the return line. If the cam is rotated 90 degrees, poppets A and C will unseat and poppets B and D will seat. Fluid
entering the inlet pressure port then passes around poppet A and to the actuator unit through the cylinder 2 port. Fluid
resuming from the actuator unit flows to the return line by entering the selector valve through the cylinder 1 port, flowing
around poppet C, and exiting through the return port. If the cam is rotated 45 degrees from the position shown in the
schematic, all poppets are seated and the selector valve is in a neutral position.
Compound selector valve. To conserve space and make installation easy when banks of units
are to be controlled, several selector valves are compounded into one unit. Each selector valve is controlled
independently, but only one connection is needed for the pressure line and one for the return line.
Control Valves. For Army aircraft, the term control valve refers to a valve that controls direction of flow
through alternate channels. Although similar in principle to a selector valve, a control valve functions more like a shutoff
valve. Some control valves are actuated manually; others, electrically. Electrical actuation may be by means of either a
solenoid or a motor. A solenoid-actuated valve is shown in figures 4-125 and 4-126. The
Figure 4-118. Cylindrical Accumulator
Figure 4-117. Pressure Reducing Valve