Ground Proximity Warning Computer Function
Figure 3 (Sheet 1)
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MAINTENANCE MANUAL
EGPWC
Ground Proximity Warning Computer Function Figure 3 (Sheet 2)
M48748
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4) Inertial Reference System
The GPWS uses latitude, longitude, inertial altitude, inertial vertical speed, track angle magnetic, pitch attitude, roll attitude, body longitudinal acceleration, body normal acceleration, inertial vertical acceleration, pitch rate, ground speed, true track, true heading, and IRU mode data from the Inertial Reference System.
5) Instrument Landing System (ILS) or ILS Multi-Mode Receiver (MMR)
The GPWS uses glideslope deviation, localizer deviation,
and selected runway heading data from the ILS or the MMR.
6) Radio Altimeter System
The GPWS uses radio altitude data from the Radio Altimeter System.
7) Stall Warning System
The GPWS uses indicated angle of attack, corrected angle of attack, flap position, stick shaker angle of attack, and minimum operating speed data from the Stall Warning System.
8) Global Positioning System (GPS)
The EGPWS uses latitude, longitude, latitude fine, longitude fine, altitude, vertical velocity, HDOP, VDOP, VFOM, HFOM, sensor status-NISF, date, UTC-time, ground speed, true track, and HIL data from the GPS, if GPS is installed and interfaced with the EGPWC.
9) Weather Radar System
The EGPWS uses status word data (predictive windshear alerts, onside/offside WXR data) from the Weather Radar System (WXR), if the WXR data input bus is connected.
(d) The following discrete signals are used in the computer logic for the warning and alerting modes:
Gear Override Switch
Flap Override Switch
Terrain Override Switch
G/S Inhibit Light/Switch
Air/Ground System
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(e)
(f)
(g)
(h)
(i)
(j)
(k)
(l)
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MAINTENANCE MANUAL
The Override switches and the Glideslope Inhibit light/switch
are used to inhibit GPWC warnings during non-normal flight
procedures. The GPWC uses the Air/Ground discrete to identify
if the airplane is in the air or on the ground.
The EGPWC also uses terrain/weather radar display bus switching
relay monitor discretes to determine if the actual position of
the terrain display relays differs from the commanded position.
The GPWC sends long-range (>120 nm) and short-range (<120 nm)
tilt values to the weather radar system.
ARINC 429 outputs are provided to the Integrated Display System
(IDS) for use by the following systems or LRUs:
EFIS/EICAS Interface Units (EIUs)
Digital Flight Data Acquisition Unit (DFDAU)
GPWS alerts and failures are used for alerting/advisory messages to the flight crew and are recorded by the Flight Data Recorder.The Enhanced GPWS provides ARINC 453 (terrain display) outputs to the EIUs.
The terrain display data is first sent to the terrain switching relays. The weather radar display data is also sent to the terrain switching relays. The WXR display data or the terrain data is then switched and provided to the the display system for display on the captain's and first officer's NDs.
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