Relay K4 is energized by the trim engage logic from AND
gate “C”.
The processor valid and servo power enable inputs
are partitioned between the A and B processors through AND
gates “D” and “E”.
The trim enable is output from the
A processor only through AND gate “B”. The trim engage command
input can be from the M/T pushbutton or autopilot engagement.
Trim engagement returns to the engage status that existed prior
to AP engagement.
AP servo power is also input to AND gate
“C” through the K1 relay.
Relay K3 is energized by the YD engage logic from AND gate “G”.
The processor valid and servo power enable inputs are
partitioned between the A and B processors. AND gate “D”
derives the servo power enable input from the A and B
processor. Servo power enable and the processor valid output
from AND gate “E” is derived from the internal power supply
monitors, the A and B heartbeat monitors, and processor valids.
The YD drive enable is output from the B processor only. YD
engage can be reset by deselecting YD or by the pilot or
copilot YD disconnect inputs to the FGC.
Relay K2 is energized by the output from AND gate “J”. The
autopilot cannot be engaged unless the yaw damper is engaged,
thus AND gate “J” needs the engage logic from AND gate “G” (yaw
damper) and gate “F” (autopilot). Again, servo power enable
and processor valid are partitioned between both processors
thru AND gates “D” and “E”.
The AP drive enable is output from
the B processor only. The autopilot cannot be engaged if the
weight-on-wheels or stick shaker discrete inputs into the FGC
are active. AP engage can be reset by deselecting AP, use of
the pilot or copilot take-off/go-around (TOGA) switches, the
pilot or copilot AP disconnect switches, or the pilot or
copilot electric trim switches.
3. B. (4) (c) Servo Power Enable Control
The purpose of the servo power control relay (relay Kl) is to
provide servo clutch power to the servo engage relays
(relays K2, K3, and K4) to provide an alternate method of servo
disengagement, and to provide cross-channel status validation
logic (relay-off crossfeeds).
The servo clutch power is controlled by both processors via
their respective servo power enable discrete outputs. The
hardware heartbeat and power supply must also be valid before
the servo clutch power can be enabled.
Relay K1 must be energized before the autopilot, yaw damper, or
trim can be engaged via relays K2, K3, and K4. Relays K2, K3,
and K4 are used for all normal engagements and disengagements
of the AP, YD, or trim. Relay K1 is used for all abnormal
disconnects.
Whenever any failures are detected, relay K1 is
22-14-00
Page 298.74
Aug 15/91
Use or disclosure of information on this page is subject to the restrictions on the tnle page of thm document.
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