Autoland Bus Isolation Schematics
Above 1500 ft:
The ASA upper window is inhibited.
The ASA lower window can indicate either
NO LAND 3
or
NO AUTOLAND
.
Both BTBs can operate.
The Bus Isolation Relay will isolate if at least one of the BTBs is open.
Between 1500 ft and 200 ft:
The ASA upper should indicate either
LAND 2
or
LAND 3
.
The ASA lower window is enabled.
Both BTBs can operate.
The Bus Isolation Relay will isolate if at least one of the BTBs is open, but will not latch until below 200 ft.
Below 200 ft:
The ASA cannot change, except to show
NO AUTOLAND
.
The Bus Isolation Relay is latched in its current position.
Only one BTB can close following a generator failure.
above 1500 ft
1500 - 200 ft
below 200 ft
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