1 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS When ASAS meets ACAS Thierry Arino (Sofréavia, IAPA Project Manager) ASAS TN2 Roma, 3-5 April 2006 ASAS Progress, Plans and Challenges

2 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Context (1/2)  ACAS is now part of the current ATM system Airborne collision avoidance function independent from the means of separation provision ACAS = TCAS II version 7 Interrogates adjacent SSR transponders and provides two levels of alert Traffic Advisory (TA): To prepare the crew for a possible RA Resolution Advisory (RA): To achieve a safe vertical distance to prevent risk of imminent collision

3 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Context (2/2)  ASAS is a promising option for the future ATM system Airborne Surveillance (AS) and Separation Assistance function Wide range of AS applications from near to long term with different levels of responsibility delegation Package I Packages II & III  Compatibility must be assured between ACAS and ASAS operations

4 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS IAPA project (1/2)  EUROCONTROL MSA Programme contribution to understanding of ACAS / ASAS interaction 11 man-year project from 2002 to 2005 DSNA, EEC, QinetiQ and Sofréavia (Project Leader)  Implications on ACAS Performances due to ASAS implementation Any operational implications for ACAS? Benefits expected from ASAS compromised? Implications for the development of future ASAS procedures and systems?

5 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS IAPA project (2/2)  Interaction between the ACAS logic and the ASAS procedure in European airspace  Focus on operational and safety perspective Airborne system integration issues are out of the IAPA scope  Focus on demanding ASAS application In terms of potential interaction with ACAS Candidate applications: S&M and C&P

6 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Selecting a demanding application  Level of interaction between ACAS and ASAS S&M, in-trail phase: None C&P, lateral overtaking: None S&M, merging phase: Some, during marginal operations C&P, vertical crossing: Some, for realistic vertical rates C&P, lateral crossing: Some, for Horizontal Miss Distance close to radar minima  Selected application: C&P, lateral crossing More demanding in terms of potential interaction with ACAS (minimum of 4 NM with RNP-1 assumptions)

7 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Operational analysis  Quantitative analysis of the ACAS alerts during nominal ASAS operations European radar data, ATM encounter model and CFMU flight plan data Real Time Simulation (RTS) data  Sensitivity analysis of the interaction with ACAS depending on ASAS separation minimum  Comparative analysis of the interaction with ACAS between conventional ATM and ASAS operations

8 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Overall approach ASAS RTS data ACAS simulations Analysis of ACAS alerts (TAs & RAs) Radar data CFMU data ATM encounter model Modified encounters with ASAS Simplified model of ASAS procedure ACAS simulations

9 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Applicability of C&P lateral crossing  Encounters located at major crossing points in core Europe  Majority in RVSM airspace 67% above FL295  Estimated frequency Once every 2 or 3 hours per sector Once per 10 flight hours possibly up to 5 times more

10 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Undesirable ACAS alerts  Frequent (but non-systematic) TAs (15%) are likely to be considered as disruptive from a pilot perspective Role of TA as precursor to RA into question May affect the pilot confidence in the ASAS procedure and airborne systems  Occurrence of disruptive and undesirable RAs (1%) is a major ACAS / ASAS interaction issue Lack of compatibility between separation provision function (supported by ASAS) and collision avoidance function (of ACAS)

11 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Influencing parameters  Interaction with ACAS is strongly dependent with applicable ASAS separation minimum No more TAs with a minimum separation of 7 NM No more RAs with a minimum separation of 5 NM  Aircraft trajectory perturbations (linked to either navigation or surveillance imperfections) Can affect TCAS Miss Distance Filtering performance  C&P lateral crossing procedures are less compatible with ACAS than current ATM operations (except for 1000-ft level-off)

12 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS layers of protection hazards accident  Establish whether ACAS can still provide protection against collision during ASAS procedure  Full-system safety assessment ACAS collision avoidance logic Enhanced traffic situational awareness ATC involvement Visual acquisition Safety analysis

13 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Overall approach  Evaluate logic performance on operational scenarios using models tuned to represent the European airspace with or without ASAS Key metric = Risk Ratio Risk of NMAC with ACAS / Risk of NMAC without ACAS ACAS logic is one part of full-system  Operational hazard analysis and contingency tree Combines logic performance with other hazards and mitigating factors Estimates a full-system risk of collision

14 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Safety benefits delivered by ACAS  ACAS will provide a significant reduction in risk of collision in C&P lateral crossing procedure Can expect a reduction to 5% of the risk without ACAS  Enhanced traffic situational awareness from ASAS and alerting aspects of ACAS make a contribution to this reduction  Full benefit is realised by operating ACAS in RA mode and following the RAs it generates Pilot who responds to RAs exposed to half the risk compared to pilot who ignores RAs or operates ACAS in TA-only mode

15 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Conclusions  ACAS safety performance during ASAS operations ACAS remains effective as the last resort safety net Safety benefits underline the need to operate ACAS  Effect of ACAS performance on ASAS application development Interaction with ACAS dependent on the nature of the ASAS application Applicable separation minimum during ASAS operations is a significant parameter  Effect of ASAS applications on ACAS performance and requirement ASAS applications can trigger undesirable ACAS alerts Possible need for modification to current TA logic

16 Roma, 3-5 April 2006 – ASAS TN2, 2 nd Workshop, Session 1 – When ASAS meets ACAS Recommendations  ACAS constraints must be taken into account when developing ASAS procedures  Consideration should be given to ACAS developments which would improve compatibility with ASAS while preserving ACAS independence Review the TA role in the context of ASAS operations  Future investigation of ACAS / ASAS interaction should be supported by a comprehensive and robust methodological framework Such as the one established within IAPA