the signals from the selector-indicator, master
sensor, a pressure ratio limiter, and three airflow control
temperature sensor, duct rate sensor, ice-limiting
valves.
sensor, and pressure ratio limiter. These signals are
Air supplied from the ground-air connection or
used to position the three airflow control valves.
from the auxiliary ventilation system does not pass
The temperature controller is composed of four
through the air cycle cooling system, so the aircraft
modules: a programming amplifier module and three
temperature control system has no control of incoming
transistorized servo-amplifier modules. The pro-
air from these sources.
gramming amplifier contains the temperature control
Temperature control is achieved, either automati-
system automatic mode control circuitry. When
cally or manually, through the three modulating valves.
automatic mode is engaged, this module integrates the
These valves route supply air through the various
sensor signals with the selector-indicator command
cooling components to produce the desired output air
signal, and produces the appropriate command signals
temperature. The three airflow control valves are driven
for the three valve servo-amplifiers. In manual mode,
by servomotors that are controlled by servo-amplifiers.
the programming amplifier contributes nothing to
The airflow valve schedule is the same for both manual
system operation. The servo-amplifiers control the
and automatic modes of operation. The basic difference
operation of the airflow valves and are identified as
in operating modes is the method of applying sensing
valve A, B, and C servo-amplifiers. In manual mode,
control to the servo-amplifiers.
the servo-amplifiers respond to command signals from
the three potentiometers in the selector-indicator. In
Temperature Control System Selector-Indicator
automatic mode, command signals come from the
Air-conditioning system control input signals
programming amplifier module.
a r e s e l e c t e d w i t h t h e s e l e c t o r- i n d i c a t o r. T h e
selector-indicator contains a push-pull knob, a cursor at
Master Temperature Sensor
the edge of the indicator face, an indicator needle, and
A master temperature sensor is mounted in each
an indicator flag. Sets of dot markings, one-dot,
system exhaust air duct to sense cabin or flight station
two-dot, and three-dot, are on the indicator face to
air temperatures. The flight station master temperature
facilitate temperature or program selection.
sensor is in an exhaust duct above and aft of the pilot
The mode of operation is selected by moving the
position. The cabin temperature sensor is in the ex-
push-pull knob: push for manual operation, pull for
haust duct above the tactical coordinator (TACCO)
automatic. The indicator flag indicates which mode has
station.
been selected (MAN or AUTO). The system control
In automatic mode, the sensor senses the
voltage (manual) or operating temperature (automatic)
temperature within the aircraft. The heart of the sensor
is selected by rotating the push-pull knob, clockwise for
is the thermistor, whose electrical resistance varies
warmer, counterclockwise for cooler. This moves the
inversely with its temperature. The changes of
cursor at the edge of the instrument face to indicate the
resistance provide reference signals to the temperature
program position (automatic) or temperature selection
controller. The controller combines these signals with
(manual). The indicator needle in the center of the dial
the signals from the duct rate sensor and the
is the indicator of the voltmeter that is connected to the
selector-indicator, and produces a command signal.
temperature controller circuitry.
The command signal is used by the temperature
There are three potentiometers inside the
controller to regulate the temperature within the
selector-indicator assembly. In manual mode, each
aircraft, by positioning the airflow control valves.
potentiometer provides a command signal to each of
the three airflow control valves (valves A, B, and C) by
Duct Rate Sensor
way of the temperature controller. When an automatic
mode is selected, valve A potentiometer provides the
A duct rate sensor is installed in the duct upstream
temperature controller with the command signal for all
of each ice-limiting sensor. It senses the temperature
three airflow control valves.
output air from the air cycle cooling system and the hot
air bypass valve (valve C). In automatic mode, the duct
Temperature Controller
rate sensor signals are integrated with the master
temperature sensor and selector-indicator signals to
The temperature controller is the heart of the
regulate system temperature.
temperature control system. It receives and integrates
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