accuracy component of NACP. As there are no ATC separation
services requirements for vertical accuracy or integrity, the FAA has
removed the vertical accuracy and integrity requirement from
NACP, NACV, NIC, and SIL in TSO-C154c and TSO-
C166b.
3. Navigation Accuracy Category for Velocity (NACV)
    The NPRM proposed requiring a NACV greater than or equal
to 1, which is equivalent to velocity accuracy of less than 10 meters
per second.
    The European Organisation for the Safety of Air Navigation
(EUROCONTROL) commented that a NACV of 1 is not sufficient
for ATC services or advanced ADS-B In applications. The ARC recommended
that NACV should not be required.
    Different air navigation service providers may need different
performance requirements depending on the airspace in which they
implement ADS-B separation services. The FAA reviewed this requirement
and concludes that a NACV is required for separation
services in the United States. The agency modeled and calculated the
NACV requirements for aircraft separation, using assumptions
unique to the U.S. environment. Based on this analysis, the FAA
determined that a horizontal velocity accuracy of less than 10 meters
per second, as proposed in the NPRM, is required for ATC surveillance
within the NAS.\33\ Therefore, this requirement is adopted as proposed.
---------------------------------------------------------------------------

    \33\ A copy of the Separation Standards Working Group report is
available from the Web site http://www.regulations.gov. The docket
number for this rulemaking is FAA-2007-29305.
---------------------------------------------------------------------------

4. Navigation Integrity Category (NIC)
    The NPRM proposed requiring a NIC greater than or equal to 7, which
provides navigation integrity of less than 0.2 NM. Boeing questioned
the necessity of this requirement. The ARC recommended that the FAA
adopt NIC requirements based on airspace, with minimum NIC values
ranging from 0 to 7.
    The FAA reviewed this requirement and determined that a NIC of less
than 0.2 NM is necessary for ATC separation services, particularly in
the approach environment. Similar to the NACP, it is not
practical to assign different NIC values based on types of airspace.
Therefore, this rule requires a NIC of less than 0.2 NM.
5. Surveillance Integrity Level
    The FAA's proposal for surveillance integrity level stated that the
surveillance integrity level is based on both the design assurance
level of the ADS-B Out avionics and the position source. Several
commenters, including Rockwell-Collins, pointed out that the proposed
definition was inconsistent with the surveillance integrity level
definition provided in DO-260A. Commenters stated that DO-260A Change 2
defined surveillance integrity level as including only the position
source. The ARC recommended that the FAA use the definition of
surveillance integrity level found in RTCA DO-

289,\34\ which also limited the design assurance to the position
source.
---------------------------------------------------------------------------

    \34\ Minimum Aviation System Performance Standards (MASPS) for
Aircraft Surveillance Applications (ASA).
---------------------------------------------------------------------------

    The FAA asserts that the design assurance of the ADS-B system needs
to represent the complete system, and not a single piece of that
system, to provide air traffic separation services. The FAA agrees that
the inconsistency between the proposed rule and the RTCA standard is
unworkable; however, RTCA has updated the design assurance requirements
in DO-260B and DO-282B to include the entire ADS-B avionics system,
rather than just the position source. The ADS-B system includes ADS-B
transmission equipment, ADS-B processing equipment, position source,
and any other equipment that processes the position data transmitted by
the ADS-B system. The DO-260B change is consistent with the rule.
6. Source Integrity Level (SIL) and System Design Assurance (SDA)
    In DO-260A (TSO-C166a) and DO-282A (TSO-C154b), SIL was defined as
surveillance integrity level and represented two separate components:
(1) The maximum probability of exceeding the NIC containment radius and
(2) a maximum probability of a failure causing false or misleading data
to be transmitted. DO-260B (TSO-C166b) and DO-282B (TSO-C154c) separate
these two components into two distinct parameters. SIL is now referred
to as source integrity level and defines the maximum probability of
exceeding the NIC containment radius; SDA now defines the maximum
probability of a failure causing false or misleading data to be
transmitted.
    The FAA proposed a SIL value of 2 or 3. A SIL of 2, as stated in
TSO-C166a and TSO-C154b, represented: (1) A maximum probability of
exceeding the NIC containment radius of 1x10-5 per hour or
per sample; and (2) a maximum probability of a failure causing false or
misleading data to be transmitted of 1x10-5 per hour.
    A SIL of 3 represented: (1) A maximum probability of exceeding the
NIC containment radius of 1x10-7 per hour or per sample and
(2) a maximum probability of a failure causing false or misleading data
to be transmitted of 1x10-7 per hour.
    The FAA proposed these two values for SIL because its separation
standards modeling determined that the probability of exceeding the NIC
containment radius must be less than 1x10-7 per hour or per
sample and the probability of a failure causing false or misleading
data must be less than 1x10-5 per hour. The FAA's TSOs and
the corresponding RTCA documents did not allow for this combination.
    Therefore, in developing and issuing the NPRM, the FAA assumed that
most operators, in upgrading their equipment for ADS-B, would equip
with a global positioning system (GPS) \35\ that would provide a NIC
containment radius of 1x10-7 per hour (a SIL of 3). However,
to require the associated maximum probability of failure causing false
or misleading data to be transmitted at 1x10-7 per hour was
not only unreasonable but also unnecessary. Therefore, the FAA proposed
that a SIL of 2 was also acceptable.
---------------------------------------------------------------------------

    \35\ GPS is a U.S. satellite-based radio navigation system that
provides a global-positioning service.
---------------------------------------------------------------------------

    With the separate SIL and SDA values available under DO-260B and
DO-282B, the rule requires a maximum probability of exceeding the NIC
containment radius of 1x10-7 per hour or per sample (which
equates to a SIL of 3), and a maximum probability of 1x10-5
per hour of a failure causing false or misleading data to be
transmitted (which equates to an SDA of 2).
    Changing the proposed probability of exceeding the NIC containment
radius from 1x10-5 per hour or per sample to
1x10-7 per hour or per sample should not impact NAS users.
This is because currently available ADS-B Out systems using GNSS will
provide an integrity metric based on 1x10-7 per hour.
7. Secondary Position Sources
    The General Aviation Manufacturers Association (GAMA), IATA, and
Rockwell-Collins commented that the final rule should specify separate
performance requirements for secondary position sources in the event
that their primary position source is unavailable.
    The FAA disagrees that a separate set of requirements is necessary
for secondary position sources because the rule does not require a
secondary source. The NACP, NACV, NIC, SDA and
SIL requirements in this rule apply regardless of the position source
in use.

D. Performance Requirements--Antenna Diversity

    The NPRM proposed that aircraft meet optimum system performance by
equipping with both a top and a bottom antenna to support ADS-B In
applications.
    Several commenters, including AOPA, did not support this aspect of
the proposal because antenna diversity significantly increases the cost
of ADS-B. AOPA also noted that historical TCAS and transponder use does
not indicate that dual antennas are necessary.
    Airservices Australia and the Australia Civil Aviation Safety
Authority noted that Australia is not requiring antenna diversity for
GA aircraft. The ARC recommended allowing non-diversity antenna
installations for VFR aircraft flying through Class B and C airspace
and below 15,000 feet MSL (1090 MHz ES) or below 18,000 feet MSL (UAT),
but not landing at a primary airport. The ARC also recommended that the
FAA undertake further studies to assess and validate the need for
antenna diversity in low-altitude airspace.
    The FAA proposed dual antennas to support ADS-B Out and ADS-B In
air-to-air applications. For ATC surveillance, only a single bottom-
mounted antenna is necessary. The commenters and the ARC identified
this element of the proposal as requiring significant costs for the GA
operators.\36\
---------------------------------------------------------------------------

    \36\ ADS-B ARC Task II Report to the FAA Appendix T, Antenna
Diversity Comments on Cost, (September 26, 2008), available at
http://www.regulations.gov, FAA-2007-29305-0221.1.
---------------------------------------------------------------------------

    The FAA has reconsidered its initial strategy for launching the
ADS-B requirements and is adopting the performance standards necessary
for ATC surveillance. Therefore, this rule does not require antenna
diversity for ADS-B to operate in any airspace. This change does not
alter or affect antenna diversity requirements for other aircraft
systems, such as transponders or TCAS II.
    Operators should be aware that a dual antenna installation could
provide additional benefits that are not included in the scope of this
rule. Airport surface situational awareness or alerting applications
may be compromised by a single-antenna installation. Operators who
equip with a single antenna may not be able to accrue all available
benefits from some or all future ADS-B In applications.
    While requirements for these applications have not yet been fully
defined, modeling performed by both the ARC and the FAA has indicated
that a single antenna may not be able to perform adequately for surface
applications. If the FAA, for example, issues a future mandate
requiring surface performance capability, operators of single-antenna-
equipped aircraft may need to upgrade the avionics installed on their
aircraft.
    Operators should also be aware that single-antenna installations
are not as capable as dual-antenna installations of receiving ADS-B
messages in an

environment with a highly congested spectrum. Because of increasing
congestion on the 1090 MHz frequency over time, single-antenna
installations of ADS-B may not be able to achieve the same range for
ADS-B In applications as aircraft with two antennas.
    This limitation on the upper bound of ADS-B In application range
for single-antenna installations does not impact any of the application
benefits cited in this rule. The FAA is actively pursuing strategies to
mitigate spectrum congestion concerns of the 1090 MHz frequency.
However, operators employing the 1090 MHz ES broadcast link should be
aware that future air-to-air applications that require longer range
reception may require dual antennas or a UAT system.

E. Performance Requirements--Transmit Power

    The NPRM proposed that aircraft equipped with UAT would have a
minimum 16-watt transmit power performance and aircraft equipped with
1090 MHz ES would have a minimum 125-watt transmit power performance.
Some commenters, particularly AOPA, argued that the proposal was not
warranted and imposed unnecessary expense. The ARC commented that using
the existing power level without antenna diversity may provide the
performance needed to make broader use of non-diversity antenna
installations.
    The FAA has determined that reducing the transmit power requirement
would significantly impact the ground infrastructure. The FAA will rely
on a series of approximately 800 ground stations to provide ATC
separation services throughout the United States. The ground stations
will be placed 150 to 200 miles apart and will require the minimum
aircraft output power specified in the rule to ensure coverage.
Lowering the aircraft output power requirements, as suggested by the
commenters, would require the FAA to expand and redesign the ADS-B
ground infrastructure. Consequently, the power levels remain unchanged
in the final rule.

F. Performance Requirements--Total and Uncompensated Latency

    In the NPRM, the FAA proposed to define latency as the time
information enters the aircraft through the aircraft antenna(s) until
the time it is transmitted from the aircraft. The FAA further proposed
that the navigation sensor should process information received by the
aircraft's antenna(s) and forward this information to the ADS-B
broadcast link avionics in less than 0.5 seconds. The processed
information then would be transmitted in the ADS-B message from the
ADS-B Out broadcast link avionics in less than 1.0 second from the time
it was received from the navigation sensor.
    Several commenters, including Airbus, Boeing, EUROCONTROL, GAMA,
and Honeywell, commented that the latency requirements are not well
defined, are too stringent, and are not consistent with other
standards.\37\ United Airlines and UPS recommended that the FAA specify
the accuracy of position information at the time of transmission.
Boeing and Honeywell recommended that the FAA specify latency, based on
the time of applicability of the position source.
---------------------------------------------------------------------------

    \37\ The commenters specifically referenced the RTCA Airborne
Surveillance Applications Minimum Aviation System Performance
Standards and DO-303 Safety ``Safety, Performance and Inoperability
Requirements Document of the ADS-B Non-Radar-Airspace (NRA)
Application.''
---------------------------------------------------------------------------

    The ARC stated that the FAA should: (1) Specify latency
requirements at the aircraft level, not the equipment level; (2)
specify the maximum uncompensated latency to minimize or eliminate
installation wiring changes of existing ADS-B Out implementations,
while meeting ATC surveillance requirements; (3) specify total latency
and uncompensated latency; and (4) reference latency to the time of
applicability of the position provided by the position sensor, rather
than the time of measurement.
    The FAA adopts three of the four ARC recommendations. First, the
FAA agrees that latency must be defined at the aircraft level and not
the equipment level. Second, the latency requirements are set at the
maximum value that will allow ATC surveillance. Although the latency
requirements will drive wiring changes in some aircraft, the
requirements will minimize the number of aircraft affected to the
maximum extent possible. Third, the FAA has defined the latency
requirements as total latency and uncompensated latency. The FAA does
not agree with the fourth recommendation to measure latency at the time
of applicability. To do so would place latency requirements only on
part of the overall system and specifically exclude the position source
latency. Since the entire system's latency, including the position
source, must be limited to ensure accuracy of the transmitted position
the rule requires latency to be measured from the position source time
of measurement and not the time of applicability.
    This rule specifies two separate latency requirements: Total
latency and uncompensated latency. Total latency is defined as the time
between when measurements are taken to determine the aircraft's
geometric position (latitude, longitude, and geometric altitude) and
when the ADS-B transmitter broadcasts the aircraft's position. Under
this rule, the total latency cannot exceed 2.0 seconds. Latency is
compensated to account for the movement of the aircraft while the unit
is processing the position information. The avionics usually compensate
latency based on velocity but may also compensate based on
acceleration.
    Uncompensated latency is defined as the time the avionics does not
compensate for latency. Under this rule, within the 2.0 second total
latency allocation, a maximum of 0.6 seconds may be uncompensated
latency. The avionics must compensate for any latency above 0.6 seconds
up to the maximum of 2.0 seconds by extrapolating the position to the
time of transmission.
    Aircraft velocity, as well as position accuracy and integrity
metrics (NACP, NACV, NIC, SDA, and SIL), must be
transmitted with their associated position measurement, but are not
required to be compensated.

G. Performance Requirements--Time To Indicate Accuracy and Integrity
Changes

    The NPRM proposed that changes in NIC and NACP must be
broadcast within 10 seconds. This proposed requirement would bind the
latency of the NIC and NACP, however this requirement would
also bind the maximum amount of time an integrity fault can exist
without an indication, as an integrity fault is indicated by changing
the NIC and NACP to zero.
    The ARC, GAMA, and Rockwell-Collins commented that 10.0 seconds is
not enough time to indicate a change in the NIC. They specifically
noted that GNSS position sources use the entire 10-second allocation,
which does not allow time for the ADS-B equipment to actually transmit
the change. Rockwell-Collins, GAMA, and the ARC recommended instead
that changes in NIC and SIL be broadcast within 12.1 seconds.
    Position sources typically provide an accuracy and integrity metric
with each position that is output. To allow GNSS-based position sources
time to detect and eliminate possible satellite faults, GNSS systems
allow the integrity metric associated with a position to actually lag
behind the output of the position. TSO-C145/146 and TSO-C196 GNSS
systems have up to 8.0 seconds to alert to an

integrity fault. TSO-C129 systems do not have an overarching integrity
fault time-to-alert requirement, but they do have navigation mode
specific integrity fault time-to-alert requirements. Specifically, TSO-
C129 systems must indicate an integrity fault within 10 seconds in
terminal and approach modes.
    The requirement to indicate a change in NIC applies to the time
between when a fault-free NIC is transmitted with a faulted position
and when the NIC is updated to indicate the fault. Thus, the clock to
indicate the change in NIC does not start at the onset of the fault,
but rather at the broadcast of the faulted position from the ADS-B
system. Thus, the total time to update the NIC is based on the
cumulative effect of--(1) the position source fault detection and
exclusion time, and (2) the worst-case asynchronous transmission
difference between when the fault-free NIC with faulted position is
transmitted and when the faulted NIC is transmitted.
    The FAA reviewed the separation standards work to determine if a
12.0 second delay in the broadcast of an integrity fault would impact
separation standards. The FAA found that no existing terminal and en
route surveillance standards would be impacted with a 12.0 second
delay, and thus the rule requires that changes in NIC be broadcast
within 12.0 seconds.
    The ARC, GAMA, and Rockwell-Collins also commented that changes in
NACP, NACV, and SIL should be broadcast within
3.1 seconds versus 10.0 seconds. The FAA determined that there is no
basis to tighten the requirement. Therefore, the 10.0 second
requirement applies to indicating changes in NACP,
NACV, SDA, and SIL.

H. Performance Requirements--Availability

    The FAA did not propose any availability \38\ requirements for this
rule. The proposed rule generated multiple comments concerning
statements in the preamble regarding availability and whether the FAA
should require operators to accomplish a preflight determination of
GNSS availability. Other commenters focused on a perceived requirement
for operators to equip with avionics that had a system availability
equivalent to Wide Area Augmentation System (WAAS) \39\.
---------------------------------------------------------------------------

    \38\ RTCA DO-229, Minimum Operational Performance Standards for
Global Positioning System/Wide Area Augmentation System Airborne
Equipment, defines the availability of a navigation system as the
ability of the system to provide the required function and
performance at the initiation of the intended operation.
Availability is an indication of the ability of the system to
provide usable service with the specified coverage area. Signal
availability is the percentage of time that navigational signals
transmitted from external sources are available for use.
Availability is a function of both the physical characteristics of
the environment and the technical capabilities of the transmitter
facilities.
    \39\ WAAS is a U.S. wide-coverage augmentation system to GPS
that calculates integrity and correction data on the ground and uses
geostationary satellites to broadcast the data to GPS/SBAS
(Satellite-Based Augmentation System (non-U.S.)) users.
---------------------------------------------------------------------------

1. Preflight Determination of Availability
    The proposal preamble explained that operators must verify ADS-B
Out availability before flight as part of their pre-flight
responsibilities. This is similar to the requirement for preflight
determination of availability for certain Required Navigation
Performance (RNP) \40\ operations.
---------------------------------------------------------------------------

    \40\ Required Navigation Performance (RNP) is a statement of the
total aircraft navigation performance necessary for operation within
a defined airspace.
---------------------------------------------------------------------------

    ATA argued that the process to determine availability could be time
consuming for operators and that the FAA should provide further
justification. Boeing stated that the NPRM did not include an
availability requirement; therefore, the FAA should correct its
statement in the NPRM preamble advising operators to make this part of
their preflight actions.
    The ARC recommended that the FAA provide preflight prediction
systems that assess the ability of typical positioning sources to meet
the position accuracy and integrity requirements.
    This rule requires operators to meet the adopted minimum position
accuracy and integrity performance requirements to operate in the
airspace described in the rule. To facilitate compliance with the rule
and assist pilots for the flight planning, the FAA will provide a
preflight availability prediction service by 2013. Therefore, prior to
departure, operators should verify that the predicted performance
requirements will be met for the duration of the flight. This service
will determine whether GNSS equipment is capable of meeting Sec.
91.227 position accuracy and integrity requirements for operating in
the airspace defined in this rule. Operators may also use their own
preflight availability prediction tools, provided the predictions
correspond to the performance of their equipment. The FAA advises
operators to consult manufacturers' information on specific avionics
and prediction services.
2. System Availability
    Numerous commenters, including the DOD, contended that the proposal
required WAAS (or implied that the positioning service used by the
aircraft have an availability equivalent to WAAS.)
    As stated in the NPRM, operators may equip with any position
source. Although WAAS is not required, at this time it is the only
positioning service that provides the equivalent availability to radar
(99.9 percent availability). The FAA expects that future position
sources such as GNSS using the L5 GPS signal, GPS using Galileo
signals, and GPS tightly integrated with inertial navigation systems
will also provide 99.9 percent availability. Operators who equip with
other position sources, such as non-augmented GPS, may experience
outages that limit their access to the airspace defined in this rule.
    If an aircraft's avionics meet the requirements of this rule but
unexpected GPS degradations during flight inhibit the position source
from providing adequate accuracy (within 0.05 NM) and integrity (within
0.2 NM), ATC will be alerted via the aircraft's broadcasted data and
services will be provided to that aircraft using the backup strategy.
An aircraft that is not equipped to meet the requirements of this rule
will not have access to the airspace for which ADS-B is required. The
FAA notes that preflight availability verification eliminates any need
for the system to meet a specified availability requirement upon
installation.

I. Performance Requirements--Continuity

    The FAA did not propose a continuity \41\ requirement in the NPRM.
Several commenters, including Airbus, GAMA, Rockwell-Collins, and the
ARC, suggested that the FAA add a continuity requirement. These
commenters argued that such a requirement would ensure that an aircraft
could continue providing the ADS-B information throughout a flight.
---------------------------------------------------------------------------

    \41\ DO-229 defines the continuity of the system as the ability
of the total system (comprising all elements necessary to maintain
aircraft position within the defined airspace) to perform its
function without interruption during the intended operation. More
specifically, continuity is the probability that the specified
system performance will be maintained for the duration of a phase of
operation (presuming that the system was available at the beginning
of that phase of operation), and predicted to exist throughout the
operation.
---------------------------------------------------------------------------

    Aircraft are to meet the performance requirements for the duration
of the operation, not just a portion of the flight. The FAA's preflight
availability prediction service will help pilots ensure that the
aircraft can continue transmitting ADS-B information throughout their
planned flight, based on expected operations. Unexpected

failures will be accommodated, as described in the discussion on
availability; therefore, there is no need for a separate continuity
requirement.

J. Performance Requirements--Traffic Information Service--Broadcast
Integrity (TIS-B)

    The NPRM did not propose any changes to the standards for TIS-B.
Boeing stated that the FAA's plans to implement TIS-B with a SIL of 0
would severely limit its utility for ADS-B In applications. Boeing
recommended that the FAA change TIS-B to provide a SIL of 2 or greater,
to be consistent with the SIL proposed for ADS-B Out. Honeywell
commented that a TIS-B integrity level should be established for value-
added, near-term applications. The ARC did not specifically comment on
the TIS-B SIL, but did recommend that the FAA include a discussion of
the FIS-B and TIS-B benefits in the preamble to the ADS-B Out final
rule.
    The TIS-B system is expected to support four of the five initial
ADS-B In applications. The FAA acknowledges that future ADS-B In
applications may require improved representation of the position
integrity metrics. With the SIL and SDA changes incorporated in DO-260B
and DO-282B and possible changes to future versions of DO-317, the FAA
plans, outside of this rulemaking effort, to evaluate the usefulness of
the broadcast of integrity parameters from TIS-B.

K. Broadcast Message Elements

1. NACP/NACV/NIC/SDA/SIL
    The NPRM did not specifically propose NACP,
NACV, NIC, or SIL as broadcast message elements in section 4
of appendix H to part 91, Minimum Broadcast Message Element Set for
ADS-B Out. These requirements were specified in section 3 of appendix H
to part 91, ADS-B Out Performance Requirements for NIC, NAC, and SIL.
    Honeywell noted that NACP, NACV, NIC, and SIL
are required message elements in DO-260A.
    To resolve any questions, the FAA has repeated the indications for
these elements in Sec.  91.227(d)(16) through (19). In addition, and
consistent with TSO-C166b and TSO-C154c, SIL and SDA are listed as
separate values.
2. Receiving ATC Services
    The NPRM proposed requiring the message element ``Receiving ATC
Services.'' Several commenters, including ACSS, Airbus, Boeing,
EUROCONTROL, United Airlines, and UPS, commented that this message
element is unnecessary and poorly defined. UPS and United Airlines
suggested that the FAA use the ground automation system to accomplish
the function of this message element. Some commenters also contended
that this message element could require an additional user interface,
which is not available on current equipment.
    The ARC recommended that the FAA clarify the definition of this
message element and explain how it can be implemented without pilot
entry. The ARC also requested that the FAA research whether both
``Receiving ATC Services'' and ``Mode 3/A Code'' are necessary.
    The FAA concludes that ``Receiving ATC Services'' is not necessary
for ATC surveillance because this information can be directly inferred
from the Mode 3/A code. Furthermore, this message element could
increase costs for an additional user interface. Therefore, this rule
does not include ``Receiving ATC Services'' as a required broadcast
message element.
3. Length and Width of the Aircraft
    The NPRM proposed requiring a message element to broadcast the
length and width of the aircraft.
    Airbus and EUROCONTROL commented that length and width information
is not necessary for surveillance or airborne ADS-B Out applications.
Airbus and an individual commenter noted that length and width
information should be quantified relative to the aircraft position
reference point or to a known offset.
    GAMA and Rockwell-Collins noted that the TSOs allow some aircraft
to continuously transmit ``in-air'' because these aircraft do not have
a means to determine their air/ground status. Rockwell-Collins
commented that the rule should require all aircraft to assess their
air/ground status and broadcast the appropriate set of messages for
that status. The ARC recommended that the FAA address this issue in the
preamble to the final rule.
    The FAA notes that TSO-C154c and TSO-C166b allow the operator to
determine whether to transmit the aircraft's latitude and longitude
referenced to the GPS antenna location or the ADS-B position reference
point. The ADS-B position reference point is the center of a box, based
on the aircraft length and width. With the position offset to the ADS-B
reference point, the ADS-B is able to report the position of the edges
of the aircraft. This rule does not require operators to apply the
position offset because ATC surveillance does not require a position
offset.
    The FAA concludes that the requirement to transmit aircraft length
and width is necessary because this message element will be used as an
input for ASDE-X systems and allows the FAA to decommission ASDE-3
radars \42\ that interface with ASDE-X, as well as the surface movement
radar systems that are at certain ASDE-X sites without ASDE-3. The
length-width code will be preset when ADS-B equipment, meeting the
standards in TSO-C154c or TSO-C166b, is installed in the aircraft.
---------------------------------------------------------------------------

    \42\ ASDE-3 is an airport radar that shows to tower controllers
the location of aircraft on the surface.
---------------------------------------------------------------------------

    ADS-B equipment transmits an airborne position message when the
aircraft is airborne, and a surface position message when the aircraft
is on the ground. Aircraft automatically determine airborne or ground
status and transmit the appropriate message. For aircraft that are
unable to determine their air-ground status automatically, the RTCA
standards and TSOs allow the aircraft to continuously transmit the
airborne position message. However, the length width code is a required
message element in this rule, and is only transmitted in the surface
position message. Thus, to comply with the rule, the aircraft must
automatically determine its air-ground status and transmit the surface
position message which includes the length width code when on the
ground.
4. Indication of the Aircraft's Barometric Pressure Altitude
    The NPRM proposed a broadcast message that would report the
aircraft's barometric pressure altitude. Several commenters, including
the ARC, GAMA, Rockwell-Collins, Sandia National Laboratories (SANDIA),
and UPS, identified an inconsistency regarding the barometric altitude
message element between the proposed rule's preamble and regulatory
text.
    The FAA agrees that the NPRM preamble was not completely clear and
should have better reflected the proposed regulatory text. The proposed
regulatory text stated that the pressure altitude reported for ADS-B
Out and Mode C/S transponder is derived from the same source for
aircraft equipped with both a transponder and ADS-B Out. The FAA
confirms that the barometric altitude reported from the aircraft's
transponder and ADS-B Out must be derived from the same source.
    In addition, the FAA is striking the January 1, 2020 compliance
date from proposed Sec.  91.217(b). If an operator chooses to use ADS-B
before January 1,

2020, the operator must meet the provisions of that section.
5. Indication of the Aircraft's Velocity
    The NPRM proposed a message element that would provide ATC with
information about the aircraft's velocity and direction. However, the
NPRM preamble mistakenly referred to velocity as airspeed. Several
commenters, including Airbus, the ARC, Rockwell-Collins, SANDIA, and
UPS, recommended that the message element reflect velocity instead of
airspeed. Rockwell-Collins noted that velocity could be derived from
other sources, including an inertial navigation system. ACSS, United
Airlines, and UPS recommended that the FAA require the velocity source
for ADS-B transmissions to be the most accurate velocity source on the
aircraft. The ARC recommended that the issue of velocity source be
referred to RTCA.
    This message element will provide ATC with the aircraft's velocity,
as well as a clearly stated direction and description of the rate at
which an aircraft changes its position. The velocity must be
transmitted with a NACV of less than 10 meters per second.
Any velocity source that meets these requirements will comply with this
rule. The FAA referred the question on velocity source to RTCA for
further review, as the ARC recommended. RTCA determined that the
velocity source must be the same source that provides the aircraft's
position, and included this requirement in DO-260B and DO-282B.
6. Indication If Traffic Alert and Collision Avoidance System II or
Airborne Collision Avoidance System Is Installed and Operating in a
Mode That May Generate Resolution Advisory Alerts
    The NPRM proposed requiring a message element that would (1)
identify to ATC whether the aircraft is equipped with TCAS II or ACAS
and (2) identify whether the equipment is operating in a mode that
could generate resolution advisory alerts. Airbus asked for more
information on why this message element is required. EUROCONTROL
commented that this message element should be internationally
harmonized before the FAA adopts this requirement. UPS asked whether
this message should be indicated if the TCAS II is operated in the
traffic advisory mode. The ARC sought to retain this message element,
but asked the FAA to clarify its intended use in the final rule.
    The TCAS installed and operating in a mode that can generate a
resolution advisory message will be used by the FAA to monitor in-
service performance to address NAS inefficiencies and take appropriate
corrective actions. This information may also be used to support future
ADS-B In applications. This message element was harmonized with the
international community in the development of DO-260B and ED-102A.\43\
---------------------------------------------------------------------------

    \43\ EUROCAE MOPS for 1090 MHz Automatic Dependent Surveillance-
Broadcast (ADS-B).
---------------------------------------------------------------------------

7. For Aircraft With an Operable Traffic Alert and Collision Avoidance
System II or Airborne Collision Avoidance System, Indication If a
Resolution Advisory Is in Progress
    The NPRM proposed a message element to indicate that a resolution
advisory is in progress. EUROCONTROL recommended that the FAA
internationally harmonize this message element before adopting the
requirement. Airbus noted that this element may be achieved with DO-
260A.
    Similar to the discussion in II.K.6. above, the message that a TCAS
resolution advisory is in progress will be used by the FAA to monitor
in-service performance to address NAS inefficiencies and take
appropriate corrective actions. This information may also be used to
support future ADS-B In applications. This message element was
harmonized with the international community in the development of DO-
260B and ED-102A.
8. Indication of the Mode 3/A Transponder Code Specified by ATC
(Requires Flightcrew Entry)
    The NPRM proposed a message element to transmit the aircraft's
assigned Mode 3/A transponder code.
    Several commenters, including ACSS, Boeing, SANDIA, and UPS, argued
that this message element should not be necessary with ADS-B
surveillance, and suggested deleting the requirement. GAMA expressed
concern that different codes in the Mode 3/A transponder and the ADS-B
could result in an indication of a traffic conflict. GAMA specifically
recommended a one code entry or revising the automation to resolve
conflicting information. Airbus and the ARC supported this message
element requirement and the ARC requested more information on its
intended use.
    The FAA has determined that the same ATC-assigned Mode 3/A code
must be transmitted by both the transponder and the ADS-B Out message.
If the code transmitted by ADS-B differs from the Mode 3/A code
transmitted by the transponder, it could result in duplicative codes or
inaccurate reporting of aircraft position. If the aircraft's avionics
are not capable of allowing a single point of entry for the transponder
and ADS-B Out Mode 3/A code, the pilot must ensure that conflicting
codes are not transmitted to ATC.
    ATC uses the Mode 3/A code to identify aircraft that are under
surveillance and possibly under ATC direction. This identifier is
necessary to issue directions to specific aircraft about nearby air
traffic. The Mode 3/A code and the International Civil Aviation
Organization (ICAO) 24-bit address are duplicative for some functions.
This duplication is necessary because many current ATC automation
systems are not yet capable of using the ICAO 24-bit address.
Therefore, the FAA retains this message element in the rule.
9. Indication of the Aircraft's Call Sign That Is Submitted on the
Flight Plan, or the Aircraft's Registration Number (Aircraft Call Sign
Requires Flightcrew Entry)
    The NPRM proposed a requirement for this message element to
indicate either the aircraft's call sign (as submitted on its flight
plan), or the aircraft's registration number. An individual commenter
disagreed with the required broadcast message element for aircraft
identity and noted that it uses unnecessary bandwidth.
    This message element correlates flight plan information with the
data that ATC views on the radar display, and facilitates ATC
communication with the aircraft. This message element also will support
certain ADS-B In applications such as enhanced visual approach.
    In the final rule, the regulatory text is amended to provide that
an operator does not need to populate the call sign/aircraft
registration field for a UAT equipped aircraft if he or she has not
filed a flight plan, is not requesting ATC services, and is using a UAT
self-assigned temporary 24-bit address. Although the FAA does not
prohibit the anonymity feature, operators using the anonymity feature
will not be eligible to receive ATC services, may not be able to
benefit from enhanced ADS-B search and rescue capabilities, and may
impact ADS-B In situational awareness benefits.
10. Indication If the Flightcrew Has Identified an Emergency, Radio
Communication Failure, or Unlawful Interference (Requires Flightcrew
Entry)
    The NPRM proposed this message element to alert ATC that an
aircraft is experiencing emergency conditions. Airbus asked the FAA to
clarify which emergency/priority codes are required.

The ARC recommended that the FAA explain in the final rule the
emergency status requirement and describe how it will be used.
    This message element alerts ATC that the aircraft is experiencing
emergency conditions and indicates the type of emergency. Both TSO-
C154c and TSO-C166b identify six unique emergency codes. All emergency
codes may be transmitted. Under this rule, only emergency, radio
communication failure, and unlawful interference are required. This
information will alert ATC to potential danger to the aircraft so it
can take appropriate action. Message elements for minimum fuel, downed
aircraft, and medical emergency are not required by this rule.\44\ ADS-
B equipment may automatically set these required emergency conditions
based on the Mode 3/A code.
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    \44\ Mode A codes 7700, 7600, and 7500 currently are reserved
for these emergencies. See Annex 10 to the Convention on
International Civil Aviation Aeronautical Telecommunications, Volume
4, Surveillance and Collision Avoidance Systems, 4th Edition, July
2007.
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11. Indication of the Aircraft's ``IDENT'' to ATC (Requires Flightcrew
Entry)
    The NPRM proposed this message element to help controllers quickly
identify a specific aircraft. United Airlines and UPS commented that
they believe controllers use the ``IDENT'' function to attain aircraft
identification information. They noted that future identification
systems should include aircraft information; therefore, they believed
this element is not necessary. FreeFlight commented that ``IDENT''
should be retained. The ARC recommended that the FAA clarify how the
``IDENT'' requirement will be used.
    The ``IDENT'' function is used regularly in current ATC operations
to help controllers quickly identify a specific aircraft. The ``IDENT''
feature also allows ATC to quickly identify aircraft that have entered
incorrect flight identification or Mode 3/A codes. The FAA is adopting
this message element in this rule.
12. Indication of the Emitter Category
    The NPRM proposed requiring a message element for an aircraft's
emitter category.
    EUROCONTROL questioned the business case behind this requirement.
UPS asked that the FAA better define the emitter categorizations in the
final rule.
    This message element is necessary for ATC separation services and
wake turbulence separation requirements. TSO-C166b and TSO-C154c
provide a list and description of the different emitter categories.
Emitter category is set during installation of the ADS-B avionics in
the aircraft and will not change over time.
13. Indication Whether an ADS-B In Capability Is Installed
    The NPRM proposed this message element to indicate to ATC whether a
cockpit display of traffic information (CDTI) \45\ is installed and
operational. Several commenters, including Boeing, EUROCONTROL, and
SANDIA, commented that this message element was poorly defined,
difficult and expensive to implement, and of little value to ADS-B In
applications and ATC surveillance. UPS asked whether a message is
required when a CDTI is installed but not operating. The ARC
recommended that the FAA clarify the use of this data element.
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    \45\ CDTI is a generic display that provides a flight crew with
traffic surveillance information about other aircraft, surface
vehicles, and obstacles, including their identification, position,
and other message set parameters. CDTI information would commonly be
displayed on a Multifunction Display (MFD).
---------------------------------------------------------------------------

    RTCA updated the definition of this message element in DO-260B and
DO-282B. The FAA adopted these updates in TSO-C166b and TSO-C154c. This
message element now indicates which aircraft are capable of receiving
ADS-B In services and therefore require TIS-B and ADS-R transmissions
from the ground. Under the new definition, this message element now
indicates whether an ADS-B In capability is installed in the aircraft,
but does not require a report of operational status.
14. Indication of the Aircraft's Geometric Altitude
    The NPRM proposed a message element indicating the aircraft's
geometric altitude.
    Several commenters, including Airbus, Boeing, Dassault, the
European Business Aviation Association (EBAA), EUROCONTROL, Honeywell,
and Rockwell-Collins, commented on the proposed requirement. Most of
the commenters questioned this message element and stated that neither
ATC surveillance nor ADS-B In require geometric altitude. Dassault,
EBAA, EUROCONTROL, and Honeywell supported this message element. The
ARC recommended that the FAA justify the need for this message element.
    Geometric altitude is the height of the aircraft above the World
Geodetic System 84 ellipsoid, which is a scientific approximation of
the earth's surface. This message element will be used within the ADS-B
ground system to confirm accuracy and identify discrepancies between
geometric altitude and barometric altitude. Additionally, the FAA will
integrate this comparison function into a continuing airworthiness
monitoring function.

L. Ability To Turn Off ADS-B Out Transmissions

    The NPRM proposed requiring a pilot to turn off ADS-B equipment if
directed by ATC, for example, if the ADS-B unit was broadcasting
erroneous information.
    The ARC, Boeing, United Airlines, and UPS recommended eliminating
the requirement to turn off ADS-B Out transmissions. A few commenters,
including British Airways, were concerned that being able to turn off
ADS-B Out, while keeping the transponder on, could require additional
design changes and increase costs because most existing equipment is
not capable of operating in this manner. Boeing stated that eliminating
erroneous ADS-B transmissions could be accomplished by turning the
transponder off or having a capability within the ground system to
allow the controller to manually remove selected targets. Rockwell-
Collins recommended that the FAA require the ADS-B equipment to detect
failures and disable ADS-B Out transmissions of erroneous data.
    The FAA modified the ground automation system to be able to exclude
incorrect ADS-B data. With this enhancement to the automation, the
aircraft does not need to have a capability for a pilot to disable ADS-
B transmissions. Therefore, the final rule does not require the pilot
to be able to turn off ADS-B Out transmissions.

M. Existing Equipment Requirements

1. Transponder Requirement
    The NPRM specified that the proposal for ADS-B equipage would not
alter existing transponder regulations.
    Several organizations and individuals, including AOPA, opposed
adding ADS-B Out performance requirements without removing the
transponder requirement. ATA and Boeing requested that the FAA make a
commitment to remove transponders. Several organizations and
individuals further commented that the FAA should pursue an ADS-B based
collision-avoidance system and reconsider the backup strategy, which is
based on secondary surveillance systems. ALPA supported the FAA's plan
to retain transponders.
    The ARC made multiple recommendations associated with

transponder removal: (1) The ADS-B implementation strategy should
include the removal of transponders from low-altitude aircraft without
an ACAS; (2) the FAA should commit to a strategy for achieving
transponder removal from low-altitude domestic aircraft; and (3) the
FAA should study whether ACAS can be modified to use ADS-B as the
primary surveillance data for collision avoidance, as well as what ACAS
upgrades are required to support NextGen.
    Removing the transponder requirement would involve substantial
changes to the ADS-B backup strategy and TCAS II/ACAS, which are
outside the scope of this rulemaking. Transponders will still be
required when the backup surveillance strategy using SSR is necessary
and to interact with TCAS- and ACAS-equipped aircraft. Separate from
this rulemaking, the FAA may consider (in coordination with the
appropriate surveillance and NextGen planning organizations), whether
transponders could eventually be removed and, if so, what steps are
necessary to accomplish this.
2. Emergency Locator Transmitter Requirement
    The NPRM did not propose any changes to the emergency locator
transmitter (ELT) \46\ requirements.
---------------------------------------------------------------------------

    \46\ An ELT is an electronic battery-operated transmitter
developed as a means of locating downed aircraft.
---------------------------------------------------------------------------

    Several commenters, including ATA and the National Business
Aviation Association (NBAA), argued that ADS-B should be used instead
of an ELT, and that ELT requirements could be included in this rule.
AOPA also recommended a long-term strategy to include ELT removal, and
stated that ADS-B could enhance current search-and-rescue procedures to
increase the number of successful rescues.
    The ARC recommended that the FAA explore whether an ADS-B tracking
service also could be used for search and rescue to aid in crash
locating. The ARC also recommended that the FAA conduct a study
considering an ADS-B-based search-and-rescue solution that would enable
removal of 121.5 MHz ELTs for certain domestic operations.
    The FAA has determined that the ADS-B system currently cannot
replace the ELT function. The ADS-B system is not required to be
crashworthy and, thus, may not be operable or able to transmit
following an aircraft accident. Additionally, current search-and-rescue
technology is not compatible with ADS-B operations because ELTs
broadcast on 121.5 or 406 MHz (not 1090 or 978 MHz). The FAA recognizes
the value of a ground application that could allow for timely and
accurate flight tracking of downed aircraft and is evaluating this
capability separate from this rulemaking.
    The FAA considered the ARC recommendation to evaluate the
feasibility of replacing the ELT with the ADS-B system. However, the
FAA has determined that ADS-B is not a feasible replacement for the
ELT, as discussed above; therefore, the FAA does not plan to undertake
such a study at this time.

N. Program Implementation

1. Timeline
    The FAA proposed that all aircraft operating in the airspace areas
specified in the rule meet the performance requirements by January 1,
2020.
    The majority of commenters recommended various options for the
implementation of ADS-B, including the discontinuation of secondary
and/or primary radar systems once ADS-B is operational NAS-wide. Some
commenters, including AIA and AOPA, requested that the FAA provide
certain basic levels of ADS-B service for several years before the ADS-
B compliance date.
    Several commenters, including ALPA and the National Transportation
Safety Board (NTSB), suggested that the compliance date or service
provision of ADS-B occur sooner than 2020, to obtain benefits more
quickly. United Airlines recommended a 2015 compliance date for
operations above FL 240. The Cargo Airline Association (CAA)
recommended lower performance requirements for a 2015 compliance date.
Several commenters, including the Aircraft Electronics Association,
FedEx, and the National Air Carriers Association, suggested extending
or adding flexibility to the 2020 compliance date.
    Numerous commenters, including ATA, Boeing, IATA, and Rockwell-
Collins, suggested a two-phased implementation strategy. The first
phase would use existing equipment, avionics standards, and
capabilities, which would allow industry and the FAA to demonstrate,
validate, and evaluate ADS-B applications. After operational experience
in the first phase was sufficient to generate the appropriate
standards, the second phase would establish a mandate for ADS-B Out
performance standards. Some commenters suggested that the second phase
be a combined ADS-B In and ADS-B Out rule.
    The ARC endorsed the proposed 2020 compliance date, but recommended
that the FAA allow operators to use existing equipage to accrue early
benefits. Specifically, the ARC recommended that the FAA: (1) Take
advantage of existing 1090 MHz ES-equipped aircraft and allow their
operation in the Gulf of Mexico for non-radar airspace and (2)
transition to a fully functional ADS-B Out capability enabled by DO-
260B,\47\ to allow access to the additional applications and services
for ADS-B In. The ARC also recommended that the FAA adopt the European
Aviation Safety Agency (EASA) Acceptable Means of Compliance 20-24
(permitting the use of early DO-260 avionics for separation) in non-
radar airspace, with appropriate measures to ensure ADS-B integrity.
---------------------------------------------------------------------------

    \47\ The ARC recommended DO-260A Change 3, which is DO-260B.
---------------------------------------------------------------------------

    After reviewing all the comments, the FAA finds that a 2020
compliance date remains appropriate because NAS users need time to
equip to the requirements of the rule. Most air carriers can use
regularly scheduled maintenance to install or upgrade their equipment.
The FAA also expects that this timeframe will provide sufficient
operational experience to make ADS-B the primary source for
surveillance in 2020.
    FIS-B and TIS-B services are already available in several areas of
the country for ADS-B In-equipped aircraft and will continue as an
integral part of the implementation of the ADS-B ground infrastructure.
NAS-wide ground infrastructure implementation is scheduled to be
complete in 2013, which would provide operators with at least 7 years
of operational experience with these services before the ADS-B
compliance date of 2020.
    The FAA examined whether it is operationally feasible and
economically beneficial to use DO-260 avionics in radar and non-radar
airspace before 2020. From an operational perspective, the FAA found
that the existing DO-260 equipment does not meet the surveillance needs
for ATC in the United States for various reasons: (1) DO-260 avionics
do not independently report the accuracy and integrity metrics; (2) DO-
260 avionics allow the integrity metric to be populated with accuracy
information during integrity outages, which is unacceptable for
aircraft separation services; (3) DO-260 avionics do not include a
message element for Mode 3/A code, which is necessary for aircraft
surveillance; and (4) the majority of existing DO-260 installations
were accomplished on a noninterference basis under the transponder
approval guidelines. (This certification verifies that the equipment

is safe onboard the aircraft, but does not issue any approval that
would permit its use for ADS-B operations.)
    Therefore, the FAA concluded that without upgrades to the
equipment, the use of DO-260 avionics will not meet the surveillance
needs in the NAS. Furthermore, without appropriate integrity
monitoring, DO-260 avionics cannot be used for separation of aircraft.
Its utility would be limited to potentially reducing separation in non-
radar areas, or increasing efficiency in radar airspace through more
timely updates of information.
    Further analysis addressed whether existing DO-260 avionics could
be beneficial to provide separation services in the Gulf of Mexico, or
to provide efficiency benefits through improved performance of User
Request Evaluation Tool (URET) \48\ and Traffic Management Advisor
(TMA).
---------------------------------------------------------------------------

    \48\ URET is an air traffic control tool that assists
controllers with timely detection and resolution of predicted air
traffic problems.
---------------------------------------------------------------------------

    To use DO-260 avionics in the Gulf of Mexico, the FAA estimated it
would incur approximately $4 million in costs to upgrade the
automation; would need to provide additional ground stations and
receiver autonomous integrity monitoring (RAIM) predictions; would need
to develop procedures; and would need to address aircraft certification
issues.\49\ Comparatively, the FAA concluded that benefits from this
action would only recover approximately 70 percent of the costs.
---------------------------------------------------------------------------

    \49\ A copy of the DO-260 Business Case Analysis is available
from the Web site http://www.regulations.gov. The docket number for
this rulemaking is FAA-2007-29305.
---------------------------------------------------------------------------

    The costs associated with using existing DO-260 avionics relative
to improved performance of URET and TMA were estimated at $31 million
and the estimated benefit in performance was $72 million. While this
analysis indicated that the benefits of improved URET and TMA
performance outweigh the costs of accommodating DO-260 equipped
aircraft,\50\ the FAA found that it raised some policy concerns.
---------------------------------------------------------------------------

    \50\ The analysis concluded that it was not cost-beneficial to
use DO-260 avionics in the Gulf of Mexico prior to 2020.
---------------------------------------------------------------------------

    First, the FAA does not expect to have the full NAS-wide ADS-B
infrastructure completed for this effort until 2013. As the ADS-B rule
would go into effect in 2020, any benefits accrued through the use of
DO-260 avionics would only be available for approximately 7 years.
Operators would be required to make a second investment in avionics to
comply with the rule in 2020.
    Second, a collection of broadcast samples indicated that there is a
wide variety of equipage among current DO-260 users. Although
approximately 7,500 aircraft in the United States transmit some ADS-B
data that would conform to DO-260, only about 1,500 aircraft transmit
enough data to be useful for 5 NM separation in the Gulf of Mexico and
input into ATC decision support tools (URET and TMA).\51\ Many DO-260
operators would require some upgrade costs to bring their existing
systems into compliance with a unified standard; these would be in
addition to the costs incurred for taking aircraft out of service for
certification. Although the user costs were not thoroughly assessed by
the ARC, the FAA estimated the costs at $15,000 per aircraft.\52\
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    \51\ A copy of the Honeywell Technology Solutions Inc. DO-260
study is available from the Web site http://www.regulations.gov. The
docket number for this rulemaking is FAA-2007-29305.