3-2 reporting. Flightcrews are advised to keep ADS-B Out and transponder with altitude reporting enabled throughout the flight (i.e., from completion of the before starting engines or pushback checklist until the shutdown checklist).
3.1.10 Flightcrews are advised not to activate ACAS II (Traffic Advisory (TA)/RA mode or TA-ONLY mode) until just prior to taking the active runway for departure, and ACAS II should be deactivated immediately after clearing the runway after landing.
3.1.10.1 Routine usage of ACAS II on the ground unnecessarily contributes to 1030/1090-megahertz (MHz) frequency congestion and can degrade the performance of ATC radars and surveillance performed by ACAS of airborne aircraft.
3.1.10.2 Flightcrews may use TA-ONLY or TA/RA mode for a short period of time before crossing an active runway to aid in visual acquisition of airborne aircraft in the vicinity (some aircraft will not display when ACAS computes that the aircraft is below 380 feet Above Ground Level (AGL)). Traffic symbols may take several seconds to display after selecting TA-ONLY or TA/RA mode.
3.1.10.3 Refer to the AFM/AFMS for details regarding the use of an automatic mode switching selection.
3.1.11 Flightcrews are advised to operate ACAS II in TA/RA mode to the maximum extent possible while airborne. Any decision to operate ACAS II in TA-ONLY mode is to be carefully considered due to the degradation of ACAS II safety functions. If a flightcrew elects to use TA-ONLY mode, the flightcrew should ensure that ACAS II is returned to the TA/RA mode as soon as possible. The following are examples that may warrant the use of TA-ONLY mode in the National Airspace System (NAS):
3.1.11.1 In the event of a Minimum Equipment List (MEL) deferral requiring the use of TA-ONLY. Refer to FAA Master Minimum Equipment List (MMEL) Policy Letter 32 (PL-32), Traffic Alert and Collision Avoidance System (TCAS).
3.1.11.2 I n the event of non-normal, abnormal, or emergency procedure scenarios;
particular in-flight failures; or performance limiting conditions, as specified by the AFM or operator.
3.1.11.3 During takeoff toward known nearby traffic that is in visual contact and that could cause an unwanted RA during initial climb, such as a visually identified helicopter passing near the departure end of the runway.
3.1.11.4 At certain airports, during particular procedures, or in circumstances identified by the operator as having a significant potential for unwanted or inappropriate RAs.
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3.2 TA Response. Respond to TAs by attempting to establish visual contact with the intruder aircraft and other aircraft that may be in the vicinity. If needed, adjust the range on the traffic display to ensure all available information on the intruder is shown. Coordinate to the degree possible with other crewmembers to assist in searching for traffic. Do not deviate from an assigned clearance based solely on TA information. For any intruder acquired visually, continue to maintain safe separation in accordance with current regulations and good operating practices.
3.2.1 Flightcrews are advised to utilize information from the traffic display to aid in visual acquisition of the intruder aircraft, including the bearing, range, relative altitude, and vertical speed trend.
3.2.2 Flightcrews are advised to utilize all available information to assist in visual acquisition, including air traffic controller traffic alerts or safety alerts.
3.2.3 The Pilot Flying (PF) is advised to continue to fly the aircraft and be prepared to respond to any RA that might follow. The Pilot Monitoring (PM) is advised to provide updates on the traffic location shown on the traffic display, using this information to assist in visual acquisition of the intruder.
3.2.4 Flightcrews are advised to confirm that the aircraft they have visually acquired is the aircraft that caused the TA to be generated using all available information.
3.2.5 Flightcrews are not advised to maneuver the aircraft based solely on the information shown on the traffic display due to limitations of bearing accuracy.
3.2.6 When visual acquisition is attained, right-of-way rules are used to maintain safe separation, unless an RA is generated. Flightcrews are not advised to initiate unnecessary maneuvers.
3.2.7 Flightcrews are advised caution when maneuvering based solely on visual acquisition, especially at high altitude or without a clearly defined horizon. Avoidance maneuvers based solely on a TA may cause the situation to deteriorate further. Visual assessment does not provide information on the intent or trajectory of the traffic and can be misleading (e.g., the pitch angle of a heavy aircraft at low speed makes it difficult to assess whether the aircraft is climbing, level, or descending).
3.2.8 Flightcrews are not advised to attempt to adjust the current flight path in anticipation of what an RA may advise.
3.2.9 TAs from TCAS I, an ACAS II in TA-ONLY mode, or ACAS Xa generating an ADS-B Only TA-ONLY (AOTO) advisory will not progress to an RA.
3.3 RA Response. Flightcrews are advised to comply with an RA to the degree displayed with an instinctive, immediate reaction. For ACAS II to work as designed, immediate and correct crew response to an RA is essential. Delayed response or reluctance of a flightcrew to comply with the RA due to ATC clearance provisions, fear of later FAA
3-4 scrutiny, or other factors could significantly decrease or negate the protection afforded by ACAS II.
3.3.1 M aneuvering in Response to an RA. When an RA occurs, the PF is advised to respond immediately by directing attention to the RA displays and to maneuver as indicated with positive control inputs, unless doing so would jeopardize the safe operation of the flight, or the flightcrew can ensure separation with definitive visual acquisition of the aircraft causing the RA. The PM provides updates on the traffic location, cross-checks between the traffic display, and monitors the response to the RA using proper Crew Resource Management (CRM).
3.3.1.1 F or ACAS II to provide safe vertical separation, initial vertical speed response is required within 5 seconds of when the RA is first displayed based on a
0.25 g vertical acceleration. Some autoflight systems have the capability to respond automatically to RAs. These systems may respond with a lower vertical acceleration yet may provide a faster response time when compared to manual flight operations.
3.3.1.2 RAs take precedence over any ATC instructions, clearances, requirements to follow a specific route, right-of-way rules, cloud clearance rules for Visual Flight Rules (VFR), or other such criteria. If a flightcrew receives ATC instructions to maneuver that conflict with an RA, the flightcrew is advised to comply with the RA. Flightcrews that deviate from an ATC clearance or instruction in response to an RA are advised to notify ATC of that deviation as soon as practicable.
3.3.1.3 Flightcrews are advised to comply with an RA while complying with an ATC clearance, if possible, when an RA and ATC clearance or instruction are congruent (e.g., when a flightcrew is able, comply with an ATC instruction and level at the assigned altitude while responding to a reduce climb or reduce descent RA).
3.3.1.4 If an RA is generated while the aircraft is turning, and the turn makes achieving the required vertical rate difficult or impossible, the turn should be stopped (i.e., leveling the wings to increase the rate of climb). Stopping the turn may close the horizontal proximity to the threat aircraft, but ACAS is evaluating the encounter and will change the RA if required.
3.3.1.5 Maneuvering in response to an RA should be limited to the minimum required to comply with the RA. An excessive maneuver response to an RA is not desirable or appropriate due to other potential conflicts (e.g., multiple threat encounter) and ATC implications, as well as the hazard of injury to the occupants of an excessively maneuvering aircraft.
3.3.1.6 Vertical speed responses should be made to avoid red arcs on the Vertical Speed Indicator (VSI) or outlined pitch avoidance areas on the Attitude
3-5 Direction Indicator and, if applicable, to accurately fly to the green arc or outlined pitch guidance area.
3.3.1.7 Comply with RAs by disconnecting the AP (if necessary) and the autothrottle system (if necessary), using prompt positive control, and thrust inputs in the direction and with the magnitude that is generated by the RA.
3.3.1.8 Some autoflight systems have the capability to respond automatically to RAs.
Pilots are advised to follow airframe manufacturer and/or operator flight path management policies and procedures in response to an RA.
3.3.1.9 During RAs, flightcrews should closely monitor the correct responses of the AP ACAS mode (if installed). The PF is advised to disengage the AP and fly the aircraft manually if the AP/Flight Director (FD) ACAS mode is not complying with RA vertical speed.
3.3.1.10 On aircraft with pitch guidance for RAs, comply with the RA pitch guidance, and verify the pitch guidance is appropriate for the RA. On aircraft without pitch guidance, achieve the required vertical speed (normally 1,500 fpm climb or descent) by first adjusting the pitch attitude using the suggested guidelines shown in the table below. Then, refer to the VSI and make all necessary pitch adjustments to place the VSI in the green arc. See Table 3-1.
Table 3-1. Initial Pitch Adjustment Response to a Resolution Advisory (Based on a Transport Category Airplane) Indicated Airspeed Pitch Adjustment Mach 0.80 2° 250 knots below 10,000 feet 4° Approach below 200 knots 5° to 7°
3.3.1.11 RAs are not coordinated with non-ACAS II-equipped aircraft (or ACAS II-equipped aircraft not operating in TA/RA mode). Threat aircraft may maneuver based on the see-and-avoid principle or ATC instructions. The threat aircraft may perform maneuvers that cause a change in the RA response.
3.3.1.12 During a coordinated RA, another ACAS II-equipped aircraft may incorrectly comply with ATC instructions contrary to the RA. This action may cause a change in the RAs generated for own-ship or multiple aircraft. Flightcrews are advised to respond immediately to any change in RA. Vertical speed response to an increase or reversal RA is required within 2.5 seconds after issuance of the advisory based on a 0.35 g vertical acceleration. Avoid red arcs or outlined pitch avoidance areas and fly to the green arc or outlined pitch guidance area.
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3.3.1.13 The PM should advise the PF on the progress of complying with the RA-generated vertical speed. The PM and any onboard observers will assist in the visual search for the threat aircraft and continue to cross-check ACAS II displayed information with other available traffic information to ensure the RA response is being flown correctly using proper CRM.
3.3.1.14 If an initial corrective RA is downgraded to a weakened RA (e.g., a “Climb, Climb” RA downgraded to a “Level Off, Level Off”), flightcrews are advised to respond to the weakened RA by adjusting the vertical speed to the rate depicted by the VSI green arc. Flightcrews should keep the VSI needle out of the red arc and/or the pitch guidance symbol out of the outlined pitch avoidance area. Attention to the RA display and prompt reaction to a weakened RA will minimize altitude excursions and potential disruptions to ATC. A proper reaction to a weakened RA will allow for proper resolution of the encounter and reduce the probability of subsequent RAs against the threat aircraft or another displayed aircraft.
3.3.1.15 Flightcrews are advised that, when operating at maximum certified altitude with an aircraft that is not climb inhibited, the proper response to a climb RA is to climb. The flightcrew is advised to comply with the RA unless doing so would jeopardize the safety of the aircraft. Flightcrews are advised to consider their energy management and specific aircraft flight envelope protection features. A stall warning will inhibit an RA.
3.3.1.16 ACAS II installations programmed to not generate a climb RA when operating at the maximum certified altitude will generate a “DO NOT DESCEND” or “DESCEND, DESCEND” RA instead.
3.3.1.17 When a “Clear of Conflict” annunciation is generated, the flightcrew is advised to immediately return to their previously assigned clearance and advise ATC, or comply with any amended clearance issued. Immediately returning should not be mistaken for aggressively returning. Another RA may be generated due to a flightcrew aggressively returning to their clearance when the threat aircraft is still a factor.
3.3.1.18 Flightcrews are advised to execute a missed approach/go-around if, as a result of an RA, the flightcrew will not be able to maintain a stabilized approach to a landing within the available runway.
3.3.2 Not Responding to RAs/Disregarding RAs.
3.3.2.1 Response to a stall warning, windshear warning, or Terrain Awareness and Warning System (TAWS) “Pull Up” alert takes precedence over an RA maneuver.
3.3.2.2 Flight path requirements affected by terrain, such as an obstacle-limited climb segment or an approach to rising terrain, may conflict with an RA. Since the basis for many approved instrument procedures and Instrument Flight Rules
3-7 (IFR) clearances is avoiding high terrain or obstacles, it is particularly important that the flightcrew maintains situational awareness and continues to use good operating practices and judgment when complying with RAs.
3.3.2.3 Flightcrews of aircraft with autoflight systems with an RA mode are advised to understand how to disable the autoflight mode if the autoflight system response is incorrect or undesired. Flightcrews should exhibit correct flight path management in automated or manual flight operations.
3.3.2.4 RAs may occur while aircraft are separated in accordance with established standards. Even when closely spaced parallel approach procedures are correctly applied, unwanted RAs may occasionally occur. However, the safety benefit provided by ACAS II takes precedence over an occasional unwanted RA. There is always the possibility another aircraft that is not associated with the parallel approach procedure becomes a threat. The term “nuisance alert” is commonly used to describe an RA when it is not desired. This is a misnomer;
ACAS II is operating as designed, and flightcrews are advised to comply with the RA. The evaluation of whether a generated RA is a valid threat may not be possible in real time.
3.3.2.5 RAs generated in the traffic pattern environment should not be dismissed as unnecessary and/or disruptive. These RAs inform the flightcrew that a hazard of collision exists.
3.3.2.6 By not responding to an RA, the flightcrew negates the safety benefits provided by own-ship ACAS and effectively takes responsibility for achieving safe separation. In so choosing, flightcrews are advised to consider the following cautions:
3.3.2.6.1 The traffic acquired visually may not be the same traffic causing the RA.
Visual perception of the encounter may be misleading. The flightcrew is advised to respond to the RA to the degree displayed with an instinctive, immediate reaction, unless there is no doubt that the aircraft acquired visually is the threat aircraft, the threat aircraft is not a collision hazard, and there are no other complicating circumstances.
3.3.2.6.2 The traffic may also be operating ACAS II, and it may maneuver in response to an RA coordinated with own-ship ACAS II.
3.3.2.6.3 It is difficult to visually determine the vertical displacement of other aircraft, especially when ground reference information is unreliable or at cruise altitudes where the horizon is obscured. Therefore, disregarding RA information and maneuvering vertically based solely on visual acquisition may result in a loss of safe separation.
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3.3.3 Maneuvering Opposite to an RA.
3.3.3.1 Maneuvers or lack of maneuvers that result in a vertical speed opposite to the RA could result in a collision with the threat aircraft.
3.3.3.2 The threat aircraft may also be operating ACAS II, and it may maneuver in an unexpected direction while responding to a coordinated RA that has been coordinated with own-ship ACAS II.
3.3.3.3 ATC may not be communicating or providing separation service with the threat aircraft. ATC may have less up-to-date altitude data than ACAS II.
ATC does not know if an RA is generated unless notified by the flightcrew. It is possible for ATC to unknowingly issue instructions that are contrary to an RA. When one aircraft in an encounter maneuvers opposite to the RA and the other aircraft maneuvers as indicated by a coordinated RA, the collision risk increases. Flightcrews are advised not to maneuver contrary to the RA based solely upon ATC instructions.
3.4 ATC Clearances and Instructions.
3.4.1 ATC Instructions During an RA.
3.4.1.1 If an RA occurs concurrently with ATC issuing a climb or descend clearance, flightcrews are advised to comply with the RA even if it differs from the ATC climb or descend instruction.
3.4.1.1.1 ACAS II may be coordinating the RA with another ACAS II aircraft. ATC is not automatically informed of RAs. Midair collisions have resulted involving two aircraft operating ACAS II, where one flightcrew complied with the RA while the other complied with ATC instructions.
3.4.1.1.2 For Precision Runway Monitor (PRM)/High Update Rate Surveillance (HURS) close parallel approaches, the Attention All Users Page (AAUP) will state, “TCAS during breakout: Follow TCAS climb/descend if it differs from ATC, while executing the breakout turn.”
3.4.1.2 If an RA requires maneuvering contrary to right-of-way rules, cloud clearance rules for VFR, or other such criteria, flightcrews are advised to comply with the RAs to resolve the immediate traffic conflict.
3.4.1.3 If an RA maneuver is inconsistent with the current clearance, including altitudes published on arrival/approach/departure procedures, respond appropriately to the RA. Since ACAS II tracks all aircraft operating transponders in the vicinity, responding to an RA assures an avoidance maneuver for that threat aircraft and for other aircraft with altitude reporting transponders.
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3.4.1.4 Flightcrews should keep deviations from regulations, clearances, and instructions to the minimum necessary to comply with an RA. While complying with the RA, if possible, comply with ATC clearances and instructions (e.g., turn to intercept an airway or localizer). Response to a stall warning, windshear warning, TAWS “Pull Up” alert, or an RA takes precedence over ATC clearances or instructions, or a requirement to follow a specific route.
3.4.1.5 Each flightcrew that deviates from an ATC clearance or instruction in response to an RA is advised to notify ATC of that deviation as soon as practicable and notify ATC when clear of conflict and returning to the previously assigned or amended clearance.
3.4.1.6 When a flightcrew informs a controller that they are responding to an RA, controllers are not to issue control instructions that are contrary to the RA procedure. After the controller has been informed of an RA, they may continue to issue control instructions and safety alerts, including terrain, obstructions, and ATC-issued traffic advisories, as appropriate.
3.4.1.7 Once the flightcrew that informed the controller of an RA has begun a maneuver in response to an RA, the controller is not responsible for providing approved separation between the aircraft that is responding to an RA and any other aircraft, airspace, terrain, or obstruction.
3.4.2 Clear of Conflict. When an RA is canceled, the “CLEAR OF CONFLICT” message is heard, and the flightcrew should advise ATC as soon as practicable that they are returning to their previously assigned clearance or should acknowledge any amended clearance issued. The flightcrew is advised to immediately return to their previously assigned clearance and advise ATC, or comply with any amended clearance issued.
3.4.2.1 Responsibility for approved separation resumes for the controller when:
• The flightcrew returns to the assigned altitude,
• The flightcrew informs the controller that the RA maneuver is complete and approved separation is met, or
• The flightcrew has executed an amended clearance and approved separation is reestablished.
3.5 Communicating an RA to ATC. To keep all parties on the frequency informed during an RA maneuver, radio communication should be in common phraseology. All transmissions should contain the name of the ATC facility, aircraft identification, and that they are responding to an RA. Communicating an RA is not required if the flightcrew complies with the RA while maintaining compliance with ATC clearances and instructions.
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3.5.1 RA Generated That Affects an ATC Clearance.
3.5.1.1 When a flightcrew receives a new clearance that is subject to a preventive RA
(e.g., “Do Not Climb, Do Not Climb”) that will not allow the flightcrew to comply with clearance instructions, the flightcrew is advised to inform ATC by stating, “[name of the ATC facility], [aircraft identification], TCAS RA, unable to comply” (e.g., “Milwaukee Approach, Skyway 123, TCAS RA, unable to comply”).
3.5.1.2 When a flightcrew receives a corrective RA to either climb or descend from their assigned altitude, or the RA otherwise affects the ATC clearance, the flightcrew is advised to inform ATC when beginning the excursion from the assigned clearance or as soon as workload allows. Flightcrews are advised to inform ATC by stating, “[name of the ATC facility], [aircraft identification], TCAS RA” (e.g., “Washington Departure, Hagar 55, TCAS RA”).
3.5.2 Clear of Conflict. When the RA is clear, the flightcrew should advise ATC that they are returning to their previously assigned clearance or a subsequent amended clearance.
Inform ATC by stating, “[name of the ATC facility], [aircraft identification], clear of conflict, returning to [assigned altitude]” (e.g., “Chicago Center, Freedom 456, clear of conflict, returning to Flight Level 410”).
4-1 CHAPTER 4. ACAS REPORTS
4.1 Pilot Reports. All unusual ACAS events should be reported and investigated. The reports will help to identify potential technical deficiencies and prompt regulators to take appropriate action.
4.1.1 Mandatory Report. When operating under IFR, and an aircraft experiences an RA where compliance with the RA is necessary to avert a substantial risk of collision, a report to the National Transportation Safety Board (NTSB) is required per 49 CFR § 830.5.
4.1.2 ATC Query. Upon query from ATC, make radio or telephone communication as appropriate to complete an ATC Mandatory Occurrence Report (MOR) after a response to an RA per FAA Order JO 7210.632, Air Traffic Organization (ATO) Occurrence Reporting.
4.1.3 Near Midair Collision (NMAC) Reports. An NMAC is defined in the AIM as an incident associated with the operation of an aircraft in which a possibility of collision occurs because of a proximity of less than 500 feet to another aircraft, or a report is received from a pilot stating that a collision hazard existed between two or more aircraft.
Flightcrews should be aware that there is no requirement to submit an NMAC report solely due to an ACAS event and that an ACAS report does not constitute an NMAC report.
4.1.3.1 It is the responsibility of the flightcrew to determine whether an NMAC did occur and, if so, to initiate an NMAC report.
4.1.3.2 Flightcrews involved in NMAC occurrences are urged to report each incident immediately by radio or telephone to the nearest FAA ATC facility or Flight Service Station (FSS).
4.1.3.2.1 Be specific, as ATC will not interpret a casual remark to mean that an NMAC is being reported.
4.1.3.2.2 The pilot should state, “I wish to report a near midair collision.”
4.1.4 FAA Hotline. The FAA Hotline accepts reports related to the safety of the National Airspace System (NAS), violations of 14 CFR, aviation safety issues, and FAA employees or FAA facilities. The FAA Hotline provides a single venue for FAA employees, the aviation community, and the public to file their reports. Visit the FAA Hotline website at https://www.faa.gov/about/office_org/headquarters_offices/aae/progra ms_services/faa_hotlines.
4.1.5 National Aeronautics and Space Administration (NASA) Aviation Safety Reporting System (ASRS) Reports. A flightcrew that experiences a significant event regarding ACAS or collision hazards may file ASRS reports at their discretion at https://asrs.arc.nasa.gov.
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4.1.6 Aviation Safety Action Program (ASAP). If a flightcrew that experiences a significant event regarding ACAS or collision hazards is part of an organization that cooperates in an ASAP, it is recommended that the flightcrew file a report to the Event Review Committee (ERC). Some organizations may not have an ASAP but may offer a similar voluntary safety reporting structure.
4.1.7 O perator Reports . Reports, as specified by the operator, concerning ACAS anomalies, procedural difficulties, or system failures are typically made by flightcrews, and may include the following:
• Pilot/observer questionnaire;
• Logbook entry and Aircraft Communications Addressing and Reporting System (ACARS); or
• Other records used by that operator, such as a captain’s report. See Appendix D, ACAS Resolution Advisory (RA) Report, for details on suggested information to include.
4.2 FAA Response to Pilot Reports of ACAS Events.
4.2.1 FAA Investigations. The FAA will not initiate enforcement action solely based on an ACAS event, provided:
• As per 14 CFR requirements, the aircraft was equipped with ACAS, and the equipment was operating at the time of the event, as applicable.
• The flightcrew complied with ATC clearances and instructions per 14 CFR § 91.123 prior to and during the ACAS-related deviation.
• The flightcrew has successfully completed the FAA-approved air carrier ACAS training program, as applicable.
4.3 Manufacturer Reports.
4.3.1 Manufacturer Monitoring and Reporting. Manufacturers are encouraged to develop procedures to ensure effective identification, tracking, and followup of abnormal ACAS-related events, as appropriate. Such procedures should focus on providing useful information to properly assess the importance of ACAS events and following up on information related to specific ACAS events as necessary to keep the industry and the FAA informed of the performance of ACAS in the NAS and in international operations.
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4.3.2 ACAS Manufacturer Reports. ACAS avionics manufacturers report problems found with specific ACAS installations in accordance with established Service Difficulty Report (SDR) procedures. Report generic problems, such as those that may relate to the definition of ACAS algorithms as defined by RTCA DO-185B, Minimum Operational Performance Standards for Traffic Alert and Collision Avoidance System II (TCAS II), and RTCA DO-385A, Minimum Operational Performance Standards for Airborne Collision Avoidance System X (ACAS X) (ACAS Xa and ACAS Xo), to the FAA Aircraft Certification Service (AIR) at 9-AVS-CAS-Issues@faa.gov.