(See figure 4-2.) Air from the inlet (13) passes
through the filter (14), and then through the
reverse-flow check valve (15). The air then enters
the reference regulator (16), where it is pressure
regulated (as a function of altitude) by an
evacuated bellows (1). The air is then passed
through a control orifice (6), a shuttle valve (8),
and to the actuator section (10) of the high-stage,
bleed-air regulator valve to open the butterfly (12).
The pressure of the air entering the regulator
sensing line (11) with the spring pressure of the
actuator section of the valve modulates the valve
toward the closed position, as regulated by
pressure from the shuttle valve. As aircraft
altitude increases, the evacuated bellows expand
and cause the reference regulator to close. The
ambient vent (5) decreases the pressure to the open
side of the actuator section, and thereby allows
the spring to close the actuator section. This action
also closes the butterfly.
When the cross-bleed start solenoid (3)
is energized, the reference regulator larger
diaphragm (2) is vented to ambient (4). Spring
pressure on the reference
regulator larger
Figure 4-2.-High stage, bleed-air regulator valve schematic.
4-4
