Mark V and Mark VII EGPWS Pilot’s Guide
System Description 060-4241-000
24 Rev H, August 2011
Mode 7 is designed to provide alerts if the aircraft encounters
windshear. Two alerting envelopes provide either a
Windshear Caution alert or a Windshear Warning alert each
with distinctive aural and visual indications to the flight crew.
EGPWS windshear is provided for certain (not all) aircraft
types and is a function of certain additionally required input
signals and enabled internal detection algorithms. These are
established during the initial installation and addressed in the
appropriate Airplane Flight Manual (AFM) or EGPWS
Airplane Flight Manual Supplement (AFMS).
Windshear
Caution
Windshear Caution alerts are given if an increasing headwind
(or decreasing tailwind) and/or a severe updraft exceeds the
defined threshold. These are characteristic of conditions
preceding an encounter with a microburst.
A Win
dshear Caution (if enabled) results in illumination of
amber Windshear Caution lights and may (if separately
enabled) also be accompanied by the aural message
“CAUTION, WINDSHEAR”. The lights remain on for as
long as the aircraft is exposed to conditions in excess of the
caution alert threshold. The Windshear Caution envelope is
illustrated in the figure below.
The Windshear Caution alerting can be disabled by EGPWS
program pin selection so that only Windshear Warning alerts
are provided.
Windshear Warning alerts are given if a decreasing headwind
(or increasing tailwind) and/or a severe downdraft exceeds the
defined threshold. These are characteristic of conditions
within or exiting an encounter with a microburst.
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