 GPWS was found to be superior in that it would warn only when necessary, provide maximum warning time with minimal unwanted alarms, and use command-type warnings.Based on these reports and NTSB recommendations, in 1992 the FAA amended §135.153 to require GPWS equipment on all turbine-powered airplanes with ten or more passenger seats.After these rules were issued, advances in terrain mapping technology permitted the development of a new type of ground proximity warning system that provides greater situational awareness for flight crews.