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787 Flight Crew Operations Manual
Warning Systems -
System Description
15.20.20 Boeing Proprietary
The EICAS advisory message TCAS is displayed if TCAS cannot display TCAS
RA guidance on either PFD, and cannot display TCAS traffic symbols on either
ND. TCAS voice alerts will not occur. An amber TCAS FAIL message is
displayed on both NDs.
Ground Proximity Warning System (GPWS)
Introduction
GPWS provides immediate alerts and look-ahead terrain alerts for potentially
hazardous flight conditions involving imminent impact with the ground.
GPWS immediate alerts are based on radio altitude, barometric altitude, ADIRS,
glideslope deviation, and airplane configuration. GPWS alerts are provided for:
• altitude loss after takeoff or go-around
• excessive and severe descent rate
• excessive terrain closing rate
• unsafe terrain clearance when not in the landing configuration
• excessive deviation below ILS glideslope
• windshear
GPWS provides bank angle voice annunciations and altitude voice annunciations
during approach.
GPWS also provides look-ahead terrain mode alerts by monitoring terrain
proximity using a world-wide terrain database. Proximate terrain data may be
displayed on the ND. If there is a potential terrain hazard, GPWS look-ahead alerts
are provided based on estimated time to impact.
Altitude used for look-ahead terrain mode alerts are a weighted combination of
radio altitude, barometric altitude, GPS, and previous flight path. Weighting is
reduced for an altitude source which becomes less reliable.
Estimated time to impact is based on airplane position, barometric altitude,
present track, vertical path, and ground speed. FMC VNAV and LNAV path is not
considered in the estimated time to impact.
Note: Terrain ahead of the airplane may exceed available climb performance. A
GPWS caution or warning does not guarantee terrain clearance.
787 Flight Crew Operations Manual
Warning Systems -
System Description
Boeing Proprietary 15.20.21
GPWS Look–Ahead Terrain Mode
The GPWS terrain database contains detailed terrain data near major airports, and
data in lesser detail for areas between airports. Terrain within 2,000 feet of
airplane altitude is displayed on the navigation display. Terrain data is not
designed to be an independent navigation aid.
Note: The GPWS terrain database, GPWS look-ahead terrain alerts, and terrain
display do not account for man-made obstructions.
The terrain display is correlated to GPS position, or to IRS position if GPS
position is intermittently unavailable.
Terrain and weather radar cannot be simultaneously displayed on the ND. When
one pilot selects terrain and the other pilot selects weather radar, each display
updates on alternating sweeps.
GPWS Look-Ahead Alerts
Voice
Annunciation
Visual
Indications Description
CAUTION
OBSTACLE
Master CAUTION
lights
Amber CAUTION
OBSTACLE
EICAS message
Amber
OBSTACLE on
both NDs and
Mini-map
40 to 60 seconds from projected impact with
obstacle.
Toggling the TERR OVRD switch to OVRD
on the GPWS page of the TCP inhibits the
alert.
TERRAIN
TERRAIN
PULL UP
PULL UP message
on both PFDs
Master WARNING
lights
Red TERRAIN
message on both
NDs
Solid red terrain on
ND
20 to 30 seconds from projected impact with
terrain.
Toggling the TERR OVRD switch to OVRD
on the GPWS page of the TCP inhibits the
alert.
CAUTION
TERRAIN
Amber TERRAIN
message on both
NDs
Solid amber terrain
on ND
40 to 60 seconds from projected impact with
terrain.
Toggling the TERR OVRD switch to OVRD
on the GPWS page of the TCP inhibits the
alert.
787 Flight Crew Operations Manual
Warning Systems -
System Description
15.20.22 Boeing Proprietary
GPWS Immediate Alerts
Voice
Annunciation
Visual
Indications Description
TOO LOW,
TERRAIN
Amber TOO LOW
TERRAIN on both
PFDs
Descent below safe altitude while too far
from any airport in the terrain database.
Toggling the TERR OVRD switch to OVRD
on the GPWS page of the TCP inhibits the
alert.
Voice
Annunciation
Visual
Indications Description
DON’T SINK Master CAUTION
light
Amber DON’T
SINK EICAS
message
Amber DON’T
SINK on both
PFDs
DON’T SINK on
both HUDs
Altitude loss with flaps and/or gear up after
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787机组操作手册Flight Crew Operations Manual 3(124)
