Report of the Second Piloted Aircraft Flight Control System - Acgsc.org

to the piston. When the spool member is displaced from the neutral position
by mvement of the input lever at point (A), the flow of fluid
through the pilot valve causes the piston to move in the direction which
returns the spool to the neutral position. It follows from the geometry
of the linkage that for every position of the linkage point (A) there is
a corresponding equilibrium position of the piston. The description of
several other forme of pilot valving and feedback linkage is available
in the literature.
Rotary servomotor. - The rotary servomotor is also shown schematically
in figure 1. Rotation of the pilot valve with respect to the output shaft
opens a pressure passage to one side of the vane and a drain passage to
the opposite side of the vane. The vane is thereby caused to rotate in
the same direction as the pilot valve. In the neutral position 'of the
valve the passages to either side of the vane are closed.
Initial assumptions. - The analysis which follows is developed with
the following initial assumptions t
1. The area of opening of the pilot valve varies liaearly with the
motion of the valve.
2. At fixed input, the ratio of pilot valve mvement'to piston mvemnt
is constant.
3. At all positions of the pilot valve the inlet and discharge openings
are equal.
4. The supply and drain pressure are constant.
5. The compreseibi~ty and mass of the hydraulic fluid are negligible.
6. Structure and mechanical linkage are rigid.
7. Mechanical fraction is negligible.
'8. Fluid friction losses in motor passages are negligible.
9. Leakage is negugible.
Response to a Step Input
Baeic dynamic considerations. - Under the condition of no load on the
output shaft and negligible internal motor mass, the pressure drop across
the piston will be zero. The fluid flow through the cylinder is therefore