Mark V and Mark VII EGPWS Pilot’s Guide
060-4241-000 System Description
Rev H, August 2011 11
The graph below shows how the upper boundary of the Mode
2 alert envelope varies as a function of the aircraft speed. As
airspeed increases from 220 knots to 310 knots, the boundary
expands to provide increased alert times at higher airspeeds.
With version -210-210 and later models, the Mode 2A upper
limit is reduced to 1250 feet (950 feet with version -218-218
and later) for all airspeeds when the Terrain Alerting and
Display (TAD) function is enabled and available. This is due
to the enhanced alerting capability provided with TAD,
resulting from high integrity GPS Altitude and Geometric
Altitude data. The Mode 2A envelope is lowered in order to
reduce the potential for nuisance alerts during an approach.
This modification allows EGPWS operation to be compatible
with RADAR vectoring minimum terrain clearances.
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