STCA is a ground based system computer program that relies on surveillance data processing to predict proximity between two or more targets. The program utilises radar information on both the vertical and horizontal planes and predicts the future position of those targets, for a time in the future, determined by a variable system parameter known as the look ahead time (generally +/- 1 min). The system then generates warnings to a controller if this prediction will result in less than a set distance (vertically or horizontally) occurring between the targets. There are no internationally accepted parameters for STCA, however in general terms STCA can operate in two different “modes”: as a separation assurance function or as collision prevention function.
Short Term Conflict Alert (STCA) is an automated system that predicts reduction of aircraft spacing to below specified parameters. An STCA function can be used as either a controller tool (STCA-T) or a safety net (STCA-N) depending upon system parameters.
IFATCA Policy is:
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.
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.
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.
|See: WP 98 – Toulouse 1998 and WP 87 – Melbourne 2005|
Last Update: October 2, 2020