System Operation
The rain-removal system is activated by
placing the windshield switch in the AIR position.
With the switch in the AIR position, a 28-volt dc
circuit is completed from the air-conditioning
circuit breaker, through the windshield switch, to
the solenoid of the rain-removal pressure-
regulator shutoff valve, to the nosewheel well
bleed-air relay, and to the windshield rain-removal
warning relay. When the nosewheel well bleed-
air relay is energized, the 115-volt ac circuit from
the bleed-air circuit breaker, through the AUTO
position of the nosewheel well bleed-air switch,
is completed to the open windings of the
nosewheel well bleed-air shutoff valve. With the
circuit completed, the windshield air caution light
will illuminate. When you move the windshield
switch to the OFF position, the windshield air
caution light will go out. The nosewheel well
bleed-air shutoff valve directs the 115-volt ac
power to the close windings of the motor. The
weight-on-wheels switch will energize the
nosewheel well bleed-air relay.
When the rain-removal pressure-regulator
shutoff valve solenoid is energized, the valve
opens and allows pressure-regulated (75±3.5 psi)
hot bleed air to flow to the ejectors of the rain-
removal nozzles. To lower the temperature of the
hot bleed air, the ejectors draw cool air from the
nose radome compartment. The cool air and hot
bleed air mix in the plenum of the nozzle
assembly. The air passes through the plenum to
26 nozzles, which direct the hot air in a wide
stream across the windshield.
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