• Early limitations

However, like all systems it has its shortcomings. It does not function when the aircraft is in landing configuration and provides limited warning of rapidly rising terrain. But as always, more advanced models were introduced in 1996. Since July 2005 every turbine passenger aircraft carrying more than 10 passengers has to have an Enhanced GPWS/Terrain Avoidance Warning System, according to the International Civil Aviation Organization (ICAO).  

• Enhanced GPWS – significant safety improvements but not yet perfect

Unlike the earlier model, EGPWS has a terrain database, which is used to warn pilots of approaching high ground. This is displayed in the cockpit in shades of green, orange and red. The pilot receives the information overlaid on his primary flight control display. However, Honeywell Chief Engineer-Flight Safety Systems Donald Bateman and father of GPWS and EGPWS cautions that, owing to the challenges involved in assembling the terrain database from a variety of sources, the system is not yet perfect. He explains that "we have better databases for Mars and Venus than we have for Earth and we are finding various anomalies around the world." However whenever an anomaly is detected it is reported back to the software makers and an update issued.