Appendix A A-4 constant Mach and climb or descend at a minimum of 300 feet per minute (fpm) during the maneuver. With these criteria, an ITP aircraft should never come closer than the 10-nautical-mile (NM) separation minimum to a reference aircraft while passing through their altitude(s).
A.4.1 ITP Distance and GS Differential Criteria. The initial distance criteria values, 15 NM and 20 NM, were selected so that when an FL change at 300 fpm and constant Mach number is maintained with the respective maximum 20- or 30-knot closing GS differential, the distance between the aircraft should not become less than the ITP minimum separation of 10 NM.
A.4.2 Relative Altitude Criteria. The design of the procedure is such that the reference aircraft may not be more than 2,000 feet above or below the ITP aircraft.
A.4.3 Similar Track Criteria. Application of the ITP is limited to geometries where the ITP aircraft and any reference aircraft are on similar tracks. Similar tracks are defined here as less than 45 degrees from one another. See Figure A-3.
Figure A-3. Similar Track A .4.4 Mach Differential. In order to ensure an acceptable closure throughout the ITP maneuver, the controller will not issue an ITP clearance if the closing Mach differential is greater than 0.06 Mach. This Mach differential check accounts for potentially unsafe closure rates due to abnormal or adverse wind gradient conditions at the intermediate altitudes.
The Mach number check may be achieved by:
1. Using the cruise Mach numbers of the ITP and reference aircraft where the Mach number technique is being used;
2. Requesting Mach numbers from the ITP and reference aircraft; or
3. Any other methodology determined appropriate and acceptable by the regulatory authority and the air navigation service provider (ANSP).
Appendix A A-5 A.4.5 ADS-B Data Quality Criteria. The ITP avionics only accept ADS-B Out aircraft broadcasting data of sufficient quality for use as reference aircraft for ITP. The ITP avionics only allow ITP when own-ship data quality is sufficient to ensure safe separation. The data quality criteria are:
1. Position accuracy for ITP and reference aircraft—ITP and reference aircraft data with horizontal position accuracies of at least 0.5 NM (95 percent);
2. Position integrity for ITP and reference aircraft—ITP and reference aircraft data with horizontal position integrity bounds of 1.0 NM at 1×10E-05; and
3. Velocity accuracy for ITP and reference aircraft—ITP and reference aircraft data with horizontal velocity accuracies of at least 10 meters/second (m/s) (19.4 kts), 95 percent.
A.5 ITP Description. To properly conduct an ITP, a qualified flightcrew uses ADS-B In avionics specifically certified to assist in verifying the initial conditions and a graphical display to monitor the relative position(s) of nearby aircraft. The procedure can only be conducted in airspace with appropriately trained ATC personnel, ITP-compatible automation, and approved ITP separation minima available. The following are the steps necessary to conduct an ITP:
A.5.1 Flightcrew Verifies Initial Criteria. Using approved avionics, the ITP flightcrew verifies that their own-ship and the reference aircraft meet initial qualifying criteria. The onboard ITP avionics indicate to the flightcrew whether all initiation criteria are satisfied.
A.5.2 Flightcrew Requests ITP. If the criteria are satisfied, the flightcrew requests the ITP clearance using the appropriate phraseology. Direct Controller Pilot Communication (DCPC) ensures unambiguous communication of the ITP request and ATC clearance.
Currently, only Controller-Pilot Data Link Communication (CPDLC) is being used in locations where ITP is approved. Preformatted messages for requesting and approving ITP have been developed; however, not all aircraft have implemented them. In aircraft that do not have preformatted messages, flightcrews use standardized free text messages as described in Table A-2, Flightcrew Standardized Free Text Controller-Pilot Data Link Communication Message Set for In-Trail Procedure, and Table A-3, Controller Free Text Controller-Pilot Data Link Communication Message Set for In-Trail Procedure, until further notice. It is essential that the correct message elements be included in the correct format to allow the controller or automation system to properly evaluate the request.
Improperly formatted or incomplete requests may be denied.
Note: ATC will not issue an ITP clearance to any aircraft unless that aircraft has initiated a proper request.
Appendix A A-6 A.5.3 Controller Issues Clearance. Upon receipt of an ITP request, the controller:
1. Confirms the ITP aircraft and the reference aircraft are on the same track.
a. Same-track criteria are not the same as the similar-track criteria, which are checked by the ITP aircraft flightcrew.
b. Same-track includes the concept of similar-track (i.e., ITP aircraft and reference aircraft are traveling in the same direction with less than a 45-degree relative track angle between the aircraft), but also includes a check on whether or not the lateral protection areas overlap (e.g., lateral separation cannot be applied). This check can only be done by the controller who knows what separation standard is being applied between the aircraft.
2. Confirms that no more than two reference aircraft have been identified in the request and are identified correctly; that is, that the Aircraft Identification (ACID) of each reference aircraft in the ITP request exactly matches the corresponding aircraft’s filed flight plan (FP).
3. Ensures both the ITP aircraft and reference aircraft are not maneuvering and not expected to maneuver during the ITP.
Note: A change of course (only) to remain on the same route would not be considered a maneuver, provided the course change is less than 45 degrees and the aircraft remain in a same track configuration.
4. Verifies that the closing Mach differential is no greater than 0.06 Mach.
5. Verifies that there are no conflicts at the requested altitude.
6. If appropriate, issues an ITP clearance.
A.5.4 Flightcrew Reassesses Criteria. Upon receiving the ITP clearance, the flightcrew confirms that all criteria are still satisfied. If the criteria are not satisfied or there has been a loss of traffic information, the flightcrew immediately rejects the ATC clearance and terminates the maneuver. Additionally, if the FL, reference aircraft, or type of maneuver (ITP versus standard FL change) does not exactly match their request or if the flightcrew receives an ITP clearance without requesting one, they will not perform the maneuver and should verify with ATC to confirm the clearance.
A.5.5 Flightcrew Executes ITP. If the criteria are still met, the flightcrew accepts the clearance and begins the requested climb or descent without delay. While executing the maneuver, the flightcrew is expected to maintain their flight-planned route, assigned Mach number (or current Mach, if none is assigned), and minimum Vertical Speed (VS) of 300 fpm and ensure they execute only the maneuver for which they have been cleared. The maneuver is complete once the flightcrew reports to ATC that they have reached the new FL.
Note: Once the ITP maneuver has been initiated, it should be completed, and the aircraft not returned to the initial altitude. Should reference aircraft data be lost or ITP display fail during the maneuver, the flightcrew should continue the maneuver to the assigned altitude using the appropriate Mach number and
Appendix A A-7 300 fpm minimum VS. Upon completion of the maneuver, notify ATC of the ITP data loss.
A.5.6 Approved ITP Variations. An ITP can be conducted with a maximum of two reference aircraft. The procedure design does not allow the reference aircraft to be more than 2,000 feet of altitude above or below the ITP aircraft, but there is no limit on the amount of altitude change the ITP aircraft may request. The reference aircraft both may be behind or ahead of the ITP aircraft or one may be ahead and one behind. Figure A-4 depicts the approved ITP variations.
Figure A-4. In-Trail Procedure Climb/Descent Variations A .5.7 Contingency Procedures. The ITP maneuver has been extensively tested both in flight and in computer simulations with consideration given to a variety of environmental and aircraft performance factors. A temporary breach of the 10 NM ITP distance does not constitute an inherently unsafe procedure and should not be the sole factor when considering abandoning the procedure. No new contingency procedures are prescribed for ITP. If, in the pilot’s judgment, the ITP maneuver (i.e., reaching the newly assigned altitude) cannot be successfully completed once the climb or descent has been initiated, they will:
1. Contact ATC and request an alternative clearance as soon as practicable given flightcrew workload and flight conditions.
2. Inform ATC of any action the flightcrew is taking or requesting. Because of the many variables, the CPDLC message should be in the “free text” format.
3. Comply with regional contingency procedures appropriate to the circumstances, or as listed in ICAO Doc 4444, Section 15.2, Special Procedures for In-Flight Contingencies in Oceanic Airspace.
Appendix A A-8 A.5.8 ITP Distance. Except when one aircraft is directly in trail of another, the ITP distance is not the same as the direct line distance between those two aircraft. (See paragraph A.3, ITP Terminology, for the exact description and Figure A-2 for examples.) Since the ITP software is designed to calculate and display ITP distance information, extensive training on the subject is not necessary. However, it is important to emphasize that range and ITP distance are different. Consequently, a lack of understanding could lead the flightcrew to misidentify the correct reference aircraft when requesting an ITP clearance. Training should include examples of the various ITP distance geometries depicted in Figure A-2.
A.5.8.1 Lateral Traffic Filters. Some ITP avionics incorporate a lateral traffic filter.
The function of the traffic filter is to eliminate any targets beyond a predetermined lateral distance of own-ship’s track from consideration as a potential reference aircraft. This is intended to prevent the flightcrew from misidentifying incorrect reference aircraft during their ITP request. The filter is most useful when in an organized track environment or where traffic may be on a parallel user-preferred route. Incorrect use may result in denied ITP requests. Training should include recommended technique for its use.
A.5.8.2 ITP Initiation Criteria. Traffic displayed as an ADS-B In target might not be presented as a valid ITP reference aircraft because it does not meet one or more ITP initiation criteria. Some of the criteria, such as position accuracy, are not displayed to the flightcrew. Training should include a discussion of the initiation criteria, which criteria are known to the flightcrew, and examples of when a displayed ADS-B In target is not an eligible ITP reference aircraft. See Table A-1 for ITP initiation criteria.
A.6 Authorization to Conduct ITP. FAA authorization is required for all U.S. aircraft operators to conduct ITP operations using ADS-B In (14 CFR § 119.49(a)(5)). This appendix provides guidance to operators on the process for requesting issuance of this authorization, including guidance on the documentation that should be submitted.
Note 1: For FAA authorization, refer to FAA Order 8900.1, Volume 3, Chapter 18, Section 3, Operations Specification (OpSpec)/Management Specification (MSpec)/Letter of Authorization (LOA) A354, Automatic Dependent Surveillance-Broadcast (ADS-B) In-Trail Procedure (ITP).
Note 2: Operators may already hold other ADS-B In authorizations. There is no need to submit documentation for an ITP authorization if that documentation has already been submitted for previous ADS-B In authorizations. The ITP application may include references to those duplicate documents instead.
A.6.1 Initial Request for Authorization. U.S. aircraft operators seeking to conduct ITP should first contact their assigned FAA office to indicate their intent. At the time of the operator’s initial request, the FAA will provide the operator with an ITP Application Checklist, which should be completed with attached supporting documents.
Appendix A A-9 A.6.2 Documentation to Submit With Formal Proposal.
A.6.2.1 Documentation Guidance. The following section provides general guidance on the documentation required for submission of a formal ITP proposal. At the discretion of the operator’s assigned principal inspector (PI), additional information may be required based on any unique aspects of their specific operation. The operator must submit a letter of request for issuance of authorization to the assigned PI. The letter of request should include the following information:
• Type of aircraft (make, model, and series (M/M/S)).
• ADS-B equipment complies with Technical Standard Order (TSO)-C195b, Avionics Supporting Automatic Dependent Surveillance – Broadcast (ADS-B) Aircraft Surveillance Applications (ASA), or later revision, or as approved for ITP by the Administrator.
• Installation has been completed following guidance in AC 20-172, Airworthiness Approval for ADS-B In Systems and Applications, or other acceptable means.
• Manufacturer’s name of the ADS-B In software.
• Proposed region(s) of operation (not applicable to 14 CFR part 91 operations).
Note: The guidance contained in paragraph A.6.2 will also be annotated on the ITP Using ADS-B In Application Checklist provided to the operator by the applicable FAA office.
A.6.2.2 Airplane Flight Manual (AFM) Compliance Documentation. Operators submit documentation that demonstrates that their aircraft have an ADS-B In system that meets the performance standards of TSO-C195b or later revision, or as approved for ITP by the Administrator.
A.6.2.3 Proposed Operations Area. Authorizations to conduct ITP are limited to specific regions of the world where the ANSP offers ITP and those procedures are determined to be acceptable to the Administrator. Routes or airspace where ITP may be authorized will be published in Aeronautical Information Publications (AIP). Include in your request a description, by flight information region (FIR) and ANSP, of the operational areas where you propose to conduct ITP. If the operator holds an OpSpec/MSpec B050, Authorized Areas of En Route Operations, Limitations, and Provisions, authorization, submit a draft OpSpec/MSpec B050 that includes the operational areas where you propose to conduct ITP, including applicable notes.
A.6.2.4 Operational Procedures. As applicable, company manuals should address any ITP-specific guidance from the Air Traffic Service Provider (ATSP) of the proposed region(s) of operation.
Appendix A A-10 A.6.2.5 Operation Manuals and Checklists. The certificate holder (CH)/operator/program manager (as applicable) should submit information
(e.g., Airplane Operations Manual (AOM) bulletin or equivalent) to the flightcrews describing ADS-B, to include:
• ITP system description;
• Normal procedures;
• En route procedures using ITP;
• Communications; and
• Non-normal or contingency procedures.
A.6.2.6 Maintenance. See Appendix C, ADS-B In Operations—Aircraft Qualification and Maintenance, for applicable maintenance guidance.
A.6.2.7 Revision of Minimum Equipment List (MEL). See Appendix C for guidance on the necessary MEL documents to be submitted for authorization of ITP.
A.6.2.8 Pilot Training. Submit applicable portions of proposed ITP-specific pilot training material and include a description of the methods used to conduct, evaluate, and manage the training. The following contains the recommended information to be included in pilot training material:
1. General understanding of ADS-B In operations (i.e., technology, capabilities, and limitations).
2. ITP system operation, including:
• Normal procedures;
• Non-normal and/or contingency procedures;
• ITP flight planning considerations;
• ITP dispatch considerations (as applicable);
• MEL considerations (as applicable);
• ITP terminology, including proper formulation of a CPDLC ITP request/clearance; and
• ITP equipment limitations.
3. Explanation of ITP distance as distinct from aircraft range, using select scenario-based examples (see Figure A-2 for ITP distance geometries):
• ITP directly in trail of a reference aircraft;
• ITP aircraft on a crossing track of reference aircraft—diverging;
Appendix A A-11
• ITP aircraft on a crossing track of reference aircraft—converging; and
• ITP aircraft on a parallel track of reference aircraft.
A.6.2.9 Dispatch/Flight Follower Training. Submit applicable portions of proposed ITP-specific dispatch/flight planning training material, to include any appropriate updates to the dispatch operations manual, or equivalent, as well as a description of the methods used to conduct, evaluate, and manage training. The following contains the recommended information to be included in dispatch/flight planning training material:
1. General understanding of ADS-B In operations;
2. Dispatch of aircraft with the ITP system unserviceable;
3. How flight planning codes are affected with ADS-B unserviceable;
4. Flight planning, fuel loading, and route change procedures associated with ITP operations;
5. Equipment needed to conduct ITP; and
6. Approved ITP routes and airspace.
Note: Dispatch/flight follower training is not required for 14 CFR part 91 operations. However, as the pilot is responsible for flight planning, the pilot should consider these items prior to flight.
Appendix A A-12 Table A-1. In-Trail Procedure Initiation/Maneuver Criteria (Reference RTCA DO-312 Supplement) In-Trail Procedure (ITP) Speed/Distance Criteria ITP Distance ≥ 15 nautical miles (NM) and Closing Groundspeed (GS) Differential ≤ 20 knots (kts) ITP Distance ≥ 20 NM and Closing GS Differential ≤ 30 kts Relative Altitude Criteria Difference in altitude between ITP and Reference Aircraft is less than or equal to 2,000 feet Similar Track Criteria Difference in track angles between ITP and Reference Aircraft is 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 at 1×10E-05 Velocity Accuracy for ITP and Reference Aircraft ITP and Reference Aircraft data with horizontal velocity accuracies of at least 10 meters/second (m/s)
(19.4 kts), 95% Closing Mach Differential (Air Traffic Control (ATC) Crosscheck) Closing Mach Differential is less than or equal to
0.06 Mach
Appendix A A-13 Table A-2. Flightcrew Standardized Free Text Controller-Pilot Data Link Communication Message Set for In-Trail Procedure In-Trail Procedure (ITP) Type (number and relative position of reference aircraft) FREE TEXT Message Element Content 1 reference aircraft (ahead) “ITP [Distance] BEHIND [Aircraft flight identification (FLT ID)]” 1 reference aircraft (behind) “ITP [Distance] AHEAD OF [Aircraft FLT ID]” 2 reference aircraft (both ahead) “ITP [Distance] BEHIND [Aircraft FLT ID] AND [Distance] BEHIND [Aircraft FLT ID]” 2 reference aircraft (both behind) “ITP [Distance] AHEAD OF [Aircraft FLT ID] AND [Distance] AHEAD OF [Aircraft FLT ID]” 2 reference aircraft (one ahead and one behind) “ITP [Distance] BEHIND [Aircraft FLT ID] AND [Distance] AHEAD OF [Aircraft FLT ID]” To request an ITP climb or descent, the flightcrew will send a Controller-Pilot Data Link Communication (CPDLC) REQUEST CLIMB TO [altitude] or REQUEST DESCENT TO [altitude] message, as applicable, with the following verbiage added to FREE TEXT as listed in Table A-2:
Example of ITP request message: REQUEST CLIMB TO FL360 ITP 25 NM BEHIND SIA228 AND 21 NM AHEAD OF AFR008.
Note: This standardized free text message set will be used until an appropriate message set is implemented.
Appendix A A-14 Table A-3. Controller Free Text Controller-Pilot Data Link Communication Message Set for In-Trail Procedure In-Trail Procedure (ITP) Type (number and relative position of reference aircraft) FREE TEXT Message Element Content 1 reference aircraft (ahead) “ITP BEHIND [Aircraft flight identification (FLT ID)]” 1 reference aircraft (behind) “ITP AHEAD OF [Aircraft FLT ID]” 2 reference aircraft (both ahead) “ITP BEHIND [Aircraft FLT ID] AND BEHIND [Aircraft FLT ID]” 2 reference aircraft (both behind) “ITP AHEAD OF [Aircraft FLT ID] AND AHEAD OF [Aircraft FLT ID]” 2 reference aircraft (one ahead and one behind) “ITP BEHIND [Aircraft FLT ID] AND AHEAD OF [Aircraft FLT ID]” To grant an ITP request, the controller will send an uplink message containing CLIMB TO AND MAINTAIN [altitude] or DESCEND TO AND MAINTAIN [altitude] containing the text in Table A-3:
Example of ITP clearance message: ITP BEHIND SIA228 AND AHEAD OF AFR008 CLIMB TO FL360 REPORT LEVEL FL360.
Note 1: The controller should never issue an ITP clearance unless one has been requested by a flightcrew.
Note 2: This standardized free text message set will be used until an appropriate message set is implemented.
Appendix B B-1 APPENDIX B. CAVS USING ADS-B IN B.1 Purpose. This appendix describes Cockpit Display of Traffic Information (CDTI) Assisted Visual Separation (CAVS) and provides guidance to operators seeking FAA authorization to conduct CAVS operations.
B.2 Background. When a flightcrew accepts responsibility to maintain visual separation from another aircraft, they should maintain constant visual surveillance of that aircraft and notify air traffic control (ATC) if they can no longer do so. Additionally, the flightcrew accepts the responsibility for wake turbulence separation from that aircraft.
Though the weather must be visual meteorological conditions (VMC) pursuant to CAVS authorization, other environmental conditions may prevent them from maintaining constant visual surveillance of the traffic, such as when the traffic is landing toward a rising or setting sun. Additionally, distances and closure rate to an aircraft directly ahead can be difficult to judge, such that avoiding wake turbulence and getting too close to the traffic can be difficult.
B.3 CAVS Concept. CAVS is an ADS-B In application that assists the flightcrew in maintaining separation from ADS-B Out-equipped aircraft during visual separation.
Currently, CAVS authorization is only for the approach phase of flight when cleared by ATC to maintain visual separation from specific traffic. Because of the accuracy and integrity of displayed traffic on ADS-B In systems approved for CAVS, CAVS information may be used as a substitute for continuous visual observation of traffic-to-follow (TTF) under specified conditions. CAVS does not relieve the pilot of the responsibility to see and avoid other aircraft. ATC maintains separation responsibility from all other aircraft and for the orderly flow of traffic to the runway. Currently, there is no new phraseology associated with CAVS and approved for the use of CAVS. ATC will be unaware that a flightcrew is using CAVS. CDTI does not replace any traffic advisories (TA) and/or Resolution Advisories (RA) provided by the aircraft’s Airborne Collision Avoidance System (ACAS). RA response is still based on the ACAS display and approved procedures.
Note: See Appendix G, CDTI Assisted Separation on Approach, for a description of CDTI Assisted Separation on Approach (CAS-A).
B.4 CAVS Arrivals. Traffic information from the CDTI is used to augment out-the-window (OTW) visual contact with an aircraft a flightcrew is assigned to follow. This will enable them to accept separation responsibility from that aircraft. Once the flightcrew has visually acquired and accepted a visual approach clearance behind TTF, the pilot may use the lead aircraft traffic information on the CDTI as a means for maintaining separation while performing a visual approach. As done today with a visual approach clearance, no specific spacing assignments will be made by ATC. The procedure can be conducted behind all weight classes except when the lead aircraft is a super.
B.5 CAVS Description. Flightcrews are reminded that CAVS is a visual separation procedure. If at any time the traffic information provided by CAVS equipment becomes unreliable, inoperative, or distracting, its use should be discontinued immediately.