(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:
(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 B 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 B-5).
(1) For TCAS/ASA integrated systems and systems with ATAS, 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 B-5 provides example notional depictions.
Note: This requirement is to be consistent with TCAS symbol convention.
A • Figure B-5. 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.
(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 B-6).
(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 B-6).
(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 30
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 B-6 provides a notional example.
Figure B-6. Directional and Non-directional Designated Traffic Symbols
(c) There must be an indication of off-scale designated traffic.
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 B-7).
(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.
ma Figure B-7. Traffic Advisory Symbols
c. Resolution Advisories (RAs) (see Figure B-8).
(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.
Note: TCAS aural alerts and resolution guidance are not affected by these requirements or recommendations.
Figure B-8. Resolution Advisory S ymbols 32
ModeA/C Modes Aircraft Aural lnhibit(s)
e.g. TAWS ADS-B In ADS R TISB ModeA/C Modes ADS-8 In ADSR TIS B Aircraft Aural lnhibit(s)
e.g. TAWS I RF Source Aural Inhibit Audio Out Annunciator Panel Out t--- --------1 -<' L--- Annunciator Panel (TAS RA Display Out t---- Class B only) Traffic Display Out Notes: 1. Traffic Display Optional for TCAS 1/ TAS.
TAS/TCAS 1/TCAS 11 RA Display (TCAS II only) Aural Inhibit TAS/TCAS 1/TCAS II Track In I RF Source RF Source Audio Out t--------1 CDTI/Annunciator >----~ ATAS Audio Out Display Out TCAS I
- or TCAS 11
- or - Panel Out Audio Out TCAS Track In Display Out ATAS TAS Class A or B CDTI legacy Traffic Display (Note 1)
- or - Annunciator Panel Notes : 1. Annunciate the aura ls for TCAS as ATAS aurals i.e. for a TCAS only alert, issue the corresponding ATAS aural alert.
Speaker
2. TCAS II aurals are triggered from the TCAS traffic file.
Aural Inhibit L__--------- CDTI Integrated Unit 05/20/15 AC 20-172B Appendix C ATAS Integration with existing Traffic Alerting Avionics Figure C-1. Example of an acceptable configuration of TAS/TCAS I/TCAS II and ATAS Figure C-2. Example of an acceptable integrated configuration 33
ModeA/C Modes ADS-B In ADSR TIS B Traffic Display I RF Out Source Audio Out [TCAS I w/ or w/o Display]
- or - [TCAS II]
- or - [TAS Class A]
- or - -----------r ------ I I I An I I
- I I I I I CJ LegacyTCA Display nunciator Panel s [TAS Class B w/ or w/o Display] Spea ker Audio Out RF Annunciator Source Panel Out ATAS I ---- - 1----- .,e I I Annunc I -0---i 1ator -=- I I I I I I I Pan el : ______ D ADS-B Traffic Display Notes: Not permitted due to non-integration.
05/20/15 AC 20-172B Figure C-3. Example of an invalid TCAS I/TAS with ATAS configuration 34
Appendix D Definitions, acronyms, and related documents
1. Definitions. The following are definitions of terms used in this document.
24-bit Address. Unique address assigned to an aircraft during the registration process.
ADS-B In- Receipt, processing, and display of other aircraft’s ADS-B transmissions.
ADS-B In is necessary to utilize airborne applications.
ADS-B Out. Transmission of an aircraft’s position, altitude, velocity, and other
information to other aircraft and ATC ground based surveillance systems.
Advisory. The level or category of alert for conditions that require flight crew awareness and may require subsequent flight crew response.
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.
Airborne Surveillance and Separation Assurance Processing (ASSAP). The processing subsystem that accepts surveillance inputs (e.g., ADS-B reports), performs surveillance processing to provide reports and tracks, and performs application-specific processing.
Surveillance reports, tracks, and any application-specific alerts or guidance are output by ASSAP to the CDTI function. ASSAP surveillance processing consists of track processing and correlation of ADS-B, TIS-B, ADS-R and TCAS reports.
Alert. A general term that applies to all advisories, cautions, and warning information; can include visual, aural, tactile, or other attention-getting methods.
Application. The function(s) for which the ASA system is used.
Aircraft Surveillance Application (ASA). An application that uses aircraft surveillance data to provide benefits to the flight crew (refer to Table 1).
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.
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.
Automatic Dependent Surveillance-Rebroadcast (ADS-R). A service of the ground system that rebroadcasts ADS-B messages from one link technology onto another. For 35
example, the SBS ground system provides ADS-R service to rebroadcast UAT messages on 1090 MHz and vice versa.
ADS-B Traffic Advisory System (ATAS). An ADS-B In application that augments flight crew traffic situation awareness in support of the see-and-avoid responsibility by providing alerts of traffic that are detected in conflict with ownship. This application is named Traffic Situation Awareness with Alerts (TSAA) in RTCA DO-317B.
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.
Basic Airborne (AIRB). The basic airborne situation awareness application enhances the flight crew’s traffic situation awareness through the provision of an on-board graphical display of surrounding traffic that transmits ADS-B data of a sufficient quality. Pilots will use the CDTI to supplement and enhance out-the-window visual acquisition and listening to radio communications.
Caution. The level or category of alert for conditions that require immediate flight crew awareness and subsequent flight crew response.
Coast Interval. The elapsed time since a report from any source has been correlated with the track.
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.
CDTI Assisted Visual Separation (CAVS). 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 even if visual contact out-the-window is momentarily lost.
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.
Correlation. The process of determining that a new measurement belongs to an existing track.
Controller Pilot Data Link Communication (CPDLC). Provides direct data communication between the pilot and the air traffic controller through a data link.
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.
Data Tag. A block of information that is displayed next to the traffic symbol in the main part of the CDTI display.
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.
Designated Traffic. Traffic upon which a designated application is to be conducted.
Desirable. The capability denoted as desirable is not required to perform the procedure, but would increase the utility of the operation.
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.
Differential Ground Speed. Calculated by taking the difference between the magnitude of the ownship ground speed and the designated traffic ground speed. The assumption is that ownship is following the designated traffic approach path over the ground. Positive values indicate closure on the designated traffic.
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.
Enhanced Visual Acquisition (EVAcq). This application is an enhancement for the out the-window visual acquisition of aircraft traffic and potentially ground vehicles.
Estimation. The process of determining a track’s state based on new measurement information.
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.
Extrapolation. The process of predicting a track’s state forward in time based on the track’s last kinematic state.
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.
Flight Information Service Broadcast (FIS-B). FIS-B is a ground broadcast service provided over the UAT data link. The FAA FIS-B system provides pilots and flight crews of properly equipped aircraft with a cockpit display of certain aviation weather and aeronautical information.
Flight Crew. One or more cockpit crew members required for the operation of the aircraft.
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.
Ground Track Angle. The direction of the horizontal velocity vector (see velocity) relative to the ground as noted in ground speed.
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.
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.
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.
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.
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.
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.
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.
Pressure Altitude. Altitude reported by a barometric pressure altimeter without corrections for local pressure settings.
Primary Surveillance Radar (PSR). A radar sensor that listens for 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.
Range Reference. The CDTI feature of displaying range rings or other range markings at specified radii from the own-ship symbol.
Reference Aircraft. An aircraft within the ITP geometric criteria for usage as reference when requesting an ITP clearance.
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.
Selected Traffic. Traffic for which additional information is requested by the flight crew.
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.
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).
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). Please refer to AC 25-11( ) for more details.
Spacing. A distance maintained from another aircraft for specific operations.
State Vector. An aircraft’s current horizontal position, vertical position, horizontal velocity, vertical velocity, and navigational accuracy and integrity.
SURF (Basic Surface). An ADS-B application that displays traffic over an airport surface map underlay, and is used to support the flight crew in making decisions about taxiing, takeoff, and landing. The underlying map may depict runways only, or runways, taxiways, and other movement areas.
Traffic Selection. Manual process of flight crew selecting a traffic element.
TCAS Potential Threat. Traffic detected by TCAS equipment on board the own-ship, that has met 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.
TCAS Proximate Traffic. Traffic, detected by TCAS equipment on board the own-ship, that is within 1200 feet vertically and 6 NM horizontally of the own-ship (RTCA/DO-185B § 1.8). If the ASA 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.
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.
Time of Applicability. The time that a particular measurement or parameter is (or was) relevant.
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.
Track Angle. See Ground Track Angle.
Track State. See State Vector.
Traffic. All aircraft/vehicles that are within the operational vicinity of own-ship.
Traffic Element. An aircraft or vehicle.
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.
Traffic Symbol. A depiction on the CDTI display of an aircraft or vehicle other than the own-ship.