In normal operation, when flaps are extended, a
The stabilator is a control surface located on either
side of the tail section of the aircraft. In flight, the
cable running from a drum on top of the flap drive
stabilator deflects symmetrically to produce pitch
gearbox to the sector assembly of the shifting
motion and asymmetrically to produce roll motion.
mechanism rotates the sector. Linkage connecting the
The maximum surface deflection of each stabilator is
sector assembly and the control stick linkage is shifted.
from 10.5 degrees trailing edge down to 24 degrees
Linkage shifting increases control stick travel.
trailing edge up.
Stabilizer down travel is increased to a 24-degree
maximum. A cable is also connected from the sector
LATERAL CONTROL SYSTEMS
assembly to the rudder cam stop shifting mechanism,
which increases rudder travel from 4 to 35 degrees each
Lateral control systems control roll about the
side of neutral.
longitudinal axis of the aircraft. Several of the different
system arrangements used by aircraft manufacturers
The pilot, at his/her option, may obtain increased
are discussed, as well as general maintenance
stabilizer and rudder throw by actuation of the spin
requirements for primary flight control systems.
recovery assist switch, eliminating the necessity of
lowering the flaps. This action ports hydraulic pressure
Aileron Control System
through the spin recovery selector valve and its flow
regulators and check valve to the spin recovery
The aileron control system, shown in figure 16-8,
cylinder, causing it to extend and shift the mechanism
is equipped with a power mechanism that provides
in the same manner as provided by the cable action.
hydraulic power to operate the ailerons. If hydraulic
The two nonbypass-type filters in the system
power fails, the mechanism can be disconnected,
placing the system in complete manual operation.
protect the intricate valving mechanisms of the
Movement of the aileron control system begins when
actuator from contamination, and are vitally important
the control stick in the cockpit moves left or right.
to proper stabilizer operation. They are checked with
When the stick is moved, cables connected to the bell
the requirements listed in the maintenance
crank in the control stick housing are moved to operate
requirements card deck, and should not be overlooked
the sector on the power mechanism. With the actuation
when troubleshooting stabilizer system malfunctions.
o f t h e s e c t o r, t h e p ow e r m e c h a n i s m o p e r a t e s ,
The stabilizer power package, used on various
transferring the movement to the mechanical linkage
Navy aircraft, is linked to the approach power
that operates the ailerons.
compensator system (APC). This system aids the pilot
The aileron power mechanism consists of two
in maintaining optimum angle of attack for approach
control valves, a dual-chambered hydraulic power
and landing. An APC potentiometer is mechanically
cylinder, cable sectors, and a system of latches and
linked to the power package, and provides electrical
related cranks. Linkage connects the control valves in
inputs to the APC system to compensate for changes in
tandem. The flight control hydraulic system powers
pitch attitude required during landing approaches. The
one valve, and the other is powered by the utility
APC system regulates the throttle position to provide
hydraulic system.
the engine thrust required to establish and maintain the
The power cylinder is a single tandem cylinder,
desired angle of attack. The potentiometer provides
composed of four chambers with pistons connected to
inputs relative to the position of the horizontal
a common shaft. Each of the two control valves
stabilizer.
operates on that portion of the power cylinder to which
it is associated. Both hydraulic systems operate
Horizontal Stabilizer (Stabilator) Control
simultaneously, and each delivers 3,000-psi pressure
System (Double Axis)
to the mechanism. If one hydraulic system should fail,
the other system will supply enough power to operate
Because of the complexity and interrelationships
the ailerons at reduced hinge movement.
of the flight control systems of newer model aircraft,
o n l y a b r i e f d e s c r i p t i o n o f a r e p r e s e n t a t ive
When the control stick moves, the control cables
stabilizer/stabilator control (pitch/roll axis) (F/A-18)
move the power mechanism sector. Through linkage,
follows. This system allows pitch about the aircraft's
the sector operates the control valves, which direct
lateral axis and roll about the aircraft's longitudinal
hydraulic fluid to the power cylinder. The cylinder
axis.
actuating shaft, which is connected to the power crank
16-8
