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060-4314-000 • Rev. C - May 2004
38
MK VI & MK VIII EGPWS Pilot Guide
TCF/TAD
INOP and
INHIBIT
Geometric
Altitude
The EGPWS TCF and TAD functions are available when all re-
quired data is present and acceptable. Aircraft position and
numerous other parameters are monitored and verified for
adequacy in order to perform these functions. If determined
invalid or unavailable, the system will display Terrain inoperative
or unavailable annunciations and discontinue the terrain display
if active.
TAD/TCF functions may be inhibited by manual selection of a
cockpit Terrain Inhibit switch. Neither loss nor inhibiting TAD/
TCF affects the basic GPWS functions (modes 1–6).
If Peaks Display is not enabled and TAD becomes unavailable
due to position error; terrain inoperative or unavailable is not
indicated when the aircraft is greater than 8000 feet above the
highest terrain or obstacle within the loaded terrain database
(area in use). If indicated below the 8000 foot threshold, it is ex-
tinguished when the aircraft climbs above, and is again displayed
once the aircraft descends below the 8000 foot threshold. This
eliminates potentially long-term illumination of terrain
inoperative or not available during the high enroute phase of
flight.
Based on GPS Altitude, Geometric Altitude is a computed pseudo-
barometric altitude Above Sea Level (ASL) designed to reduce
or eliminate errors potentially induced in Corrected Barometric
Altitude by temperature extremes, nonstandard pressure altitude
conditions, and altimeter miss-sets. This ensures an optimal
EGPWS Terrain display and alerting capability. Geometric Altitude
also allows continuous EGPWS operations in QFE environments
without custom inputs or special operational procedures.
Geometric Altitude requires a MSL based GPS Altitude
input with its associated Vertical Figure Of Merit (VFOM) and
Receiver Autonomous Integrity Monitoring (RAIM) failure indica-
tion, standard (uncorrected) altitude,
Radio Altitude, Ground Speed, Roll Angle, and aircraft
position (Latitude and Longitude). Additionally, corrected
Barometric Altitude, Static Air Temperature (SAT), GPS mode, and
the number of satellites tracked are used if available.
Содержание MK VI
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