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Stabilizer control system | Up
Aviation Structural Mechanic (H&S) 3&2 - How airplanes are built and how to maintain them | Next
Secondary Flight Controls |
Series Mode.—In this mode, input signals from the
automatic flight control system (AFCS) may be used
independently or combined with manual inputs to
control stabilizer movement.
Parallel Mode.—In this mode, input signals from the
AFCS alone control stabilizer movement.
Directional Control Systems
Directional control systems provide a means of
controlling and stabilizing the aircraft about its vertical
axis. Most aircraft use conventional rudder control
systems for this purpose. The rudder control system is
operated by the rudder pedals in the cockpit, and is
powered hydraulically through the power mechanism.
In the event of hydraulic power failure, the hydraulic
portion of the system is bypassed, and the system is
powered mechanically through control cables and
linkage. When the pilot depresses the rudder pedals, the
control cables move a cable sector assembly. The cable
sector, through a push-pull tube and linkage, actuates
the power mechanism and causes deflection of the
rudder to the left or right.
F-14 Flight Control Systems
The F-14 flight control systems include the rudder,
the stabilizer, and the spoiler control systems; the wing
surfaces control system; the angle-of-attack system; and
the speed brake control system. Because of the
complexity of the F-14 flight control systems, only a
brief description is presented.
RUDDER CONTROL (YAW AXIS). -Rudder
control, which affects the yaw axis, is provided by way
of the rudder pedals. Rudder pedal movement is
mechanically transferred to the left and right rudder
servo cylinders by the rudder feel assembly, the yaw
summing network, and a reversing network.
SPOILER CONTROL (LATERAL AXIS). -
Spoiler control is provided through the control stick
grip, roll command transducer, roll computer, pitch
computer, and eight spoiler actuators (one per spoiler).
The spoilers, when used to increase the effect of roll-axis
control can only be controlled when the wings are swept
forward of 57 degrees. Right or left movement of the
control stick grip is mechanically transferred to the roll
command transducer, which converts the movement to
inboard and outboard spoiler roll commands.
DIRECT LIFT CONTROL (DLC).—DLC moves
the spoilers and horizontal stabilizers to increase aircraft
vertical descent rate during landings without changing
engine power.
Figure 1-8.—Wing oversweep position-manual control (F-14).
WING SURFACE CONTROL SYSTEM. -The
wing surface control system controls the variable-
geometry wings to maximize aircraft performance at all
speeds and altitudes. The system also provides high lift
and drag forces for takeoff and landing, and increased
lift for slow speeds. At supersonic speeds, the system
produces aerodynamic lift to reduce trim drag.
The wing sweep control, initiated at the throttle
quadrant, provides electronic or mechanical control of
a hydromechanical system that sweeps the wings. See
figure 1-7. The wings can be swept from 20 degrees
through 68 degrees in flight. On the ground, mechanical
control allows awing sweep position of 75 degrees. See
figure 1-8. This position is used when flight deck
personnel spot the aircraft or when maintenance
personnel need to enable the wing sweep control
self-test.
Electronic Control.—Wing sweep using electronic
control is initiated at the throttle quadrant. Four modes
are available: automatic, aft manual, forward manual, or
bomb manual. Selection of these modes causes the air
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