the corresponding half of the PC cylinder. The second
In this system, left and right control stick
movements transfer mechanically to the aileron and
half of the servo valve directs PC No. 2 hydraulic
spoiler/deflector control linkage. The viscous damper
pressure to the other half of the cylinder. If one system
cylinder is connected in the linkage. It resists rapid
fails, the other system operates the ailerons and
control stick movement, presenting overcontrol of the
spoiler/deflectors.
aileron system when the control augmentation mode of
Input control linkage connected to the servo valve
the AFCS is engaged. The control augmentation mode
control arm of the PC cylinders positions the valve
of the AFCS improves lateral and longitudinal stability
slider to direct pressure to the actuating pistons. The
of the aircraft.
actuating piston extends or retracts the cylinder
The load-limiting links located throughout the
housing. As the cylinder housing moves, the servo
system protect control linkage and components from
valve control arm repositions the servo valve slider.
excessive loads. These links have a breakout force, so
When the ailerons and spoiler/deflectors position is
they normally act as a fixed link. Loads that exceed the
equal to the demand input, the servo valve slider is
breakout force cause the links to extend or retract and
again at neutral. Fluid flow is blocked to and from the
absorb the overload.
cylinder until a new control system input is initiated.
Artificial feel is provided by the mechanical feel
The spoiler/deflector on each wing operates with
spring assembly. The assembly simulates air load
the upward throw of the aileron on that wing. They are
resistance at the control stick. When released, the
located in the left and right-hand wing center sections,
control stick returns to neutral by the feel spring
forward of the flaps. The spoiler extends upward into
preload.
the airstream, disrupting the airflow and causing
decreased lift on that wing. The deflector extends
The roll-feel isolation actuator prevents excessive
down into the airstream and scoops airflow over the
forces from reaching the control stick. When the
wing surface aft of the spoiler, preventing airflow
control stick is deflected, linkage to the feel isolation
separation in that area.
actuator servo valve repositions the servo valve slider
and directs hydraulic pressure to the actuating pistons.
A stop bolt on the spoiler/deflector bell crank
The cylinder housing is connected to the control
limits movement of the spoiler to 60 degrees of
linkage and moves in the direction corresponding to
deflection. The deflector is mechanically slaved to the
stick movement. As the cylinder housing moves, the
spoiler. It can be deflected to a maximum of 30 degrees
servo valve slider repositions to neutral, blocking fluid
when the spoiler is at 60 degrees. The spoiler deflectors
flow to and from the actuator until new inputs are
open only with the upward movement of the ailerons.
initiated.
They are normally closed. The linkage motion lost
when the aileron is down is absorbed by the spoiler
The AFCS roll actuator connects to the control
deflector load-limiting link.
linkage by a scissor link. Normally, this scissor link
acts as a simple idler. When the actuator receives
Spoiler Control System
signals from the AFCS, it causes the linkage to act as a
variable link. This action produces control system
On one model aircraft, spoiler action is provided
inputs completely independent of the control stick.
through the control stick grip, roll command
transducer, roll computer, pitch computer, and eight
Output motion from the AFCS linkage is
spoiler actuators (one per spoiler). When used to
transmitted through control system linkage to the
increase the effect of roll-axis control, the spoilers can
aileron trim and mixing linkage. The mixing linkage
only be controlled when the wings are swept forward at
directs inputs to both the aileron and spoiler/deflector
57 degrees.
linkage. Dead-band stops within the mixing linkage
allow the ailerons to reach a trailing edge up position of
Right or left movement of the control stick grip
2 degrees 30 minutes, 15 minutes, before any
mechanically transfers to the roll command transducer.
spoiler/deflector motion is initiated.
The transducer converts the movement to inboard and
outboard spoiler roll commands. Because the spoilers
The power control cylinders for the ailerons and
are vital for landing, the left and right-wing inboard
the spoiler/deflectors are tandem type. Power control
and No. 1 mid-spoilers are controlled by the roll
No. 1 and power control No. 2 hydraulic systems
computer. The spoilers are powered by the combined
supply hydraulic pressure. Half of the servo valve on
each cylinder directs PC No. 1 hydraulic pressure to
hydraulic power systems. The left and right outboard
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