During preventive maintenance inspections, you inspect actuating cylinders in accordance with the applicable maintenance requirements cards (MRCs) for the specific aircraft. Actuating cylinders are inspected for leakage and binding. You should clean the exposed portion of the piston shaft with a dry-cleaning solvent, and then wipe it with a clean cloth moistened with hydraulic fluid. All mounting fittings are lubricated with specified grease only.

NOTE: All lubrication fittings and lubri-cation areas must be cleaned prior to lubrication, and all excess lubricants must be removed at 
its completion. 

External leakage is the most common trouble encountered with actuating cylinders. This can be caused by static or dynamic seals. Static seal leakage around end caps or fittings may be stopped by tightening the affected components or replacing the leaking seal. Dynamic seal leakage around an actuator shaft will require seal replacement. Refer to the appropriate MIM or 03 manual for specific maintenance instructions.

Applying too much torque while tightening fittings or other components under pressure may cause catastrophic failure. Such failures can result in injury to personnel or damage to the aircraft.

Internal leakage is harder to detect. This leakage is usually caused by failure of piston seals, and will require repair. Internal leakage is usually indicated by weak, sluggish, or slow movement of the actuator. Refer to the appropriate MIM or 03 manual for repair instructions. This problem is usually resolved by replacement of the actuator. After the repairs are made, you must test the actuator to verify its performance.