Short-term conflict alert (STCA) is an automated warning system for
air traffic controller
An Air traffic controller (ATC) is a person responsible for the coordination of traffic in their assigned airspace. Typically stationed in area control centers or control towers, they monitor the position, speed, and altitude of aircraft and c ...
s (ATCO). It is a ground-based safety net intended to assist the controller in preventing collision between aircraft by generating, in a timely manner, an alert of a potential or actual infringement of
separation minima.
Description
ICAO Doc 4444 requires that radar systems should provide for the display of safety-related alerts including the presentation of actual and predicted conflict.
It is worth mentioning that ICAO Doc 4444 does neither provide definitions of the term STCA nor ''conflict alert''. Instead the term STCA is ambiguously used in
ATC community to identify such alerts as well as for data processing systems providing the alert function.
As an implementation STCA is part of the predictive safety net functions. It uses surveillance information derived from
radar
Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...
s,
ADS-B or
multilateration
Trilateration is the use of distances (or "ranges") for determining the unknown position coordinates of a point of interest, often around Earth ( geopositioning).
When more than three distances are involved, it may be called multilateration, f ...
as well as environmental data and optional
flight plan
Flight plans are documents filed by a aviator, pilot or flight dispatcher with the local Air Navigation Service Provider (e.g., the Federal Aviation Administration, FAA in the United States) prior to departure which indicate the plane's planned ...
information in order to predict the movement of aircraft. This process is usually working unnoticeably to the air traffic controller unless a (potential) separation infringement is identified. In this case STCA will generate an alarm to inform the air traffic controller about the hazardous situation identifying the conflicting aircraft.
Due to the uncertainty of trajectory prediction the look ahead time of STCA system is typically limited to approx. 2 minutes.
Extending the look ahead time is not beneficial as more and more nuisance alerts will be generated.
Related systems
In addition to STCA, other ground-based safety net functions are typically implemented to support the ATCO. These in include
* ''
Minimum safe altitude warning'' (MSAW); and
* ''Area proximity warnin''g (APW), sometimes also called ''danger area infringement warning'' (DAIW).
The equivalent system on board an aircraft is
TCAS. This system alerts pilots to possible conflicts, and suggests remedial actions, in the form of a climb or descent. Unlike TCAS, STCA does not normally suggest remedial action. If action is required, the controller will normally give a turn command to the aircraft, eliminating the possibility that his command will contradict that given by TCAS.
Other concepts of air safety are:
* making a
flight plan
Flight plans are documents filed by a aviator, pilot or flight dispatcher with the local Air Navigation Service Provider (e.g., the Federal Aviation Administration, FAA in the United States) prior to departure which indicate the plane's planned ...
and
* using
airways.
See also
*
TopSky
References
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External links
SKYbrary article on STCA
Aviation safety
Air traffic control
Warning systems