Figure 11-5.--Control surface actuating cylinder.
two end cap assemblies, the two control valves, and the
NOTE: All lubrication fittings and lubrication
previously mentioned synchronizing rod.
areas must be cleaned prior to lubrication, and all
excess lubricants must be removed at its completion.
In this particular installation, the piston shaft end is
attached to the aircraft structure and remains
External leakage is the most common trouble
stationary. The cylinder body is attached to the control
encountered with actuating cylinders. Static or
surface, and provides control surface deflection by its
dynamic seals can cause this. Static seal leakage
movement. Two adjustable stops are provided as a
around end caps or fittings may be stopped by
means of adjusting actuator movement, thereby
tightening the affected components or replacing the
limiting the travel of the control surface. When these
leaking seal. Dynamic seal leakage around an actuator
steps are used in an aileron or elevator control system,
shaft will require seal replacement. Refer to the
one stop limits the UP travel, and the other limits the
appropriate maintenance instructional manual (MIM)
DOWN travel. In a rudder system, one stop limits the
or 03 Manual for specific maintenance instructions.
travel to the right, and the other to the left.
WARNING
MAINTENANCE OF ACTUATING
CYLINDERS
Applying too much torque while tightening
fittings or other components under pressure may
During preventive maintenance inspections, you
cause catastrophic failure. Such failures can result
inspect actuating cylinders in accordance with the
in injury to personnel or damage to the aircraft.
applicable maintenance requirements cards (MRCs)
for the specific aircraft. Actuating cylinders are
Internal leakage is harder to detect. This leakage is
inspected for leakage and binding. You should clean
usually caused by failure of piston seals, and will
the exposed portion of the piston shaft with a
require repair. Weak, sluggish, or slow movement of
dry-cleaning solvent, and then wipe it with a clean
the actuator usually indicates internal leakage. Refer
cloth moistened with hydraulic fluid. All mounting
fittings are lubricated with specified grease only.
to the appropriate MIM or 03 Manual for repair
11-6
