is located in each engine pylon, and one is located
in the forward upper left section of the
ECS compartmen. The pressure regulating
valve is normally closed, and is electrically
controlled and pneumatically actuated. The
pressure regulator valve has two functions; to
regulate deice air pressure when energized and
to shut off deice air when de-energized. The
pressure regulator valve functions on differential
pressure to maintain an outlet duct pressure
of 26±2 psi. Acuation of the pressure
regulator valve to the regulating function is
accomplished by setting the deice switch on the
ENVIRONMENTAL panel on the center console
to WING EMP.
The pressure regulator valve is normally closed
because the valve sleeve is spring-loaded closed.
Inlet air pressure (chamber C) is sensed by the
control air pressure regulator, which, when the
deice system is operating, maintains an output of
constant reference pressure to control the opening
side of the sleeve (chamber B). Chamber A is the
closing side of the valve sleeve and is vented to
the pressure regulating valve outlet pressure.
Figure 1-12.—Deice pressure regulating valve.
1-15
