TAWS

TAWS cross-references the aircraft's GPS position with an onboard terrain database and generates visual and audio alerts when the projected flight path would impact terrain. Class B TAWS, the type common in light GA aircraft, is purely GPS-based and does not require a radar altimeter. Class A TAWS (full Enhanced GPWS) is required in larger transport-category aircraft and includes additional modes such as windshear detection.

For VFR pilots, a TAWS display showing terrain clearance is a useful situational awareness tool on mountain or cross-country flights. For IFR operations in mountainous terrain, it is essentially mandatory. Accurate GPS position is the foundation of the whole system, so TAWS works best alongside a WAAS GPS navigator.