piston. It pushes the piston further into its bore, causing fluid to be expelled from the bore. When the
falling face of the cam comes under a piston, the piston's return spring pulls the piston down in its bore.
This causes fluid to be drawn into the bore.
Each bore has a check valve that opens to allow fluid to be expelled from the bore by the piston's
movement. These valves are closed by spring pressure during inlet strokes of the pistons. This fluid is
drawn into the bores only through the central inlet passages. The bores only through the central inlet
passages. The movement of the pistons in drawing in and expelling fluid is overlapping, resulting in a
nonpulsating fluid flow.
Figure 1-7. Typical Rotating-Cam Piston Pump.
Stationary-cam pump. The operation and construction of a stationary-cam pump are
identical to that of the rotating cam except that the cylinder block turns, not the cam. The
stationary-cam pump is not used on the Army's OV-1, AH-1G, and UH-1C.