787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Warning Systems -
System Description
Copyright © The Boeing Company. See title page for details.
15.20.22 D615Z003-TBC
The EICAS advisory message TCAS is displayed if TCAS cannot display TCAS
RA guidance on either PFD, and cannot display TCAS traffic symbols on the NDs
or mini-maps. TCAS voice alerts do not occur. An amber TCAS FAIL message is
displayed on the NDs and mini-maps.
Ground Proximity Warning System (GPWS)
Introduction
GPWS provides immediate alerts, and look-ahead obstacle and terrain alerts for
potentially hazardous flight conditions involving imminent impact with the
obstacles and the ground.
GPWS immediate alerts are based on radio altitude, barometric altitude, ADRS,
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
[Option – Bank angle callouts]
GPWS provides bank angle voice annunciations and altitude voice annunciations
during approach.
GPWS also provides look-ahead terrain mode alerts by monitoring obstacle and
terrain proximity using a world-wide terrain database and an obstacle database.
The obstacle database is not yet world wide. Proximate obstacle and terrain data
may be displayed on the NDs and mini-maps. If there is a potential obstacle or
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 groundspeed. FMC VNAV and LNAV path is not
considered in the estimated time to impact.
Note: Obstacles or terrain ahead of the airplane may exceed available climb
performance. A GPWS caution or warning does not guarantee obstacle or
terrain clearance.
August 14, 2009
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