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EGPWS LINE MAINTENANCE MANUAL
CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO.: 060-4199-180 REV: G SHEET 38 of 68
3.8.1 ARINC 552 / ALT 55 RADIO ALTITUDE VALIDITY FLAG DISCRETES
Three Radio Altitude validity flags may be used by the EGPWS, one for each of the three possible ARINC 552 or
ALT 55 Radio Altimeters inputs.
Type Validity from ARINC 552 or ALT 55 Radio Altimeter.
Signal Status: Valid or Invalid
Level 6 Audio readout
Radio Altitude Validity Discrete #1
Valid =>
Invalid =>
“Radio Altimeter 1 Valid”
“Radio Altimeter 1 Invalid”
Radio Altitude Validity Discrete #2
Valid =>
Invalid =>
“Radio Altimeter 2 Valid”
“Radio Altimeter 2 Invalid”
Radio Altitude Validity Discrete #3
Valid =>
Invalid =>
“Radio Altimeter 3 Valid”
“Radio Altimeter 3 Invalid”
3.8.2 GND LANDING GEAR DISCRETE
Type Supplied by landing gear or landing gear selector handle position-sensitive switch. This input can
be paralleled with, or used exclusively by a Gear Override Switch if an alternate source of Gear
Position is used.
Signal Status: Landing Gear Down or Landing Gear Up
Fault monitoring: Indication of landing gear selected for more than 60 seconds at airspeeds above 290 knots will
result in a gear switch fault which will cause a GPWS INOP indication.
Note: This can be caused either by a gear switch fault or by the Gear Override switch being left in the on position.
Level 6 Audio readout
Landing Gear Discrete
or Gear Override
Selected =>
Not Selected =>
“Landing Gear Down”
“Landing Gear Up”
3.8.3 +28V LANDING GEAR DISCRETE
Type Supplied by landing gear or landing gear selector handle position-sensitive switch. This input can
be paralleled with, or used exclusively by a Gear Override Switch if an alternate source of Gear
Position is used.
Signal Status: Landing Gear Down or Landing Gear Up
Fault monitoring: Indication of landing gear selected for more than 60 seconds at airspeeds above 290 knots will
result in a gear switch fault which will cause a GPWS INOP indication.
Note: This can be caused either by a gear switch fault or by the Gear Override switch being left in the on position.
Level 6 Audio readout
+28 V Landing Gear Discrete
or Gear Override
Selected =>
Not Selected =>
“28V Landing Gear Down”
“28V Landing Gear Up”