Mark V and Mark VII EGPWS Pilot’s Guide
060-4241-000 System Description
Rev H, August 2011 9
Continued
Glideslope
Deviation
Bias
If a valid ILS Glideslope front course is received and the
aircraft is above the glideslope centerline, the outer (sinkrate)
boundary is adjusted to desensitize the sinkrate alerting. This
is to prevent unwanted alerts when the aircraft is safely
capturing the glideslope (or repositioning to the centerline)
from above the beam.
If the Aural Declutter feature is disabled, the Sinkrate alert
boundary remains fixed and the aural message “SINKRATE”
repeats continuously until the outer boundary is exited.
Through Envelope Modulation, both boundaries can be biased
to the right at certain airports to minimize nuisance alerts or
warnings.
The EGPWS offers a Steep Approach option for given aircraft
types that desensitizes the alert boundaries to permit steeper
than normal approaches without unwanted alerts. If Steep
Approach is selected (active) then the cockpit self-test is
inhibited if the aircraft is on the ground.
For Airbus A318/319/320/321 with version -226-226/-003 or
later, when Steep Approach is active
below 130 ft and no other Mode 1 bias functions are allowed
to operate (Envelope Modulation or above the beam
Glideslope bias).
Excessive
Closure to
Terrain
Mode 2 provides alerts to help protect the aircraft from
impacting the ground when rapidly rising terrain with respect
to the aircraft is detected. Mode 2 is based on Radio Altitude
and on how rapidly Radio Altitude is decreasing (closure
rate). Mode 2 exists in two forms, 2A and 2B.
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