Honeywell SPZ-8000 - Flight Director Mode Selection

Honeywell ##@R.cE
3. B. (3) Flight Director Mode Selection (See Figure 255.)
There are nine mode select pushbutton switches located on the GP-820
Flight Guidance Controller as shown on sheet 1. When one of these
switches is pushed, a ground (PB ARM) is
provided at llJ1-38 to the
FZ-820 to interrupt the “A” processor. Also, when a switch is
pushed, the ground to the GP-820
PISO is removed and 5 volts is
applied to the parallel input of the
PISO. The clock and strobe for
the PISO is
received from the FZ-820.
The pushbutton serial data
output from the PISO device is routed to the SIPO device of the
FZ-820 which provides a parallel output to the “A” processor. A
signal representing the mode selected is provided on the ASCB to the
symbol generator to annunciate the mode selected on the PFD.
Figure 255, sheets 2 through 15, show the logic conditions required
to annunciate each mode and also the conditions that will reset or
clear a selected mode.
For example, VOR ARM (sheet 2) is
annunciated on the PFD when the LNAV switch is pushed on the GP-820
and the following conditions are met:
. Tuned to VOR frequency (NAV VOR Select)
. Not tuned to localizer (~)
. Lateral beam sensor has not tripped (LBS TRIP)
. All inputs to the OR gate to clear (CLR) or reset (R) the
flip-flop are not present.
If VOR is annunciated in white indicating the mode is armed, the
mode will be reset if any of the following inputs are present to the
“OR” gate to reset (R) the flip-flop:
;tR CAP 1
PFD CMD SEL
NAV SOURCE CHANGE
TKOD
● AP ENG
Also, the mode will be cleared if any of the following inputs are
present the OR gate to clear (CLR) the flip-flop:
. Flight guidance computer valid not present (FGC VALID)
. Inertial reference system miscompare and inertial reference
system No. 3 valid not present (IRS MISCOMPARE
● IRS 3 VALID)
. Selected di ital air data computer valid not present
(SDADC VALI;)
. Tuned to a localizer frequency (TTL)
● CPL valid not present for two seconds (CPL VALID ● 2 SEC)
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Aug 15/91
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