TM 1-1520-238-T-7
11–51
11–7.
SYSTEM DESCRIPTION (cont)
11–7
(c) The SPAD, during normal operation, is part of the mechanical control linkage. When jamming
prevents normal pedal movement, a force of 90 foot-lbs. on either directional pedal causes the SPAD shear pin to
shear, severing the mechanical control linkage. When the pilot’s shear pin is severed, BUCS is activated. The
BUCS select trigger switch on the CPG’s collective switch must be closed to activate BUCS. The BUCS ON
indicator on the pilot and CPG caution/warning panels lights when BUCS is activated. If BUCS fails, the BUCS
FAIL indicator on the pilot and CPG master caution/warning panels lights.
(d) The directional magnetic brake assembly is a 28 VDC controlled unit that engages to establish a
directional trim position. The feel trim assembly is a spring loaded device that overrides the directional magnetic
brake assembly when the directional pedals are moved against the magnetic brake assembly. The feel spring
assembly allows directional pedal inputs to override the directional force trim setting. When the directional pedals
are not engaged against the feel spring assembly, directional flight trim maintains current trim position.
(e) The directional mechanical control linkage (fig. 11–25) provides an increase or decrease in
directional pedal movement to the directional servocylinder.
M70-259A
CPG CYCLIC STICK
(LVDT AND SPAD)
PILOT CYCLIC STICK
(LVDT AND SPAD)
MIXER ASSEMBLY
SCISSORS
ROTATING
SWASHPLATE
TORQUE
LINK
LATERAL
LINK
LATERAL
SERVOCYLINDER
LATERAL MECHANICAL
CONTROL LINKAGE
(PILOT ONLY) LATERAL
FEEL SPRING ASSEMBLY
AND MAGNETIC BRAKE
Figure 11–23.
Lateral Cyclic Control System Interface Diagram
