Review of Policy: Short Term Conflict Alert (STCA)

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Review of Policy: Short Term Conflict Alert (STCA)

54TH ANNUAL CONFERENCE, Sofia, Bulgaria, 20-24 April 2015

WP No. 90

Review of Policy:
Short Term Conflict Alert (STCA)

Presented by TOC

Summary

This is a review of the IFATCA policies regarding STCA (Short Term Conflict Alert). Several policy statements have been identified as being “old” and others are in need of modernization (updating). ICAO has published in document 4444 (PANS-ATM) the new chapter 8, where all ATS Surveillance systems are now grouped together. This new chapter 8 does not only contain provisions for radar, but also provisions for new ATS surveillance systems such as for instance MLAT (Multi-lateration) or ADS-B. These new surveillance systems are by now fully integrated (and recognized as such) by ICAO. There is a requirement that this is as well reflected in the policies of IFATCA. Any automated ATM System equipped with ATS surveillance can be fitted with ground-based safety nets such as for instance a short term conflict alert – STCA.

Introduction

1.1 ICAO is currently in the process of drafting a new manual regarding ground-based Safety Nets (ground-based SNETs). Our Federation is fully involved in this drafting process. Part of the draft work is trying to find agreement on the official definitions for all the ground-based Safety Nets that will be governed by this new manual. The SNETs discussed are: STCA (Short Term Conflict Alert), MSAW (Minimum Safe Altitude Warning), APW (Area Proximity Warning) and also APM (Approach Path Monitoring).

1.2.  The relevant IFATCA policy statements are currently part of this selection process, as all these proposed definitions and system descriptions are discussed by the task force drafting the new ICAO Manual. During the initial discussions held at ICAO level it was discovered that some of the IFATCA policy statements (e.g. for STCA) are having a terminology that is outdated or are not fully reflecting the operational reality of today.

1.3.  This WP is analysing all the relevant STCA policies of IFATCA. Where necessary the working paper is proposing an update or a refinement of the text (or terminology).

Discussion

2.1.  The STCA policy of IFATCA was adopted during the annual IFATCA world conference of the year 2005 in Melbourne, Australia. The STCA policy reads (in full):

IFATCA policy is:

Ground based safety nets, like STCA, can enhance overall safety in the automated ATC systems. Therefore each automated ATC radar system should be provided with a groundbased safety net system such as STCA, as a last resort, that only should be used to advise the controller of potential losses of separation.

Controllers shall be involved during the design and development phase with proper introduction and training as necessary when implementing STCA systems.

It is important that, for each individual ATC radar unit, parameters and nuisance filters in STCA systems are developed and tested that are suitable for the area involved and adjusted to the procedures, airspace layout, separation standards, radar source, traffic mix, etc. The systems’ logic and parameters should be flexible.

In ATC areas where STCA will be installed, studies and real time simulations shall be carried out to ensure that possible conflicting warnings with TCAS can be kept to a minimum.

An STCA function should not be considered when developing a safety case, unless it can be demonstrated that the functionality is used in a separation assurance mode of operation.

 

2.2.  Several of these policy statements – as mentioned during the introduction – require our attention. They use wordings, or s terminology that is either outdated and sometimes not anymore reflecting the last changes made by ICAO. The first paragraph that requires changes states:

Ground based safety nets, like STCA, can enhance overall safety in the automated ATC systems. Therefore each automated ATC radar system should be provided with a groundbased safety net system such as STCA, as a last resort, that only should be used to advise the controller of potential losses of separation.

 

2.3.  Comments

This is a good example for why some (minor) changes to the definitions and terminology used by the policy statements regarding STCA are needed. The proposed refinement and improvements do concern in particular the use of new ATS-Surveillance systems. This, as not only radar can be used for an STCA (or any ground-based safety net in use by ATC), but also surveillance systems such as MLAT (multi-lateration) or ADS-B are by now able to offer to the automated ATM systems the required surveillance data permitting that an STCA can be operated.

2.4.  Back in 2007 – with amendment 5 of the PANS-ATM – ICAO has regrouped all the “old” radar provisions into chapter 8. At the same time new ATS surveillance systems were added. So, they are by now officially approved by ICAO. By doing this, ICAO was acknowledging the fact that not only radar can provide safe ATS surveillance data to ground ATC, but also other surveillance systems (e.g. ADS-B, or MLAT) are capable of providing ATS surveillance to ATC and ATM systems with the required degree of reliability and precision.

2.5. It is proposed to reword the above-mentioned IFATCA policy statements (in 2.2.) to change the paragraph to:

“Ground based safety nets, like STCA, can enhance overall safety in the automated ATC systems. Therefore each automated ATM system with ATS surveillance should be provided with a ground-based safety net system such as STCA, as a last resort, that only should be used to advise the controller of potential losses of separation”.

The use of the terminology “radar” (stated in isolation) is not anymore of actuality. My adopting these changes, IFATCA does align its policies with the changes made by ICAO in document 4444. This modification makes as well sure that the policy is fully aligned with the operational reality of today.

2.6 Two paragraphs further down (in the STCA policy of IFATCA) another policy statement is in need of a similar update, as the text currently reads:

It is important that, for each individual ATC radar unit, parameters and nuisance filters in STCA systems are developed and tested that are suitable for the area involved and adjusted to the procedures, airspace layout, separation standards, radar source, traffic mix, etc. The systems’ logic and parameters should be flexible.

 

2.7. It is proposed to reword (slightly) the above mentioned IFATCA policy statement, so that it would read (proposal):

It is important that, for each individual ATC unit with ATS surveillance, parameters and nuisance filters in STCA systems are developed and tested that are suitable for the area involved and adjusted to the procedures, airspace layout, separation standards, surveillance source, traffic mix, etc. The systems’ logic and parameters should be flexible.

2.8 Comments

Several times the term “radar” is used again. This needs to be changed as IFATCA must acknowledge that by now “ATS surveillance” is the official and correct term. And that ATS surveillance service does not only include radar, but as well other ATS surveillance systems such as MLAT or ADS-B. The rest of the STCA Policy statements of IFATCA remain still valid and so they remain up-to-date and there is no perceived need for further changes or improvements.

Conclusions

3.1 Several IFATCA policy statements regarding STCA have been discovered as being outdated and in need of modernization. ICAO has created the chapter 8 of PANS-ATM (4444) through Amendment 5 (back in 2007). This change had acknowledged the fact that new ATS surveillance systems, such as MLAT or ADS-B have gained in maturity. So, they can by now be considered as “surveillance”, or ATS surveillance systems. Meaning that ATS surveillance and ATS surveillance systems for ICAO are not anymore limited to “radar” only.

3.2. This change needs to be reflected in the IFATCA policy statements – in particular the policy of IFATCA for STCA. The current STCA policy still uses (on several occasions) the term “radar”. This needs to be changed so that the terminology gets adapted to ICAO, but as well to the operational reality of today.

Recommendations

4.1.  It is proposed that the following IFATCA STCA policy statement:

Ground based safety nets, like STCA, can enhance overall safety in the automated ATC systems. Therefore each automated ATC radar system should be provided with a ground-based safety net system such as STCA, as a last resort, that only should be used to advise the controller of potential losses of separation.

Is replaced with:

Ground based safety nets, like STCA, can enhance overall safety in the automated ATC systems. Therefore each automated ATM system with ATS surveillance should be provided with a ground-based safety net system such as STCA, as a last resort, that only should be used to advise the controller of potential losses of separation

4.2.  It is proposed that following IFATCA STCA policy statement:

It is important that, for each individual ATC radar unit, parameters and nuisance filters in STCA systems are developed and tested that are suitable for the area involved and adjusted to the procedures, airspace layout, separation standards, radar source, traffic mix, etc. The systems’ logic and parameters should be flexible.

Is replaced with:

It is important that, for each individual ATC unit with ATS surveillance, parameters and nuisance filters in STCA systems are developed and tested that are suitable for the area involved and adjusted to the procedures, airspace layout, separation standards, surveillance source, traffic mix, etc. The systems’ logic and parameters should be flexible.

Last Update: May 14, 2020  

May 14, 2020   47   Jean-Francois Lepage    2015    

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