For various flight conditions, the ground proximity warning system (GPWS) provides aural and visual warnings of airplane closeness to the terrain. The potentially dangerous flight modes are:
(1) Mode 1 - Large Descent Rate(2) Mode 2 - Large Terrain Closure Rate
(3) Mode 3 - Too Much Altitude Loss During Climbout (at Takeoff or in Go-Around) When Not In Landing Configuration
(4) Mode 4 - Not Enough Terrain Clearance
(5) Mode 5 - Too Much Deviation Below The Glide Slope Centerline
(6) Mode 6 - Aural Callouts When Descending Through Selected Radio Altitudes
(7) Mode 7 - Windshear Detection
The system consists of:
(1) 1 - Ground Proximity Warning Computer (GPWC) or Enhanced GPWC
(2) 1 - GND PROX Light - G/S INHB Switch/Light
(3) 1 - WINDSHEAR Light
(4) 1 - PULL UP Light
(5) 1 - Ground Proximity Test Switch
(6) 1 - Gear Override Switch(7) 1 - Flap Override Switch
The ground proximity warning computer (GPWC), or Enhanced GPWC, is located on the E1-5 rack in the main equipment center. The GPWC (or EGPWC) LRU is the main element of the Ground Proximity Warning System (GPWS).
The GPWC LRU front panel contains a toggle switch and an 8-character LED BITE display.Present status or flight history data shows on the BITE display when the toggle switch is selected.
The computer receives and processes input signals to determine the alert and warning mode conditions. It also generates the aural and visual alert and warning messages.
The computer continuously monitors the validity of input signals and internal functions. System failures detected are stored in a non-volatile memory.