Douglas DC-8 SIXTY Series Maintenance Manual

OOUQLAS
AlltCU1FT
CO., INC:.
DC-B s,xrY /SERIES
HiAINTENANC~ MANUAL
AUTO THRO'rl'LE - DESCRll'TION
}Jill
OPIBA'l'ION
1. ~cription
A, The auto throttle system pr'Q'tides the meano for o.utomaticnlly controlling
the engine throttlea during npproach/lo.nding procedures, The systell'I
functiorw as an independent systcrn util!xing a reference signal output
f'roro a speed co=nd compute!.'. Although the speed command computer is not
a part of the auto throttle control system, it is required for system
operation.
J).
The
system is comprised of an auto throttle lever,
a
computer with control
and interlock circuits, linear accelerometer, servo drive unit (servo
drive and sear box), throttle levers drive clutch, engage switch, dis-
engage solenoid, quick•disconnect buttons, and an auto throttle off
warning light {see Figures l and lA).
c.
computer
{l) The auto throttle computer contains the electronic circuits required
t.o
process the referen'.e signal from the speed COll!m(lnd computer and
generate the electrical out1mt to conrna.nd servo drive movement, The
computer also provide" minor loop ,-,to.bilization, eil:cuit interlock
functions, throttle logic circuit f'uncU.ons, and warning li{l:ht
functions.
(2) The control and interlock circuits monitor servo drive co:r.mand signals
for system operation within safe maneuver boundaries. Throttle po,;dtion
sensing, through the mnximtun and minimUJn authority switches, is used
to prevent the servo system from driving the throttles into resions of
excessively high or
low
engine thrust operation.
(3) Nonitoring within the computer includes comparison of eo;iw.and signal
input 11ith tachometer feedback. System engage logic ia interrupted
when
any
malfunction is detected, thus disengaging the system.
(4)
The i'ront panel self-test assembly includes a meter and selector
switch f'or testing
all
system components.
D.
Servo Drive System
(1)
The servo drive system includes the servo drive and the ail'pla.ne
gearpack unit located at tl1e fo:r;iard end of' the pilot's control pedes-
~al
in
the flight compartment. '.I.he servo drive includes motor, rate
generator, and reduction ecars. '!.'he airplane geari,ack includes a
reduction gear train and chain sprocket.
Oct 15/67
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