Appendix A A-7 Acronym Term HMD Helmet-Mounted Display HMD Horizontal Miss Distance HS Hybrid Surveillance HUD Head-Up Display HURS High Update Rate Surveillance ICAO International Civil Aviation Organization IFR Instrument Flight Rules IMC Instrument Meteorological Conditions inHg Inches of Mercury IRS Inertial Reference System LOA Letter of Authorization LODA Letter of Deviation Authority LOFT Line-Oriented Flight Training mb Millibars MEL Minimum Equipment List MHz Megahertz MMEL Master Minimum Equipment List Mode S Mode Select MOPS Minimum Operational Performance Standards MOR Mandatory Occurrence Report MRB Maintenance Review Board MRBR Maintenance Review Board Report MSpec Management Specification NAS National Airspace System NASA National Aeronautics and Space Administration NM Nautical Mile NMAC Near Midair Collision NSP National Simulator Program NTSB National Transportation Safety Board OpSpec Operations Specification PAI Principal Avionics Inspector
Appendix A A-8 Acronym Term PF Pilot Flying PFD Primary Flight Display PI Principal Inspector PL Policy Letter PM Pilot Monitoring PMI Principal Maintenance Inspector POI Principal Operations Inspector PRM Precision Runway Monitor QFE The atmospheric pressure at aerodrome elevation (or at runway threshold) QNE The barometric pressure used for the standard altimeter setting (29.92 inHg) QNH The barometric pressure as reported by a particular station RA Resolution Advisory RBDM Risk-Based Decision Making RVSM Reduced Vertical Separation Minimum RWC Remain Well Clear SA Safety Assurance SAFO Safety Alert for Operators SDP Standard Datum Plane SDR Service Difficulty Report SL Sensitivity Level SMS Safety Management System SRM Safety Risk Management SSR Secondary Surveillance Radar STBY Standby STC Supplemental Type Certificate TA Traffic Advisory Tau (τ) Time to Closest Point of Approach TAWS Terrain Awareness and Warning System TC Type Certificate TCAS Traffic Alert and Collision Avoidance System (also known as ACAS) TFC Traffic
Appendix A A-9 Acronym Term TOPA TCAS Operational Performance Assessment TSO Technical Standard Order TSOA Technical Standard Order Authorization UAT Universal Access Transceiver USAF United States Air Force UTC Universal Coordinated Time VFR Visual Flight Rules VMD Vertical Miss Distance VSI Vertical Speed Indicator XPDR Transponder ZTHR Altitude Threshold (Z-axis Threshold) A.6 Definitions.
A.6.1 Active Surveillance. Using ACAS interrogations and subsequent replies to update or acquire an ACAS track.
A.6.2 Airborne Collision Avoidance System (ACAS). A family of airborne devices meeting specified TSO and RTCA requirements that function independently of the ground-based ATC system to provide collision avoidance information.
A.6.2.1 ACAS I. An ACAS providing only TAs to assist pilots in the visual acquisition of intruder traffic. TCAS I is currently the only example of a developed ACAS I.
A.6.2.2 ACAS II. An ACAS that provides TAs and RAs, including vertical maneuvers that should or should not be performed to attain or maintain minimum safe vertical separation from a threat aircraft. TCAS II and ACAS Xa are currently the only examples of an ACAS II.
A.6.2.3 ACAS III (in development). An ACAS that provides TAs and RAs, including vertical and horizontal maneuvers that should or should not be performed to attain or maintain minimum safe separation from a threat aircraft.
A.6.3 ACAS II Maneuver Training. Part of flight training that includes the integration of ACAS II knowledge with the specific skills required to demonstrate satisfactory performance of a particular ACAS II procedure or maneuver, or series of procedures or maneuvers.
Appendix A A-10 A.6.4 A CAS Academic Training (as applied herein) . Part of ground training that exclusively addresses acquiring the required ACAS concepts, systems, limitations, or procedures knowledge (rather than skills), and demonstration of that knowledge. ACAS academic training generally is accomplished using a combination of classroom methods (standup instruction, computer-based instruction, tutorial, etc.), flight manual information bulletins, or self-study.
A.6.5 ACAS E vent. For the purpose of this AC, one or more of the following occurrences or situations are related to ACAS:
A.6.5.1 ACA S II Resolution Advisory (RA) or Traffic Advisory (TA). Issuance of any ACAS II RA or TA as specified by a flightcrew.
A.6.5.2 In-Flight Traffic Conflicts. Other ACAS-related in-flight traffic conflicts or potential conflicts as determined by a flightcrew.
A.6.5.3 Near Midair Collision (NMAC). NMACs involving an ACAS-equipped aircraft.
A.6.5.4 System Error. ATC system error involving an ACAS-equipped aircraft.
A.6.5.5 System Failures. System failures related to a traffic conflict, potential traffic conflict situation, or ACAS general system performance.
A.6.5.6 System Safety Performance. Other ACAS occurrences or situations related to potential ACAS or ATC system safety performance.
A.6.6 A ircraft Certification Service (AIR) Office. The FAA offices responsible for oversight of design, production, airworthiness certification, and continued airworthiness programs for all U.S. civil aviation products and foreign import products.
A.6.7 Aircraft Evaluation Division (AED). The FAA offices that contribute an operational perspective to engineering activities and identify applicable operating regulations. In certification projects, a primary responsibility of AED is to evaluate, as appropriate, flightcrew type rating requirements, minimum equipment required for dispatch, and continued airworthiness. AED provides consultation, coordination, and assistance to AIR in certification programs and the development of Airworthiness Directives (AD).
A.6.8 Air Traffic Control Radar Beacon System (ATCRBS). Secondary surveillance radar system with ground-based interrogators and airborne transponders capable of operation on Modes A and C.
A.6.9 Altitude Threshold (ZTHR). The projected minimum altitude threshold or Z-ax is Threshold (ZTHR) for the issuance of a preventive RA. The ZTHR varies with aircraft altitude.
A.6.10 Automatic Dependent Surveillance-Br oadcast (ADS-B). A function on an aircraft or vehicle that automatically broadcasts its own-ship identity, state vector (horizontal and
Appendix A A-11 vertical position and velocity), associated quality and performance parameters (accuracy and integrity), and other information. Broadcast links include the 1090 MHz Extended Squitter (ES) and the UAT broadcast on 978 MHz.
A.6.11 Bearing. The angle of another aircraft in the horizontal plane, measured clockwise from the longitudinal axis of own-ship.
A.6.12 Closest Point of Approach (CPA). The occurrence of minimum range between own-ship and another aircraft.
A.6.13 Coast. Condi tion that occurs when ACAS does not receive a reply to an interrogation from an aircraft where ACAS has established a track, resulting in the logic continuing the track based on previous track characteristics.
A.6.14 Coordination (as related to ACAS II). The process where A CAS II units in conflicting aircraft operating in TA/RA mode communicate with one another to generate complementary RAs to resolve an encounter (e.g., one ACAS generates a climb RA, and the other ACAS generates a descend RA).
A.6.15 Discrete. Separate, complete, and distinct signal.
A.6.16 Encounter. A situation when two or more aircraft are in proximity to each other so that an RA is generated on at least one of them.
A.6.17 False Advisory. An advisory determined by postevent analysis to have been caused by a false track or an ACAS malfunction.
A.6.18 Flight Standardization Board (FSB). The FAA board responsible for establishing or revising crew qualification requirements (e.g., training, checking, currency, and type rating(s)) for specific aircraft. FSBs are established for each large turbojet, turboprop, and special 14 CFR § 21.41 airplane type used in air transportation, as well as other 14 CFR part 25 airplanes, transport category multiengine helicopters, and large multiengine piston airplanes.
A.6.19 Flight Standards District Office (FSDO). A Flight Standards (FS) office staffed with personnel who serve the aviation industry and the public on matters relating to the certification and operation of air carriers and General Aviation (GA) aircraft.
A.6.20 Follow-On Supplemental Type Certificate (STC) (as related to ACAS). The following examples are follow-on STCs:
A.6.20.1 AC AS II Installation. A previously approved ACAS II installation that is installed in a subsequent type or model aircraft.
A.6.20.2 Display Configuration. Changes of display configuration; weather radar/ACAS display; supporting system inputs, such as radar altimeter; or other aircraft interfaces, such as TAWS, etc.
Appendix A A-12 A.6.21 Horizontal Miss Distance (HMD). The horizontal range between two aircraft at the CPA.
A.6.22 Hybrid Surveillance (HS). Combined use of active and passive surveillance to update an ACAS track.
A.6.23 Initial Type Certificate (TC)/Supplemental Type Certificate (STC) (as related to ACAS).
The first FAA ACAS airworthiness approval in accordance with a TC or an STC of any one or combination of the following components: an ACAS processor (computer), a directional antenna, and/or a Mode S transponder.
A.6.24 Intruder. A n aircraft that has satisfied the ACAS TA generation criteria.
A.6.25 Maintenance Review Board (MRB). An FAA board responsible for establishing maintenance requirements for a specific aircraft type. MRB requirements are usually formulated in conjunction with information provided by the manufacturer and prospective operators through industry working groups. Responsible Flight Standards offices apply MRB requirements in reviewing and approving the maintenance program of an air carrier.
A.6.26 Master Minimum Equipment List (MMEL). An FAA document listing stipulation that may provide authorization for the continuation of flight beyond a terminal point with certain inoperative equipment. AED develops MMELs in conjunction with an FOEB established for each aircraft type. FAA MMELs serve as the basis for an operator to develop specific MELs applicable to its particular aircraft and operational requirements.
A.6.27 Mode A. ATCRBS S SR equipment or mode of operation that replies to interrogations with a 4-digit transponder code with 4,096 possible codes (non-altitude reporting).
A.6.28 Mode C. ATCRBS SS R equipment or mode of operation that replies to interrogations with aircraft pressure altitude information.
A.6.29 Mode S. Mode Select (S), SS R equipment, or mode of operation that replies to interrogations with transponder code, aircraft pressure altitude information, a discrete address, and other aircraft information.
A.6.30 Multiple Threat Encounter. An e ncounter involving two or more threats against own-ship being processed simultaneously by the ACAS.
A.6.31 National Airspace System (NAS). The common network of U.S. airspace; air navigation facilities; equipment and services; airports or landing areas; aeronautical charts, information, and services; rules, regulations, and procedures; technical information, human resources, and material; and system components shared jointly with the military.
A.6.32 National Simulator Program (NSP). Program consisting of simulator evaluation specialists responsible for evaluating FSTDs to aid the POI in approving use of a specific FSTD in a training program.
Appendix A A-13 A.6.33 Other Traffic. A n aircraft that is more than 6 nautical miles (NM) laterally or more than 1,200 feet vertically from own-ship.
A.6.34 Passive Surveillance. The use of ADS-B Out pos ition messages to update the ACAS track of other aircraft.
A.6.35 Pressure Altitude. The height above a Standard Datum Plane (SDP), a theoretical level where the weight of the atmosphere is 29.92 inches of mercury (inHg)/1013.25 millibars (mb). Aircraft transponders transmit and ACAS uses pressure altitude so that ACAS can function correctly with relative altitude between aircraft regardless of the barometric scale setting of the altimeter. When an aircraft is below Flight Level (FL) 180, ATC automation corrects the pressure altitude received from the transponder for nonstandard pressure to display the estimated indicated altitude of the aircraft to the controller.
A.6.36 Principal Inspector (PI). Refers to one of the following three FAA inspectors who is selected as primary for an air carrier:
A.6.36.1 Prin cipal Avionics Inspector (PAI). The FAA inspector responsible for overseeing all avionics issues relative to a specific operator, including input on training programs, OpSpecs, MEL requests, etc.
A.6.36.2 Principal Maintenance Inspector (PMI). The FAA inspector responsible for overseeing all maintenance issues relative to a specific operator, including input on training programs, OpSpecs, MEL requests, etc.
A.6.36.3 Principal Operations Inspector (POI). The FAA inspector responsible for overseeing all operational issues relative to a specific operator, including training programs, OpSpecs approval, MEL approval requests, etc.
A.6.37 Proximate Traffic. Tr affic shown on the traffic display that is within 6 NM laterally and 1,200 feet vertically of own-ship that does not meet the threshold for a TA or an RA.
A.6.38 Relative Altitude. The d ifference in altitude between own-ship and another aircraft. The value is positive when the other aircraft is higher and negative when the other aircraft is lower.
A.6.39 Resolution Advisory (RA). Aura l voice and display information provided by ACAS II to a flightcrew, advising that a particular maneuver should or should not be performed to attain or maintain minimum safe vertical separation from a threat aircraft.
A.6.39.1 Altitud e Crossing RA. An RA that directs a flightcrew to cross through the altitude of a threat aircraft to achieve safe vertical separation.
A.6.39.2 Coordinated Crossing RA. Initial RA coordinated between aircraft operating ACAS II and that direct the aircraft to cross in altitude.
Appendix A A-14 A.6.39.3 Corrective RA. An RA that advises the flightcrew to either deviate from current vertical speed, such as climb when the aircraft is level, or to maintain an existing climb or descent rate.
A.6.39.4 Increase Rate RA. An RA that is issued after an initial climb or descend RA that indicates additional climb or descent rate is required to achieve safe vertical separation. An increase rate RA requires a climb or descent rate of 2,500 fpm.
A.6.39.5 Initial RA. First RA generated during an encounter.
A.6.39.6 Preventive RA. An RA that requires a flightcrew to avoid certain deviations from current vertical rate, such as a do not climb RA when the aircraft is level.
A.6.39.7 Reversal RA. An RA that indicates a change in the direction previously generated by ACAS II and that is required to achieve safe vertical separation
(e.g., an initial descend RA that reverses to a climb RA).
A.6.39.8 Subsequent RA. A modified RA generated during an encounter after the initial RA but before a “Clear of Conflict” annunciation. Subsequent RAs may be weakened, strengthened, or reversed.
A.6.39.9 Weakened RA. An initial corrective RA that changes to an RA calling for a return to level flight because ACAS II has determined that safe vertical separation is projected (e.g., a climb RA weakens to a do-not-descend advisory once the desired vertical separation has been achieved).
A.6.40 Sense. A direction that an RA may take (either cli mb or descend) relative to the existing flight path of own-ship.
A.6.41 Significant ACAS Events. Si gnificant ACAS events are those that meet any one of the following guidelines:
A.6.41.1 Altitu de Excursion. There is an altitude excursion of more than 1,000 feet from an assigned level altitude.
A.6.41.2 Coordinated Crossing RA. ACAS II generates a coordinated crossing RA.
A.6.41.3 Descent RA. ACAS II generates a descent RA when own-ship is below 1,000 feet AGL.
A.6.41.4 Performance. ACAS is suspected of not performing as designed.
A.6.41.5 Reversal RA. ACAS II generates a reversal RA.
A.6.41.6 Loss of Standard Air Traffic Control (ATC) Separation. There is a loss of standard ATC separation resulting from compliance with an ACAS II-generated RA.
Appendix A A-15 A.6.42 Squitter. Spontaneous transmission generated by Mode S transponders a nd ADS-B transmitters.
A.6.43 Standard Datum Plane ( SDP). A theoretical level where the weight of the atmosphere is
29.92 inHg/1013.25 mb.
A.6.44 Supplemental Type Certificate (STC). An FAA certificate attesting to the fact that modification to the respective aircraft, engines, or other components meet 14 CFR airworthiness requirements.
A.6.45 Tau ( τ). Greek symbol representing the time to CPA.
A.6.46 Traffic Alert and Collision Avoidance System (TCAS) I and II. See ACAS I and ACAS II.
A.6.47 TCAS Operational Performance Assessment (TOPA). Program to characterize and assess the performance of ACAS in the U.S. NAS and, when appropriate, make recommendations to improve operational performance.
A.6.48 Threat. An aircraft that has satisfied the ACAS II RA generation criteria.
A.6.49 Track. Estimated position and velocity of a single aircraft based on correlated surveillance data reports.
A.6.50 Traffic. Ai rcraft with an operating transponder capable of being tracked and displayed by an aircraft operating ACAS.
A.6.51 Traffic Advisory (TA). Aural voice and display information provided by ACAS to a flightcrew, identifying the location of nearby traffic that meets certain minimum separation criteria.
A.6.52 Type Certificate (TC). An FAA certificate attesting to the fact that the respective aircraft, engines, or other components meet 14 CFR airworthiness requirements.
A.6.53 Vertical Miss Distance (VM D). The relative altitude between own-ship and displayed aircraft at CPA.
Appendix B B-1 APPENDIX B. SAMPLE ACAS GROUND AND FLIGHT TRAINING PROGRAM B.1 Introduction. This appendix provides a set of training standards for ACAS flightcrew training. The information contained in this appendix related to Traffic Advisories (TA) is also applicable to ACAS I users. Training standards are divided into areas of instruction required for ground training (academics) and the performance objectives for the maneuvers required in flight training.
B.2 ACAS II Ground Training. ACAS II ground training should cover, in general terms, ACAS II theory to the extent appropriate to ensure proper operational use. Aircrews should understand basic concepts of ACAS II logic, Closest Point of Approach (CPA), time to CPA (represented by the Greek symbol tau (τ)), and altitude separation thresholds for the issuance of Resolution Advisories (RA), as well as the relationship between displayed traffic information and issuance of TAs and RAs. The ground training program should address the following:
B.2.1 T heories of Operation .
B.2.1.1 Objective. Demonstrate knowledge of how ACAS II functions.
B.2.1.2 Criteria. The pilot must demonstrate an understanding of the following functions:
1. S urveillance:
a. ACAS II interrogates other aircraft operating a transponder within a nominal range of 14 nautical miles (NM).
b. ACAS II surveillance range will be reduced in geographic areas with a large number of ground interrogators and/or aircraft operating ACAS II. A minimum surveillance range of 4.5 NM is guaranteed for airborne ACAS II aircraft.
2. C ollision Avoidance:
a. TAs can be generated against any aircraft operating a transponder even if the aircraft is non-altitude reporting (and own-ship is below 15,500 feet pressure altitude).
b. RAs can be generated only in the vertical plane and only against aircraft that are reporting altitude.
c. RAs generated against a threat aircraft operating ACAS II are coordinated to ensure complementary RAs are generated.
d. Failure to respond to an RA deprives own-ship of the collision protection provided by its ACAS II. In encounters where both aircraft are operating TA/RA mode, failure to respond to an RA by one aircraft restricts the RA maneuvers available to the other ACAS II-equipped aircraft.
Appendix B B-2 B.2.2 Advisory Thresholds.
B.2.2.1 Objective. Demonstrate knowledge of the criteria for issuing TAs and RAs.
B.2.2.2 Criteria. The pilot should be able to demonstrate an understanding of the methodology used by ACAS II to generate TAs and RAs and the general criteria for the issuance of these advisories, including the following:
1. ACAS II advisories are typically based on time to CPA. The separation standards provided by Air Traffic Control (ATC) are different from ACAS TA and RA thresholds.
2. In encounters with a slow closure rate, ACAS II advisories will be generated based on distance.
3. The timing of TA and RA generation varies with altitude. The threshold for TA and RA is longer at higher altitudes:
a. TAs generally occur 8 to 15 seconds prior to an RA.
b. RAs generally occur from 15 to 35 seconds before the projected CPA.
c. RAs are chosen to provide the desired Vertical Miss Distance (VMD) at CPA. As a result, RAs may generate a climb or descent through the altitude of the threat aircraft.
B.2.3 ACAS II Limitations.
B.2.3.1 Objective. To verify the pilot is aware of the limitations of ACAS II.
B.2.3.2 Criteria. The pilot should demonstrate a knowledge and understanding of the ACAS II limitations, including the following:
1. ACAS II may neither track nor display aircraft that are not operating a transponder, including transponders that have failed.
2. ACAS II will automatically fail if the input from the barometric altimeter, radio altimeter, or transponder is lost.
3. In some installations, the loss of information from other onboard systems, such as an Inertial Reference System (IRS) or Attitude and Heading Reference System (AHRS), may result in an ACAS II failure. Individual operators should ensure their flightcrews are aware of what types of aircraft system failures will result in an ACAS II failure.
4. Some aircraft within 380 feet Above Ground Level (AGL) (nominal value) will not be displayed. If ACAS II can determine that an aircraft below this altitude is airborne, it will display it.
5. ACAS II may not display all proximate aircraft operating a transponder in areas of high-density traffic.
Appendix B B-3
6. Because of design limitations, the bearing displayed by ACAS II is not sufficiently accurate to support the initiation of horizontal maneuvers based solely on the traffic display.
7. Because of design limitations, TCAS II may neither display nor generate an advisory against aircraft with a vertical speed of more than 10,000 feet per minute (fpm).
8. A stall warning, Terrain Awareness and Warning System (TAWS) “Pull Up” alert, or windshear warning takes precedence over a TA or an RA. When either a stall warning, TAWS “Pull Up” alert, or windshear warning is active, TA and RA aural annunciations will be inhibited, and ACAS II will automatically switch to the TA-ONLY mode of operation.
ACAS II will remain in TA-ONLY mode for 10 seconds after the TAWS “Pull Up” alert or windshear warning is removed.
B.2.4 ACAS II Inhibits.
B.2.4.1 Objective. To verify the pilot is aware of the conditions that certain functions of ACAS II are inhibited.
B.2.4.2 Criteria. The pilot should demonstrate a knowledge and understanding of the various ACAS II inhibits, including the following:
1. Increase descent RAs are inhibited below 1,450 feet AGL.
2. Descend RAs are inhibited below 1,100 feet AGL.
3. All RAs are inhibited below 1,000 feet AGL.
4. All ACAS II aural annunciations are inhibited below 500 feet AGL.
5. The altitudes and configurations that inhibit climb and increase climb RAs. ACAS II can still generate climb and increase climb RAs when operating at the maximum altitude or certified ceiling. Responses to climb RAs while operating at the maximum altitude or certified ceiling are expected to be complied with in the normal manner.
Note: In some aircraft types, climb or increase climb RAs are never inhibited.
B.2.5 Operating Procedures.
B.2.5.1 Pilot Knowledge. The pilot should demonstrate the knowledge required to operate ACAS II and interpret the information presented by ACAS II.
B.2.5.2 Training Topics. This training should address the following topics: