Page 4-24 500 SERIES INSTALLATION MANUALRev Q 190-00181-024.11 TERRAIN AWARNESS AND WARNING SYSTEM (TAWS) ANDTERRAINThe terms “TAWS” and “TERRAIN” are used to identify two different configurations of 500 Series unitMain Sub-System. The “TAWS” configuration complies with the Terrain Awareness and Warning System(TAWS) requirements of TSO-C151b for Class B, whereas the “TERRAIN” configuration provides asubset of the functionality of “TAWS”.The following table identifies the high-level differences between TAWS, TERRAIN, and those units withneither (None):Function TAWS TERRAIN NoneTSO-C151b Class B Certified Yes No NoTAWS/TERRAIN Display( Shows terrain elevations relative to the aircraft ) Yes Yes NoVisual Alerting( Includes popup alerting ) Yes Yes NoAural Alerting Yes No NoExternal Visual Alerting Capability Yes No NoReduced Terrain Clearance (RTC) Avoidance( Forward Looking Terrain Avoidance (FLTA) sub-function )Yes Yes NoImminent Terrain Impact Avoidance( Forward Looking Terrain Avoidance (FLTA) sub-function )Yes Yes NoPremature Descent Alert (PDA) Yes Yes NoExcessive Rates of Descent Alert( Ground Proximity Warning System (GPWS) Alertingsub-function )Yes No NoNegative Climb Rate/Altitude Loss After Takeoff( Ground Proximity Warning System (GPWS) Alertingsub-function )Yes No No“Five Hundred” Voice Callout( Ground Proximity Warning System (GPWS) Alertingsub-function )Yes No NoInhibit Capability( Inhibits FLTA and PDA visual and aural alerting ) Yes Yes NoTAWS Test System Capability Yes No NoWorldwide Terrain Database Yes Yes NoAirport Layer Database Yes Yes NoObstacle Database Yes Yes No500 Series TERRAIN functionality is a subset of the TAWS functionality and has been certified as a non-TSO-function. As such, a subset of the TSO-C151b specification is used as the requirement basis.500 Series TERRAIN and TAWS functionality is not designed nor approved for use in helicopters.