• RTCA/DO-289, ASA MASPS, provides ASA system requirements for the processing of TIS-B messages and target data.
• RTCA/DO-260A, 1090 MHz data link MOPS
• RTCA/DO-282A, Universal Access Transceiver (UAT) data link MOPS
• RTCA Paper 053-04/SC186-221, “Interim Guidance for UAT Avionics Operating with Safe Flight 21 ADS-B, TIS-B and FIS-B Ground Infrastructure”.
8. Airworthiness Considerations. The performance attributes of TIS-B data, specifically its accuracy and latency, may not be sufficient to support some future ASA applications. The ASSAP/CDTI function of the airborne system should determine suitability of target data for specific applications (see Appendix D of this AC).
Depending on the application, flight crews may need to be aware whether the quality of the ADS- B/TIS-B data is sufficient to support the current application. This issue is addressed in more detail in Appendix H, Human Factors Considerations of this AC.
Interoperability Assumptions
TIS-B requires no direct interaction with equipment on other aircraft. Rather, it is based on uplink of data on these aircraft collected by ground-based surveillance systems. Therefore there are no air-to-air interoperability issues.
Ground Test and Flight Test
TIS-B does not require any additional avionics other than those described in Appendix D (cockpit display and surveillance processor) and Appendix E (ADS-B link systems) of this AC. Ground and flight test procedures for these systems can be found in the minimum equipment standards referenced in those Appendices.
AFM
The performance, variability, and limitations of TIS-B should be described in the AFM.
Training and Crew Qualifications
No new training or crew qualifications are required specifically for TIS-B services. See Appendix D of this AC for any airborne surveillance application-related training or crew qualification requirements.
Continuing Airworthiness and Maintenance
TIS-B is a service supported in full by ASA application systems (a cockpit display such as CDTI and a surveillance processor) and ADS-B receiving avionics. Where the system installation remains the same as the current cockpit display and surveillance processor (See Appendix D of this AC) and ADS-B data link system (See Appendix I of this AC), the use of these systems to support TIS-B results in no changes to current maintenance practices or continuing airworthiness instructions.
APPENDIX F Page F- 3
APPENDIX G.
Traffic Alert and Collision Avoidance System (TCAS) and Aircraft Surveillance Applications (ASA) Integration
1. Purpose. This Appendix provides guidance for the integration of Aircraft Surveillance Applications (ASA) traffic information with Traffic Alert and Collision Avoidance System (TCAS) traffic information on one traffic display.
2. Background. Integration of TCAS and ASA as described in this Appendix refers strictly to the combined display of surveillance information from multiple sources. ASA more accurately describes the operations supported by ADS-B surveillance data and will be referred to within this Appendix to describe applications supported by this capability.
There are two approved TCAS systems: TCAS I and TCAS II. TCAS I displays proximate traffic and alerts the crew, via a “Traffic Advisory” (TA), to other aircraft that may become potential near midair collision threats. TCAS II enhances TCAS I by providing recommended vertical escape maneuvers to the crew, via a “Resolution Advisory” (RA), to avert potential near midair collisions. Referred to internationally as the Airborne Collision Avoidance System or ACAS, it is the internationally recognized global collision avoidance system required in international airspace by the International Civil Aviation Organization (ICAO). Two versions of TCAS—TCAS II Version 6.04A “Enhanced” and TCAS II Version 7—meet the current US requirements for TCAS equipage in domestic US Airspace.
TCAS has the specific function of collision avoidance, whereas ASA, supported by ADS-B, is a general surveillance system that supports multiple applications. ASA can make use of surveillance information from various sources, including TCAS, for enhanced traffic situational awareness. ASA may also support advanced applications beyond situational awareness.
ASA technology provides an opportunity for observing traffic at much longer ranges than TCAS, and provides opportunities for new applications, which can lead to enhanced capacity and efficiency in NAS operations. Conflict detection at longer ranges could provide an enhancement for air traffic management and in the end result in fewer TCAS traffic and resolution advisories.
NOTE: The generic term “TCAS,” used in the remainder of this appendix, applies to TCAS, TCAS II Version 6.04A, and TCAS II Version 7. When the generic term TCAS is used in combination with ACAS (e.g., “TCAS-ACAS”) it applies to TCAS II Version 7 only.
3. Integration Guidance. Since TCAS is required for certain classes of aircraft, it is likely that some aircraft will be equipped with both TCAS and ASA. It is also conceivable that aircraft equipped with only one system may require conflict resolution with aircraft equipped with only the other. This section provides guidance for integrating TCAS and ASA where both are installed on the same aircraft.
3.1 Independence of TCAS. Care must be taken to preserve the independence of TCAS as a collision avoidance system, while allowing ASA to provide useful information to the flight crew.
Any combination of surveillance data must not degrade the performance of the TCAS equipment, the performance of the system with which TCAS is combined, or any technical performance specification stated in any performance standard for the TCAS system or other equipment.
APPENDIX G Page G- 1
3.2 Indicating the Source of Traffic Data. The primary purpose of the traffic display in a TCAS installation is to aid the flight crew in the visual acquisition of transponder equipped traffic. A traffic display that provides traffic information from multiple surveillance sources should have the capability to indicate the source of the surveillance data (e.g., through pilot selection). Furthermore, the source of traffic alerts (i.e., TCAS TA/RA and ASA Caution/Warning) should be continuously indicated on the traffic display.
3.3 Display of Correlated Traffic Targets. A single target should be displayed for each tracked aircraft. If both ASA and TCAS are tracking a target, and the ASA software can correlate the tracks, and a TCAS advisory is not in effect for that target, then the ASA track should be used to position the target on the display. If a TCAS Advisory is in effect, the TCAS track should be used to position the target on the display.
3.4 Traffic Symbols. TCAS II symbols are specified in RTCA/DO-185A, and TCAS I display requirements are specified in RTCA/DO-197A. An acceptable traffic symbol set for ASA traffic displays, including integrated ASA/TCAS traffic displays, are provided in Appendix H of this AC, Section 16. Other symbols and features may be used provided the applicant uses human factors principles to demonstrate that a clear and substantial benefit can be derived by its use.
Otherwise, the integrated display must depict or provide the symbols, features, or information provided in RTCA/DO-185A for TCAS II, and RTCA/DO-197A for TCAS I.
3.5 Traffic with Directional Information. If valid directional data is available for any ASA/TCAS correlated traffic, the traffic symbols may indicate directionality unless a TCAS Resolution Advisory is in effect.
3.6 Alert Prioritization. Integrated ASA/TCAS traffic displays must be designed such that TCAS advisories (TA/RA), both aural and visual, have priority over ASA alerts and other traffic information (see also this AC, Appendix H, Section 3). All ASA alerts must be suppressed when a TCAS advisory (TA/RA) is in effect. ASA applications may, in the future, be shown to be acceptably safe, where an ASA system may suppress TCAS advisories (TA/RA) when performing an application (e.g. Closely Spaced Parallel Approaches). However these applications are considered future capabilities, which are beyond the scope of this guidance. This AC may be used in combination with other FAA approved guidance material to provide additional functionality.
3.7 ASA/TCAS Alert Discernability. ASA traffic alerts, both aural and visual, must be easily discernable from TCAS alerts. ASA alerts must not be depicted as a red square.
3.8 TCAS Aural Alerts. TCAS aural alerts (described in RTCA/DO-185A and RTCA/DO- 197A) must remain clear and unambiguous on a system that integrates TCAS and ASA systems.
3.9 Inhibiting ASA Aural Alerts. A means should be provided to manually inhibit ASA aural alerts. There should be a means of indicating to the flight crew that ASA alerting has been inhibited.
3.10 Selected Traffic. The additional information associated with selected traffic (i.e., in data tag or data block) should not interfere with the legibility of the TCAS TA/RA symbols and their data tags.
Page G - 2 APPENDI X G
4. Existing Guidance/Policy. AC 20-151, “Airworthiness Approval of Traffic Alert and Collision Avoidance systems (TCAS II) Version 7.0 and Associated Mode S Transponders.” This document (AC 20-151) describes the airworthiness approval process for TCAS II version 7.0, which includes some reduction in flight tests for systems that will be upgraded to version 7.0.
AC 120-55B, “Air Carrier Operational Approval and Use of TCAS II”. This AC describes system performance and provides a means to address TCAS issued related to installation and use regarding compliance with 14 CFR parts 121, 125, and 129 requirements for air carriers.
5. Regulatory Basis.
Automatic Dependent Surveillance-Broadcast. There is no United States regulatory requirement at this time for carriage of ADS-B equipment. Several ICAO member States are exploring the benefits of ADS-B and plan on implementation of ADS-B technology initially as an air traffic management tool.
Traffic Alert and Collision Avoidance System. The regulatory requirement for U.S. operations can be found in 14 CFR.
Airborne Collision Avoidance System (ACAS). The ICAO mandate for ACAS is found in Annex
10. The ACAS carriage requirements are based on maximum gross takeoff weight. The effective date for the ICAO mandate is 2005.
APPENDIX G Page G- 3
APPENDIX H.
Human Factors Considerations for the Display of Traffic Surveillance Information
Table of Contents – Appendix H
1. Introductio n
2. Other Traffic Surveillance Information
3. Information Presentation, General
4. Own-ship Symbol
5. Traffic Symbols, General
6. Traffic Source, Update Rate, and Time-of-Applicability
7. Traffic Data Fields
8. Traffic Altitude and Vertical Speed
9. Alerting Traffic
10. Selected Traffic
11. Traffic Velocity Vector and Ground Track History
12. Display Zooming, Panning, and Orientating
13. Databases
14. Surface Traffic
15. Multifunction Display Integration
16. Acceptable Traffic Surveillance Symbols
1. Introduction. This Appendix provides human factors guidance for the display of traffic surveillance information in aircraft. This Appendix applies to ADS-B and TIS-B as the traffic surveillance technologies. TCAS is not addressed, except in explicitly noted cases in which an ASA traffic surveillance display is integrated with a TCAS traffic display (See also Appendix G of this AC). The guidance in this Appendix is based on the assumption of a color plan view display of traffic information.
Human factors guidance that is specific to particular surveillance equipment can be found in other Appendices. General human factors guidance that is not specific to traffic surveillance (e.g., guidance on aircraft displays and controls) still applies, but is not provided in this advisory circular. See also Appendix C of this AC for references.
2. Other Traffic Surveillance Information. The Table of Contents above lists the guidance topics provided in this Appendix. Other traffic information that is not addressed in this Appendix, but which might be additionally displayed, includes:
Traffic Intent Traffic Identification Format
APPENDIX H Page H- 1
Coupled Traffic Traffic/Own-ship Category Traffic Length/Width Codes Traffic Geometric Altitude Degraded Traffic Directionality Degraded Traffic Position Depiction of Selected Traffic Depiction of Traffic Air/Ground Status Depiction of Surface Vehicles and Obstacles Traffic Decision-Aid Information (e.g., speed recommendation) Traffic Closure Rate Traffic Wake Vortex Information Application-Specific Traffic Information The above list is provided not only to understand the scope of this Appendix, but also to consider the large amount of other information that aircraft traffic displays might present.
3. Information Presentation, General.
3.1 Traffic Information Complexity. Traffic displays must allow each flight crew member to perform their duties without unreasonable concentration or fatigue (see 14 CFR § 2X.771(a)), and should therefore present information in a way that minimizes clutter, is intuitive, is simple to learn, and is consistent with applicable industry standards (see Appendix C).
3.2 Traffic Information Clarity. Traffic information should be discernable, legible, and unambiguous within all flight environments (e.g., ambient illumination), and when displayed in combination with other information (e.g., electronic map).
3.3 Use of Color. Color should not be used as the sole means of encoding traffic information, but instead should be used in addition to other encoding means (e.g., shape, size, border pattern).
3.4 Number of Colors. No more than six colors should be used for information encoding on the traffic display. The use of additional colors for purposes other than information encoding should not detract from the discernability of colors used for information encoding. See SAE ARP4032 for additional guidance on the use of color.
3.5 Manual Decluttering. The traffic display should have the capability for manual decluttering or filtering of information that is not essential for continuous display within the given operational application and flight crew task. The ability to return to the previous or default setting should also be provided.
3.6 Ease of Decluttering. It should be possible to accomplish the most important and/or common declutter function(s) with a simple action.
3.7 Identifying Removed Information. Information removed through decluttering should be easily identifiable (e.g., through accessible list of active/inactive filters).
3.8 Filters and Invalid Information. The traffic symbol associated with invalid or unknown information (e.g., altitude not reported) should not be removed by filtering or decluttering operations that are based on that information.
NOTE: In addition to targets with invalid information, other specific traffic targets may also be displayed despite filtering and decluttering operations. See also Section 9, “Alerting Traffic,” and Section 10, “Selected Traffic.”
Page H - 2 APPENDI X H
3.9 Information Prioritization for Overlay. To ensure visibility of the most important symbols and their associated proximate data, the following prioritization should be followed for information overlay, from highest to lowest priority:
1. Own-ship
2. Airborne traffic with warnings
3. Airborne traffic with cautions
4. Selected traffic
5. Other airborne traffic
6. Other surface traffic
Selected Traffic that is on the surface should only overlay other airborne traffic if appropriate for the application. Any information prioritization scheme should be demonstrated to be safe and effective.
NOTE: Altitude, range, and other information may be used for further prioritization and tie breaking, as appropriate for the application. For additional information overlay guidance on displays that integrate ASA and TCAS traffic, see Appendix G, “TCAS and ASA Integration.”
4. Own-ship Symbol
4.1 Indication of Own-ship. When own-ship is within the traffic display’s field of view, a depiction of own-ship should be provided.
4.2 Own-ship Symbol Discernability. The own-ship symbol should be easily discernable from traffic and other symbols.
4.3 Own-ship Symbol Color. The color of the own-ship symbol should not be the same as traffic symbols, as recommended in AC 20-131A and RTCA/DO-185A.
NOTE: Separate colors facilitate quick recognition and identification of the own-ship. Cyan or white are acceptable colors.
4.4 Obstruction of Own-ship Symbol. The own-ship symbol should be unobstructed.
NOTE: Exceptions may be allowable for multi-function displays depicting higher priority information required by regulation that could temporarily obstruct the own-ship symbol.
4.5 Representation of Own-ship Location. The location on the own-ship symbol corresponding to the location on the own-ship should not cause pilot confusion about the ownship position relative to traffic. The location on non-directional symbols should be the symbol center. For directional symbols, other locations on the symbol may be used. Both locations (on the own-ship symbol and on own-ship) should be described in the Pilot’s Operating Guide. See also this Appendix, Paragraph 5.5, “Representation of Traffic Location.”
4.6 Indication of Own-ship Directionality. If valid own-ship directionality data is available to the traffic display, the own-ship symbol should be depicted as a directional symbol.
4.7 Loss of Own-ship Directionality. If own-ship directionality becomes invalid (i.e., neither valid track angle nor valid heading data is available to the traffic display) the following traffic display criteria should be applied:
APPENDIX H Page H- 3
a) The loss of own-ship directionality is clearly annunciated,
b) The display of traffic and other surveillance information is conditional on the following display orientation and surveillance information source criteria:
For North-up Orientation:
• The own-ship is depicted with a non-directional symbol.
• The own-ship symbol is positioned near the center of the traffic display.
• Surveillance information measured relative to own-ship (e.g., weather from own-ship radar, TCAS traffic) is removed. See NOTE.
• The removal of surveillance information is clearly annunciated.
• Surveillance information measured independently from own-ship (e.g., ADS-B/TIS-B traffic, up-linked weather) may remain on the display.
For Heading-up Orientation:
• Surveillance information measured independently from own-ship (e.g., ADS-B/TIS-B traffic, up-linked weather) is removed. See NOTE.
• The removal of surveillance information is clearly annunciated.
• Surveillance information measured relative to own-ship (e.g., weather from own-ship radar, TCAS traffic) may remain on the display.
c) Each display orientation mode listed in (b) above, if provided, is manually selectable. Automatic selection is allowable.
NOTE: Own-ship directionality may be invalid for a short period of time before the above display criteria applies (see RTCA/DO-257A for related guidance). Each ASA participant should input to ASSAP the highest quality state data that is available on-board (see RTCA/DO-289). In some situations, own-ship directionality data for the traffic display might be derived solely from GNSS track (see this Appendix, Section 14, “Surface Traffic”), such that a loss of directionality is not improbable. Traffic that is tracked and correlated by both TCAS and ASA systems (see Appendix G) may not have to be removed. For guidance on traffic display orientation, see this Appendix, Section 12, “Display Zooming, Panning, and Orientating.” If own-ship directionality becomes valid, automatic reversion is allowable.
5. Traffic Symbols, General
5.1 One Symbol Per Aircraft. If a target aircraft is displayed, it should be depicted by exactly one symbol.
5.2 Misleading Information. The attributes of traffic symbols (e.g., orientation, size, color, shape) should not provide misleading information about actual traffic states (e.g., position).
5.3 Indication of Traffic Directionality. If valid traffic target directionality data is available to the traffic display, the traffic target symbol should be depicted as a directional symbol. Traffic targets for which directionality information is not available or invalid should be depicted as a non-directional symbol.
5.4 Loss of Traffic Directionality. If directionality data for a traffic target becomes unavailable or invalid for an unacceptable period of time for the application (see RTCA/DO-289) the traffic symbol should revert to a non-directional shape (e.g., diamond) and any other directionality cues
(e.g., velocity vector) should be removed.
Page H - 4 APPENDI X H
5.5 Representation of Traffic Location. The location on the traffic symbol corresponding to the location on the aircraft that it represents should not cause pilot confusion about the traffic position. The location on non-directional symbols should be the symbol center. For directional symbols, other locations on the symbol may be used. Both locations (on the symbol and on the corresponding aircraft) on all traffic symbols should be clearly identified in the Pilot’s Operating Guide, along with the associated limitations. See also this Appendix, Paragraph 4.5, “Representation of Own-ship Location.”
NOTE: The choice of both locations (on the symbol and on the corresponding aircraft) can have safety consequences. For airborne applications (i.e., large display range), the choice of the location on the symbol has the greater influence on conveying traffic position. For surface applications (i.e., small display range), the choice of the location on the aircraft might also be a factor. Pilot confusion about traffic location includes dynamic situations, such as when an aircraft symbol automatically changes shape (e.g., due to loss of directionality or a change in air/ground status).
6. Traffic Data Source, Update Rate, Time-of-Applicability. Traffic data that is received by own-ship might be transmitted from multiple sources. Traffic data has associated data link performance measures, some of which are largely influenced by the traffic data source. In this AC, “Traffic Data Source” refers to the surveillance system technology (i.e., ADS-B or TIS-B, but not TCAS unless explicitly noted). “Update Rate” refers to the frequency at which new traffic information is updated on the traffic display (versus from the data source). “Time-ofapplicability” refers to the instant at which traffic information applies, which might vary among traffic due to different sampling/reporting times, information network latency, etc. It is the responsibility of the ASSAP (Aircraft Surveillance and Separation Assurance Processing) to perform the traffic tracking function, including correlation, registration, smoothing, extrapolation, coasting. See also Appendix D, “Aircraft Surveillance Applications (ASA) Systems,” and RTCA/DO-289.
6.1 Minimum Update Rate. The traffic display should be capable of updating traffic positions at a rate of at least once per second.
6.2 Indication of Traffic Data Source. The traffic display should be capable of indicating:
a) The source(s) of any traffic on the display
b) The source(s) of traffic that is able to be received. This will help the flight crew determine that equipment is functioning properly, even when traffic is not displayed.
NOTE: The indication of traffic data source may be through textual or symbolic depiction, and may be presented on a part time basis through pilot selection. See also Appendix H, Section 16, “Acceptable Traffic Surveillance Symbols,” and Appendix G, “TCAS and ASA Integration.”
6.3 Indication of Unavailable Traffic Data. The traffic display should provide an explicit indication (e.g., text message) when a failure or degradation in traffic data sources and equipment results in a loss of functionality.
NOTE: The presence/absence of traffic symbols is not an explicit indication. At any given moment, the source of displayed traffic data can be from a combination of ADS-B and one or more TIS-B ground sites, such that some level of traffic data source redundancy exists. In these cases the loss of a data source might not result in a loss of functionality.
APPENDIX H Page H- 5
6.4 Same Time-of-Applicability. The traffic display should show the positions of all displayed traffic at the same time-of-applicability.
6.5 Automatic Removal of Invalid Traffic. If a traffic target position becomes invalid, the display should automatically remove the traffic symbol and its associated data fields.
NOTE: The continued loss of signal from traffic data sources, or continued loss of traffic horizontal position information, might eventually result in an invalid target position estimate.
Related guidance on time values is provided in RTCA/DO-289.
6.6 Indication of Automatic Removal of Traffic. The automatic removal of traffic symbols due to signal loss or invalid data should be explicitly indicated on the display.
NOTE: The absence of traffic is not an explicit indication. In order to avoid unnecessary distractions to the flight crew, exceptions may apply for some traffic targets.
6.7 Traffic Jitter. Traffic symbols should be positioned on the display such that jitter is not distracting to pilots.
NOTE: Jitter that is unavoidable (e.g., due to technology limitations) may be allowable. See also this AC, Appendix F, “TIS-B.”
7. Traffic Data Fields. Traffic Data Fields are areas within the display that are dedicated to providing information associated with individual traffic symbols, such as altitude or flight identification. A “data field” refers generically to two specific approaches: traffic “data blocks” and traffic “data tags.” Data blocks typically reside in a fixed location on the traffic display, independent of the target symbol location. In contrast, data tags are always located near the target symbol.
7.1 Minimum Data Tag Information for Airborne Traffic. Data tags for airborne traffic should display altitude and the vertical speed indicator.
NOTE: Exceptions apply when data is invalid or unavailable. It may be allowable to suppress the display of altitude and/or vertical speed on some traffic data tags to reduce clutter. See also this Appendix, Paragraph 7.3, “Indication of Unavailable Data,” and Paragraph 8.8, “Indication of Traffic Vertical Speed.”
7.2 Traffic Identification. Data fields for airborne and surface traffic should have the capability to display the identification of the flight or vehicle (e.g., Flight ID, Call Sign, Vehicle ID).
7.3 Indication of Unavailable Data. The traffic display should have the capability to indicate any data field information that is unavailable or invalid.
7.4 Association with Traffic Symbol. Any traffic data field should be clearly associated with its corresponding traffic symbol.
7.5 Data Field Color. Data field information should be the same color as the corresponding traffic symbol, in order to facilitate the association between traffic symbol and data field.
NOTE: Additional coloring (e.g., text outline) may be allowable to maintain legibility, as long as the association between the data field and the traffic symbol is not compromised.
Page H - 6 APPENDI X H