Performance (Autothrottle)Computer; Autothrottle System Description - Honeywell SPZ-8000 Maintenance Manual

4. c. (3) Autothrottle System Description
Each PZ-800 Performance Computer contains an input/output card, an
autothrottle card, and a servo card. Two PZ-800 Performance
Computers are included
for redundancy; however,
only one computer
controls both throttles when selected.
The PZ-800 processes inputs
from many different sources. The primary interface is the ASCB.
This high-speed bidirectional
bus supplies a wealth of information
from the
rest
of the SPZ-8000 Digital Automatic Flight Control
System (AFCS). Other interfaces include hardwired aircraft
discretes, analog input/output for servo control, and RS-232 for
test and debug.
The GP-820 Flight Guidance Controller is centrally located on the
glareshield and is
used to control both the autopilot and the
autothrottle. An
A/T ARM pushbutton is provided to enable the
autothrottle system. Speed and altitude selections are tied
directly
to the AFCS and passed to the autothrottle via
ASCB.
Likewise, several flight guidance mode selections are available;
these are also relayed to the autothrottle by the AFCS.
This
ensures that autothrottle control modes are always coordinated with
AFCS modes. Speed selection can be made
in terms of calibrated
airspeed or
Mach number, or
if FMS mode is active, the speed command
is determined by the flight management system and displayed
in the
same window on the GP-820 Flight Guidance Controller.
In addition to the arm button on the GP-820 Flight Guidance
Controller, there are several cockpit switches which directly affect
autothrottle operation. Engage/disengage, positive-disconnect, and
takeoff/go-around switches are located on the throttles.
The
positive disconnect switch provides a direct-to-hardware means for
disengaging the autothrottle servos. The takeoff/go-around button
is used to select takeoff on the ground or go-around mode
in the
air. Engine synchronization switches (overhead panel) select engine
synchronization and the
engine parameter to be equalized.
The autothrottle uses information broadcast on ASCB by the FZ-820
Flight Guidance Computer and other systems. The other systems
include DC-884 Display Controllers, Inertial Reference Systems,
AZ-81O Digital Air Data Computers, NZ-920 Navigation Computers,
PZ-800 Performance Computers, DA-884 Data Acquisition Units, and
FC-880 Fault Warning Computers.
Display controllers (DC) are located to the left and right of the
flight guidance controller on the glareshield; engine limits
selected on the DC are used by the autothrottle. Inertial reference
systems (IRS) provide acceleration measurements, as well as certain
aircraft parameters (e.g., pitch angle, roll angle). Digital air
data computers
(DADC) supply altitude, temperature, and airspeed
data, as well as flap position and V~O values. Navigation and
performance computers optimize aircraft performance and can be
coupled to the autothrottle (and AFCS)
for automatic flight. Data
acquisition units relay important engine data and aircraft
discretes. Fault warning computers interface with the autothrottle
to log faults and run ground maintenance tests.
22-14-00
Page 298.179
Apr 15/93
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