Embraer EMB145 Operation Manual page 1622

GROUND PROXIMITY WARNING SYSTEM
The purpose of the Ground Proximity Warning System (GPWS) is to
avoid accidents caused by Controlled Flight Into Terrain (CFIT) and
also severe windshear.
The GPWS is based on radio altitude ("look down") information. Some
airplanes may be optionally equipped with the Enhanced Ground
Proximity Warning System (EGPWS). The EGPWS incorporates
GPWS functions with additional features like Terrain Clearance Floor,
Terrain Look Ahead Alerting and Terrain Awareness Display. These
functions use airplane geographic position, airplane altitude and an
internal terrain database to predict potential conflicts between the
airplane's flight path and terrain, and to provide graphic displays of the
conflicting terrain.
NOTE: − Unless otherwise indicated, the system description below is
applicable to the GPWS and to the EGPWS.
− Airplanes equipped with EGPWS version 216 and on
incorporates additional features like Peaks Mode, Runway
Field Clearance Floor, Obstacle Alerting and Geometric
Altitude.
The GPWS/EGPWS is a useful navigation aids when flying at low
altitude, generally within 2500 ft above terrain. It provides voice
messages, EICAS message and PFD indication (EGPWS only) to alert
the flight crew, so that they may take appropriate action.
The GPWS/EGPWS interfaces with the followings systems and
equipment:
− Radio Altimeter - The radio altimeter provides altitude above ground,
how fast the altitude decreases as a result of airplane sinkage or
ground profile change and the validity signal.
− IC-600s - The IC-600s provide glideslope deviation, localizer
deviation, selected decision height, selected course, packed discrete
and selected terrain range.
− ADCs - The ADCs provide uncorrected barometric altitude, corrected
barometric altitude, computed airspeed, true airspeed, barometric
altitude rate and static air temperature.
− AHRSs/IRS - The AHRSs/IRS provide magnetic heading, pitch and
roll angle, longitudinal and normal acceleration.
REVISION 39
AIRPLANE
OPERATIONS
MANUAL
CREW
AWARENESS
Page
2-04-30 1
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01