pump, a ram air valve, a ground cooling fan, a
coolant filter, a low-pressure sensor, a high-
temperature sensor, a coolant temperature
sensor, and an airflow valve.
Liquid-To-Air Heat Exchanger
The liquid-to-air heat exchanger extracts heat
from the liquid coolant that flows through the two
pass counter flow channels within the heat
exchanger. A single-pass air circuit dissipates heat
extracted by the heat exchanger. A thermostatic
temperature control valve, mounted in the
inlet/outlet manifold of the heat exchanger and
set in parallel with the heat exchanger core, senses
coolant temperature. The control valve mixes
bypass and core fluid to maintain a delivery
temperature of 80° to 90°F (27° to 32 °C) to the
radar transmitter. In the cold position (bypass
valve fully closed), a bleed flow of 0.05 to 0.10
gpm is provided to aid in purging the core
during system servicing.
Liquid Coolant Pump
The liquid coolant pump assembly is a self-
priming, submerged, centrifugal pump with a
cylindrical two-section reservoir and a fill level
gauging mechanism. Air bleeding of the reservoir
is done by manually actuating a bleed valve
connected to the reservoir. The guaging
mechanism in the pump unit combines inputs
from coolant temperature and reservoir piston
position to change a fluid level indicator
on the service panel and supply a signal to
the Digital Display Indicator to latch a fluid low
code.
Ram Air Valve
An actuator opens and closes the ram air
valve. The motor is switched off at the end of each
stroke by internal limit switches, which also set
up circuitry to reverse actuator travel upon the
next power application. The actuator drives the
valve closed when a ground is supplied through
either a weight on wheels relay or the air data
computer when ram air is hot. The actuator drives
the valve open when both grounds are lost. A
failure in the actuator operation causes a weapons
system fail code to latch in the Digital Display
Indicator in the nosewheel well.
Ground Cooling Fan
The ground cooling fan is electrically powered
and supplies a flow of ambient air for heat
transfer from the liquid cooling heat exchanger
during aircraft ground operations.
Coolant System Filter
Coolant is filtered before passing through the
radar transmitter. When the replaceable filter
element is contaminated, resulting differential
pressure will extend a manually reset indicator
on the filter assembly, providing a visual
contamination indication.
Low-Pressure Sensor
The low-pressure sensor located in the coolant
line provides a ground to the maintenance status
display and recording system until coolant
pressure falls below preset limits. The loss of
ground causes a weapon system fail code to latch
in the Digital Display Indicator.
High-Temperature Sensor
The coolant high-temperature sensor, located
in the coolant line, provides a ground to the
maintenance status display and recording system
until coolant temperature rises above preset limits.
The loss of ground causes a weapon system fail
code to latch in the digital display indicator in the
nosewheel well.
Coolant Temperature Sensor
The coolant temperature sensor located in the
coolant line provides coolant temperature readings
to the ACS temperature/flow controller, allow-
ing the controller to modulate the airflow valve.
Airflow Valve
The radar liquid cooling airflow valve is
pneumatically modulated to limit, as necessary,
conditioned air to the heat exchanger. The ACS
controller supplies electrical power to the airflow
valve torque motor, which controls pneumatic
pressure to the airflow valve. The valve is spring-
loaded closed.
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