ACAS/ASAS Interaction: IAPA Project Overview

1. ACAS / ASAS interactionIAPA ProjectThierry Arino – Sofréavia, Project Manager ASAS TN – Session 3 Airborne spacing applications

2. Project overview • Context • ACAS (ACAS II) is now part of the current ATM system • ASAS is a promising option for the future ATM system • Compatibility must be assured between current & future systems • IAPA Project • EUROCONTROL ACAS Programme contribution • Provide guidelines for the development of ASAS applications(in the context of ACAS / ASAS interaction) • Comparative analysis (with & without ASAS) based ondata-oriented methodology • Structure with 3 phases • Phase I (Nov 02/Oct 03): Framework & preliminary analysis • Phase II (Oct 03/Oct 04): Full set of simulations • Phase III (Oct 04/Jun 05): Final reports & guidelines

3. Preliminary analysis • Context • Support the selection of a challenging ASAS application(from an ACAS / ASAS interaction perspective) • Method • Construction of artificial encounters involving two aircraftwith various performances • Identification of encounter parameters influencingthe ACAS alert triggering • Study limitations • « Perfect » Communication, Navigation and Surveillance • Aircraft proportions not representative of a given airspace • Case study analysis

4. ASAS applications of interest • Challenging & mature Package I AS applications • Availability of documentation & simulation data • Package I / ASPA-S&M application • Merging phase • In-trail phase • Package I / ASPA-C&P application • Lateral overtaking • Vertical crossing • Lateral crossing • Possible extension of previous ASPA applications into ASEP applications (Package II)

5. ASPA-S&M, merging phase • Parameters of interest • Altitude at WPT • Required spacing at WPT • Angle of convergence at WPT • Relative initial speed between leading and trailing a/c • Potential TAs but only with required spacing close to 3 NM(unlikely for typical operations)

6. ASPA-S&M, in-trail phase • Parameters of interest • Required spacing at WPT • Relative initial altitude and spacing between leading and trailing a/c • Length of the base turn • No ACAS alerts when on same leg with required spacing > 3 NM • No ACAS alerts when on opposite legs with base leglength > 3 NM

7. ASPA-C&P, lateral overtaking • Parameters of interest • Encounter altitude • Track spacing • Relative speed between both a/c • No ACAS alerts with track spacing > 3 NM

8. ASPA-C&P, vertical crossing • Parameters of interest • Encounter altitude • HMD between both a/c • Required vertical spacing between both a/c when level • Relative vertical and horizontal speed between both a/c • Potential TAs and RAs (EMOTION-7 OP06 issue: Unnecessary RAsin 1000-ft level-off geometries)

9. ASPA-C&P, lateral crossing • Parameters of interest • Encounter altitude • Required spacing at the track crossing point • Angle of convergence at the track crossing point • Relative speed between both a/c • TAs very likely with required spacing < 5 NM • Potential RAs if Miss Distance Filtering (MDF) not effective

10. Conclusion • Main outcomes for IAPA Phase I • Likelihood & duration of TA: Highly geometry & altitude dependent • MDF performance: Critical to prevent undesirable RAs • Major influencing factors of ACAS / ASAS interaction • Airborne spacing values • Aircraft trajectory quality • Framework for IAPA Phase II and III • Operational environment definition (ASPA-C&P, lateral crossing) • Simulation framework • Simplified model of the application behaviour • ATM encounter model • Impact of ASAS operations on safety benefit provided by ACASstill to be investigated