777 AIRCRAFT MAINTENANCE MANUAL
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
GPWS -INTRODUCTION
Purpose
The purpose of the ground proximity warning system (GPWS) is to alert the flight crew of an unsafe condition when near the terrain. It also supplies a warning for windshear conditions.
Description
The GPWS uses aural messages, lights, and displays to give alerts and warnings in the flight deck.
GPWS Modes
These are the GPWS modes:
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Mode 1 -Large descent rate
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Mode 2 -Too much of a closure rate when approaching terrain that is rising
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Mode 3 -Too much altitude loss during climbout (at takeoff or in go-around) when not in landing configuration
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Mode 4 -Not enough terrain clearance when the airplane is not in landing configuration
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Mode 5 -Too much deviation below the glideslope centerline
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Mode 6 -Aural callouts when descending through selected radio altitudes
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Mode 7 -Warning for windshear conditions.
The GPWS also alerts the flight crew to early descent on approach, or to terrain threats ahead of the airplane.
Abbreviations and Acronyms
* AOA -angle of attack
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BITE -built-in test equipment
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EFIS -electronic flight instrument system
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FMC -flight management computer
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GPS -global positioning system
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GPWC -ground proximity warning computer
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GPWS -ground proximity warning system
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IVS -inertial vertical speed
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LED -light emitting diode
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MAT -maintenance access terminal
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MMR -multi-mode receiver
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MWL -master warning light
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ND -navigation display * ovrd -override
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PCMCIA -personal Computer Memory Card International Association
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PFD -primary flight display
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PWS -predictive windshear
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RA -radio altitude
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RT -receiver-transmitter
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TCAS -traffic alert and collision avoidance system
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TCF -terrain clearance floor
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WEU -warning electronic unit
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WES -warning electronic system
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WXR -weather radar
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GPWS -INTRODUCTION
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GPWS -GENERAL DESCRIPTION
General Description
The main component of the ground proximty warning system (GPWS) is the ground proximity warning computer (GPWC). It uses inputs from other systems to determine if an unsafe condition is present and then gives the proper annunciations.
The GPWS displays terrain forward of the airplane, and also alerts the flight crew of early descent when landing.
Visual annunciations show on these places:
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Primary flight displays (PFDs)
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Navigation displays (NDs)
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GND PROX light
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Master warning lights.
Aural annunciations come from the aural warning speakers.
The GPWC sends terrain data to the airplane information management system (AIMS) cabinets to show on the NDs.
These components control GPWS:
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Electronic flight instrument system (EFIS) control panels (CPs)
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Control display units (CDUs)
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Glideslope inhibit switch
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Override switches.
The program pins selects options available for the GPWC.
The GPWC sends discretes to the weather radar (WXR) system and to the traffic alert and collision avoidance system (TCAS).
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GPWS -GENERAL DESCRIPTION
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GPWS -FLIGHT DECK COMPONENT LOCATIONS
GPWS Component Locations
These are the GPWS components in the flight deck:
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Ground proximity glideslope inhibit switch and ground proximity light
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Ground proximity gear override switch
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Terrain override switch
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Ground proximity flap override switch.
Other Systems Component Locations
These are the components in the flight deck that have an interface with the GPWS:
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Left and right aural warning speakers
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