Figure 17-8.--Primary servo cylinder.
valve to operate before the power piston clevis. The
flows into the lower chamber. The piston will rise
power piston is then mechanically displaced.
because of a pressure area differential. If the pilot
valve moves down, the fluid in the lower chamber
Fluid under pressure entering the servo cylinder
flows to return. The piston will be forced downward by
upper port closes the bypass valve and enters the upper
upper chamber pressure.
chamber. With the pilot valve in neutral, fluid cannot
When flight control movements stop, the piston
escape from the lower chamber, and the piston remains
will continue to move until the ports of the pilot valve
motionless. If the pilot valve moves upward, fluid
17-9