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MK XXII EGPWS Installation Manual
CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 060-4314-225 REV: C
SHEET
99
3.3.13.9 Terrain Awareness Inhibit
The Terrain Awareness inhibit discrete, inhibits the Terrain Awareness modes in the MK XXII
EGPWS.
This discrete is typically connected to an “alternate action switch” in the cockpit. The
recommended label for this switch is “Terrain Override” although labeling for this switch should be
consistent with existing cockpit nomenclature.
“Terrain Inhibited” will be annunciated during cockpit Self-Test if these functions are inhibited.
Discrete Position / Status Connector Pin
TA Inhibit Inhibit = Gnd
Not Inhibit = Open
J1-12
3.3.13.10 Self Test Discrete
The cockpit Self Test discrete is provided to manually initiate test of the EGPWC, EGPWS aircraft
interface, and to annunciate system configuration and status information. This discrete is typically
supplied by a momentary action cockpit ‘push to test’ switch, typically part of the GPWS WARN
Lamp assembly.
This discrete must be momentarily connected to ground to activate the Self Test. Activation of
this discrete continuously for more than 60 seconds will result in the ‘Self Test Invalid’ fault which
will cause a GPWS INOP indication.
Discrete Position / Status Connector Pin
Self Test Self Test = Gnd
Normal = Open
J1-34
3.3.13.11 Glideslope Inhibit Discrete
The Glideslope Inhibit Discrete, also known as the Backcourse Inhibit, provides an inhibit to the
Glideslope alert when on a backcourse approach.
The Glideslope Inhibit is usually connected to the Flight Director or FMS backcourse discrete
output.
Discrete Position / Status Connector Pin
Glideslope Inhibit +28 Inhibit = +28V
Not Inhibit = Gnd/Open
J1-38
Glideslope Inhibit Gnd Inhibit = Gnd
Not Inhibit = +28V /Open
J1-19