electrically actuated and operated. The valve is
installed in the hot bleed-air duct in the starboard
engine compartment. The valve is controlled by
the nosewheel well bleed-air switch on the fuel
management panel. When the switch is set to the
OFF position, the valve is closed by 115-volt ac
power from the bleed-air circuit breaker. When
the switch is set to the AUTO position, power is
routed to the nosewheel well bleed-air relay. When
the windshield switch on the air-conditioning
panel is moved to the AIR position, or when left
main landing gear weight-on-wheels switch is
closed, the relay is activated and the valve opens.
If electric power is lost, the valve will remain in
the last selected position. The valve has a position
indicator that can be viewed with the starboard
engine-bay door open.
SHUTOFF VALVE. The rain-removal pres-
sure-regulator shutoff valve is a pneumatically
operated, solenoid-controlled, 2-inch valve
installed in the hot bleed-air duct to the rain-
removal nozzle assembly. (See fig. 3-8.) Operation
of the valve is controlled by the windshield switch
on the air-conditioning control panel. Placing the
switch to the AIR position energizes the solenoid
of the valve. When the inlet pressure to the valve
is between 15 and 50 psi, the valve is fully opened.
When it is between 100 and 250 psi, the valve
regulates the outlet pressure to the rain-removal
nozzle at 75±3.5 psi. By placing the windshield
switch to OFF, it de-energizes the solenoid. This
causes the valve to close and shuts off the flow
of bleed air to the rain-removal nozzle.
In the closed position, air from the upstream
side of the valve passes through the control air
passages to chamber A and leaks past the pilot
valve stem to chamber B. With equal pressure on
both sides of the large diaphragm, the pressure
on the small diaphragm and the spring force on
Figure 3-8.-Rain-removal Pressure-regulator shutoff valve.