AC 20-165A

U.S. Department of Transportation Federal Aviation Administration

Advisory Circular

Subject: Airworthiness Approval of Automatic Dependent Surveillance - Broadcast (ADS-B) Out Systems Date: 11/07/12 Initiated by: AIR-130 AC No: 20-165A

This Advisory Circular (AC) provides guidance for the installation and airworthiness approval of Automatic Dependent Surveillance – Broadcast (ADS-B) Out systems in aircraft.

Susan J. M. Cabler Assistant Manager, Aircraft Engineering Division

i Table of Contents

P a r a g r a p h P a g e Chapter 1. General Information --------------------------------------------------------------------------- 1

1-1. Purpose of this Advisory Circular (AC). -------------------------------------------------------------- 1

1-2. Who This AC Applies To. ----------------------------------------------------------------------------- 1

1-3. Where to Find This Advisory Circular. --------------------------------------------------------------- 1

1-4. Scope. ---------------------------------------------------------------------------------------------------- 1

1-5. Background. --------------------------------------------------------------------------------------------- 2 Chapter 2. The Approval Process & Necessary Documentation -------------------------------------- 4

2-1. ADS-B System Approval Process. -------------------------------------------------------------------- 4

2-2. Aircraft Flight Manual. --------------------------------------------------------------------------------- 4

2-3. Continuing Airworthiness Requirements.------------------------------------------------------------- 5 Chapter 3. ADS-B System Installation Guidance------------------------------------------------------- 7

3-1. General Installation Guidance. ------------------------------------------------------------------------- 7

3-2. ADS-B Equipment. ------------------------------------------------------------------------------------10

3-3. Position Source. ----------------------------------------------------------------------------------------13

3-4. Barometric Altitude Source.---------------------------------------------------------------------------17

3-5. Heading Source.----------------------------------------------------------------------------------------18

3-6. TCAS Status Source. ----------------------------------------------------------------------------------18

3-7. Pilot Interface.------------------------------------------------------------------------------------------19

3-8. ADS-B Antenna Interface. ----------------------------------------------------------------------------22

3-9. Vertical Rate Source. ----------------------------------------------------------------------------------24

3-10. Air-Ground Considerations.-------------------------------------------------------------------------25

3-11. Foreign Airspace Requirements ---------------------------------------------------------------------26 Chapter 4. Test & Evaluation-----------------------------------------------------------------------------27

4-1. Ground Test.--------------------------------------------------------------------------------------------27

4-2. Flight Test.----------------------------------------------------------------------------------------------31

4-3. In-Flight Test with FAA Ground System.------------------------------------------------------------31

4-4. International Flight Test Options.---------------------------------------------------------------------35

4-5. Subsequent Flight Test Data Reuse. ------------------------------------------------------------------35 Appendix 1. Message Elements Descriptions -------------------------------------------------------A1-1 Appendix 2. Identifying and Qualifying ADS-B Position Sources -------------------------------A2-1 Appendix 3. Latency Analysis-------------------------------------------------------------------------A3-1 Appendix 4. Definitions --------------------------------------------------------------------------------A4-1 Appendix 5. Acronyms ---------------------------------------------------------------------------------A5-1 Appendix 6. Related Documents----------------------------------------------------------------------A6-1

ii Table of Contents (Continued)

List of Figures F i g u r e P a g e

Figure 1. Functional Overview of ADS-B OUT System2

Figure 2. Example of Aircraft Length and Width Code Determination12

List of Tables T a b l e P a g e

Table 1. Emitter Category13

Table 2. Accuracy and Integrity Requirements27

Table 3. Minimum and Maximum Transmitted Power from TSO-C166b30

Table 4. Minimum and Maximum Transmitted Power from TSO-C154c30

Table 5. Turns33

Table 6. Climb Speeds33

Table 7. Decent Speeds33

Table 8. Accuracy and Integrity Requirements During Flight34

Table 9. NACP ValuesA1-4

Table 10. NIC ValuesA1-5

Table 11. SIL Values, Probability of Exceeding the NIC Containment RadiusA1-6

Table 12. Source Integrity Level SupplementA1-6

Table 13. System Design AssuranceA1-7

Table 14. Estimated GNSS Availabilities (Minimum Threshold Constellation)A2-5

Table 15. Latency Analysis ExampleA3-5

Chapter 1. General Information

1-1. Purpose of this Advisory Circular (AC).

a. This AC provides guidance for the initial installation and airworthiness approval of Automatic Dependent Surveillance - Broadcast (ADS-B) Out equipment in aircraft.

b. This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to install ADS-B OUT equipment. However, if you use the means described in this AC, you must follow it entirely.

c. This AC is primarily intended for installations compliant with the aircraft requirements of Title 14 of Code of Federal Regulations (14 CFR) 91.227. Airworthiness compliance will be evaluated based on the applicable intended function rule (e.g., 14 CFR 23.1301, 25.1301, 27.1301,

29.1301) recognizing that the intended function is to meet the equipment requirements in 14 CFR

91.227. It is possible to receive airworthiness approval for your ADS-B OUT system with a different intended function; however, we strongly discourage this type of installation unless the installation is in accordance with the criteria for ADS-B OUT in foreign non-radar airspace (e.g., Approved Means of Compliance (AMC) 20-24, Certification Considerations for the Enhanced ATS in Non-Radar Areas using ADS-B Surveillance (ADS-B-NRA) Application via 1090 MHZ Extended Squitter).

Applicants using this AC to install ADS-B systems that are not compliant with 14 CFR 91.227 must follow all aspects of this AC or propose alternate means as appropriate to the Federal Aviation Administration (FAA).

1-2. Who This AC Applies To. This AC is for anyone who is applying for an initial Type Certificate (TC), Supplemental Type Certificate (STC), amended TC, or amended STC for the installation and continued airworthiness of ADS-B OUT equipment.

1-3. Where to Find This Advisory Circular. You can find this AC on the Federal Aviation Administration’s (FAA’s) websites, http://www.faa.gov/regulations_policies/advisory_circulars/ or http://rgl.faa.gov/.

1-4. Scope. This AC only addresses the installation of ADS-B OUT systems. Installation guidance for ADS-B IN can be found in the latest version of AC 20-172, Airworthiness Approval for ADS-B IN Systems and Applications. Installation guidance for Flight Information Services - Broadcast (FIS-B) can be found in AC 20-149, Safety and Interoperability Requirements for Initial Domestic Flight Information Service-Broadcast. If Technical Standard Order, (TSO), TSO-C166b, 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), or TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz, equipment being installed has a receive capability, but that receive capability is not integrated into the aircraft to support ADS-B IN display applications, you do not need to demonstrate specific ADS-B receive performance during the ADS-B OUT installation approval. Appendix 5 provides a list of definitions that are specific to this

2 AC. Appendix 6 provides a list of acronyms that are used in the AC. The latest version of a document should be used where () follows its name. Appendix 7 provides a list of related documents.

1-5. Background.

a. ADS-B is a next generation surveillance technology incorporating both air and ground aspects that provide Air Traffic Control (ATC) with a more accurate picture of the aircraft’s three-dimensional position in the en route, terminal, approach and surface environments. The aircraft provides the airborne portion in the form of a broadcast of its identification, position, altitude, velocity, and other information. The ground portion is comprised of ADS-B ground stations which receive these broadcasts and direct them to ATC automation systems for presentation on a controller’s display. In addition, aircraft equipped with ADS-B IN capability can also receive these broadcasts and display the information to improve the pilot’s situation awareness of other traffic.

b. ADS-B is automatic because no external interrogation is required. It is dependent because it relies on onboard position sources and broadcast transmission systems to provide surveillance information to ATC, and other users. Figure 1 provides a functional overview of an aircraft ADS-B system.

Figure 1. Functional Overview of ADS-B OUT System.

Note: Heading is an optional interface. Traffic Alert and Collision Avoidance System (TCAS) status is only required for aircraft equipped with TCAS II.

c. ADS-B IN and ADS-B OUT. ADS-B OUT refers to an aircraft broadcasting own-ship information. ADS-B IN refers to an aircraft’s ability to receive ADS-B information, such as ADS-B ADS-B Antenna ADS-B Antenna ADS-B Equipment Position/ VelocityHeading Air/ Ground Status Pilot Input TCAS Status Baro Altitude

3 messages from other aircraft or Traffic Information Services-Broadcast (TIS-B), and Automatic Dependent Surveillance - Rebroadcast (ADS-R) from the ground infrastructure.

d. Links. There are two ADS-B link options, 1090 extended squitter (1090ES) and universal access transceiver (UAT). The 1090ES equipment operates on 1090 MHz and has performance requirements specified in TSO-C166b. The UAT operates on 978 MHz and has performance requirements specified in TSO-C154c. This AC addresses installing equipment meeting the requirements of either TSO.

Note: 14 CFR 91.225 requires 1090ES in Class A airspace.

4 Chapter 2. The Approval Process & Necessary Documentation

2-1. ADS-B System Approval Process.

a. This AC addresses the initial airworthiness approval through the type certification or supplemental type certification process of an ADS-B OUT system that meets the equipment requirements of 14 CFR 91.227. Information on the STC and TC process can be found in the latest revisions of AC 21-40, Guide for Obtaining a Supplemental Type Certificate and Order 8110.4, Type Certification.

b. This AC covers installation of the ADS-B equipment, updates to the flight manual, updates to the instructions for continued airworthiness (ICA), guidance for interfacing systems, ground test, and flight test.

c. The ADS-B system is depicted in figure 1 and includes the ADS-B equipment, a position source, a barometric altitude source, an air-ground status source, a TCAS II source if the aircraft is equipped with TCAS II, an optional heading source, and all associated antennas and displays.

Specifically list the components that make up the ADS-B system on the master drawing list. You may demonstrate interoperability with multiple components for a given function. For example, you may request approval for a secondary position source, or add multiple unique position sources to the STC.

2-2. Aircraft Flight Manual. Include ADS-B OUT operating limitations, normal operating procedures, and system description in the Airplane Flight Manual (AFM), Rotorcraft Flight Manual (RFM), AFM Supplement (AFMS), or RFM supplement (RFMS). The flight manual must also indicate if that installation meets the equipment requirements of 14 CFR 91.227. This can be accomplished by adding the following statement to the General or Normal Procedures section of the flight manual:

“The installed ADS-B OUT system has been shown to meet the equipment requirements of 14 CFR 91.227.”

a. Operating limitations. The flight manual should describe any operating limitations as specified by the equipment manufacturer or as a result of installation considerations.

b. Normal operating procedures. Describe normal and non-normal operating procedures for the system in the flight manual.

(1) Describe any actions expected of the pilot.

(2) Describe how to enter the Mode 3/A code, Flight ID, operate the IDENT function, and activate or deactivate emergency status. If the ADS-B system and transponder do not have a single point of entry for the Mode 3/A code, IDENT, and emergency status, then the flight manual procedures must ensure conflicting information is not transmitted from the ADS-B system and transponder.

(3) Describe any ADS-B OUT displays and provide instructions to the pilot on how to respond to any error conditions.

(4) Describe how the ADS-B OUT system can be disabled, if there is an ability to disable the ADS-B system, and the means through which the pilot can detect that the system has been disabled. The flight manual must address the ramifications of turning off the ADS-B OUT system, including the ramifications to the transponder and TCAS II if disabling the ADS-B OUT system also disables the transponder or the TCAS II.

(5) Include guidance in the flight manual on when to enable the ADS-B system. The ADS-B system must be enabled (turned ON) during all phases of flight operation including airport surface movement operations. ADS-B IN surface applications and ATC surface surveillance will use ADS-B broadcasts, thus it is important for aircraft ADS-B OUT systems to continue to transmit on the airport surface. If the ADS-B function is embedded in a Mode S transponder, the flight manual, checklists, and any operator procedures manuals must be updated accordingly with ADS-B operations guidance.

Note: Historically, transponders have been turned on by the flight crew when entering the runway for takeoff and turned off or to standby when exiting the runway after landing. When ADS-B is integrated into a Mode S transponder, the existing guidance for transponder operation must be updated to ensure the ADS-B is operating during airport surface movement operations.

c. System Description. Describe the ADS-B OUT system and the interface with other systems on the aircraft in the flight manual.

2-3. Continuing Airworthiness Requirements.

a. ADS-B OUT equipment. Follow the ADS-B equipment manufacturer’s guidance for periodic inspection and maintenance of the ADS-B system. ICA must be provided and must address any maintenance requirements to maintain the ADS-B equipment.

b. ADS-B functionality in a transponder. Transponders which incorporate ADS-B functionality (such as with 1090ES) must continue to meet the operational requirements of 14 CFR 91.413, 91.215, and 91.217 and comply with the transponder system tests and inspections called out in 14 CFR part 43, appendix F. See AC 43-6, Altitude Reporting Equipment and Transponder System Maintenance and Inspection Practices.

c. Altimetry systems and altitude reporting equipment. Altitude reporting equipment connected to the ADS-B system must comply with all applicable 14 CFR 91.217, 91.411, and part 43 appendix E test and inspection requirements. See AC 43-6. If the altimetry system is compliant with the Reduced Vertical Separation Minimum (RVSM) standards, the requirements and tolerances stated in the approved RVSM maintenance program must be met. ADS-B installation does not alter these requirements.

d. Maintenance and design changes to interfacing components. The ADS-B system interfaces with multiple external components, such as position sources and altimetry sources. The installer should list all interfacing components in the ICA. It is important that any future maintenance or design changes to these interfacing components be accomplished in such a way that continued satisfactory performance of the overall ADS-B system is maintained.

(1) Maintenance of the ADS-B system. The ADS-B system installation must include ICAs that meet the typical requirements for a system installation, which includes how to accomplish a complete functional check of the system.

(2) ADS-B source system components. While the installer may not have access to the specific source system ICAs to incorporate changes into those specific documents, the installer must do an analysis of the source systems to determine what maintenance actions on those source systems would require a functional test of the ADS-B system to verify that the system is operating properly. In particular, those systems providing a dedicated input to the ADS-B system which cannot be verified by other means should be tested as part of the ADS-B system as a whole. Once the installer identifies those actions, they must provide recommended language for the operator to include in their ICAs. If the installer determines that removal and replacement of the GPS receiver requires a full functional check of the ADS-B system because the GPS input to the ADS-B cannot be verified by other means, their instructions to the operator should indicate this. For example:

Modify the R&R ICA instructions in your GPS maintenance manual to include the following statement: “Removal and replacement of the GPS receiver also requires a full functional check of the ADS-B system per MM XX-XX-XX, Pg xxx. Make a log book entry for accomplishment of this test.”

(3) Design changes to interfacing components. Ensuring continued airworthiness of the ADS-B system following upgrades of interfacing components could be problematic if the installer of the ADS-B system is unaware of design changes to interfacing components, or if the installer of the updated interfacing component is unaware of a potential impact to the ADS-B system. To avoid this problem, the ADS-B system installer must update the ICA for each interfacing system with a process that ensures continued airworthiness of the ADS-B system following design changes to the interfacing component.

7 Chapter 3. ADS-B System Installation Guidance

3-1. General Installation Guidance.

a. Environmental qualification. Ensure the environmental qualification of the installed equipment is appropriate for the aircraft in accordance with AC 21-16G, RTCA/DO-160 Versions D, E, F, and G “Environmental Conditions and Test Procedures for Airborne Equipment.”

b. System Safety assessment. The ADS-B System Design Assurance (SDA) parameter indicates the probability of an ADS-B system malfunction causing false or misleading position information or position quality metrics to be transmitted. SDA may be preset at installation for systems that do not utilize multiple position sources with different design assurance levels, otherwise the system must be capable of adjusting the SDA broadcast parameter to match the position source being employed at the time of transmission.

(1) Compliant architecture. ADS-B equipment meeting the minimum performance requirements of TSO-C166b or TSO-C154c that is directly connected to a position source meeting the minimum performance requirements of any revision of TSO-C129, Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS), TSO-C145, Airborne Navigation Sensors Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS), TSO-C146, Stand-Alone Airborne Navigation Equipment Using the Global Positioning System (GPS) Augmented by the Wide Area Augmentation System (WAAS), or TSO-C196, Airborne Supplemental Navigation Sensors for Global Positioning System Equipment Using Aircraft-Based Augmentation, may set the SDA = 2 without further analysis. For installations in aircraft with more complex system architectures, a system safety assessment, as described below, is required to set the SDA. Installations with uncertified equipment must set SDA = 0.

(2) Conducting the system safety assessment. ADS-B systems using position sources not listed in paragraph 3-1b(1) or systems with intermediary devices such as data concentrators must accomplish a system safety assessment and set the SDA according to the results of the assessment. Systems integrated through a highly integrated data bus architecture must complete the system safety assessment. The system safety assessment must demonstrate that the installed system meets all TSO-C166b or TSO-C154c requirements to set the SDA = 2 or 3. This can be accomplished using the methods, for example, as described in AC 25.1309-1(), Systems Design and Analysis, AC 23.1309-1(), System Safety Analysis and Assessment for Part 23 Airplanes, SAE ARP 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, or SAE ARP 4754a, Certification Considerations for Highly- Integrated or Complex Aircraft Systems.

Note: Although the direct effects to your aircraft of an ADS-B failure may be minor, the ADS-B information will be used by other ADS-B equipped aircraft and by ATC, thus the provisions in AC 23.1309-1() that allow reduction in failure probabilities and design assurance level for aircraft under 6,000 pounds do not apply to the ADS-B system.

8 If the system contains different design assurance levels for hardware and software, then the worst case design assurance level should be used. For example, if the hardware assurance level is level C, and the software assurance level is B, the SDA would indicate that the system has been qualified commensurate with a Major failure condition. If the ADS-B system is integrated with a non-compliant GPS, the SDA must be set to 0.

(3) Existing equipment design assurance. The aircraft installation may make use of some equipment certified for use with an existing transponder system. There is no intent for this safety assessment to drive the replacement of existing altimetry, flight crew controls, heading instruments, or antennas. In contrast, the position source installation must be compliant with the guidance in this AC including design assurance considerations.

c. Position latency. Latency is the difference between the time a measurement is taken to determine the aircraft’s geometric position and the time when that position measurement is transmitted by the aircraft’s ADS-B equipment. Limiting the latency in ADS-B systems minimizes the errors in the reported position. TSO-C166b and TSO-C154c ADS-B equipment typically compensate for latency by extrapolating the position based on velocity information. All applicants must demonstrate compliance with the latency requirements in paragraph 3-1c(1). This can be done by equipping with a compliant architecture listed in paragraph 3-1c(2) or performing an analysis detailed in paragraph 3-1c(3). Latency terms are further defined in appendix 3 of this AC.

Note: To demonstrate compliance with 14 CFR 91.227 you must calculate latency from the position source time of measurement (TOM). Do not calculate latency from the position source time of applicability, as defined in DO-260B, Minimum Operational Performance Standards for 1090 MHz Automatic Dependent Surveillance-Broadcast (ADS-B), with Corrigendum 1 and DO-282B with corrigendum 1.

(1) Position latency requirements. There are two position latency requirements associated with ADS-B OUT.

(a) Total latency. Total latency is defined as the difference between the time when the position is measured and when the position is transmitted from the aircraft. In order to meet 14 CFR 91.227, the total latency must be less than or equal to 2.0 seconds.

(b) Uncompensated latency. Uncompensated latency is the difference between the time of applicability for the transmitted position and the actual time the position is transmitted from the ADS-B system. In order to meet 14 CFR 91.227, the uncompensated latency must be less than or equal to 0.6 seconds. The aircraft must compensate for any latency greater than 0.6 seconds but must not overcompensate by more 0.2 seconds (i.e. lead the aircraft position).

Note: RTCA Special Committee 186 recommends ADS-B OUT systems transmit position information with an uncompensated latency of less than or equal to 0.4 seconds. This recommendation is to support future ADS-B IN applications. The 14 CFR 91.227 latency requirements support ATC separation services and the initial basic ADS-B IN applications. However, we encourage you to minimize

9 uncompensated latency as much as possible in your installation. Recommendations for minimizing latency are included in appendix 3 of this AC.

(2) Compliant architecture. ADS-B systems which directly connect a position source meeting the minimum performance requirements of any revision of TSO-C145, TSO-C146, or TSO-C196 with ADS-B equipment meeting the minimum performance requirements of TSO-C166b or TSO-C154c meet the total latency and uncompensated latency requirements. Systems with a compliant architecture do not need to accomplish a position and velocity latency analysis.

(3) Position latency analysis. If you are installing an ADS-B system that does not have a compliant architecture described in paragraph 3-1c(2), you must accomplish a latency analysis to demonstrate that the installed ADS-B system meets the total latency and uncompensated latency requirements. Systems integrated through a highly integrated data bus architecture must complete the latency analysis. Appendix 3 of this AC provides for an acceptable method to complete the latency analysis.

d. Integrity metric latency. There is an allowance for Global Navigation Satellite System (GNSS) position sources to delay the update of the integrity containment radius while attempting to detect and exclude faulted satellites. 14 CFR 91.227 allows up to 12 seconds for the ADS-B system to transmit a change in the Navigation Integrity Category (NIC). This 12 second allowance is available for any position source, not just GNSS position sources. The 12 seconds includes both the time for the position source to detect the fault and time for the ADS-B system to transmit the fault indication. The requirement to indicate a change in NIC applies to the time between when a faulted position is first transmitted and when the updated NIC is transmitted indicating the fault. 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 faulted position is transmitted and when the NIC indicating the fault is transmitted.

(1) Compliant architecture. ADS-B equipment meeting the minimum performance requirements of TSO-C166b or TSO-C154c that are directly connected to a position source meeting the minimum performance requirements of any revision of TSO-C145, TSO-C146, or TSO-C196 will typically meet the integrity latency requirements. For these systems you only need to demonstrate, through analysis, that a non-isolated GNSS satellite fault detected by the position source is properly passed to the ADS-B equipment and that the ADS-B equipment indicates an invalid position by transmitting the position integrity and accuracy metrics equal to zero.

Note: GNSS Sensor ARINC Characteristic 743A-5, allows flexibility in how information is transferred during a GNSS satellite fault, thus it is necessary to ensure a non-isolated satellite failure results in the ADS-B indicating an invalid position.

(2) Integrity metric latency analysis. If you are installing an ADS-B system without a compliant architecture described above, you must accomplish a latency analysis to demonstrate the ADS-B system meets the integrity metric latency requirements. The latency analysis should include the maximum time for a position source to indicate an integrity fault, any delay added by an intermediary device such as a data concentrator, and the delay added by the ADS-B equipment.