IAPA END OF PHASE 1 SUMMARY
Future Simulations within Phase II
Introduction
In November 2003, Phase 1 (of 3) was
completed of IAPA (Implications on Airborne Collision Avoidance System (ACAS)
Performances due to Airborne Separation Assistance System (ASAS)
implementation). The IAPA project investigates the potential ACAS and ASAS
interaction issue, and is focused on operations in the ECAC area (European
Civil Aviation Conference – 41 member states). The project is sponsored by
EUROCONTROL Headquarters in
Scope and Purpose
The project tries to ascertain:
· whether there are any significant operational implications for ACAS II performance due to possible ASAS implementation in the ECAC area; and
· whether the benefits expected from ASAS could be compromised due to the operations of ACAS II.
Focus is on identifying potential operational issues and providing recommendations, which are related to the potential interaction between the ACAS logic and the ASAS procedures.
The IAPA study relies on the tools which were developed, and the methodology which was established, for the Full System Safety Study and the ACAS / RVSM (Reduced Vertical Separation Minimum) interaction study completed within the framework of the ACASA (Airborne Collision Avoidance Systems Analysis) project.
The study comes within the scope of the
EUROCONTROL ACAS Programme and is also of particular interest for several areas
dealing with ASAS development. The main objective is to provide guidelines on
any identified ACAS and ASAS interaction issue for the development of future
ASAS applications in
Project Breakdown
The project is composed of three main steps:
· Phase I (November 2002 / October 2003) defined the initial scope of the ACAS and ASAS interaction issue;
· Phase II (November 2003 / October 2004) is conducting a full set of simulations; and
· Phase III (October 2004 / June 2005) draws conclusions and summarises the work performed during the previous phases.
Main Achievements of Phase I
Phase I of the IAPA project involved selecting an appropriate ASAS application i.e. an application with the potential for studying a maximum number of significant and realistic issues from an ACAS safety and operational performance perspective.
This selection was supported by a preliminary analysis of the ACAS / ASAS interaction for a selected set of Package I Airborne Surveillance applications presenting the potential for an extension into airborne separation applications (Package II).
Following the identification of a potential interaction between ACAS and ASAS, Phase I has also established the framework required for an in-depth investigation:
· the operational environment and the selected ASAS application (i.e., Airborne Spacing – Crossing & Passing, lateral crossing with “pass behind” and “pass in-front” procedures) have been defined;
· a simulation framework has been proposed involving three different scenarios with full ASAS / ADS-B equipage and a set of ACAS / ASAS interaction indicators;
· a simplified model of the selected ASAS application has been developed; and
· an ATM encounter model has been specified, with the objective of supporting the development of an ASAS encounter model.
This framework will be further developed within Phase II (with the ASAS encounter model) and will support the full set of planned simulations.
Future Simulations within
Phase II
Within Phase II, the in-depth investigation of the potential ACAS / ASAS interaction will be performed through various studies based on different sources of data:
·
ASAS
encounter model;
·
modified
radar data;
·
fast-time
simulations; and
·
real-time
simulations.
The rationale for conducting simulations on different sources of data is to compensate for the limitations related to anyone of them, and to identify a larger set of issues.
The use of a common simulation framework during the various IAPA data-oriented studies should allow for the validation of ACAS / ASAS interaction trends identified with each source of data.
Furthermore, it is also planned to investigate the impact of ASAS operations on the safety benefit provided by ACAS, through a dedicated safety case based on the EUROCAE (European Organisation for Civil Aviation Equipment) ED78A Operational Safety Assessment methodology.
Conclusions of Phase 1
The IAPA project is one European contribution to address the potential ACAS and ASAS interaction issue. This contribution is required because of the planned evolutions of the European Air Traffic Management (ATM) system with a greater involvement of the flight crews in separation provision, which may impact the forecasted performance of both ACAS II and the ATM system change itself.
Figure 1: Screen shot of
CENA’s OSCAR (Offline Simulator Collision Avoidance Resolution) tool analysing IAPA
selected airborne spacing application crossing & passing with TCAS II logic
- Traffic Advisory (filled circle) during “pass behind” lateral crossing
encounter between a jet and a
turboprop aircraft both flying level at FL240 with initial tracks converging at
an angle of 90°.
The main results of the preliminary analysis of the potential ACAS / ASAS interaction issue are the following:
· the likelihood and duration of Traffic Advisories (TAs) are highly geometry and altitude dependent;
· the “Miss Distance Filter” performance of TCAS II logic version 7.0 is critical to prevent the issuance of undesirable Resolution Advisories (RAs);
· the major influencing factors on the ACAS / ASAS interaction are:
- the airborne spacing values; and
- the aircraft trajectory quality.
· It is not yet possible to determine the implications, due to ACAS / ASAS interaction issues, for ACAS safety performance.
In addition, in view of the major assumptions and limitations of the preliminary ACAS / ASAS interaction study performed within IAPA, definitive conclusions shall not be drawn for any of the Package I applications.
It is emphasised that it is necessary to investigate further the set of ACAS / ASAS interaction issues identified. The work methodology and framework developed during Phase I will facilitate this task.
Recommendations from Phase 1
The work conducted within IAPA Phase I demonstrated that:
· ACAS / ASAS interaction issues must be taken into account when developing ASAS applications envisaged for implementation;
· further in-depth analysis of the identified ACAS / ASAS interaction issues should be performed; and
· the impact of ASAS operations on safety benefits provided by ACAS needs to be investigated.
IAPA Phase II (started November 2003) will capitalise upon the methodology and framework which has been developed, and the preliminary analysis which has been undertaken, within IAPA Phase I.
For more details see IAPA Project Phase 1 Report
For more information and contact details see
Eurocontrol ACAS Programme web site: http://www.eurocontrol.int/acas/