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.
Appendix D D-1 APPENDIX D. ACAS RESOLUTION ADVISORY (RA) REPORT Your participation in the reporting of ACAS events is essential to the success of ongoing evaluation of ACAS performance. Use the following information to guide your reporting of the ACAS event through the pilot report options outlined in this AC.
Reporting Pilot: ________________ Date: _____/_____/_____ Time: __________ UTC Origin: _________ Destination: _________ Call Sign: __________ A/C Type: _________ Registration Number: __________ Transponder Code: ____________ ATC Control Name: ____________ ATC Control Frequency: _______________ Actual Altitude: ___________ Cleared Altitude: ___________ Own Position: _______________________________ (Lat./Long. or Nav Aid/Radial/Distance) Phase of Flight: Departure (Takeoff to 10,000 feet) Climb (10,000 feet to Cruise) Cruise Descent (Cruise to 10,000 feet) Holding Pattern Approach (Below 10,000 feet) THREAT AIRCRAFT (if known) Call Sign: _____________ A/C Type: Commercial General Aviation Military Other Make/Model: _____________ Actual Altitude: ___________ Cleared Altitude: ___________ Did you have the aircraft in visual contact? Yes No If yes: Before TA / After TA. Before RA / After RA.
Was a TA generated? Yes No Were multiple TAs generated against the same intruder? Yes No Initial RA Generated: Descend, Descend Climb, Climb Monitor Vertical Speed Climb, Crossing Climb Descend, Crossing Descend Maintain Vertical Speed, Maintain Maintain Vertical Speed, Crossing Maintain Adjust Vertical Speed, Adjust ________ feet/minute Level Off, Level Off Did the initial RA change to any of the following?
Adjust Vertical Speed, Adjust Level Off, Level Off Increase Climb Increase Descent Climb, Climb NOW Descend, Descend NOW Descend, Descend Climb, Climb Range to threat aircraft at RA? __________ Bearing to threat aircraft at RA? ___________ Relative altitude of threat aircraft at RA? ____________feet Estimated Closest Proximity: Range ____________NM Altitude ____________NM Your response to the RA was: Climb Descend Change in Vertical rate Level Off Turn No Response No Response Necessary Was the event reported to ATC? Yes No Did ATC provide traffic information on the threat aircraft? Before RA After RA No Did the RA conflict with ATC instructions? Yes No If you did not comply with the RA, please explain why:
______________________________________________________________________________ ______________________________________________________________________________
REMARKS (please provide comments/concerns on this encounter):
______________________________________________________________________________ ______________________________________________________________________________
Advisory Circular Feedback Form If you find an error in this AC, have recommendations for improving it, or have suggestions for new items/subjects to be added, you may let us know by contacting the Flight Technologies and Procedures Division at 9-AWA-AFS400-Coord@faa.gov or the Flight Standards Directives Management Officer at 9-AWA-AFB-120-Directives@faa.gov.
Subject: AC 90-120, Operational Use of Airborne Collision Avoidance Systems Date: _____________________ Please check all appropriate line items:
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