Figure 6-12.--Cabin pressurization components.
There are three ports leading into the pressure
diaphragm. The solenoid valve is electronically con-
regulator valve diaphragm chamber. The first port is
nected to the cabin pressurization switch on the en-
located on the spring-loaded closing side of the
vironmental control panel (fig. 6-13).
diaphragm. It admits pressure from the cabin pressure
regulator control. The second port is the ambient vent
port. It is also located on the spring-loaded closing side
of the diaphragm. The third port is located on the
opening side of the diaphragm. A sensing line is
attached to the third port to connect the cabin pressure
regulator control and the cabin pressure exhaust duct.
The pressure admitted to the diaphragm through the
third port is equivalent to cabin air pressure. The
difference between them causes the pressure regulator
valve to modulate between the open and closed
positions.
Cabin Pressure Regulator Safety Valve
The pressure regulator safety valve is an
independent, pneumatically operated, balanced type of
poppet valve that limits cabin-to-ambient pressure
differentials to 7.07 (+0.2 and 0.0) psi. If the
difference between cabin pressure and ambient
pressure reaches the calibrated limit, the change in
pressure acting on the limit control diaphragm
overcomes the metering valve spring-load and allows
Figure 6-13.--Environmental control panel.
6-15
