62ND ANNUAL CONFERENCE, Montego Bay, Jamaica, 8-12 May 2023WP No. 91TPM Review – STCAPresented by TOC |
Summary
The purpose of this working paper is to review the IFATCA policy ATS 3.18 related to Short Term Conflict Alert (STCA).
Introduction
1.1. As a part of IFATCA’s ongoing policy review the Short Term Conflict Alert (STCA) policy is to be reviewed. This policy was identified as needing further review during the Technical and Professional Manual (TPM) Review in 2022 (Virtual, WP 61).
1.2. The existing STCA policy can be found in the ATS section of IFATCA’s (TPM) in ATS 3.18.
1.3. The last review of the STCA policy was conducted in 2015 (Sofia, WP 90).
Discussion
2.1. Reason for Review
2.1.1. TPM Review ATS (Major Edits) stated: “The policy is very wordy and may benefit from more and concise language. It is therefore proposed that a policy review is conducted next year.”
2.1.2. The goals of this paper are to take the existing policy, remove excess verbiage and clean up the policy.
2.2. Description
2.2.1. According to SKYbrary, STCA is a system to warn the controller “of any situation where user defined minimum separation distances between any pair of surveillance tracks is, or is predicted to be violated within a short look ahead time (usually 2 minutes)”.
2.2.2. SKYbrary also states that it “is achieved via a visual alert on the radar display, though some systems also provide an audible alert.”
2.2.3. The STCA system then generates a visual and/or an aural warning to a controller.
2.2.4. Eurocontrol Guidelines for Short Term Conflict Alert explains the purpose of STCA as follows, “STCA adds independent alerting logic to the control loop by generating indications of existing or pending situations, related to the proximity of aircraft as well as their relative positions and speed, which require attention/action. STCA is intended to function in the short term, if applicable providing warning times of up to 2 minutes.”
2.3. Policy Review
2.3.1.
| 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. |
This section refers STCA back to the safety net concept. The TPM defines a safety net as “Airborne and / or ground based function, the sole purpose of which is to alert the pilot or controller of the imminence of collision of aircraft, aircraft and terrain / obstacles, as well as penetration of dangerous airspace.” But the utilisation of STCA goes beyond solely that of a “last resort” in some units. The rest of the wording is excess and can be more concisely stated through revised wording:
STCA, as a safety net, shall be provided to each ATM-system with ATS-surveillance.
2.3.2. The central section of the policy reads:
| 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 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. 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. |
The themes of this part of the policy can be reduced to a more brief version.
Revised wording reads as follows:
STCA parameters shall be adjustable and nuisance filters for each individual ATC unit with ATS surveillance, are developed, and tested for the area involved and adjusted to the procedures, airspace layout, separation standards, surveillance source, traffic mix, etc.
2.3.3.
| 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. |
This section has a very minor change for ICAO Harmonization changing should to shall. Revised Wording:
An STCA function shall 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.
Conclusions
3.1. IFATCA’s STCA policy stays relevant, but requires some editorial changes.
Recommendations
4.1. It is recommended that ATS 3.18 Short Term Conflict Alert Policy is amended to read:
STCA, as a safety net, shall be provided to each ATM-system with ATS-surveillance.
STCA parameters shall be adjustable and nuisance filters for each individual ATC unit with ATS surveillance, are developed, and tested for the area involved and adjusted to the procedures, airspace layout, separation standards, surveillance source, traffic mix, etc.
An STCA function shall 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.
and included in the TPM.
References
SKYbrary.
IFATCA WP No. 98 Short Term Conflict Alert, Toulouse, France 1998.
IFATCA WP No. 90 Review of Policy, STCA, Sofia, Bulgaria 2015.
IFATCA TPM ATS 3.18 Short Term Conflict Alert.
Eurocontrol Guidelines for Short Term Conflict Alert Edition 1.0 January 2017.
IFATCA WP No. 61 TPM Review – ATS (Major Edits), Virtual 2022.
IFATCA TPM Version 65.0 – July 2022.
Last Update: September 16, 2023