A Premature Descent Alert (PDA) function.The FLTA function looks ahead of the aircraft along and below its lateral and vertical flight path and provides suitable alerts if a potential CFIT threat exists. A Forward Looking Terrain Avoidance (FLTA) function.TAWS equipment must provide the following functions:
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Full details of regulatory requirements are given later in this article. In essence, Class A systems are required for all but the smallest commercial air transport aircraft, while Class B systems are required by larger General Aviation (GA) aircraft and recommended for smaller commercial or GA aircraft. TAWS equipment is classified as Class A or Class B according to the degree of sophistication of the system. The terms EGPWS and TAWS have effectively become interchangeable and to avoid confusion, the original GPWS, which is becoming increasingly scarce, will be referred to in this article as 'basic GPWS'. Subsequently, other OEMs produced similar systems and all have been generically identified by ICAO as Terrain Awareness and Warning Systems (TAWS). A comprehensive set of reliable cautions and warnings can be generated which use both the radio altimeter and relative position. This system relates aircraft position, which should be from a GPS source which can be internal to the equipment or fed frim the aircraft FMS, to an almost worldwide terrain/obstacle/airport database which the equipment manufacturer regularly updates.
However, it suffered from a significant limitation because it was dependent on the radio altimeter as the means to measure proximity to terrain which meant that there was insufficient time to avoid a sudden change in terrain in the form of steeply rising ground.įrom 1997, the Honeywell Enhanced Ground Proximity Warning System (EGPWS) which had been explicitly developed in order to overcome the above limitation, began to be fitted to aircraft. This 'basic' GPWS was mandated in many countries and was responsible for a significant reduction in the number of CFIT accidents. landing gear status) and ILS glideslope deviation. Subsequent improvements added aeroplane configuration (e.g.
The first implementation of TAWS was Ground Proximity Warning System (GPWS) and was introduced in the 1970s as a means to combat the high incidence of CFIT accidents and near-accidents. Terrain Avoidance and Warning System (TAWS)Įnhanced Ground Proximity WarningSystem (EGPWS) DefinitionĪ system that provides the flightcrew with sufficient information and alerting to detect a potentially hazardous terrain situation and so the flightcrew may take effective action to prevent a CFIT event.Ī Terrain Avoidance and Warning System (TAWS) is a safety net that automatically provides a distinctive warning to pilots when the their aeroplane is, based only on the radio altimeter reading and terrain closure rates derived therefrom, in potentially hazardous proximity to terrain.