Honeywell SPZ-8000 Maintenance Manual page 572

Honeywell &!#%.cE
Outside the normal capture range of the localizer signal
(between one and two dots), pressing the LNAV button on the
GP-820 Flight Guidance Controller will cause the PFD to
annunciate:
LOC
in white.
HDG in green.
The aircraft is now flying the desired heading intercept and
the system is armed for automatic localizer beam capture.
With the aircraft approaching the selected course intercept,
the lateral beam sensor (LBS) is monitoring localizer beam
deviation, beam rate, and TAS. At the computed time, the LBS
will trip and capture the localizer signal. The flight
guidance computer now drops the heading select mode and
generates the proper
roll command to bank the aircraft toward
localizer beam center. When the LBS trips, the PFDwill
display LOC in green and it is boxed for 5 seconds to emphasize
that the capture phase has occurred.
As the aircraft continues toward localizer beam center, the
computer enters the LOC CAP 2 submode. With the aircraft
almost lined up on localizer beam center, the computer will
automatically change to the LOC TRACK 1 and the LOC TRACK 2
submodes. The LOC CAP 2 and LOC TRACK submodes provide tighter
control law programming on the localizer signal to better
maintain a truer flightpath along the localizer beam. There
are no visual indications in the cockpit that these submodes
have occurred.
When the course select pointer was set on the PFD using the
course knob on the GP-820 Flight Guidance Controller, the
course select error signal was established. This signal
represents the difference between actual aircraft heading and
desired aircraft course.
The course select error signal is routed from the DC-884
Display Controller to the FZ-820 Flight Guidance Computer and
the SG-884 Symbol Generator through the avionics standard
communications bus (ASCB).
Next,
the course error signal is TAS.(true airspeed) gain
programmed. TAS gain programming is performed to achieve
approximately the same aircraft response for a given command,
regardless of the aircraft's altitude and airspeed. The TAS
computation is derived from airspeed and barometric altitude
information provided by the AZ-81O Digital Air Data Computer
through the ASCB.
After being TAS gain programmed, the course
error signal is summed with radio deviation information.
22-14-00
Page 298.92
Aug 15/91
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