This Report presents the background and the results of the Feasibility of ACAS RA Downlink Study (FARADS).

Following a summary of the findings, a way forward is outlined.

A study of all technical means for the downlink of ACAS RA information was initially conducted in 2004. This report updates the finding of the original study to incorporate emerging technology developments such as ACAS Monitor and Wide Area Multilateration (WAM).

A study of all technical means for the downlink of ACAS RA information and to rank these techniques against evaluation criteria. Four candidate techniques were analysed in detail and several others in less depth. The four core techniques were: Mode S RA Report, RA Broadcast, ACAS Coordination Messages, and 1090 Extended Squitter.

The carriage of ACAS is mandatory in European airspace, and has been demonstrated to reduce the risk of midair collision through the resolution advisories (RAs) that it issues.

The FARADS programme is assessing the feasibility of downlinking RAs to controllers. Part of the assessment is an investigation of whether downlinking RAs will further reduce the risk of midair collision. The current study has developed a PC based ‘contingency tree’ tool which, when supplied with accurate event probabilities, will enabled any safety benefit to be evaluated.

A model of the latencies associated with the downlink of ACAS RA information to ATC centres has been specified and implemented as a software application. The model has been used to investigate the performance of two candidate downlink methods (Mode S RA Report, and 1090 MHz extended squitter) in a set of scenarios representative of those that can be expected in European airspace.

The preliminary results presented here show that RA downlink can greatly increase the timeliness of information for improved situational awareness in all contexts, and in safety critical situations will be in time to allow prevention of unwanted controller involvement in RA encounters.

This report documents the Cognitive Task Analysis for the proposed ACAS RA Downlink. It is produced in conjunction with the Human Reliability Assessment and the Safety Case.

The document is the combined FHA/PSSA report of RA Downlink. It reports on the findings of FHA/PSSA workshop and subsequent analysis.

The report documents safety assessment of RA Downlink. It addresses the safety of RA Downlink based on the selected operational concept. It does not cover safety issues resulting from the implementation phase or transfer to operation of RA Downlink.

FARADS is investigating the feasibility of showing simplified ACAS resolution advisories on controller screens. As part of this study, an experiment was conducted in which resolution advisories (RAs) were displayed to controllers. As part of this study, an experiment was conducted in which resolution advisories (RAs) were displayed to controllers. This experiment took place from 17 November to 28 November 2003, and a total of 30 controllers from ten European Area Control Centres participated. The majority of the participants see clear operational benefits in the provision of RA information to the controller. Because RA downlink is faster and more reliable than a pilot report of an RA, it can support the controller’s anticipation of aircraft manoeuvres. This can be considered an improvement in situational awareness. Furthermore, most participants expect RA downlink to decrease the likelihood of contradictory ATC clearances to the conflict aircraft.

The present report describes the conduct and the results of RADE-2A, an experiment that was conducted to assess the impact of displaying simplified ACAS Resolution Advisories (RAs) to the controller. The RADE-2A experiment took place from October 4 to December 1, 2005 and involved 12 controllers from 4 different European ACCs.

The results of the RADE-2A experiment point to some operational benefits of RA downlink. Contradictory clearances to aircraft involved in an RA were exclusively observed in the absence of RA downlink. Controller’s recollection of RA events caused by pilot or controller error was superior if RA downlink was provided. In contrast, there was no evidence for negative effects of RA downlink, such as cognitive tunnelling on the RA event and a lower ability to separate other traffic in the sector.

The present document provides the results report for the RADE-2 prototype simulations (RADE-2P). The prototype experiments were successful in showing the feasibility of carrying out RA downlink experiments in an interactive setting. TCAS Resolution Advisories (RA) could be elicited satisfactorily and with sufficient simulation realism by the subject matter experts (SME) within the proposed simulation environment.

The present report describes the conduct and the results of RADE-2T, an initial experiment that was conducted to assess the impact of displaying simplified ACAS Resolution Advisories (RAs) to the controller in a Terminal Control environment. The RADE-2T experiment took place from January 10 to January 19, 2006 and involved 4 controllers from 2 different European Approach Control units.

The results of the initial experiment were inconclusive with regard to the operational impact of RA downlink in a Terminal Control.

The study did reveal that an experimental test of RA downlink in a Terminal Control environment is very demanding, with respect to realising a sufficient number of RAs without compromising simulation realism.

The study deals with this analysis of RA downlink data originating from six Mode-S radars with a coverage including most of the European core area. The data were collected from September 2007 to March 2008. This represents a little more than 1,300,000 flight hours.

This Report provides a factual account of the presentations and discussions during the 27th October 2009 RA Downlink Workshop. The Report contains a strong stakeholder message that is expected to influence the work programmes of EUROCONTROL and SESAR.

The results of the Questionnaire distributed during the final session of the RA Downlink Workshop.

A document summarising the RA Downlink Workshop held at EUROCONTROL HQ on 31 May 2006.

Link to ACAS Bulletins and Safety Messages on the Mode S and ACAS Programmes website.

This document is designed for the training of people involved in the implementation and the use of the Airborne Collision Avoidance System (ACAS). However, it is not, per se, designed for the complete training of controllers or pilots. The principal and essential technical and operational features of ACAS are introduced. For a deeper knowledge, the reader is advised to refer to ICAO and RTCA documentation listed in the bibliography section.

Article from the September 2006 issue of The Controller about RA Downlink Workshop.

Article from HindSight no. 6.

Paper presented at the 14th Annual International Symposium on Aviation Psychology, 23 - 26 April 2007, Dayton Ohio USA

Article from HindSight no. 6.

Paper Presented at the 7th American Institute of Aeronautics and Astronautic Aviation Technology, Integration, and Operations Conference (ATIO) Belfast, Northern Ireland.

Paper presented at 3rd EUROCONTROL Annual Safety R&D Seminar, Rome, Italy, 24 - 26 October 2007.

Paper presented at the 7th USA/Europe ATM R&D Seminar, 2 - 5 July 2007, Barcelona, Spain (the Best Paper in the Safety in ATM stream).

Article from HindSight no. 5.

Article from HindSight no. 10.

Presentation at the 43rd Annual IFATCA Conference, Hong Kong 2004.

Presentation at the 43rd Annual IFATCA Conference, Hong Kong 2004.

Press release in English and French.

Press release