Appendix 6 APPENDIX 6. DEFINITIONS
1. Aircraft Certification Office (ACO). FAA offices responsible for determining an aircraft’s airworthiness regarding issuance of type certificates (TC), Supplemental Type Certificates (STC), issues related to Title 14 of the Code of Federal Regulations (14 CFR) parts 21, 23, 25, 33, and other similar airworthiness rules. ACOs are also responsible for technical assessment of service difficulties including issuance of Airworthiness Directives (AD).
2. Aircraft Evaluation Group (AEG). FAA offices responsible for operational aspects of newly certificated, modified, or in-service aircraft. AEGs establish FAA criteria for pilot qualification, minimum equipment lists (MEL), initial airworthiness, other such requirements as they relate to 14 CFR parts 43, 61, 91, 121, 135, and other operationally related regulations.
3. Altitude Limit (ALIM). ALIM is the specified projected amount of vertical separation that Traffic Alert and Collision Avoidance System (TCAS) is designed to provide between aircraft.
The value of ALIM varies with aircraft barometric altitude.
4. Altitude Threshold (ZTHR). The projected minimum ZTHR for the issuance of a preventive Resolution Advisory (RA). The ZTHR varies with aircraft altitude.
5. Certificate-Holding District Office (CHDO). A Flight Standards office that is responsible for administration of a part 121 and part 135 operating certificate for a particular operator.
6. Closest Point of Approach (CPA). The occurrence of minimum range between your own TCAS aircraft and the intruder.
7. Coordination (as related to TCAS). The process by which TCAS units in conflicting aircraft communicate with one another to select complementary RAs to resolve an encounter
(e.g., one unit selects a climb command and the other a descend command).
8. Flight Standards District Office (FSDO). An FAA field office serving an assigned geographical area and staffed with Flight Standards personnel who serve the aviation industry and the general public on matters relating to the certification and operation of air carriers and General Aviation (GA) aircraft.
9. 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 part 41 airplane type used in air transportation, as well as other part 25 airplanes, transport category multiengine helicopters, and large multiengine piston airplanes.
10. Follow-On STC (as related to TCAS). A TCAS STC other than as described in paragraph 8. The following examples are follow-on STCs:
a. TCAS II Installation. A previously approved TCAS II installation, which is installed in a subsequent type or model aircraft.
Appendix 6
b. Display Configuration. Changes of display configuration (weather radar/TCAS display), supporting system (radar altimeter), or other aircraft interface ground proximity warning system GPWS), etc.).
11. Initial Type Certificate (TC)/Supplemental Type Certificate (STC) (as related to TCAS). The first FAA TCAS airworthiness approval in accordance with a TC or STC of any one or combination of the following components: a TCAS processor (computer), TCAS directional antenna, and/or Mode S transponder.
NOTE: For previously approved TCAS systems, if the part number of any of the above components changes due to a significant modification, the system change requires an initial TC/STC.
12. Intruder. An aircraft that has satisfied the TCAS traffic advisory (TA) detection criteria.
13. Master Minimum Equipment List (MMEL). An FAA document listing stipulations in accordance with parts 121, § 121.628 and 135, § 135.180 that provides authorization for the continuation of flight beyond a terminal point with certain inoperative equipment. AEGs develop 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.
14. 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. FAA CHDOs apply MRB requirements in reviewing and approving each carrier’s proposed maintenance program.
15. 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, manpower, and material; and system components shared jointly with the military.
16. National Simulator Program (NSP). Program consisting of simulator evaluation specialists responsible for evaluating FSTDs to aid the principal operations inspector (POI) in approving use of a specific flight simulation training device (FSTD) in a training program.
17. Other Traffic. Traffic shown on the traffic display that are not classified as proximate, TA, or RA.
18. Principal Inspector (PI). Refers to one of the following three FAA inspectors who is selected as primary for TCAS for an air carrier (normally the POI):
a. Principal Avionics Inspector (PAI). The FAA inspector responsible for overseeing all avionics issues relative to a specific operator, to include input on training programs, operations specifications (OpSpecs), MEL requests, etc.
AC 120-55C CHG 1 Appendix 6 3/18/13
b. 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.
c. Principal Maintenance Inspector (PMI). The FAA inspector responsible for overseeing all maintenance issues relative to a specific operator, to include input on training programs, OpSpecs, MEL requests, etc.
19. Proximate Traffic. An aircraft that is within 6 nautical miles (NM) in range and ± 1,200 feet vertically, but which does not meet the TCAS thresholds of a TA or RA.
20. Resolution Advisory (RA). Aural voice and display information provided by TCAS to a flightcrew, advising that a particular maneuver should or should not be performed to attain or maintain minimum safe vertical separation from an intruder.
a. Altitude Crossing RA. An RA that directs a pilot to cross through the intruder aircraft’s altitude to achieve safe vertical separation.
b. Coordinated Crossing RA. Initial RAs coordinated between TCAS-equipped aircraft and that direct the aircraft to cross in altitude.
c. Corrective RA. An RA that advises the pilot to either deviate from current vertical speed, such as climb when the aircraft is level or to maintain an existing climb or descent rate.
d. Increase Rate RA. An RA that is issued after an initial climb or descend RA, which indicates that 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 feet per minute (fpm).
e. Preventive RA. An RA that requires a pilot to avoid certain deviations from current vertical rate, such as a don’t climb RA when the aircraft is level.
f. Reversal RA. An RA that indicates a change in the direction previously issued by TCAS and is required to achieve safe vertical separation. For example, an initial descend RA that reverses to a climb RA.
g. Turn Around RA. An initial corrective RA issued to a TCAS aircraft with an established vertical rate that directs the aircraft in the opposite direction. For example, a -1,500 fpm descend RA issued while climbing at +2,000 fpm.
h. Weakened RA. An initial corrective RA that changes to an RA calling for a return to level flight because TCAS has determined that safe vertical separation is projected. For example, a climb RA weakens to a do-not-descend advisory once the desired vertical separation has been achieved.
21. Significant TCAS Events. Significant TCAS events are those which meet any one of the following guidelines:
Appendix 6
a. Standard Air Traffic Control (ATC) Separation. There is a loss of standard ATC separation resulting from compliance with a TCAS-generated RA.
b. Performance. TCAS is suspected of not performing as designed.
c. Descent RA. TCAS issues a descent RA when own aircraft is below 1,000 feet above ground level (AGL).
d. Altitude Excursion. There is an altitude excursion of more than 1,000 feet from an assigned level altitude.
e. Turn Around RA. TCAS issues a turn around RA.
f. Coordinated Crossing RA. TCAS issues a coordinated crossing RA.
22. Supplemental Type Certificate (STC). An FAA certificate attesting to the fact that modifications to the respective aircraft, engines, or other components meet 14 CFR airworthiness requirements.
23. Tau. Greek symbol representing the time to CPA.
24. Threat. An intruder which has satisfied the threat detection criteria and thus requires an RA.
25. Traffic. Aircraft with an operating transponder capable of being tracked and displayed by a TCAS-equipped aircraft.
26. Traffic Advisory (TA). Aural voice and display information provided by TCAS to a flightcrew, identifying the location of nearby traffic that meets certain minimum separation criteria.
27. Traffic Alert and Collision Avoidance System (TCAS). A family of airborne devices meeting specified Technical Standard Order (TSO) and RTCA/DO-185 requirements, current edition, which function independently of the ground-based ATC system to provide collision avoidance information.
a. TCAS I. A TCAS providing only TAs to assist pilots in the visual acquisition of intruder traffic.
b. TCAS II. A TCAS which provides TAs and RAs in the vertical plane, such as climb or descend.
28. TCAS Academic Training (as applied herein). Part of ground training which exclusively addresses acquiring the required TCAS concepts, systems, limitations, or procedures knowledge (rather than skills), and demonstration of that knowledge. TCAS academic training generally is accomplished using a combination of classroom methods (standup instruction, slide/tapes, computer based instruction, tutorial, etc.), flight manual information bulletins, or self-study. See paragraph 9b for an expanded explanation of what should be taught.
AC 120-55C CHG 1 Appendix 6 3/18/13
29. TCAS Event. For the purpose of this AC, one or more of the following occurrences or situations are related to TCAS:
a. TCAS, RA, or TA. Issuance of any TCAS RA or TA as specified by a flightcrew, regardless of whether it is valid, unwarranted, or a nuisance;
b. In-Flight Traffic Conflicts. Other TCAS-related in-flight traffic conflicts or potential conflicts as determined by a flightcrew;
c. Near Midair Collision (NMAC). NMACs involving a TCAS-equipped aircraft;
d. System Failures. TCAS system failures related to a traffic conflict, potential traffic conflict situation, or TCAS general system performance;
e. System Error. ATC system error involving a TCAS-equipped aircraft; or
f. System Safety Performance. Other TCAS occurrences or situations related to potential TCAS or ATC system safety performance.
30. TCAS Maneuver Training. Part of flight training that includes the integration of TCAS knowledge with the specific skills required to demonstrate satisfactory performance of a particular TCAS procedure or maneuver, or series of procedures or maneuvers.
31. TCAS Operational Performance Assessment (TOPA). Program to characterize and assess the performance of TCAS in U.S. NAS and, when appropriate, make recommendations to improve operational performance.
32. Type Certificate (TC). An FAA certificate attesting to the fact that the respective aircraft, engines, or other components meet 14 CFR airworthiness requirements.
Page 5 (and 6)