Page 17-14
Section III Sub-section 17
AVIONICS
P/N 140-590032-0007
Revision A4: Sep, 2010
Pilot’s Operating Manual
ENHANCED GROUND PROXIMITY WARNING SYSTEM (EGPWS) with WINDSHEAR
The EGPWS provides voice and visual predictive warnings to the flight crew alerting them to the
proximity of possible terrain hazards by presenting PULL UP and GND PROX annunciations on the
PFD, graphical representations of terrain and peaks elevation value on the PFD/MFD. The EGPWS also
provides Windshear Caution and Warning alerts. Alerts appear on the PFD, when commanded by the
EGPWS system, in addition to Mode and Fault annunciations when appropriate.
The Enhanced Ground Proximity Warning Computer (EGPWC) combines data input from the
Integrated Avionics Processor System (IAPS) and the Global Positioning System (GPS) into a flight
profile which is analyzed with regard to radio altitude. Depending on the flight mode, airspeed and
absolute altitude, the computer generates voice and visual cautions and warnings based on pre-
programmed values and airplane performance specifications.
The EGPWC receives inputs from the Angle of Attack (AOA) and Stick Shaker Margin with other
discrete inputs to calculate the minimum safe altitude. The EGPWC also has Envelope Modulation and
Aural Declutter. The Envelope Modulation is an automatic feature which tailors the operation of the
EGPWS at certain locations to reduce nuisance warnings and/or give added protection. The Aural
Declutter feature reduces the repetition of the warning messages.
EGPWS Features
The EGPWS system has 7 operating modes, all of which are controlled by switching logic based upon
radio altitude, airspeed, vertical speed, landing gear, flap position and terrain closure.
The EGPWC can detect and warn of both increasing and decreasing performance windshears and also
compute the Terrain Clearance Floor (TCF) when the airplane is on approach, using high resolution
terrain database grids.
The TCF is usually computed at 700 ft Above Ground Level (AGL) until the airplane is within 15 nautical
miles (nm) from the airport. The TCF then slopes over the next 3 nm from 700 ft AGL to 400 ft AGL.
This level extends from 12 nm to 4 nm from the airport. The TCF then slopes from 400 ft AGL to 0 ft to
let the airplane land. Adjacent to the runway the TCF alert envelope is limited to a minimum of 245 ft
AGL.
Reference Figures 6 and 7 for depictions of Terrain Clearance.
The Terrain Awareness Display (TAD) gives an image of the surrounding terrain on the Weather Radar
screen using green, yellow and red dots in differing densities. This display is generated by the EGPWC
which compares the terrain data to the position and altitude of the airplane, if no terrain data is available
the area is colored magenta.
When a "CAUTION TERRAIN" alert is generated, approximately 60 seconds before a potential conflict,
areas within ± 90° of the airplane track which enter the terrain caution envelope are shown as solid
yellow areas.
When a "TERRAIN TERRAIN PULL UP" warning is generated, approximately 30 seconds before a
potential conflict, areas of terrain within ± 90° of the airplane track which enter the terrain warning
envelope are shown as solid red areas.
