# AC 20-172A: Airworthiness Approval for ADS-B In Systems and Applications

- Type: Advisory circular (guidance, not mandatory unless a rule or AD requires it)
- Status: Historical
- Version in force: [AC 20-172B](https://openairdocs.org/ac/20-172), approved May 20, 2015. This is a historical version
- Approved: March 23, 2012
- Last reviewed: April 17, 2012
- Family: AC 20-172
- Cancels: [AC 20-172](https://openairdocs.org/ac/20-172)
- Cancelled by: [AC 20-172B](https://openairdocs.org/ac/20-172)
- 14 CFR parts: 23, 25
- Pages: 43
- PDF: https://openairdocs.org/files/sha256/8e/2d/8e2d00c6c1db870846f0cc8e8c01373bbebb1c8cde3f1bdd09fe3b9d0187aefe
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/A577CA07065F4A26862579CD007889E0.0001
- DRS record last changed: November 21, 2025
- Page: https://openairdocs.org/ac/20-172A

## Versions

- [AC 20-172B](https://openairdocs.org/ac/20-172) (Current), approved May 20, 2015, 49 pages
- [AC 20-172A](https://openairdocs.org/ac/20-172A) (Historical), approved Mar 23, 2012, 43 pages
- [AC 20-172](https://openairdocs.org/ac/20-172?v=DD15646062B13416862578460053DB86) (Historical), approved Feb 28, 2011, 40 pages

## Text

Each page's text from the PDF; open the PDF at a page with #page=N.

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U.S. Department of Transportation Federal Aviation Administration

Advisory Circular

Subject: Airworthiness Approval for ADS-B In Systems and Applications Date: 3/23/12 Initiated by: AIR-130 AC No: 20-172A

This advisory circular (AC) provides guidance for the initial and follow-on installations of Automatic Dependent Surveillance – Broadcast (ADS-B) In systems supporting ground and airborne traffic applications. These applications are defined in TSO-C195a, Avionics Supporting Automatic Dependent Surveillance – Broadcast (ADS-B) Aircraft Surveillance Applications (ASA). The applications discussed in this AC are designed to support basic situational awareness as well as the In-Trail Procedure. As more advanced applications mature, this AC will be updated to reflect those added to TSO-C195a.

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

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ii

Table of Contents

Paragraph Page

Chapter 1. General Information … 1

1-1. Purpose … 1

1-2. Audience … 1

1-3. Scope … 1

1-4. Background … 2

Chapter 2. ADS-B In System Installation Guidance … 4

2-1. System Overview … 4

2-2. Equipment Classes … 4

2-3. ADS-B Applications … 5

2-4. Cockpit Display of Traffic Information (CDTI) … 6

2-5. Airborne Surveillance and Separa tion Assurance Processing (ASSAP) … 8

2-6. ADS-B In Receiver and Antenna … 8

2-7. Integration Considerations … 9

Chapter 3. Test and Evaluation … 11

3-1. General … 11

3-2. Ground Tests … 11

3-3. Flight Tests … 13

Appendix 1. Latency Analysis … A1-1

1. Purpose … A1-1

2. Analysis … A1-1

3. Traffic Latency Analysis.................................................................................................. A1 -1

4. Traffic Time of Applicability Analysis … A1-1

5. Own Ship Position Latency Analysis … A1-2

6. Own Ship Position Time of Applicability … A1-2

Appendix 2. Symbology Requirements for the CDTI … A2-1

1. Traffic Symbols and Variations … A2-1

2. Alerts … A2-3

3. TCAS Alert Symbology for TCAS/A SAS Integrated Systems … A2-6

Appendix 3. Definitions and Acronyms … A3-1

1. Definitions: … A3-1

2. Acronyms … A3-9

Appendix 4. Related Documents … A4-1

1. FAA Documents. ............................................................................................................. A 4-1

2. RTCA, Inc. Documents (RTCA DO) documents: … A4-3

3. ARINC Documents:......................................................................................................... A4- 3

4. SAE Documents … A4-4

5. How to Get Related Documents … A4-4

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iii Table of Contents (Continued)

List of Tables

Table 1. ADS-B In Equipment Classes … 4

Table 2. ITP Maneuver Criteria … 15

List of Figures

Figure 1.  ADS-B In System Overview … 2

Figure 2.  Traffic Latency Block Diagram … A1-2

Figure 3.  Own-ship Latency Block Diagram Simple Architecture … A1-3

Figure 4.  Own-ship Latency Block Diagram Alternate Architecture … A1-3

Figure 5.  Basic Directional Symbol … A2-1

Figure 6.  Basic Non-Directional Symbol … A2-2

Figure 7.  Directional and Non-directional On-ground Traffic Symbols … A2-2

Figure 8. Basic Surface Vehicle Symbol…………………………………………………….A2-3

Figure 9.  Proximate Directional and Non-directional Traffic Symbol … A2-4

Figure 10.  Directional and Non-directional Designated Traffic Symbols … A2-5

Figure 11.  Traffic Advisory Symbols … A2-6

Figure 12.  Resolution Advisory Symbols … A2-7

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1 Chapter 1. General Information.

1-1. Purpose.

a. This advisory circular (AC) provides guidance material for the installation of ADS-B In technology in aircraft. ADS-B In includes reception of ADS-B, Traffic Information Services-Broadcast (TIS-B) and Automatic Dependent Surveillance – Rebroadcast (ADS-R) messages, but does not include reception of Flight Information Service – Broadcast (FIS-B) messages.

b. The installation of ADS-B In avionics provides the pilot(s) with supplemental information. No existing responsibility is changed by virtue of installation of this equipment and application(s). The situational awareness applications defined in TSO-C195a supplement, but do not replace, a pilot’s see and avoid responsibility, as required by Title 14 of the Code of Federal Regulations (14 CFR) 91.113(b).

c. 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 In equipment. However, if you use the means described in this AC, you must follow it entirely. The term “must” is used to indicate mandatory requirements when following the guidance in this AC. The terms “should” and “recommend” are used when following the guidance is recommended but not required to comply with this AC. A list of definitions and acronyms relevant to this AC can be found in appendix 3.

d. This AC provides guidance information intended for new approvals. This AC is not intended to modify, change or cancel existing equipment design or airworthiness approvals.

Equipment with existing approvals can continue to be installed within the provisions of their original design and airworthiness certification.

1-2. Audience. This AC is for installers of ADS-B In equipment, and can assist in obtaining design approval for installation. The installed design can be approved under a type certificate (TC), supplemental type certificate (STC), including approved model list supplemental type certificate (AML-STC), amended type certificate, or amended supplemental type certificate (ASTC).

1-3. Scope. This AC addresses initial and follow-on installations of ADS-B In systems that comply with TSO-C195a, Avionics Supporting Automatic Dependent Surveillance – Broadcast (ADS-B) Aircraft Surveillance Applications (ASA). Data from a previously approved installation design may be reused to fulfill some of the data requirements for a follow-on installation design as appropriate. For example, the latency analysis between a GPS position source and the ADS-B equipment may be reused on a follow-on installation provided that the hardware and software part numbers for both units are identical. Modifications to previously approved hardware or software must be evaluated to determine data applicability. All installations of ADS-B In should also provide ADS-B Out. Installation guidance for ADS-B Out can be found in AC 20-165, Airworthiness Approval of Automatic Dependent Surveillance - Broadcast (ADS-B) Out Systems.

Installation guidance for flight information service-broadcast (FIS-B) applications that make use of the Surveillance and Broadcast Services (SBS) ground system will be covered in a future AC.

Installation guidance for other FIS-B equipment can be found in AC 20-149, Safety and Interoperability Requirements for Initial Domestic Flight Information Service–Broadcast. A list

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2 of related documents can be found in appendix 4 of this AC.

1-4. Background.

a. The ADS-B system, shown in figure 1, 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, and surface environments. The aircraft provides broadcast messages 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 “see” these broadcasts from other ADS-B equipped aircraft and display them to improve the pilot’s situational awareness of other traffic, both airborne and on the ground. Suitably equipped surface vehicles may also be visible to ADS-B In capable aircraft.

Figure 1. ADS-B In System Overview ATC RADAR Non-ADS-B Target Transponder Reply Track ADS-B 1090 MHz ADS-B on Alternate Link ADS-B on UAT Common Link e.g., 1090MHz ATC ADS-B Ground Station ADS-B Direct Target Sources Traffic Information System Broadcast (TIS-B) ADS-R 1090 MHz TIS-B (1090 and UAT Format)ADS-B Rebroadcast (ADS-R) ADS-B Receiver Airborne Surveillance and Separation Assurance Processor TCAS Position Sensor Barometric Altimeter Other Aircraft Systems Surveillance Tracks Display Data Control Data ADS-B TIS-B ADS-R Reports Antenna Aircraft ADS-B Receiver and Traffic Display Cockpit Display of Traffic InformationSystem Control Data CrewFlight ATC ADS-B Ground Station

b. ADS-B Out refers to an appropriately equipped aircraft broadcasting own-ship information. ADS-B In refers to an appropriately equipped aircraft’s ability to receive and display other aircraft’s ADS-B information and ground station broadcast information, such as

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3 traffic information service - broadcast (TIS-B) and automatic dependent surveillance rebroadcast (ADS-R). The TIS-B service provides traffic based on ground surveillance of transponder equipped aircraft. The ADS-R service provides traffic from aircraft equipped with an alternate ADS-B link.

c. 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, 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). The UAT operates on 978 MHz and has performance requirements specified in TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance – Broadcast (ADS-B) Equipment Operating on Frequency of 978 MHz.

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4 Chapter 2. ADS-B In System Installation Guidance.

2-1. System Overview. ADS-B In refers to an appropriately equipped aircraft’s ability to receive and display other aircraft’s ADS-B information and ground station broadcast information, such as TIS-B and ADS-R. The information can be received by an appropriately equipped aircraft on either of two radio frequency (RF) links: 1090 ES or 978 MHz UAT. The received information is processed by onboard avionics and presented to the flight crew on a display. In this AC, guidance is provided for the display of traffic information while on the airport surface and while airborne. This information supports the applications defined in TSO-C195a. This AC will be updated to add appropriate guidance for additional applications as they mature.

2-2. Equipment Classes. TSO-C195a defines minimum performance standards that provide a basis for installation of ADS-B In equipment in aircraft. The TSO defines three avionics equipment classes: (A) cockpit display of traffic information (CDTI) (surface only); (B) CDTI;

and (C) airborne surveillance and separation assurance processing (ASSAP). Class A equipment is intended to support the display of ADS-B traffic while own-ship is on the surface and moving slower than 80 knots. Class A equipment must deactivate the CDTI when airborne or at speeds greater than 80 knots. Class B equipment supports the display of ADS-B traffic when airborne as well as on the ground. Class C equipment processes ADS-B messages to generate traffic data for a CDTI. Table 1 shows which applications are supported by the three equipment classes. An installation requires both the CDTI and ASSAP functions, which are explained in paragraphs 2-4 and 2-5 of this AC, respectively.

Table 1. ADS-B In Equipment Classes

Criticality Equipment Classes Application Loss of Function Hazardous Misleading Information CDTI (Surface Only) (A) CDTI (B) ASSAP (C) 1 Enhanced Visual Acquisition (EVAcq) Minor Major Not Permitted B1 C1 2 Basic Surface (Runways) Minor Major (> 80 Knots) Minor (< 80 Knots) A2 B2 C2 3 Basic Surface (Runways + Taxiways) Minor Major (> 80 Knots) Minor (< 80 Knots) A3 B3 C3 4 Visual Separation on Approach (VSA) Minor Major Not Permitted B4 C4 5 Basic Airborne (AIRB) Minor Major Not Permitted B5 C5 6 In-Trail Procedures (ITP) Minor Major Not Permitted B6 C6

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2-3. ADS-B Applications.

a. ADS-B In avionics enable one or more of the following aircraft surveillance applications: enhanced visual acquisition (EVAcq); basic airborne (AIRB); visual separation on approach (VSA), basic surface (SURF) (runways and taxiways, or runways only); and In-Trail Procedures (ITP). Refer to table 1 to see which applications are supported by the three equipment classes.

b. The basic airborne application (AIRB) displays ADS-B traffic on a plan view (bird's eye view) relative to own-ship. This application is the minimum requirement for installations that implement other applications such as VSA or ITP. Each aircraft symbol displayed conveys position, direction, and altitude information. Optionally, additional information, like identity, may be displayed. The traffic information assists the flight crew in visually acquiring traffic while airborne. This application improves both safety and efficiency by providing the flight crew with enhanced traffic awareness. Installations that provide in flight moving map displays in addition to traffic should comply with TSO-C165, Electronic Map Display Equipment for Graphical Depiction of Aircraft Position.

c. The enhanced visual acquisition application (EVAcq), also displays ADS-B traffic on a plan view (bird's eye view) relative to own-ship. This application is designed to support only the display of ADS-B traffic, including ADS-R, TIS-B, and TCAS derived traffic.

Implementations that include other application classes must use the AIRB application instead.

The traffic information assists the flight crew in visually acquiring traffic while airborne.

EVAcq does not relieve the pilot of see and avoid responsibilities found in 14 CFR 91.113b.

This application is expected to improve both safety and efficiency by providing the flight crew enhanced traffic awareness. Installations that provide in-flight moving map displays in addition to traffic should comply with TSO-C165, Electronic Map Display Equipment for Graphical Depiction of Aircraft Position.

d. The visual separation on approach (VSA) application builds upon the basic airborne application (AIRB). It allows the pilot to select an aircraft to follow on approach. Additional information about the selected aircraft, including range and ground speed, is displayed to enhance the pilot’s situational awareness. The CDTI display is used to assist the flight crew in acquiring and maintaining visual contact during a visual approach. The application improves both the safety and the performance of visual approach operations. The VSA application should not be confused with creating a new approach operation. No operational responsibility is changed when using the VSA application.

e. The basic surface application (SURF) with runways and taxiways displays ADS-B traffic on a plan view (bird's eye view) relative to own-ship, superimposed on a map of the airport surface. This map consists of all runways at supported airports and includes taxiways when that data is available. Aircraft on-ground and in-air as well as properly equipped surface vehicles are differentiated by symbols to aid the pilot in visual acquisition. The surface application improves flight crew situational awareness during taxi, takeoff, and landing phases of flight.

This application reduces the possibility of runway incursion and collision. These installations should also comply with TSO-C165 Electronic Map Display Equipment for Graphical Depiction of Aircraft Position for airport moving map displays. The SURF application with

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6 runways only does not display taxiways.

f. The In-Trail Procedure (ITP) application enables aircraft that desire flight level changes in procedural airspace to achieve these changes on a more frequent basis, thus improving flight efficiency and safety. The ITP achieves this objective by permitting a climb-through or descend-through maneuver between properly equipped aircraft, using a new distance-based longitudinal separation minimum during the maneuver. The ITP requires the flight crew to use information derived on the aircraft to determine if the initiation criteria (see Table 2, Section 3-3) required for an ITP are met. The initiation criteria are designed such that the spacing between the estimated positions of ownship and surrounding aircraft exceed the separation minima with acceptable probability throughout the maneuver. ITP requires specific application-unique processing and display parameters. In addition, ITP will require an operations approval by the FAA flight standards organization. Guidance for this operations approval will be contained in a future update to AC 90-114, Automatic Dependent Surveillance- Broadcast (ADS-B) Operations.

g. The displayed ADS-B information addressed by this AC is not intended for maneuvering based solely on presence or absence of traffic on the display. As future applications are fielded, we expect that certain maneuvers may be found to be safe and acceptable. The analysis and safety studies to justify such procedures are not yet completed.

When those activities are concluded and the maneuvers are shown to be safe and acceptable in the national airspace system (NAS), appropriate maneuvers are expected to be allowed based in part on the displayed ADS-B In information. We will revise this guidance accordingly at that time. Operational guidance will be published by FAA flight standards organization.

**2-4. CDTI.**

a. Displays. The ADS-B In system includes at least one flight deck traffic display (i.e., CDTI) depicting the relative position and related information of ADS-B equipped aircraft in a plan view (bird's eye view). The CDTI display may be presented on a dedicated display or integrated into and presented on an existing display (e.g., electronic flight information system (EFIS), multi-function display (MFD)). CDTI equipment should be compliant with the Class A or Class B requirements of TSO-C195a. Class A equipment supports only the Basic Surface application. CDTI equipment should be installed in accordance with manufacturer instructions.

Installation in the forward field of view (14 CFR 23.1321, 25.1321, 27.l321, and 29.1321) will provide the best situational awareness and support subsequent upgrades to other ADS-B applications. Side-mounted displays are acceptable for the basic situational awareness applications and ITP, but have limited potential to support more advanced applications. The display must be installed such that the crew has an unobstructed view of the display when seated in the normal position. For general installation guidance on displays, refer to AC 25-11A and AC 23.1311-1B.

b. ITP Installations. ITP installations must include a CDTI mounted in the forward field of view or as a side mounted display. The traffic display (plan view) must be visible during the ITP vertical maneuver. It is recommended but not required that a graphical vertical/profile view of the traffic be available for flight crews to aid in assessing initiation criteria. This is particularly helpful in situations where there is a significant angle between the track of the own aircraft and the ITP Traffic aircraft (the angle can be any value less than 45

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7 degrees and still be a valid ITP situation). In these cases, relative geometry (ahead of and behind) may not be intuitive.

c. Traffic Symbols. The FAA worked closely with the industry to standardize the ADS-B In symbols and features. The resulting symbols are provided in appendix 2. The traffic display should depict the symbols, features, and information defined in the appendix. However, manufacturers may propose alternate symbols in order to integrate ADS-B with existing flight deck symbology. These alternate symbols will need to be justified by human factors analysis as part of the certification process. Alternate symbol sets are not allowed without additional justification. There is one exception to this guidance. It is acceptable to pair a TSO-C195a Class C ASSAP unit with an existing certified traffic display using legacy symbols (e.g. TCAS, TAS) when either the AIRB or EVAcq application are installed. Minor TSO changes or enhancements, may be made to the previously approved traffic display without requiring the equipment to be made fully compliant to TSO-C195a requirements. This exception only applies to previously approved traffic displays. If any other applications beyond EVAcq or AIRB are installed, the display must be fully compliant with TSO-C195a.

(1) Traffic Symbol and Own Ship Symbol Reference Point. The pilot’s guide for the ADS-B equipment must specify the location of the horizontal position reference point on the traffic symbols and the own ship symbol. For example, this position may be the center of the symbol or the tip of the traffic directional arrow. The own ship horizontal position reference point should be consistent with the existing flight deck philosophy. The traffic and own ship symbols are an abstract representation and are not required to reflect the physical extent of the aircraft. This becomes more evident when implementing the surface application with the underlying airport map.

d. Required Controls. The CDTI control panel may be a dedicated control panel or it may be incorporated into another control, such as a multifunction control display unit (MCDU) or Flight Management Computer (FMC) control display unit (CDU). CDTI controls must be readily accessible from the normal seated position. Pilot controls for the ADS-B In equipment must be provided as follows:

(1) A means to adjust the display range between the minimum and maximum values.

(2) A means to adjust the altitude band between the minimum and maximum values.

(3) A means to adjust the brightness of the display.

e. Optional Controls. The following optional controls may be provided:

(1) A means to select between display of relative and actual altitude.

(2) A means to select at least one traffic element.

(3) A means to select alternate display criteria (e.g., filters and vertical views).

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(4) A means to declutter, which removes optional traffic information when display of the information is not desired. If decluttering is implemented,

(a) A means must be provided for the flight crew to control the decluttering.

(b) The flight crew must be able to perform the declutter operation by a simple action.

(c) The flight crew should be able to return to the previous state by a simple action.

(d) If automatic decluttering is implemented, a means should be provided for the flight crew to control the automated decluttering function.

(e) An indication that decluttering is active must be provided.

(5) A means to pan the view. If panning is implemented:

(a) There must be a means to control panning.

(b) There must be a means to return to the original view with a simple action.

(6) A means to designate traffic for an application. For example, equipment may allow a selected aircraft to be designated for the visual separation on approach application.

2-5. Airborne Surveillance and Separation Assurance Processing (ASSAP). The ASSAP subsystem accepts ADS-B reports, TIS-B reports, ADS-R reports, and traffic alert and collision avoidance system (TCAS) tracks (if installed). ASSAP correlates sources, generates tracks, and performs application-specific processing. Surveillance tracks and application-specific alerts or guidance are output by ASSAP to the CDTI function. The ASSAP equipment must be compliant with the Class C requirements of TSO-C195a and should be installed in accordance with manufacturer instructions. TCAS processors track transponder-equipped aircraft.

Therefore, TSO-C195a equipment requires installations with TCAS to provide these tracks to the ASSAP equipment to complete the traffic picture. TCAS in this AC is meant to apply to all versions of certified traffic advisory system (TAS) or TCAS compliant with TSO-C147, TSO-C118, or TSO-C119c. Hybrid surveillance TCAS are included. For aircraft installations without TCAS, the TIS-B service provides tracks of transponder-equipped aircraft.

2-6. ADS-B In Receiver and Antenna. The installation must include a UAT (per TSO-C154c) or a 1090 ES (per TSO-C166b) receiver. Ideally, installation of a dual-band receiver would allow for dual-link interoperability where ADS-R coverage is not provided. The ASSAP equipment may interface with the ADS-B receiver equipment or it may be integrated.

If TCAS is installed, the ADS-B In equipment must contain or interface with the TCAS equipment so that the TCAS tracks may be used. Guidance material concerning the installation of the UAT or 1090ES equipment, and associated antenna(s), is provided in AC 20-165.

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2-7. Integration Considerations.

a. System Definition. ADS-B In installations include the ADS-B In receiver, antennas, traffic processor, control panels, and display components. All of these component part numbers must be identified as part of the integrated system. Any change to any of the components’ hardware or software requires evaluation of the potential impact to the ADS-B In function.

b. Equipment Compatibility Requirements. A critical component of the ADS-B In system is the positioning sensor. Compatibility between the sensor and the surveillance processor must be established by the equipment manufacturer(s) and detailed in an installation manual or supplement. Position source compatibility should consider the position source requirements in AC 20-165. Compatibility between all other system components should be documented in an installation manual or supplement.

c. Aircraft Integration with ADS-B In System.

(1) Provide electrical power and grounding in accordance with the manufacturer’s installation manual. Conduct an electrical load analysis to verify that there is adequate power capacity for the ADS-B In equipment.

(2) Ensure that the total latency to receive, process, and display traffic data is less than 3.5 seconds. Ensure that traffic time of applicability is within 1 second of the time of display. Ensure the total latency of own-ship position at the display is less than 3.5 seconds.

Ensure that the own-ship time of applicability is within 1 second of the time of display.

Perform a latency analysis in accordance with appendix 1 to demonstrate compliance. The total latency figures here are to be interpreted to mean when an ADS-B message is received. They do not address data age issues while the system is waiting to receive the next position report for an existing track. Data age and timeout requirements are handled separately for each application in TSO-C195a compliant equipment.

(3) The same position source used to provide own ship data for transmission on ADS-B Out should be used to provide position to the ASSAP equipment. Position sources interfaced to the ASSAP equipment must meet the quality metric requirements in DO-317A, section 2.2.4. Further guidance on integration with ADS-B position sources can be found in AC 20-165. Future applications may require that ASSAP and the ADS-B Out equipment use the same position source. Aircraft manufacturers should plan accordingly to prevent extensive redesign. An alternate position source may be used to provide own ship position to the CDTI display, but the accuracy, latency, and display time of applicability requirements still apply (refer to appendix 1). Provide connections in accordance with the manufacturer’s installation manual.

(4) Follow manufacturer’s instructions for strapping and/or programming of configurable aircraft parameters. Manufacturers are highly encouraged to provide instructions to installers for setting the global navigation satellite system (GNSS) antenna offset parameter during installation. The GNSS antenna offset information can be extremely valuable for ADS-B In surface situation awareness and future surface collision alerting applications on large aircraft with GNSS antenna far from the nose.

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(5) Verify that the equipments’ environmental qualifications (e.g., RTCA/DO- 160() environmental categories) are suitable for the aircraft type and equipment location.

(6) Any limitations associated with use of the ADS-B In equipment must be recorded in the Aircraft Flight Manual.

(7) ITP requests and clearances can only be granted using Direct Controller Pilot Communication (DCPC). Although it may be possible to perform ITP requests and clearances via voice communications, in most non-radar regions this means requests and clearances must be accomplished using Controller Pilot Datalink Communications (CPDLC). ITP requests can be lengthy and prone to typographical errors. It is recommended that ITP designs integrate the CDTI and data link systems in order to populate ITP requests automatically. An alternative is to provide the request text on the CDTI so that the flight crew can reference the text while entering the information manually. This reduces the possibility of human error while entering the ITP request. Examples of standardized free text CPDLC message formats for an ITP request (downlink message) can be found in Change 1 to RTCA/DO-306.

d. System Safety Analysis. Unannunciated failures and hazardously misleading data must be improbable/remote for Class B and C equipment; but can be probable for Class A equipment. Loss of function can be probable for all Classes. This can be shown using the methods described in AC 25.1309-1(), System Design and Analysis, AC 23-1309-1(), System Safety Analysis and Assessment for Part 23 Airplanes, AC 27-1B, Certification of Transport Category Rotorcraft, Change 3, or in AC 29-2C, Certification of Normal Category Rotorcraft, Change 3 as appropriate.

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11 Chapter 3. Test and Evaluation.

3-1. General. Installation of an ADS-B In system should be accomplished on an aircraft with an ADS-B Out system. ADS-R and TIS-B services are only provided to aircraft that indicate, in their ADS-B Out messages, that they are an ADS-B In aircraft. This chapter assumes that the ADS-B Out system complies with AC 20-165, and defines additional tests for the installed system.

3-2. Ground Tests.

a. Ground tests should be conducted on each aircraft installation. Ground tests should include the verification that ADS-B Out, ADS-R, and TIS-B message elements can be accurately received and processed. If ADS-B In equipment is integrated with TCAS, then TIS-B reception is not required for airborne traffic. However if the surface applications are implemented, TIS-B surface targets must be processed even by an installation that includes TCAS. Ground tests should include verification of the integration with a position sensor, since own-ship state data is used to generate the displayed data. In addition, any message elements that are presented on the CDTI display should be verified for accuracy. See AC 20-165 for a list and detailed explanation of each of the message elements. Ground test equipment should be capable of generating all of the different types of messages, including ADS-B Out, ADS-R, and TIS-B messages. If targets of opportunity are available to validate the ADS-B In functionality, they may be used in lieu of dedicated test equipment. Verify that the system receives and displays the following traffic information when stimulated appropriately:

(1) Relative horizontal position.

(2) Ground speed of surface traffic (if implemented).

(3) Directionality (Heading or Track Angle).

(4) Pressure altitude of airborne traffic relative to own-ship.

(5) Vertical trend of airborne traffic.

Note: ASSAP must indicate a climb/descent when traffic vertical velocity exceeds 500 feet per minute (fpm). Indication of vertical trend is allowed to occur at smaller vertical rates.

(6) Air/Ground status of traffic.

(7) Flight ID (if implemented).

(8) TIS-B/ADS-R service status (when not installed with TCAS).

(9) Differential ground speed (if implemented).

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b. TCAS-equipped aircraft provide inputs to ASSAP. Verify that the system receives and displays the following information when stimulated appropriately:

(1) Traffic range.

(2) Traffic bearing.

(3) Traffic pressure altitude.

(4) Traffic vertical trend.

(5) Traffic TCAS alert status (i.e., no threat, proximity traffic, traffic advisory, or resolution advisory).

c. If the ADS-B In system supports the surface application, verify that the airport runways are depicted accurately. If taxiway data is available, verify that the airport taxiways are depicted accurately.

d. Evaluate simulated failures of the aircraft sensors integrated with the ADS-B In equipment to determine that the resulting system failure state agrees with the predicted results.

All system failures should be indicated clearly. The effects of system failures should be described in a manual.

e. Observe all of the electronic systems on the flight deck to determine that the ADS-B equipment is not a source of interference (conducted or radiated) to previously installed systems or equipment, and that operation of the ADS-B In equipment is not adversely affected by the previously installed systems and equipment.

f. Evaluate the general arrangement and operation of controls, displays, circuit breakers, indicators, and placards of the ADS-B In and CDTI equipment.

(1) Evaluate the ADS-B In system controls to determine that they are appropriately designed and located to prevent inadvertent actuation. Pay close attention to line select keys, touch screens, or cursor-controlled trackballs, as these can be susceptible to unintended mode selection resulting from their location in the flight deck (for example, proximity to a foot rest or adjacent to a temporary stowage area).

(2) Evaluate the CDTI display to ensure that all information is, at a minimum, legible, unambiguous, and attention-getting (as applicable).

(3) Evaluate the traffic symbols presented on the CDTI display for compliance with the standard recommended symbols from RTCA/DO-317A, which are summarized in appendix 2 of this AC.

g. Evaluate the ADS-B In self-test features.

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h. If possible, verify the dynamic performance of displayed traffic by observing any available ADS-B Out, ADS-R, TCAS (if installed), or TIS-B traffic in the area.

i. Evaluate the overall CDTI system installation for satisfactory accessibility and visibility under all lighting conditions.

3-3. Flight Tests.

a. Flight tests must be conducted for each initial installation of a unique configuration of ADS-B In receiver, position sensor, ASSAP, and CDTI equipment. Flight test data from a different aircraft may be used to establish suitability in follow-on installations. Flight testing must be conducted in the range of a cooperative ADS-B Out-equipped aircraft. Flight testing should be conducted within TIS-B and ADS-R coverage. The flight test should verify the following:

(1) The other aircraft flight identification (if implemented).

(2) The ability to select a desired target aircraft (if implemented).

(3) The ability to display ground speed of the selected target aircraft (if implemented).

(4) The bearing from own-ship to the other aircraft.

(5) The distance from own-ship to the other aircraft.

(6) The relative altitude of the other aircraft.

(7) The direction of travel (ground track) of the other aircraft.

(8) The ground speed of the other aircraft (if implemented).

(9) The targets are appropriately displayed during maneuvers throughout the normal flight envelope.

(a) Movement of displayed target information should not result in objectionable jitter, jerkiness, or ratcheting effects.

(b) Movement of displayed target information should not blur, shimmer, or produce unintended dynamic effects such that the information becomes distracting or difficult to interpret.

(c) Filtering or coasting of data intended to smooth the movement of CDTI displayed target information should not introduce significant positioning errors or create system lag that makes it difficult to perform the intended task.

(d) False or redundant tracks should not occur regularly during the flight. This would indicate that the track correlation is not performing properly. This could indicate that the

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14 TCAS antenna bearing is performing poorly, as an example.

b. If implemented, verify that the information provided on the CDTI display is suitable for the surface application. Depending upon which surface class has been installed, either runways only will be depicted or both runways and taxiways will be depicted.

c. If ITP is installed, evaluate the ITP functionality. The intent of ITP Flight Testing is to validate that the equipment functions properly when installed on the aircraft. It is not the intent of the ITP flight test to exhaustively test ITP geometries. Individual ITP scenarios to test each ITP geometry may be performed in a conformed ground simulator environment. The scenarios below were chosen to be representative of key operational ranges at which the equipment operates differently. The TCAS validation functionality in particular is difficult to test adequately on ground or in a laboratory environment. This is due to the challenge of creating an RF simulation that accurately reflects the in flight environment and aircraft installation effects. A flight test of ITP should successfully demonstrate the three scenarios below. For each of the scenarios, perform the steps in this paragraph. Verify that the reference traffic is being displayed as a valid reference aircraft for the ITP application. Verify that the reference aircraft is shown on the ADS-B traffic display and any dedicated ITP display. This indicates that the ADS-B surveillance portion of ITP is functioning successfully. Verify that the ITP distance computed agrees with the planned value for the flight profile. The computed value may vary from the planned value due to variations from planned aircraft speeds, range, and position. Differences should be documented and investigated after the flight for correctness. Enter CPDLC commands for an ITP request using either automatically generated messages or manually through free-text input by the pilot. If automatically generated, verify that the CPDLC text accurately represents the ITP reference aircraft information. If the local air traffic facility is equipped and able to receive the CPDLC message successfully, then exercise the CPDLC link and request an acknowledgement from ATC. If the local air traffic facility is not equipped, then the CPDLC link does not need to be exercised. CPDLC installation guidance is covered in AC 20-140() Guidelines for Design Approval of Aircraft Data Link Communication Systems Supporting Air Traffic Services (ATS). During any or all of the scenarios, alter the position, altitude, or ground speed of the aircraft in order to violate the ITP initiation criteria (refer to Table 2 below). Verify that the ITP equipment indicates that an ITP maneuver is not possible. If implemented, verify that the proper reason is indicated for the ITP maneuver not being available.

(1) Scenario 1 ITP Reference aircraft < 30nm: Perform a flight test with two aircraft, one being the Ownship aircraft and the other being the Reference aircraft. Position the aircraft so they are in-trail between 20 and 30 nautical miles and within 15 knots of ground speed. If TCAS validation is implemented, the ITP equipment will use TCAS measurements (range, bearing, and altitude) to validate ADS-B position for version 0 and version 1 targets.

(2) Scenario 2 ITP Reference aircraft > 30nm: Position the aircraft so they are in-trail greater than 30 nautical miles, but within the capability of the manufacturer’s TCAS to get occasional replies, and within 15 knots of ground speed. If TCAS validation is implemented, the ITP equipment will use TCAS measurements of opportunity (range, bearing, and altitude) to validate ADS-B position for version 0 and version 1 targets when able. At this range, TCAS may not be able to sustain a track due to spotty transponder replies. It is the

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15 responsibility of the TCAS manufacturer to provide the approximate maximum range at which TCAS measurements are still available.

(3) Scenario 3 ITP Reference aircraft outside of TCAS range: Position the aircraft so they are on similar tracks (within 45 degrees), outside of the manufacturer provided TCAS measurement range, and within 15 knots of ground speed. In this geometry, TCAS validation will be unavailable.

Table 2. ITP Maneuver Criteria

ITP Speed/Distance Criteria ITP Distance >= 15 NM and Closing Ground Speed Differential <= 20 knots or ITP Distance >= 20 NM and Closing Ground Speed Differential <= 30 knots Relative Altitude Criteria Difference in altitude between the ITP and Reference Aircraft is less than or equal to 2000 feet Similar Track Criteria Difference in track angles between ITP and Reference Aircraft less than +/- 45 degrees Position Accuracy for ITP and Reference Aircraft ITP and Reference Aircraft data with horizontal position accuracies of at least 0.5 NM (95%) Position Integrity for ITP and Reference Aircraft ITP and Reference Aircraft data with horizontal position integrity bounds of 1.0 NM @ 1x10E-05 Velocity Accuracy for ITP and Reference Aircraft ITP and Reference Aircraft data with horizontal velocity accuracies of at least 10 m/s (19.4 knots) 95% Closing Mach Differential (ATC Crosscheck) Closing Mach Differential equal or less than 0.06 Mach

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Appendix 1

A1-1 Appendix 1. Latency Analysis

1. Purpose. The purpose of this appendix is to provide guidelines on accomplishing a latency analysis of your ADS-B In system to demonstrate that it complies with the end-to-end budget for ADS-B applications. It is important to minimize latency and the uncertainty of latency (i.e., how the latency differs between updates) at the system integration level. The easiest way to ensure this design goal is met is to provide a direct connection between the position source and the ADS-B equipment. Any other system blocks between them will increase latency and uncertainty. In some cases, an increase in uncertainty can have a more detrimental effect than the latency itself. Refer to RTCA/DO-317A appendix J for additional information on the interfaces described below.

2. Analysis. For ADS-B In installations, the latency analysis consists of two parts; the traffic latency analysis and the own-ship position latency analysis. Together, these analyses must show:

a. That the total latency allowance is not exceeded and,

b. The own-ship position and traffic positions are estimated to a time of applicability within 1 second of the time of display.

Note: Manufacturers should ensure installation instructions adequately address latency to assist the installer.

3. Traffic Latency Analysis. Figure 2 depicts a block diagram of the ADS-B In system and the recommended latency budget allocated to each block. To demonstrate that the system does not exceed the total latency budget, determine the applicable latencies for each component and total all of the individual component latencies. You must include all sources of latency, including, but not limited to: the ADS-B receiver, the ASSAP equipment, the CDTI equipment, and any intermediary devices. The total for your system between interface D and interface G must not exceed 3.5 seconds. It is acceptable for a manufacturer to allocate the total budget among their system components as needed. However, this design choice will limit the flexibility of pairing their equipment with other manufacturers. In calculating worst case latency, the traffic latency analysis must assume the simultaneous processing of the maximum number of traffic symbols the system is designed to support.

4. Traffic Time of Applicability Analysis. Demonstrate by analysis that the traffic displayed to the flight crew has been estimated forward to be within 1 second of the time of display. For instance, if the latency analysis in the previous paragraph comes to 2.6 seconds, the traffic must be estimated forward 2.6 seconds +/- 1 second by the system prior to displaying that traffic.

The actual estimate for each individual piece of traffic will vary as the received ADS-B messages arrive asynchronously. The analysis must demonstrate that this variation is handled appropriately. The analysis must also demonstrate that any variation in the latency due to processes within the equipment chain does not cause the time of applicability to violate the 1 second tolerance. If different vendors’ equipment are paired together to create a complete system, latency performance data for each system component must originate with the

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Appendix 1

A1-2 component manufacturer. Reverse engineering another vendor’s latency performance is not an acceptable means of compliance. Manufacturers are encouraged to include their individual component latency performance in an installation manual to facilitate proper ADS-B system integrations.

Figure 2. Traffic Latency Block Diagram

5. Own-Ship Position Latency Analysis. Refer to figures 3 and 4 which depict block diagrams of two potential implementations of ADS-B In system architectures with recommended latency budgets allocated to each block. For either architecture, the ASSAP equipment must receive the own-ship position data with less than 600 ms of compensation error and less than 1 second of total latency. For this portion of the analysis, total latency starts at the time of measurement of the position source (A3) and ends when ASSAP has received the complete position update (B3). Own-ship total latency at the time of display (G) must not exceed 3.5 seconds.

6. Own-Ship Position Time of Applicability. Demonstrate by analysis that the own-ship position displayed to the flight crew has been estimated forward to be within 1 second of the time of display. The 1 second tolerance must include any compensation error present in the system between interfaces A3 and G. Determine the total latency from the position source time of measurement (A3) to the time of display (G). This latency will depend on the path of own-ship position data and vary by system architecture. Refer to Figure 3 and Figure 4 for examples of two potential architectures. The analysis must demonstrate that any variation in the latency due to processes within the equipment chain does not cause the time of applicability to violate the 1 second tolerance. If different vendors’ equipment are paired together to create a complete system, data for each system component must originate with the component manufacturer. Reverse engineering another vendor’s latency performance is not an acceptable means of compliance. Manufacturers are encouraged to include their individual component latency performance in an installation manual to facilitate proper ADS-B system integrations.

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Appendix 1

A1-3

Figure 3. Own-Ship Latency Block Diagram Simple Architecture

Figure 4. Own-Ship Latency Block Diagram Alternate Architecture

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Appendix 2

A2-1 Appendix 2. Symbol Requirements for the CDTI

1. Traffic Symbols and Variations. The “basic” traffic symbol is used to depict airborne traffic. Traffic symbols can be modified from the basic symbol to provide special status information, such as on-ground, selected, designated, and alerted. The symbols depicted are examples. The line width, physical size, and hue of the figures are not requirements. The requirements are stated in the associated text.

a. Basic Directional (see Figure 5).

(1) If directionality is valid, the basic directional traffic symbol must be depicted with an arrowhead shape oriented by the directionality.

(2) The color must be cyan or white.

(3) The color must be the same color as the basic non-directional symbol.

(4) The color should not be the same color as the own-ship symbol.

(5) For displays that do not integrate aircraft surveillance applications system (ASA) with TCAS, the symbol may be filled or unfilled.

(6) For TCAS/ASA-integrated systems, the symbol must be unfilled.

Figure 5. Basic Directional Symbol

b. Basic Non-Directional (see Figure 6).

(1) If directionality is invalid, the basic non-directional traffic symbol must be depicted with a diamond shape.

(2) The color must be cyan or white.

(3) The color must be the same color as the basic directional symbol.

(4) The color should not be the same color as the own-ship symbol.

(5) For displays that do not integrate ASA with TCAS, the symbol may be filled or unfilled.

(6) For TCAS/ASA-integrated systems, the symbol must be unfilled.

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Appendix 2

A2-2 Figure 6. Basic Non-Directional Symbol

c. Traffic Directionality. If the traffic symbol indicates directionality, the directionality of the traffic symbol must be displayed relative to the display orientation.

Note: The traffic directionality in air is based on traffic ground track angle, and not necessarily traffic heading. This is important for monitoring traffic such as helicopters that can fly backwards and to account for winds.

d. Traffic Application Capability. The traffic symbol may provide an indication of traffic application capability.

Note 1: Traffic information that does not meet the minimum requirements for enhanced visual acquisition (EVAcq) should not be sent to the CDTI display from ASSAP.

Note 2: ASSAP may provide TCAS-only data that does not support EVAcq. TCAS data will still be displayed.

e. Traffic On-Ground Status (see Figure 7).

(1) If traffic is on-ground, the basic traffic symbol must be modified by changing the color.

(2) The color may be brown/tan.

(3) The size of on-ground traffic symbols may be decreased for additional encoding, and/or to reduce clutter.

(4) The symbol may be filled or unfilled.

Note: Additionally, altitude information is removed from the data tag.

Figure 7. Directional and Non-directional On-ground Traffic Symbols

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Appendix 2

A2-3

f. Basic Ground Vehicle

(1) The basic Ground Vehicle symbol must be depicted as a top-down wheeled rectangular shape.

(2) The color should be the same as that used for the basic Traffic On-Ground symbol. The color may be brown/tan.

(3) Ground Vehicle directionality may be indicated by adding a triangular shape to one end of the rectangle, and orienting the entire symbol by directionality. Figure 8 provides an example notional depiction.

(4) The symbol may be filled or unfilled.

Figure 8. Basic Surface Vehicle Symbol

2. Alerts. The following requirements, per TSO-C195a, apply generally to CDTI-displayed alerts based on both ASA and TCAS systems. Additional TCAS-specific alert symbol requirements are provided in Appendix 2 section 3.

a. Traffic that triggers an alert must be indicated on the Traffic Display with a symbol variation. The following requirements only apply to the alerted traffic symbol:

(1) If traffic directionality is valid, directionality information must not be removed during alerts.

(2) The traffic symbol must change to amber/yellow for caution level alerts.

(3) The traffic symbol must change to red for warning level alerts.

(4) For traffic without valid directionality:

(a) If traffic has a caution level alert, the traffic symbol may be modified by changing the shape to a circle.

(b) If traffic has a warning level alert, the traffic symbol may be modified by changing the shape to a square.

(5) For traffic with valid directionality:

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Appendix 2

A2-4

(a) If traffic has a caution level alert, the traffic symbol may be modified by changing the shape to a circle with a directional inlay.

(b) If traffic has a warning level alert, the traffic symbol may be modified by changing the shape to a square with a directional inlay.

Note: Caution and warning level alerts may use the same traffic symbols as TCAS traffic advisories and resolution advisories, respectively.

(See Appendix 2 section 3)

(6) For airborne applications, alerting traffic that lies outside the configured traffic display range should be positioned at the measured relative bearing, and at the configured display maximum range (i.e., edge of display), and with a symbol shape modification that indicates that the traffic is off-scale.

Note: A half-symbol at the display edge is one acceptable indication method.

b. Proximate Traffic (see Figure 9).

(1) For TCAS/ASA integrated systems, the traffic symbol must indicate airborne TCAS proximate status.

(2) If proximate traffic is displayed, the basic traffic symbol must be displayed as filled. Figure 9 provides example notional depictions.

Note: This requirement is to be consistent with TCAS symbol convention.

Figure 9. Proximate Directional and Non-directional Proximate Traffic Symbols

c. Selected Traffic.

(1) Selected traffic is traffic that is selected by the flight crew. Traffic selection results in display of additional traffic information beyond what is presented in the minimum data tag, and may enable other functions (e.g., designating traffic).

(2) If traffic selection is implemented:

(a) There must be some means of distinguishing the selected traffic from other traffic on the traffic display.

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Appendix 2

A2-5

(b) A border must not be used to indicate selected traffic.

Note 1: A border is a discernable line that surrounds an existing symbol. Border types include fixed-shape or conformal.

Note 2: Borders are reserved for depicting designated traffic (see Figure 10).

(3) When traffic is selected, additional information on that traffic must be displayed in a data block or a data tag.

Note: Generally, selecting traffic will bring up the additional information in a data block, but a data tag can also be used for this purpose.

(4) There must be an indication of off-scale selected traffic.

Note: A Selected half-symbol at the display edge and appropriate bearing is one acceptable method of indication.

d. Designated Traffic (see Figure 10).

(1) Designated traffic is traffic upon which a designated application is to be performed. For example, in visual separation on approach (VSA), the traffic to be followed may be displayed as “designated” so that the application and the flight crew both know the specific traffic upon which to act.

(2) If traffic designation is implemented:

(a) There must be some means of distinguishing the designated traffic from other traffic.

(b) If traffic is designated, the basic traffic symbol should be modified by adding a shape-conforming border. Figure 10 provides a notional example.

Figure 10. Directional and Non-directio nal Designated Traffic Symbols

(c) There must be an indication of off-scale designated traffic.

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Appendix 2

A2-6 Note: A half-symbol at the display edge and appropriate bearing is one acceptable method of indication.

(d) The loss of “designated” status (e.g., due to signal loss or invalid data) must be indicated to the flight crew.

3. TCAS Alert Symbology for TCAS/ASA-Integrated Systems.

a. If traffic directionality is valid, directionality information must not be removed during a TCAS traffic advisory or resolution advisory.

Note: Directionality information, if available, may assist the flight crew in visual search and identification of the alerted traffic.

b. Traffic Advisories (see Figure 11).

(1) If traffic has a TA, the traffic symbol must be modified by changing the color to amber/yellow, and changing the shape to a circle.

(2) Traffic with valid directionality must include a directional inlay.

(3) The size of TA traffic symbols may be increased to accommodate the shape modification.

(4) Line widths and fill may be changed to improve color interpretation and saliency.

Figure 11. Traffic Advisory Symbols

c. Resolution Advisories (RAs) (see Figure 12).

(1) If traffic has an RA, the traffic symbol must be modified by changing the color to red, and changing the shape to a square.

(2) Traffic with valid directionality must include a directional inlay.

(3) The size of RA traffic symbols may be increased to accommodate the shape modification.

(4) Line widths and fill may be changed to improve color interpretation and saliency.

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Appendix 2

A2-7 Note: TCAS aural alerts and resolution guidance are not affected by these requirements or recommendations.

Figure 12. Resolution Advisory Symbols

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Appendix 3

A3-1 Appendix 3. Definitions and Acronyms

1. Definitions. The following are definitions of terms used in this document.

a. 24-bit Address. Unique address assigned to an aircraft during the registration process.

b. ADS-B In- Receipt, processing, and display of other aircraft’s ADS-B transmissions.

ADS-B In is necessary to utilize airborne applications.

c. Advisory. The level or category of alert for conditions that require flight crew awareness and may require subsequent flight crew response.

d. Aircraft Surveillance Applications System (ASAS). An aircraft system based on airborne surveillance that provides assistance to the flight crew in operating their aircraft relative to other aircraft.

e. Alert. A general term that applies to all advisories, cautions, and warning information;

can include visual, aural, tactile, or other attention-getting methods.

f. Application. The function(s) for which the ASA system is used.

g. Aircraft Surveillance Application (ASA). An application that uses aircraft surveillance data to provide benefits to the flight crew.

h. Antenna Offset Parameter. The distance from the nose of the aircraft to the GPS antenna. For large aircraft, this offset is important in accurately placing the aircraft symbol on the airport map.

i. Automatic Dependent Surveillance-Broadcast (ADS-B). A function on an aircraft or surface vehicle operating within the surface movement area that periodically broadcasts its state vector (horizontal and vertical position, horizontal and vertical velocity) and other information.

ADS-B is automatic because no external stimulus is required to elicit a transmission. It is dependent because it relies on on-board navigation sources and on-board broadcast transmission systems to provide surveillance information to other users.

j. Automatic Dependent Surveillance-Rebroadcast (ADS-R). A service of the ground system that rebroadcasts ADS-B messages from one link technology onto another. For example, the SBS ground system provides ADS-R service to rebroadcast UAT messages on 1090 MHz and vice versa.

k. Availability. An indication of the ability of a system or subsystem to provide usable service. Availability is expressed in terms of the probability of the system or subsystem being available at the beginning of an intended operation.

l. Background Application. An application that applies to all traffic of operational interest. One or more background applications may be in use in some or all airspace (or on the

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Appendix 3

A3-2 ground), but without flight crew input or automated input to select specific traffic. Background applications include: basic airborne, surface (runways and taxiways OR runways only).

m. Caution. The level or category of alert for conditions that require immediate flight crew awareness and subsequent flight crew response.

n. Coast Interval. The elapsed time since a report from any source has been correlated with the track.

o. Cockpit Display of Traffic Information (CDTI). The pilot interface portion of the Aircraft Surveillance Applications System. This interface includes traffic display(s) and all the controls that interact with such a display. At a minimum, CDTI includes a graphical plan-view (top down) traffic display. Additional graphical and non-graphical display surfaces may also be included. The CDTI receives position information of traffic and Ownship from the airborne surveillance and separation assurance processing (ASSAP) function. The ASSAP receives such information from the surveillance sensors and Ownship position sensors.

p. Compensated Latency. Latency can be compensated by extrapolating position using the last known position measurement, the elapsed time, and the last known velocity measurement.

The elapsed time used to extrapolate is called compensated latency.

q. Conformal. A desirable property of map projections. A map projection (a function that associate points on the surface of an ellipsoid or sphere representing the earth to points on a flat surface such as the CDTI display) is said to be conformal if the angle between any two curves on the first surface is preserved in magnitude and sensed by the angle between the corresponding curves on the other surface.

r. Correlation. The process of determining that a new measurement belongs to an existing track.

s. Controller Pilot Data Link Communication (CPDLC). Provides direct data communication between the pilot and the air traffic controller through a data link.

t. Data Block. A block of information about selected traffic that is displayed somewhere around the edge of the CDTI display, rather than mixed in with the symbols representing traffic in the main part of the display.

u. Data Tag. A block of information that is displayed next to the traffic symbol in the main part of the CDTI display.

v. Designated Application. An application that operates only on specifically-chosen (either by the flight crew or automation) traffic. They generally operate only for a specific flight operation.

w. Designated Traffic. Traffic upon which a designated application is to be conducted.

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Appendix 3

A3-3

x. Desirable. The capability denoted as desirable is not required to perform the procedure, but would increase the utility of the operation.

y. Direct Controller Pilot Communication (DCPC). Direct communication established between the controller and the pilot without having to relay through another unit or going through a secondary means of delivery for that information. Currently, this is accomplished by conventional voice radio operations or CPDLC.

z. Differential Ground Speed. Calculated by taking the difference between the magnitude of the own ship ground speed and the designated traffic ground speed. The assumption is that own ship is following the designated traffic approach path over the ground. Positive values indicate closure on the designated traffic.

aa. Display Range. The maximum distance from own-ship that is represented on the CDTI display. If the CDTI display is regarded as a map, then longer display ranges correspond to smaller map scales, and short display ranges correspond to larger map scales.

bb. Enhanced Visual Acquisition (EVAcq). This application is an enhancement for the out-the-window visual acquisition of aircraft traffic and potentially ground vehicles.

cc. Estimation. The process of determining a track’s state based on new measurement information.

dd. Extended Runway Center Line. An extension outwards of the center line of a runway, from one or both ends of that runway.

ee. Extended Squitter. A long (112 bit) Mode S transmission that is spontaneously produced by the radio as opposed to a response to a Mode S Interrogation. Extended Squitter is the mechanism used to provide ADS-B messages from a Mode S transponder.

ff. Extrapolation. The process of predicting a track’s state forward in time based on the track’s last kinematic state.

gg. Field of View. The field of view of a CDTI is the geographical region within which the CDTI shows traffic. Some documents call this the field of regard.

hh. FIS-B. The ground-to-air broadcast of meteorological and aeronautical information.

ii. Flight Crew. One or more cockpit crew members required for the operation of the aircraft.

jj. Geometric Altitude. Provided as height above ellipsoid and referenced to WGS-84 reference datum.

kk. GNSS Sensor Integrity Risk. The probability of an undetected failure that results in navigation system error (NSE) that significantly jeopardizes the total system error (TSE) exceeding the containment limit.

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Appendix 3

A3-4

ll. Ground Speed. The magnitude of the horizontal velocity vector (see velocity). In these minimum operational performance standards (MOPS) it is always expressed relative to a frame of reference that is fixed with respect to the earth’s surface such as the WGS-84 ellipsoid.

mm. Ground Track Angle. The direction of the horizontal velocity vector (see velocity) relative to the ground as noted in ground speed.

nn. Hazard Classification. Refer to AC 25-1309-1(), System Design and Analysis, or AC 23.1309-1(), System Safety Analysis and Assessment for Part 23 Airplanes, as applicable.

oo. Horizontal Velocity. The component of velocity in a local horizontal plane. For Global Positioning System (GPS) sensors, that plane is tangent to the WGS-84 ellipsoid and is vertically displaced such that it contains the navigation sensors’ reference point. For inertial navigation system (INS) equipment, the local plane is perpendicular to the local gravity vector.

pp. Height Above Ellipsoid. Height above the WGS-84 reference ellipsoid.

qq. International Civil Aviation Organization (ICAO). A United Nations organization that is responsible for developing international standards, and recommending practices, and procedures covering a variety of technical fields of aviation.

rr. In-Trail Procedure (ITP). A procedure that allows an aircraft to climb-through or descend-through another aircraft’s altitude in order to make a desired flight level change.

ss. Latency. The time incurred between two particular interfaces. Total latency is the delay between the time of a measurement and the time that the measurement is reported at a particular interface (the latter minus the former). Components of the total latency are elements of the total latency allocated between different interfaces. Each latency component will be specified by naming the interfaces between which it applies.

tt. Mixed Equipage. An environment where all aircraft do not have the same set of avionics capabilities. For example, some aircraft may transmit ADS-B and others may not, which could have implications for ATC and pilots. A mixed equipage environment will exist until all aircraft operating in a system have the same set of avionics capabilities.

uu. Multilateration. A surveillance system that uses the time of receipt of transponder transmissions to determine the position of the aircraft.

vv. Nautical Mile (NM). A unit of length used in the fields of air and marine navigation.

In this document, a nautical mile is always the international nautical mile of 1852 m exactly.

ww. Navigation Accuracy Category Position (NACP). The NACp parameter describes the accuracy region about the reported position within which the true position of the surveillance position reference point is assured to lie with a 95% probability at the reported time of applicability.

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Appendix 3

A3-5 xx. Navigation Accuracy Category Velocity (NACV). The NACv parameter describes the accuracy about the reported velocity vector within which the true velocity vector is assured to be with a 95% probability at the reported time of applicability.

yy. Navigation Integrity Category (NIC). The NIC parameter describes an integrity containment region about the reported position, within which the true position of the surveillance position reference point is assured to lie at the reported time of applicability. For the conditions and probability of assurance associated with the integrity containment region, see the source integrity level (SIL) parameter.

zz. Navigation Sensor Availability. An indication of the ability of the guidance function to provide usable service within the specified coverage area, and is defined as the portion of time during which the sensor information is to be used for navigation, during which reliable navigation information is presented to the crew, autopilot, or other system managing the movement of the aircraft. Navigation sensor availability is specified in terms of the probability of the sensor information being available at the beginning of the intended operation.

aaa. Navigation System Integrity. This relates to the trust that can be placed in the correctness of the navigation information supplied. Integrity includes the ability to provide timely and valid warnings to the user when the navigation system must not be used for navigation.

bbb. Own-ship. From the perspective of a flight crew, or of the ASSAP and CDTI functions used by that flight crew, the own-ship is the ASA participant (aircraft or vehicle) that carries that flight crew and those ASSAP and CDTI functions.

ccc. Persistent Error. An error that occurs continuously once it begins. Such an error may be the absence of data or the presentation of data that is false or misleading. An unknown measurement bias may, for example, cause a persistent error.

ddd. Positional Uncertainty. A measure of the potential inaccuracy of an aircraft’s position-fixing system and, therefore, of ADS-B-based surveillance. Use of the Global Positioning System (GPS) reduces positional inaccuracy to small values, especially when the system is augmented by either space-based or ground-based subsystems.

eee. Pressure Altitude. Altitude reported by a barometric pressure altimeter without corrections for local pressure settings.

fff. Primary Surveillance Radar (PSR). A radar sensor that listens to the echoes of pulses that it transmits to illuminate aircraft targets. PSR sensors, in contrast to secondary surveillance radar (SSR) sensors, do not depend on the carriage of transponders on board the aircraft targets.

ggg. Range Reference. The CDTI feature of displaying range rings or other range markings at specified radii from the own-ship symbol.

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Appendix 3

A3-6 hhh. Secondary Surveillance Radar (SSR). A radar sensor that listens to replies sent by transponders carried on board airborne targets. SSR sensors, in contrast to primary surveillance radar (PSR) sensors, require the aircraft under surveillance to carry a transponder.

iii. Selected Traffic. Traffic for which additional information is requested by the flight crew.

jjj. Sensor. A measurement device. An air data sensor measures atmospheric pressure and temperature, to estimate pressure altitude, and pressure altitude rate, airspeed, etc. A primary surveillance radar sensor measures its antenna direction and the times of returns of echoes of pulses that it transmits to determine the ranges and bearings of airborne targets. A secondary surveillance radar sensor measures its antenna direction and the times of returns of replies from airborne transponders to estimate the ranges and bearings of airborne targets carrying those transponders.

kkk. Separation. The minimum distance between aircraft/vehicles allowed by regulations.

Separation requirements vary by factors such as radar coverage (none, single, composite), domain (terminal, en route, oceanic), and flight rules (instrument or visual).

lll. Separation Violation. Violation of appropriate separation requirements.

mmm. Simple Action. A flight crew action that may be performed within a short period of time and without requiring significant concentration that would distract from the main aviation tasks (e.g., a button press).

nnn. Spacing. A distance maintained from another aircraft for specific operations.

ooo. Source Integrity Level (SIL). The SIL field defines the probability of the reported horizontal position exceeding the radius of containment defined by the NIC, without alerting, assuming no avionics faults. Although the SIL assumes there are no un-annunciated faults in the avionics system, the SIL must consider the effects of a faulted signal-in-space (SIS), if a signal-in-space is used by the position source.

ppp. State Vector. An aircraft’s current horizontal position, vertical position, horizontal velocity, vertical velocity, and navigational accuracy and integrity.

qqq. Traffic Selection. Manual process of flight crew selecting a traffic element.

rrr. TCAS Potential Threat. Traffic detected by TCAS equipment on board the own-ship, that has passed the Potential Threat classification criteria for a TCAS TA and does not meet the Threat Classification criteria for a TCAS RA (RTCA/DO-185B § 1.8). If the ASAS own-ship CDTI display is also used as a TCAS TA display, then information about TCAS potential threats will be conveyed to the CDTI via the ASSAP function.

sss. TCAS Proximate Traffic. Traffic, detected by TCAS equipment on board the ownship, that is within 1200 feet and 6 NM of the own-ship (RTCA/DO-185B § 1.8). If the ASA

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Appendix 3

A3-7 system own-ship CDTI display is also used as a TCAS display, then information about TCAS proximate traffic will be conveyed to the CDTI, possibly via the ASSAP function.

ttt. TCAS-Only Traffic. A traffic element about which TCAS has provided surveillance information, but which the ASSAP function has not correlated with traffic from other surveillance sources such as ADS-B, ADS-R, or TIS-B.

uuu. Time of Applicability. The time that a particular measurement or parameter is (or was) relevant.

vvv. Track. (1) A sequence of reports from the ASSAP function that all pertain to the same traffic target. (2) Within the ASSAP function, a sequence of estimates of traffic target state that all pertain to the same traffic element.

www. Track Angle. See Ground Track Angle.

xxx. Track State. See State Vector.

yyy. Traffic. All aircraft/vehicles that are within the operational vicinity of own-ship.

zzz. Traffic Element. An aircraft or vehicle.

aaaa. Traffic Information Service – Broadcast (TIS-B). A surveillance service that broadcasts traffic information derived from one or more ground surveillance sources to suitably equipped aircraft or surface vehicles, with the intention of supporting ASA applications.

bbbb. Traffic Symbol. A depiction on the CDTI display of an aircraft or vehicle other than the own-ship.

cccc. Transponder. A piece of equipment carried on board an aircraft to support the surveillance of that aircraft by secondary surveillance radar sensors. A transponder receives on the 1030 MHz and replies on the 1090 MHz downlink frequency.

dddd. Uncompensated Latency. Latency can be compensated by extrapolating position using the last known position measurement, the elapsed time, and the last known velocity measurement. The remaining time between the present and the elapsed time the equipment has compensated for is called uncompensated latency.

eeee. Visual Separation on Approach. The CDTI is used to assist the flight crew in acquiring and maintaining visual contact during visual separation on approach. The CDTI is also used in conjunction with visual, out-the-window contact to follow the preceding aircraft during the approach. The application is expected to improve both the safety and the performance of visual separation on approach. It may allow for the continuation of visual separation on approach when they otherwise would have to be suspended due to the difficulty of visually acquiring and tracking the other preceding aircraft.

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A3-8 ffff. Velocity. The rate of change of position. Horizontal velocity is the horizontal component of velocity and vertical velocity is the vertical component of velocity.

gggg. Warning. The level or category of alert for conditions that require immediate flight crew awareness and immediate flight crew response.

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Appendix 3

A3-9

2. Acronyms:

AC Advisory Circular (FAA) ACM Airborne Conflict Management ADS-B Automatic Dependent Surveillance – Broadcast ADS-R Automatic Dependent Surveillance – Rebroadcast AGL Above Ground Level AIRB Basic Airborne Situation Awareness AML Approved Model List AMMD Aerodrome Moving Map Display ASA Aircraft Surveillance Applications ASAS Aircraft Surveillance Applications System ASSAP Airborne Surveillance and Separation Assurance Processing ASTC Amended Supplemental Type Certificate ATC Air Traffic Control ATCRBS Air Traffic Control Radar Beacon System ATS Air Traffic Services CDTI Cockpit Display of Traffic Information CFR Code of Federal Regulations CNS Communications, Navigation, Surveillance CPDLC Controller Pilot Data Link Communication DCPC Direct Controller Pilot Communication EFB Electronic Flight Bag EFIS Electronic Flight Instrument System EHSI Electronic Horizontal Situation Indicator EPU Estimated Position Uncertainty EUROCAE European Organization for Civil Aviation Equipment EVAcq Enhanced Visual Acquisition FAA Federal Aviation Administration FIS-B Flight Information Services - Broadcast FMS Flight Management System Fpm Feet Per Minute

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Appendix 3

A3-10 Ft Feet GA General Aviation GNSS Global Navigation Satellite System GPS Global Positioning System HAE Height Above Ellipsoid HMI Hazardously Misleading Information ICAO International Civil Aviation Organization ID Identification IFR Instrument Flight Rules ITP In-Trail Procedure kts Knots m meter (or “metre”), the SI metric system base unit for length MCDU Multi-Function Control and Display Unit MFD Multi-Function Display MHz Mega Hertz MOPS Minimum Operation Performance Standards (RTCA documents) N/A Not Applicable or No Change NAC Navigation Accuracy Category (sub “p” is for position and sub “v” is for velocity) NAS National Airspace System NIC Navigation Integrity Category NM Nautical Mile OEM Original Equipment Manufacturer PVT Position, Velocity, and Time RA Resolution Advisory (TCAS II) RC Radius of Containment RMS Root Mean Square RNAV Area Navigation RNP Required Navigation Performance s second, the SI metric system base unit for time or time interval SA Situation Awareness SAE Society of Automotive Engineers

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Appendix 3

A3-11 SBS Surveillance and Broadcast Services SC Special Committee SDA System Design Assurance SIL Source Integrity Level (sub BARO is for barometric altitude) SSR Secondary Surveillance Radar SURF Basic Surface Situation Awareness SV State Vector TA Traffic Advisory (TCAS II) TAS Traffic Advisory System TCAS Traffic Alert and Collision Avoidance System TCAS I TCAS system that does not provide resolution advisories TCAS II TCAS system that provides resolution advisories TIS-B Traffic Information Service – Broadcast TOA Time of Applicability TSO Technical Standard Order UAT Universal Access Transceiver UTC Universal Time, Coordinated, formerly Greenwich Mean Time VDL-4 Very High Frequency Data Link Mode 4 VEPU Vertical Estimated Position Uncertainty VSA Visual Separation on Approach WGS-84 World Geodetic System-1984

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Appendix 4

A4-1 Appendix 4. Related Documents

1. FAA Documents.

AC 20-131( ), Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) and Mode S Transponders.

AC 20-138( ), Airworthiness Approval of Global Navigation Satellite System (GNSS) Equipment.

AC 20-140(), Guidelines for Design Approval of Aircraft Data Link Communication Systems Supporting Air Traffic Services (ATS).

AC 20-151( ), Airworthiness Approval of Traffic Alert and Collision Avoidance Systems (TCAS II) Version 7.0 & 7.1 and Associated Mode S Transponders.

AC 20-153( ), Acceptance of Data Processes and Associated Navigation Databases.

AC 20-159( ), Obtaining Design and Production Approval of Airport Moving Map Display Applications Intended For Electronic Flight Bag Systems.

AC 20-165(), Airworthiness Approval of Automatic Dependent Surveillance - Broadcast (ADS-B) Out Systems.

AC 21-40( ), Guide for Obtaining a Supplemental Type Certificate.

AC 23.1309-1( ), System Safety Analysis and Assessment for Part 23 Airplanes.

AC 23.1311-1(), Installation of Electronic Display in Part 23 Airplanes.

AC 25-11(), Electronic Flight Deck Displays.

AC 25-1309-1( ), System Design and Analysis.

AC 25.1322-1(), Flight Crew Alerting.

AC 27-1( ), Certification of Normal Category Rotorcraft.

AC 29-2( ), Certification of Transport Category Rotorcraft.

AC 43-6( ), Altitude Reporting Equipment and Transponder System Maintenance and Inspection Practices.

AC 90-114( ), Automatic Dependent Surveillance-Broadcast (ADS-B) Operations.

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Appendix 4

A4-2 AC 120-76( ), Guidelines For The Certification, Airworthiness, and Operational Approval of Electronic Flight Bag Computing Devices.

TSO-C5, Direction Instrument, Non-Magnetic (Gyroscopically Stabilized).

TSO-C6, Direction Instrument, Magnetic (Gyroscopically Stabilized).

TSO-C8( ), Vertical Velocity Instruments.

TSO-C10( ), Altimeter, Pressure Actuated, Sensitive Type.

TSO-C66( ), Distance Measuring Equipment (DME) Operating Within the Radio Frequency Range of 960-1215 Megahertz.

TSO-88( ), Automatic Pressure Altitude Reporting Code-Generating Equipment.

TSO-C106( ), Air Data Computer.

TSO-C112( ), Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment.

TSO-C118 ( ), Traffic Alert And Collision Avoidance System (TCAS) Airborne Equipment, TCAS- I.

TSO-C119( ),Traffic Alert and Collision Avoidance System (TCAS) Airborne Equipment, TCAS II With Optional Hybrid Surveillance.

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).

TSO-C147( ), Traffic Advisory System (TAS) Airborne Equipment.

TSO-C154c, Universal Access Transceiver (UAT) Automatic Dependent Surveillance Broadcast (ADS-B) Equipment Operating on the Frequency of 978 MHz.

TSO-C165( ), Electronic Map Display Equipment for Graphical Depiction of Aircraft Position.

TSO-C166b, Extended Squitter Automatic Dependent Surveillance - Broadcast (ADS-B) and Traffic Information Service - Broadcast (TIS-B) Equipment Operating on the Radio Frequency of

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Appendix 4

A4-3 1090 Megahertz (MHz).

TSO-C195a, Avionics Supporting Automatic Dependent Surveillance - Broadcast (ADS-B) Aircraft Surveillance Applications (ASA).

TSO-C196( ), Airborne Supplemental Navigation Sensors for Global Positioning System Equipment Using Aircraft-Based Augmentation.

2. RTCA, Inc. Documents (RTCA DO) documents:

RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification.

RTCA/DO-208, Minimum Operational Performance Standards for Airborne Supplemental Navigation Equipment Using Global Positioning System (GPS).

RTCA/DO-229D, Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Airborne Equipment.

RTCA/DO-247, The Role of the Global Navigation Satellite System (GNSS) in Supporting Airport Surface Operations.

RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware.

RTCA/DO-257A, Minimum Operational Performance Standards for the Depiction of Navigational Information on Electronic Maps.

RTCA/DO-260B, Minimum Operational Performance Standards for 1090 MHz Automatic Dependent Surveillance-Broadcast (ADS-B).

RTCA/DO-282B, Minimum Operational Performance Standards for Universal Access Transceiver (UAT) Automatic Dependent Surveillance-Broadcast (ADS-B).

RTCA/DO-306, Change 1. Safety and Performance Standard for Air Traffic Data Link Services in Oceanic and Remote Airspace (Oceanic SPR Standard).

RTCA/DO-316, Minimum Operational Performance Standards (MOPS) for Global Positioning System/Aircraft Based Augmentation System Airborne Equipment.

RTCA/DO-317A, Minimum Operational Performance Standards (MOPS) For Aircraft Surveillance Applications System (ASAS).

3. ARINC Documents:

ARINC 718A, Mark 4 Air Traffic Control Transponder (ATCRBS/MODE S).

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Appendix 4

A4-4 ARINC 735B, Mark 2 Traffic Alert and Collision Avoidance System (TCAS).

ARINC 738A, Air Data and Inertial Reference System (ADRS).

ARINC 743A, GNSS Sensor.

4. SAE Documents.

SAE ARP 4754A, Guidelines for Development of Civil Aircraft Systems.

SAE ARP 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment.

5. How to Get Related Documents:

a. You can get copies of the 14 CFR parts referenced in this AC online from the GPO electronic CFR Internet website at www.gpoaccess.gov/cfr/.

b. Order copies of RTCA documents from RTCA Inc., , 1150 18th St. NW, Suite 910, Washington, D.C. 20036. For general information, telephone (202) 833-9339 or fax (202) 833- 9434. You can also order copies online at http:/www.rtca.org.

c. Order copies of ARINC documents from ARINC Incorporated, 2551 Riva Rd., Annapolis, MD, 21401. Telephone +1 800-633-6882, fax +1 410-956-5465.

You can also get copies from their website at www.arinc.com.

d. Order copies of SAE documents from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, telephone (724) 776-4970, fax (724) 776-0790. Also, order copies online at www.sae.org.

e. Order copies of advisory circulars from the U.S. Department of Transportation, Subsequent Distribution Office, M-30, Ardmore East Business Center, 3341 Q 75th Avenue, Landover, MD 20785. You can also get copies from our website at http://www.faa.gov/regulations_policies/advisory_circulars/ or www.airweb.faa.gov/rgl.

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