Honeywell SPZ-8000 Maintenance Manual page 597

3. B. (8) (i) Pitch Autopilot Mode Flow (See
Figure
The Ditch autor.)ilot diaqram shows two
260, sheet 7.)
signal paths
for the
vert{cal command.
The ?irst path is with the-autopilot
disengaged and routes the vertical command to the symbol
generator for the PFD only. This path is discussed in
paragraph 3.B.(8)(i)l. The second path is with the autopilot
engaged, and routes the vertical command to both the symbol
generators for the PFD and to the elevator servo drive motor.
This path is discussed in paragraph 3.B.(8)(i)~.
When the autopilot is engaged and no vertical flight director
mode is selected, the system will automatically revert to the
basic autopilot mode of pitch attitude
hold. This is discussed
in paragraph 3.B. (8)(i)~. The go-around mode of operation is
discussed in paragraph 3.B.(8)(i)~.
~ Vertical
With the
vertical
Pitch
. Pitch
Steering Command With Autopilot Disengaged
autopilot disengaged, the selected flight director
command is routed through the following:
Rate Limiter
Limiter
. Go-Around Switch
. AP Engage Switch
Pitch Bar Bias Switch
The command is then routed to the symbol generators on the
ASCB.
Pitch bar bias (PBB) is a fixed voltage level used to bias
the vertical flight director command bar out of view to
prevent the pilot from flying invalid data. The vertical
command bar is biased out of view if:
No flight director mode is selected.
. The flight director is not valid.
Flight director valid is comprised of the following:
"A" CPU heartbeat monitor valid which provides validity
logic to engage/disengage the autopilot functions. The
heartbeat monitor is hardware independent from the CPU,
so that no single fault can disable both the CPU and the
monitor. The heartbeat monitor output is provided as an
interrupt to the nonmonitored processor.
Flight director flag/annunciator valid which is a direct
discrete output from the "A" CPU to drive the FD flag on
the EADI and enable the annunciator drivers in the same
side guidance controller channel.
22-14-00
Page 298.121
Aug 15/91
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