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

The centering characteristics except centering speed are determined, in this
case, from the friction of the system elements. Break-away force indicated
by poirrts (1C) and (16), is simply a combination of cylinder and control
friction. The centering poaitional error at point (6) is the intersection
of the 12 lb. cylinder friction line and the 2 lb. conk03 friction Une.
Figure 6 illustrates a surface deflection cycle in a boost syatem
. employing a balanced slide valve with no centering spring. The operating
load of this valve consists of 2.5 lbs. constant friction as indicated by
b w slope diagonal line of Fig. 6. Starting again frcm point (I), equilibrim
in neutral, a slowly applied control force proceeds vertically to (2)
b
where valve friction first is overcome. The valve dl1 direct presume to
the c;ylinder proceeding along the 2.5 lb. valve action line until control
force ie no longer increased. The system will continue to move, proceeding
horizontally to point (3) where the valve readjusts toward neutral Pnd the
system atolls at point (3). With a slow decrease in control force, the
valve dll immediately readjust and assist (as demanded) the return of
surface to neutral proceeding along valve action line until the control
force reduces to 2 lb. forward control friction (0 force at pilot). Tbs
system will continue across the 2 lb. line to point (2) where a reverse
valve load will bring the valve to neutral and stall the mechanism. The
outer loop pobts (4), (5), (6) and (1) are again the path of control follees
at the pilot and was constructed by adding or subtracting forward control
friction fmm the previously determined points.
Starting at point (3), if the control load is rapidly released, the
valve load will exceed 2.5 lb., thus fully opening the valve and centering
the mechanism at f'ull flow rate. The values of valve friction and forward
controls friction selected result in zero positional error. However, the
analysis waa simplified thus far by neglecting friction in the driven linbge.
"
*
Figure 7 illustrates a surface deflection cycle similar to Figure 6 with
the valve friction increased to 3.3 lb ., a control friction of 2 Ib., and
uith a driven linkage friction of 10 lb. introduced. The break-awry force 18
b.6 lb. With this system condition the centering stall point (4) oocurs at
-10 lb. surface load meesured at the boost package. Diamond shaped points
(9), (10) and (11) are surface loads as measured at the surface. These points
are offset horizontally by + 10 lb., which is the driven linkage fzLction from
the oorresponding system co-ndition points. Poht (11) indicates that the
actual surface load is zem at the mechanism stall point and thus zero canterlug
positional error is. achieved. Thia is accomplished, as illustrated in
the upper left corner of Figure 7, by establishing optimum valve friction f'rom
the intersection point of the controls friction and driven linkage friction.
This tzLck of power operation to a perfectly centered position is
damndent upon certain qualifications:
1. No centering spring within control valve.