Short Term Conflict Alert
Encyclopedia
Short Term Conflict Alert (STCA) is an automated warning system for air traffic controller
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
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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
s, ADS-B or multilateration
as well as environmental data and optional flight plan
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.
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:
Air traffic controller
Air traffic controllers are the people who expedite and maintain a safe and orderly flow of air traffic in the global air traffic control system. The position of the air traffic controller is one that requires highly specialized skills...
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
Separation (air traffic control)
In air traffic control, separation is the name for the concept of keeping an aircraft outside a minimum distance from another aircraft to reduce the risk of those aircraft colliding, as well as prevent accidents due to wake turbulence....
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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 ATCAir traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
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
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
s, ADS-B or multilateration
Multilateration
Multilateration is a navigation technique based on the measurement of the difference in distance to two or more stations at known locations that broadcast signals at known times. Unlike measurements of absolute distance or angle, measuring the difference in distance results in an infinite number of...
as well as environmental data and optional flight plan
Flight plan
Flight plans are documents filed by pilots or a Flight Dispatcher with the local Civil Aviation Authority prior to departure...
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 extend to STCA other ground based safety net functions are typically implemented to support the ATCO. These in include- Minimum Safe Altitude WarningMinimum Safe Altitude WarningMinimum Safe Altitude Warning is an automated warning system for air traffic controllers . It is a ground-based safety net intended to warn the controller about increased risk of controlled flight into terrain accidents by generating, in a timely manner, an alert of aircraft proximity to terrain...
(MSAW); and - Area Proximity Warning (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 planFlight planFlight plans are documents filed by pilots or a Flight Dispatcher with the local Civil Aviation Authority prior to departure...
and - using airwaysAirway (aviation)In aviation, an airway is a designated route in the air. Airways are laid out between navigational aids such as VORs, NDBs and Intersections ....
.