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Cutaway view of selector valve body
Slide-Type Selector Valve - 14018_318

Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them
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You can rotate the camshaft by moving the control handle in either direction from neutral. This action rotates the lobes, which unseat one pressure poppet and one return poppet. See figure 8-9. The valve is now in a working position. Pressure fluid, entering the pressure port, travels through the vertical fluid passages in both pressure poppet seats. Since only one pressure poppet is unseated by the cam lobe, the pressure fluid flows past this open poppet to the inside of the poppet seat. From there it flows out the diagonal fluid passages, and then out one cylinder port and to the actuator. Return fluid coming from the actuator is coming in the other cylinder port, through the diagonal fluid passages, past the unseated return poppet, through the vertical fluid passages, and out the return port to the system reservoir. By rotating the camshaft in the opposite direction until the stop pin hits, the opposite pressure and return poppets are unseated, and the fluid flow is reversed. This causes the actuator to move in the opposite direction. Selector valves should be checked periodically for leakage and security of mounting. The operating linkage should be inspected for ease of operation. Malfunctioning selector valves are usually the result of foreign particles or damaged parts. A malfunctioning valve should be removed and checked for free movement of the camshaft. The valve maybe disassembled and all parts cleaned with clean hydraulic fluid. O-rings should be replaced while the valve is disassembled. Both external and internal leakage may be caused by damaged or worn O-rings. External leakage could be caused by a damaged gasket under the sealing plug or the end packing on the camshaft. Internal leakage could be caused by a damaged center packing on the camshaft, a damaged bottom gasket on the poppet seat, or a damaged O-ring packing on the poppet. NOTE: All selector valves that require repair or adjustment must be done in accordance with the applicable MIM or 03 manual. After repair or adjustment, all valves must be tested for proper operation and leakage. Figure 8-9.—Working view of a poppet-type selector valve. 8-11







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