Short-term conflict alert

ICAO Doc 4444 requires that radar systems should provide for the display of safety-related alerts including the presentation of actual and predicted conflict.{{cite book |title=Rules of the Air and Air Traffic Services |publisher=ICAO|id=Doc 4444-RAC/501}} 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 radars, 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.{{Cite web |title=Ground Based Safety Nets |url=http://www.airport-int.com/article/ground-based-safety-nets.html |date=12 April 2007|website=Airport International|accessdate=22 May 2010 |url-status=usurped|archive-url=https://web.archive.org/web/20110707100636/http://www.airport-int.com/article/ground-based-safety-nets.html|archive-date=2011-07-07}} Due to the uncertainty of trajectory prediction the look ahead time of STCA system is typically limited to approx. 2 minutes.{{cite web |title=Short Term Conflict Alert (STCA) |url=http://www.skybrary.aero/index.php/STCA |accessdate=22 May 2010 |via=SKYbrary}} Extending the look ahead time is not beneficial as more and more nuisance alerts will be generated.

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 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.{{cite web|url=http://www.aviationmanuals.com/references/2008-01/ACAS_Bulletins-BUL10.pdf|title=ACAS II Bulletin No. 10|author=EUROCONTROL|author-link=EUROCONTROL|accessdate=23 July 2009|date=November 2007|url-status=dead|archiveurl=https://web.archive.org/web/20091122225322/http://www.aviationmanuals.com/references/2008-01/ACAS_Bulletins-BUL10.pdf|archivedate=22 November 2009}}

Other concepts of air safety are:

• making a flight plan and
• using airways.

• TopSky

{{Reflist|colwidth=40em}}

• [http://www.skybrary.aero/index.php/STCA SKYbrary article on STCA]

Category:Aviation safety

Category:Air traffic control

Category:Warning systems