RADAR LIQUID COOLING SYSTEM
The F-18 aircraft radar liquid cooling system
(fig. 1-15) circulates liquid coolant to remove heat
from the radar transmitter high-voltage RF energy
modules. Coolant heated by the transmitter is
routed through a closed loop system to a heat
exchanger. The heat exchanger subjects heated
coolant to cooling air, and the coolant is returned
by a pump. (A temperature control valve is
integral to the heat exchanger to maintain a
minimum coolant temperature level.) One of three
sources of air is induced across the heat exchanger
to provide coolant temperature control. During
normal flight operations, ram air is induced across
the heat exchanger by an electrically powered ram
air scoop. At high ram air temperature conditions
(hot day—low altitude or high speed—high
altitude), the ram air scoop is closed by a signal
from the air data computer, and conditioned air
from the air cycle ACS is delivered to the heat
exchanger. For ground operation, with aircraft
weight on wheels, a cooling fan supplies cooling
air to the heat exchanger. When cooling air is
supplied from the air cycle ACS, a coolant
temperature sensor operates through the ACS
temperature/flow controller to modulate an
airflow valve and limit preconditioned air to the
heat exchanger. The coolant is filtered and the
system monitored for filter contamination, ram
air door actuator position, low pressure, high
temperature, and coolant quantity.
A system servicing panel and quick-disconnect
fittings are located in the left fuselage. Quick-
disconnect fittings are also provided in the coolant
lines at the radar transmitter high-voltage module
to aid in transmitter replacement by a preserviced
unit.
The radar liquid cooling system is made up
of a liquid-to-air heat exchanger, a liquid coolant
Figure 1-15.—Radar liquid cooling system.
1-20
