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A
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MAINTENANCE MANUAL

 2.  Component Details (Fig. 1)_________________
 A. Ground Proximity Warning Computer
 (1)  
The enhanced ground proximity warning computer (EGPWC) is located on the E1-4 rack in the main equipment center. The EGPWC LRU is the main element of the Enhanced Ground Proximity Warning System (EGPWS). The LRU frontpanel contains three EGPWC status indicator LEDs that light to show internal or external EGPWS failures. The front panel also contains a self test switch. Pressing this switch provides access to the EGPWC self test modes, the present faults, and the fault history. The faults are annunciated through the flight deck speakers or through headphones connected to the jack located below the switch. The EGPWC front panel also has a PCMCIA interface that can be used to upload program and terrain database updates and download fault history data. There are four status LEDs to show the progress of the memory card data transfer. The EGPWC has a front panel 15-pin, D-type portable PC test connector to allow a serial data connection (RS-232) to a PC-compatible computer.

 The EGPWC operational software and terrain database may be updated using a PC card inserted into the front panel PCMCIA interface slot. Once the card is inserted, the EGPWC will automatically download data and update software without further user intervention. The data on the card is protected by checksums to ensure data integrity.

 (2)  
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.
 B. Override Switches
 (1)  The GND PROX FLAP OVRD switch is used to inhibit the Mode 4 caution message. The switch provides an open or ground discrete to the GPWC. Open indicates normal flap operation; ground indicates a flap inhibit to the GPWC. The inhibit signal is generated by pressing the switch. The switch illuminates when pressed.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

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MAINTENANCE MANUAL

 (2)  
The GND PROX GEAR OVRD switch is used to inhibit the Mode 4 caution message. The switch provides an open or ground discrete to the GPWC. Open indicates normal gear operation; ground indicates a gear inhibit to the GPWC. The inhibit signal is generated by pressing the switch. The switch illuminates when pressed.

 (3)  
The GND PROX TERR OVRD switch is used to inhibit Terrain Clearance Floor (TCF) and Terrain Awareness Alerting and Display (TAAD) at the same time. The switch provides an open or ground discrete to the EGPWC. Open indicates normal TAAD and TCF operation; ground indicates a TAAD and TCF inhibit to the EGPWC. The inhibit signal is generated by pressing the switch. The switch illuminates when pressed. This switch does NOT inhibit Modes 1 - 7.

 C. PULL UP Warning Indication
 (1)  The red ground proximity warning PULL UP message shows on the Captain's and First Officer's PFDs. The message shows when a PULL UP warning occurs.
 D. WINDSHEAR Warning Indication
 (1)  The red ground proximity warning WINDSHEAR message shows on the Captain's and First Officer's PFDs. The message shows when a Mode 7 WINDSHEAR warning occurs.
 E. GND PROX Light-G/S INHB Light/Switch
 (1)  The amber GND PROX advisory light/G/S INHB light/switch provides a momentary contact to ground and an amber light. The momentary contact to ground provides the Mode 5 glideslope inhibit discrete to the GPWC. The GND PROX light illuminates when there is a GPWS alert condition. The mode 5 caution may be inhibited by pressing the light/switch provided the advisory condition has not already occurred.
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