Combination Aileron/Spoiler Deflector System
Navy aircraft employ more than one system for
lateral control of the aircraft. Figure 9-14 shows an
aileron and spoiler/deflector arrangement to achieve
an increased roll rate about the longitudinal axis.
In this system, left and right control stick
movements transfer mechanically to the aileron and
spoiler/deflector control linkage. The viscous damper
cylinder is connected in the linkage. It resists rapid
control stick movement, presenting overcontrol of the
aileron system when the control augmentation mode
of the AFCS is engaged. The control augmentation
mode of the AFCS improves lateral and longitudinal
stability of the aircraft.
The load-limiting links located throughout the
system protect control linkage and components from
excessive loads These links have a breakout force, so
they normally act as a fixed link. Loads that exceed
the breakout force cause the links to extend or retract
and absorb the overload.
Artificial feel is provided by
the mechanical feel spring
assemb]y. The assembly simulates air load
resistance at the control stick. When released, the
control stick returns to neutral by the feel spring
preload.
The roll-feel isolation actuator prevents excessive
forces from reaching the control stick. When the
control stick is deflected, linkage to the feel isolation
actuator servo valve repositions the servo valve slider
and directs hydraulic pressure to the actuating pistons.
The cylinder housing is connected to the control
linkage and moves in the direction corresponding to
stick movement. As the cylinder housing moves, the
servo valve slider repositions to neutral, blocking
fluid flow to and from the actuator until new inputs
are initiated.
The AFCS roll actuator connects to the control
linkage by a scissor link. Normally, this scissor link
acts as a simple idler. When the actuator receives
signals from the AFCS, it causes, the linkage to act
as a variable link. This action produces control
system inputs completely independent of the
control stick.
Output motion from the AFCS linkage is
transmitted through control system linkage to the
aileron trim and mixing linkage. The mixing linkage
directs inputs to both the aileron and spoiler/deflector
linkage. Dead-band stops within the mixing linkage
allow the ailerons to reach a trailing edge up position
of 2 degrees 30 minutes, 15 minutes, before any
spoiler/deflector motion is initiated.
The power control cylinders for the ailerons and
the spoiler/deflectors are tandem type. Power control
No. 1 and power control No. 2 hydraulic systems
supply hydraulic pressure. Half of the servo valve on
each cylinder directs PC No. 1 hydraulic pressure to
the corresponding half of the PC cylinder. The
second half of the servo valve directs PC No. 2
hydraulic pressure to the other half of the cylinder. If
one system fails, the other system operates the
ailerons and spoiler/deflectors.
Input control linkage connected to the servo valve
control arm of the PC cylinders positions the valve
slider to direct pressure to the actuating pistons. The
actuating piston extends or retracts the cylinder
housing. As the cylinder housing moves, the servo
valve control arm repositions the servo valve slider.
When the ailerons and spoiler/deflectors position is
equal to the demand input, the servo valve slider is
again at neutral. Fluid flow is blocked to and from
the cylinder until a new control system input is
initiated.
The spoiler/deflector on each wing operates with
the upward throw of the aileron on that wing. They
are located in the left- and right-hand wing center
sections, forward of the flaps. The spoiler extends
upward into the airstream, disrupting the airflow and
causing decreased lift on that wing. The deflector
extends down into the airstream and scoops airflow
over the wing surface aft of the spoiler, preventing
airflow separation in that area.
A stop bolt on the spoiler/deflector bell crank
limits movement of the spoiler to 60 degrees of
deflection. The deflector is mechanically slaved to
the spoiler. It can be deflected to a maximum of 30
degrees when the spoiler is at 60 degrees. The spoiler
deflectors open only with the upward movement of
the ailerons. They are normally closed. The linkage
motion lost when the aileron is down is absorbed by
the spoiler deflector load-limiting link.
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Spoiler Control System
On one model aircraft, spoiler action is provided
through the control stick grip, roll command
transducer, roll computer, pitch computer, and eight
spoiler actuators (one per spoiler). When used to
increase the effect of roll-axis control, the spoilers can
only be controlled when the wings are swept forward
at 57 degrees.
Right or left movement of the control stick grip
mechanically transfers to the roll command
transducer. The transducer converts the movement to
inboard and outboard spoiler roll commands.
Because the spoilers are vital for landing, the left- and
right-wing inboard and No. 1 mid-spoilers are
controlled by the roll computer. The spoilers are
powered by the combined hydraulic power systems.
The left and right outboard and No. 2 mid-spoilers are
controlled by the pitch computer. These spoilers are
powered by the mid-outboard spoiler/high lift backup
module. This combination provides positive spoiler
control if either computer or hydraulic power source
malfunctions.
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