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:
Appendix B B-4 B.2.5.2.1 Use o f Controls.
1. Objective. To verify the pilot can properly operate all ACAS II and display controls.
2. Criteria. The pilot should demonstrate the proper use of controls, including the following:
a. Aircraft configuration required to initiate a self-t est.
b. Steps required to initiate a self-test.
c. Recognizing when the self-test was successful and when it was unsuccessful. When the self-test is unsuccessful, recognizing the reason for the failure and, if possible, correcting the problem.
d. Recommended usage of traffic display range selection. Low ranges are used in the terminal area, and the higher display ranges are used in the en route environment and in the transition between the terminal and en route environment.
e. If available, recommended usage of the above/below mode selector.
Above mode should be used during climb, and below mode should be used during descent.
f. Recognition that the configuration of the traffic display (i.e., range and Above/Below selection) does not affect the ACAS II surveillance volume.
g. Selection of appropriate ranges on the traffic display to increase situational awareness of close-in traffic when an advisory is generated.
h. If available, proper selection of the display of absolute or relative altitude and the limitations of using the absolute display option if a barometric correction is not provided to ACAS II.
i. Proper configuration to display the appropriate ACAS II information without eliminating the display of other needed information.
j. Selection of various ACAS II and transponder operating modes.
B.2.5.2.2 Display I nte rpretation.
1. Objective. To verify a pilot understands the meaning of all information that can be displayed by ACAS II.
2. Criteria. The pilot should demonstrate the ability to properly interpret information displayed by ACAS II, including the following:
a. Other traffic (i. e., traffic within the selected display range that is not proximate traffic, a TA, or an RA).
b. Proximate traffic (i.e., traffic that is within 6 NM and 1,200 feet).
c. Non-altitude reporting aircraft.
Appendix B B-5
d. ADS-B Only TA-ONLY (AOTO) traffic.
e. No-bearing TAs and RAs.
f. Off-scale TAs and RAs. The selected range should be changed to ensure that all available information on the intruder or threat aircraft is displayed.
g. TAs. The minimum available display range that allows the traffic to be displayed should be selected to provide the maximum display resolution.
h. RAs (traffic display). The minimum available display range of the traffic display that allows the traffic to be displayed should be selected to provide the maximum display resolution.
i. RAs. Pilots should demonstrate knowledge of the meaning of the red and green areas, or the meaning of pitch or flight path angle cues displayed on Primary Flight Displays (PFD), RA displays, Head-Up Displays (HUD), etc. For displays using red and green areas, demonstrate knowledge of when the green areas will and will not be displayed.
j. If appropriate, awareness that navigation displays oriented Track-Up may require a pilot to make a mental adjustment for drift angle when assessing the bearing of proximate traffic.
k. ACAS II symbology differences when incorporated with ADS-B In.
B.2.5.2.3 Use of the TA-ONLY Mode.
1. Objective. To verify that a pilot understands the appropriate times to select the TA-ONLY mode of operation and the limitations associated with using this mode.
2. Criteria. The pilot should demonstrate the following:
a. Knowledge of the standard operating procedures for the use of TA-ONLY mode.
b. Reasons for using TA-ONLY mode and situations where the use of TA-ONLY may be desirable.
c. The TA aural annunciation is inhibited below 500 feet AGL. As a result, TAs generated below may not be noticed unless the TA display is included in the routine instrument scan.
B.2.5.2.4 Crew Coordination.
1. Objective. To verify pilots adequately brief other crewmembers on how ACAS advisories will be handled. This portion of the training may be combined with other training, such as Crew Resource Management (CRM).
Appendix B B-6
2. Criteria. Pilots should demonstrate during their preflight briefing the procedures that will be used in responding to TAs and RAs, including the following:
a. Division of duties between the Pilot Flying (PF) and Pilot Monitoring (PM), including a clear definition of who will fly the aircraft during a response to an RA;
b. Expected callouts;
c. Conditions where an RA may not be complied with and who will make this decision; and
d. Communications with ATC.
Note: The operator should specify the conditions under which an RA need not be complied with.
B.2.5.2.5 Reporting Requirements.
1. Objective. To verify the pilot is aware of the requirements for reporting RAs to the controller and other authorities.
2. Criteria. The pilot should demonstrate the following:
a. The use of the standard phraseology in this AC, and
b. Where information can be obtained regarding the need for making written reports when an RA is generated.
B.3 ACAS II Maneuver Training. The scenarios included in the maneuver training should include initial RAs that require a change in vertical speed (corrective RA); initial RAs not requiring a change in vertical speed; maintain rate RAs; altitude crossing RAs; increase rate RAs; reversal RAs; weakened RAs; RAs generated while the aircraft is at a maximum altitude; and multiple threat encounters. The scenarios should also include demonstrations of the consequences of not responding to RAs, slow or late responses, and maneuvering opposite to the direction called for by the displayed RA as follows:
B.3.1 TA Responses.
B.3.1.1 Objective. To verify the pilot properly interprets and responds to TAs.
B.3.1.2 Criteria. The pilot should demonstrate:
1. Proper division of responsibilities between the PF and PM. The PF should continue to fly the airplane and be prepared to respond to any RA that might follow. The PM should provide updates on the traffic location shown on the ACAS II traffic display and use this information to help visually acquire the intruder.
2. Proper interpretation of the displayed information. Both pilots confirm that the aircraft they have visually acquired is the aircraft that has caused the
Appendix B B-7 TA to be issued. Use should be made of all information shown on the display, note being taken of the bearing and range of the intruder (amber circle), whether it is above or below (data tag), and its vertical speed direction (trend arrow).
3. All available information is used to assist in visual acquisition.
4. Unnecessary requests for traffic information are not made following TAs.
5. No maneuvers are made based solely on the information shown on the ACAS II display.
6. When visual acquisition is attained, right-of-way rules are used to maintain or attain safe separation. Unnecessary maneuvers are not initiated. The limitations of making maneuvers based solely on visual acquisition are understood.
B.3.2 RA Responses.
B.3.2.1 Objective. To verify the pilot properly interprets and responds to RAs.
B.3.2.2 Criteria. The pilot should demonstrate the following:
1. Proper division of responsibilities between the PF and PM. The PF should respond to the RA with the correct flight path management techniques, including manual flight operations or effective use of the autoflight system (when ACAS II mode is available). The PM should provide updates on the traffic location, check the traffic display, and monitor the response to the RA. Proper CRM should be used. If standard operating procedures require the Pilot in Command (PIC) to fly all RAs, transfer of aircraft control should be demonstrated.
2. Proper interpretation of the displayed information. The pilot recognizes any threat aircraft causing an RA (red square on the traffic display) and responds appropriately.
3. For RAs requiring a change in vertical speed, initiation of a response in the proper direction is made within 5 seconds of the RA being displayed.
The change in vertical speed is accomplished with an acceleration of approximately 0.25 g to obtain the required vertical rate. ATC is notified of the RA response without delay after initiating the maneuver using the standard phraseology.
4. Recognition of, and the proper response to, modifications to the initially displayed RA.
a. For increase rate RAs, the vertical speed is increased within
2.5 seconds of the RA being displayed. The change in vertical speed is accomplished with an acceleration of approximately 0.35 g.
Appendix B B-8
b. For reversal RAs, the maneuver is initiated within 2.5 seconds of the RA being displayed. The change in vertical speed is accomplished with an acceleration of approximately 0.35 g.
c. For weakened RAs, the vertical speed is modified to initiate a return toward level flight within 2.5 seconds of the RA being displayed. The change in vertical speed is accomplished with an acceleration of approximately 0.25 g.
d. For RAs that strengthen, the maneuver to comply with the revised RA is initiated within 2.5 seconds of the RA being displayed. The change in vertical speed is accomplished with an acceleration of approximately 0.25 g.
5. Recognition of altitude crossing encounters and the proper response to these RAs.
a. For RAs that do not require a change in vertical speed, that the vertical speed needle or pitch angle remains outside the red area on the RA display.
b. For maintain rate RAs, that the vertical speed is not reduced. Pilots should recognize that a maintain rate RA may result in crossing the altitude of the threat aircraft.
c. That if a justified decision is made to not comply with an RA, the resulting vertical rate is not in a direction opposite to the sense of the displayed RA.
d. That the deviation from the current clearance is minimized by leveling the aircraft when the RA weakens, and when “Clear of Conflict” is annunciated, executing a prompt return to the current clearance; and notifying ATC using the standard phraseology as soon as permitted by flightcrew workload after resuming the current clearance.
e. That, when possible, an ATC clearance or instruction is complied with while responding to an RA (e.g., if the aircraft can level at the assigned altitude while responding to a reduce climb or reduce descent RA, it should be done).
f. That when simultaneous conflicting instructions to maneuver are received from ATC and an RA, the RA is complied with, and ATC is notified using the standard phraseology as soon as permitted by flightcrew workload.
g. Awareness that ACAS II is designed to cope with a multiple threat encounter, and that ACAS II can optimize separation by climbing or descending toward one of them (e.g., ACAS II only considers aircraft that it considers a threat when generating an RA. As such, it is possible for ACAS II to generate an RA against one threat that results in a maneuver toward another aircraft that is not classified as a threat. If
Appendix B B-9 the second aircraft becomes a threat, the RA will be modified to provide separation from that aircraft.).
h. The consequences of not responding to an RA and maneuvering in the direction opposite to the RA.
i. A prompt response is made when a climb RA is generated while the aircraft is at the maximum altitude.
j. If applicable, compliance with an Autopilot (AP) RA and demonstration of the ability to return to course, address mode conflict issues, etc.
B.3.3 C haracteristics of Training Equipment Suitable for Maneuver Training .
B.3.3.1 Acceptable Characteristics. Flight Training Devices (FTD), simulators, and computer-based trainers should have certain characteristics to be effective.
This is due to the interactive nature of ACAS II, the variety of encounter scenarios possible, the immediate and standardized pilot response required, and the instant and correct display interpretation that is necessary. Thus, training equipment used for ACAS II flight training should have the following characteristics:
• The ability to functionally represent traffic displays, controls, indications, and annunciations;
• The ability to depict selected traffic encounter scenarios, including traffic display and audio advisories;
• The ability to show proper ACAS II reaction to depicted scenarios and advisories; and
• The ability to interactively respond to pilot inputs regarding ACAS II advisories, including responses to RAs displayed on relevant vertical speed and pitch indicators.
B.3.3.2 Simulator and ACAS II Fidelity. For a particular ACAS II, one may accomplish maneuver training in ACAS II-qualified simulators or FTDs that represent the specific aircraft or an aircraft that has similar characteristics. For the purposes of ACAS II maneuver training, simulators or FTDs may use simplified ACAS II algorithms or displays and do not require ACAS II logic or an ACAS II processor. Traffic displays do not have to be identical but should be functionally equivalent to the specific aircraft in use by the operator.
B.3.3.3 FTD or Simulator Approval. The National Simulator Program (NSP) qualifies Flight Simulation Training Devices (FSTD) as meeting 14 CFR part 60 requirements, and the Principal Operations Inspector (POI) approves them for use in a training program. Any one or combination of the following ACAS II-qualified devices may be used:
Appendix B B-10
• Level A through D simulators,
• Level 4 through 7 FTDs, or
• Other ACAS II training devices that are shown to be suitable for ACAS II training and are approved by the POI.
Appendix C C-1 APPENDIX C. SAFETY MANAGEMENT SYSTEM (SMS) CONSIDERATIONS FOR
ACAS II TA-ONLY MODE OPERATIONS C.1 SMS. Per AC 120-92, Safety Management Systems for Aviation Service Providers, the defining characteristic of an SMS is that it is a Risk-Based Decision-Making (RBDM) system. An SMS is built by structuring the safety management of an operator around four components: safety policy, Safety Risk Management (SRM), Safety Assurance (SA), and safety promotion. Organizations that are required to comply with 14 CFR part 5 should use the SRM and SA components of an SMS to perform RBDM and monitoring on ACAS II use and the policies and procedures thereof. All operators are recommended to implement a formal process for gathering feedback on ACAS II use. This includes any irregularities, malfunctions, and lessons learned. An operator is recommended to use this formal process during design, installation, modifications, or improvements to procedures and/or training. In this appendix, an example will be discussed for SMS consideration for ACAS II TA-ONLY mode operations.
C.1.1 SRM. S RM provides a system for identifying hazards and mitigating risk based on a thorough understanding of the organization’s systems and their operating environment.
C.1.1.1 W hen SRM is needed, an operator should apply SRM to the implementation of new systems, revision of existing systems, development of operational procedures, and identification of hazards or ineffective risk controls through the SA process.
C.1.1.2 SRM Processes. There are five processes necessary to control and mitigate risk: system analysis, hazard identification, safety risk analysis, safety risk assessment, and safety risk controls.
Example: SRM is recommended for an operator of an ACAS II-equipped aircraft if the operator were to consider advising their flightcrews to select TA-ONLY mode for approach at a specific airport. This procedure removes a risk control. A risk control is a means to reduce or eliminate the effects of hazards (in this case, the risk control offered by the Traffic Advisory (TA)/Resolution Advisory (RA) mode of the ACAS II). SRM is recommended to describe the system; identify the hazards; and analyze, assess, and control the risk.
C.1.1.3 System analysis and hazard identification proactively identify and address potential problems before the new or revised systems or procedures are put into place. In the example, the use of TA-ONLY mode presents hazards that an operator should identify for the system that they operate. The knowledge gained in the system analysis and subsequent risk analysis will later be used to develop a mitigating strategy.
C.1.1.4 Safety risk analysis estimates the severity and likelihood of a potential accident due to exposure to an identified hazard (in this case, a hazard associated with the selection of TA-ONLY mode on approach).
Appendix C C-2 C.1.1.5 Safety risk assessment is completed once the risk has been analyzed. The operator should assess whether the risk is acceptable. A common tool used in risk assessment decisions is a risk matrix. A risk matrix enables an organization to assess risks, compare potential effectiveness of proposed risk controls, and prioritize risks where multiple risks are present by providing a way to integrate the severity of the outcome and the probability of occurrence.
If the risk is found to be acceptable, then the system may be placed into operation and monitored in the SA process. If the operator decides the risk is not acceptable, the operator will need to follow the next step in SRM, where an operator will develop risk controls.
C.1.1.6 Safety risk control is conducted after hazards and associated risks are fully understood. Risk controls are utilized to reduce the likelihood or severity of a hazard and mitigate the associate risk. Risk controls should be designed for risks that are deemed unacceptable.
C.1.2 SA. S A works in partnership with SRM. In SA, the process continues with measuring and monitoring the performance of the system operation, with the designed risk controls in place. SA processes are a means of assuring the safety performance of the organization, keeping it on track, correcting it where necessary, and identifying needs for rethinking existing processes. SA requires monitoring and measuring safety performance of operational processes and continuously improving the level of safety performance. Strong SA processes will yield information used to maintain the integrity of risk controls. SA steps include system monitoring, data acquisition, analysis of data, system assessment, and corrective action. Data acquisition involves a variety of sources, including continuous monitoring, internal audits (by operational departments), internal evaluations (by other departments within the company), external auditing (third-party audits), investigations, and employee reporting and feedback systems.
Example: A n SA process is recommended for an operator of an ACAS II-equipped aircraft if the operator is evaluating and monitoring the use of TA-ONLY mode for approach at a specific airport.
C.1.2.1 Continuous Monitoring. One source of data may be continuous monitoring. In the monitoring of the operational environment and operational processes, it comes to the attention of the operator that the flightcrews are not complying with the company policy.
C.1.2.2 Analysis of Data. Analysis involves examining data acquired from various sources to make inferences about the effectivity of the risk controls.
C.1.2.3 Safety Performance Assessment. In the assessment step, collected safety performance data has been analyzed, and the results are used for informed decision making. The assessment process is where these decisions are made.
In this example, conformity with the risk controls appear to be unsatisfactory, and desired results are not being obtained. If this occurs, the SRM processes would be triggered.
Appendix C C-3 C.1.2.4 The final step within SA is continuous improvement. This process is designed to ensure that the operator is correcting substandard safety performance identified during the safety performance assessment to continuously improve safety performance.
C.2 TA-ONLY Considerations for SMS.
C.2.1 RAs can 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. Additionally, 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 should comply with the RA.
C.2.2 Flight Standards (FS) has identified several considerations associated with operating ACAS II in TA-ONLY mode. An operator is advised to consider the following list during the SRM process. This list is nonexhaustive, and additional unique considerations, hazards, or ineffective risk controls are to be identified that are applicable to the environment of an individual operator:
1. Likelihood of aircraft positioned so that they are at risk for a collision, including uncontrolled/noncompliant (with Air Traffic Control (ATC) clearances or instructions) traffic.
2. Pilot reaction time to establish visual contact with the intruder aircraft.
3. Pilot reluctance to comply with an RA, in TA/RA mode, due to complacency associated with unwanted or expected RAs.
4. Difficulty of visually acquiring and monitoring an intruder aircraft in meteorological conditions that reduce the ability to accurately judge the flight path of the intruder aircraft (e.g., sun angle, haze, lack of defined horizon, and nighttime).
5. Difficulty of visually acquiring and monitoring an intruder aircraft on a parallel or converging approach course (i.e., intruder aircraft may possibly be adjacent or behind the flight path of own-ship).
6. Difficulty of ascertaining the flight path of the intruder aircraft (e.g., visual perception of the encounter may be misleading).
7. Difficulty understanding the flight trajectory of the traffic on an adjacent final approach segment or elsewhere due to traffic display bearing accuracy limitations.
8. In low closure rate scenarios (e.g., Closely Spaced Parallel Operations (CSPO)) with TA-ONLY mode selected, after receiving the initial TA, no auditory ACAS II advisories will be generated after the initial TA. The flightcrew may, over time, have reduced awareness of the flight path of the intruder aircraft.
9. Increased flightcrew workload during the approach phase (e.g., selecting TA-ONLY mode and monitoring the flight path of all intruder aircraft.)
Appendix C C-4
10. Increased flightcrew workload during a missed approach/go-around/balked landing
(e.g., selecting TA/RA mode and monitoring the flight path of possible adjacent missed approach traffic).
11. Lack of RA maneuver generation when TA-ONLY mode was selected on an approach, and the flightcrew fails to return to TA/RA mode in the event of a missed approach/go-around/balked landing.
12. If a flightcrew does not intend to respond to an RA and operates in TA-ONLY mode, other ACAS II-equipped aircraft operating in TA/RA mode will have maximum flexibility in generating RAs to resolve encounters.