An indicator, located on top of the valve housing,
The P-3 aircraft uses an ice detector system to warn
shows the position of the valve--open or closed. This
the pilot, visually, of an icing condition. A warning
indicator enables you to visually check the operation of
light is installed on the center instrument panel in the
the valve while it is still installed in the anti-ice system.
flight station.
Modulating Valves
COMPONENTS
The P-3 anti-icing system has three modulating
The hot bleed air is directed and regulated to the
valves installed in each wing. These valves are
leading edge ejector manifold through shutoff valves,
thermostatically controlled and pneumatically
modulating valves, thermostats, skin temperature
operated. They maintain the constant engine
sensors, and overheat warning sensors (fig. 5-2).
compressor bleed air temperature required for the wing
Shutoff Valves
leading edge. When anti-icing is not required, the
valves operate as shutoff valves.
The wing anti-ice system contains several shutoff
The modulating valves (fig. 5-3) have pilot
valves. The fuselage bleed air shutoff valves, installed
solenoid valves that are electrically controlled by three
in the cross-ship manifold on the right and left wings,
switches on the bleed air section of the ice protection
isolate the wings from the fuselage duct section. In
panel. When the solenoid is energized, it admits
addition, they may be used to isolate one wing duct
filtered, regulated, bleed air pressure to one side of a
from the other wing duct. Each valve is individually
diaphragm chamber in the valve. The other side of the
controlled by a guarded toggle switch mounted on the
diaphragm chamber is spring-loaded to the closed
bleed air section of the ice control protection panel.
position. Movement of the diaphragm operates a main
A bleed air shutoff valve is also installed in each
line butterfly valve.
engine nacelle. These shutoff valves are physically
When the valve opens, hot air is admitted to the
identical. They are of the butterfly-type and are
leading edge distribution system. The hot air goes
actuated by an electric motor.
Figure 5-2.--Wing leading edge anti-icing cross section.
5-4
