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.
e. System design assurance (SDA) and source integrity level (SIL) latency.
14 CFR 91.227 requires changes in the SDA or SIL be broadcast within 10 seconds. Changes in the SDA or SIL will typically only occur when a secondary position source is integrated into an ADS-B system and that secondary position source has a different SDA or SIL than the primary position source. If you integrate multiple position sources with different SDAs or SILs, demonstrate during ground testing that a change in position source results in an updated SDA and SIL within 10 seconds. If integrating an ADS-B transmitter with a non-compliant GPS, the SDA and SIL must be set to 0.
f. Populating message elements. 14 CFR 91.227 lists parameters that must be populated
(i.e. not a null value) for operation in airspace defined by 14 CFR 91.225. All parameters transmitted by the ADS-B system must conform to the standards in TSO-C166b or TSO-C154c and may not contain false or misleading information.
3-2. ADS-B Equipment.
a. Equipment eligibility. ADS-B equipment must meet the requirements specified in TSO-C166b or TSO-C154c.
b. Installation guidance.
(1) UAT systems with Mode S transponders. Do not install a UAT ADS-B OUT system which has the capability to transmit a random 24-bit address in an aircraft which also has a Mode S transponder unless the random 24-bit feature is disabled. The ATC automation system would interpret the different 24-bit addresses as two separate aircraft, and alert controllers to a conflict that does not actually exist.
(2) Mixed transmit/receive classifications. TSO-C166b and TSO-C154c allow Class A transmit-only and Class A receive-only equipment configurations. There are no restrictions for installing a certain class of receive equipment with a different class of transmit equipment.
For example, a Class A3 transmit-only unit can be used in the same aircraft with a Class A1 receive-only unit. It is also acceptable to have a TSO-C166b transmitter and a TSO-C154c receiver and vice versa.
(3) Stand alone 1090ES transmitters. RTCA/DO-260B, paragraph 2.2.2.2 only allows Class A0 and B0 1090ES stand-alone (not integrated with a transponder) transmitters.
This AC does not cover installation approval for class A0 or B0 1090ES transmitters because they are not compliant with 14 CFR 91.227.
(4) Multiple ADS-B OUT systems. If the aircraft has the ability to operate a 1090ES and a UAT ADS-B OUT system at the same time, the systems must have a single point of entry for the emergency code, IDENT, and Mode 3/A code. Neither system may use a random address feature. If dual ADS-B OUT systems of the same link are installed (e.g., to increase dispatch reliability), the installation must preclude operation of both systems simultaneously.
11 Note: 1: We recommend that you do not install both 1090ES and UAT ADS-B OUT capability on the same aircraft.
Note: 2: Installation of dual 1090ES and UAT ADS-B IN capability is acceptable and encouraged.
c. Configuration of associated parameters. The following paragraphs provide additional guidance on setting key ADS-B OUT parameters. Definitions for each of the following associated parameters are included in appendix 1.
(1) International Civil Aviation Organization (ICAO) 24-bit address. You must set the ICAO 24-bit address during installation in accordance with the ADS-B equipment manufacturer’s instructions. For U.S. civil aircraft, the ICAO 24-bit address is established as a function of the aircraft’s registration or “N” number. You can determine the appropriate address for U.S. registered aircraft on the following FAA website: http://registry.faa.gov/aircraftinquiry/.
Use of a random 24 bit address is discussed further in paragraph 3-7.b.(3) of this AC.
Note: 1: The ICAO 24-bit address is also used by the Mode S transponder. For the addition of ADS-B (1090ES) in an existing Mode S transponder installation, verify that the ICAO 24-bit address decodes to the current aircraft registration number.
Note: 2: The ICAO 24-bit address will have to be updated if the aircraft’s registration number changes.
(2) Aircraft length and width. This parameter must be configured during installation.
Do not set the length and width parameter to a value of “0”, as the length and width code is required by 14 CFR 91.227. The length and width code chosen should be the smallest value that encompasses the entire aircraft. For example, the length and width code for a helicopter with a refueling boom would include the rotor blades or any other fixed object that extends from the fuselage, see figure 2.
12 Figure 2. Example of Aircraft Length and Width Code Determination.
Reported Length (using next higher value) Reported Width (using next higher value) Actual length of aircraft Actual width of aircraft Aerial Refueling boom GNSS antenna location
(3) ADS-B IN capability. This parameter must be configured to indicate if the aircraft has an ADS-B IN system installed. For ease of installation, the parameter does not have to indicate the operational status of the ADS-B IN system. If the aircraft has both 1090ES ADS-B IN and UAT ADS-B IN systems installed, both the 1090ES ADS-B IN and UAT ADS-B IN capability should be set accordingly.
(4) Emitter category. Table 1, Emitter Category, provides guidance on setting the emitter category.
13 Table 1. Emitter Category
Emitter Category Description No Emitter Category Do not use this emitter category. If no emitter category fits your installation, seek guidance from the FAA as appropriate.
Light Airplane < 15,500 pounds Any airplane with a maximum takeoff weight less than 15,500 pounds. This includes very light aircraft (light sport aircraft) that do not meet the requirements of 14 CFR 103.1.
Small Airplane ≥ 15,500 to < 75,000 pounds Any airplane with a maximum takeoff weight greater than or equal to15,500 pounds but less than 75,000 pounds.
Large Airplane ≥ 75,000 to < 300,000 pounds Any airplane with a maximum takeoff weight greater than or equal to 75,000 pounds but less than 300,000 pounds that does not qualify for the high vortex category.
Large Airplane with High Vortex Any airplane with a maximum takeoff weight greater than or equal to 75,000 pounds but less than 300,000 pounds that has been determined to generate a high wake vortex. Currently, the Boeing 757 is the only example.
Heavy Airplane ≥ 300,000 pounds Any airplane with a maximum takeoff weight equal to or above 300,000 pounds.
Highly Maneuverable > 5 G and > 400 TAS Any airplane, regardless of weight, which can maneuver in excess of 5 G’s and maintain true airspeed above 400 knots.
Rotorcraft Any rotorcraft regardless of weight.
Glider / Sailplane Any glider or sailplane regardless of weight.
Lighter than Air Any lighter than air (airship or balloon) regardless of weight.
UAV Any unmanned aerial vehicle or unmanned aircraft system regardless of weight.
Ultralight Vehicle A vehicle that m eets the requirements of 14 CFR 103.1.
Light sport aircraft should not use the ultralight emitter category unless they meet 14 CFR 103.1.
3-3. Position Source.
a. Equipment eligibility. 14 CFR 91.227 is performance based and does not require any specific position source. The existing navigation equipment and airworthiness standards should be used, however they must be augmented to address the unique issues associated with ADS-B. A TSO authorization alone is not sufficient to ensure ADS-B compatibility. The position source must also comply with the appendix 2 minimum performance requirements. Compliance with the appendix 2 requirements may be documented in the position source manufacturer’s installation instructions.
Note: Not all GNSS position sources will provide the same availability. See appendix 2 for more information on GNSS availability. The FAA recommends TSO-C145 or TSO-C146 position sources that meet the appendix 2 requirements to maximize availability and ensure access to the airspace identified in 14 CFR 91.227 after January 1, 2020.
b. Installation guidance.
(1) Installation guidance. The position source must be installed in accordance with the applicable guidance. New GNSS position sources must be installed in accordance with AC 20-138C, Airworthiness Approval of Positioning and Navigation Systems.
(2) Position source and ADS-B equipment interface. Unless the ADS-B equipment manufacturer has analyzed the interface between the position source and the ADS-B equipment you are installing, and specifically listed the position source in the ADS-B equipment’s installation manual, you must provide an analysis of the interface between the position source and the ADS-B equipment which demonstrates that the position, velocity, position accuracy, position integrity, and velocity accuracy information taken from the position source is properly interpreted by the ADS-B equipment. When installing modifications to a position source, the installer must determine and test those portions of the ADS-B system that are impacted by the modification and ensure the ADS-B system is not adversely impacted.
Note: This analysis will require engineering design data from the ADS-B equipment manufacturer and / or the position source manufacturer.
(3) Secondary position source. There is no requirement to have a secondary position source input. However, if you interface a secondary position source to the ADS-B system, it must meet the requirements in appendix 2.
Note: If a position source is unable to provide 14 CFR 91.227 accuracy and integrity values, it will not qualify the aircraft to operate in airspace defined by 14 CFR 91.225 after January 1, 2020.
(4) Position source selection. If multiple position sources are interfaced to the ADS-B equipment, source selection can be accomplished manually by the pilot, automatically by the aircraft’s navigation system, or by the ADS-B equipment. We discourage automatic selection of the ADS-B position source based solely on the navigation source in use because operational requirements sometimes dictate a navigation source that may not provide the best ADS-B performance. If the ADS-B equipment accomplishes the position source selection, it should do so in accordance with TSO-C166b or TSO-C154c. If multiple sources are interfaced to the ADS-B system, there should be a means for the flight crew to readily determine which source is selected. Describing how this selection is performed in the AFM is one acceptable means of compliance.
Note: TSO-C166b and TSO-C154c require the ADS-B equipment to use a single position source for the latitude, longitude, horizontal velocity, and accuracy metrics, and integrity metrics.
(5) Position source. The ADS-B position source does not need to be the same position source used for navigation. It is acceptable for a GNSS position source to be embedded in the ADS-B equipment and provide position information to the ADS-B without providing any navigation information to other on-board systems. As addressed in appendix 2, an integrated GNSS position source should still meet the requirements of TSO-C145, TSO-C146, or