the attitude of the aircraft. The trim inputs may be provided by the pilot or the automatic flight control system. The actuator has two operating speeds-high speed for manual trim and low speed for AFCS trim. Directional Trim Directional trim is necessary to compensate for yaw of the aircraft. Rudder trim is basically similar to the aileron trim. When the momentary throw rudder trim switch moves left or right, the trim actuator energizes to move the load-feel bungee, repositioning the rudder power mechanism input crank. The rudder linkage and the rudder are repositioned accordingly to a new neutral position. Most aircraft with power-controlled actuators work in a similar manner, using an electric trim actuator to change the neutral position of linkage, deflecting the rudder to maintain the desired directional stability. Like the lateral and longitudinal trim systems, rudder trim action can be accomplished manually or automatically. Trim position indicators provide a cockpit indication of the amount of trim or surface deflection required by each trim system. CONTROL SYSTEM MAINTENANCE Organizational maintenance of the secondary flight control system includes checking system operation, rigging, periodic inspection, lubrication, isolation of malfunctions, and replacement of faulty components. Proper operation of the gearboxes, intercon- necting splined shafts, and screw jack actuators are dependent on proper lubrication. Lack of proper lubrication will generally result in binding and excessive loading of torque tube assemblies. Lack of proper lubrication promotes corrosion. Space and time limitations during shipboard operations often detract from the timely access to some of the slat and flap actuators. In many cases a wing spread and extension of the surfaces are necessary. Attention to these corrosion-prone areas will materially contribute to trouble-free operation of the screw jack mechanisms. Repair of most of the gearboxes and screw jack actuators at the intermediate level of maintenance is limited to replacement of nuts, bolts, washers, gaskets, bearings, and shims. At the intermediate level of maintenance, components of a secondary flight control system may be disassembled for routine maintenance, such as cure date seal and miscellaneous parts replacement. NOTE: Before disassembly of any com- ponent, reference should be made to the “Intermediate Maintenance” section of the applicable MIM or accessories manual to determine repair procedures and test equipment requirements. If the component is beyond the repair capability of a given activity, it should be forwarded through channels to an authorized higher level repair activity. The repair process for many of the flap hydraulic components will generally include the following considerations: 1. Clean the disassembled part, using a suitable solvent followed by air drying with low-pressure air. 2. Inspect all parts, using a strong light and some means of magnification, or one of the nondestructive methods of metal inspection. Threaded parts are inspected for crossed, stripped, worn, or otherwise damaged threads. Springs are checked for distortion, permanent set, and alignment. Spring alignment may be verified by rolling them on a smooth, flat surface. The free length, compressed length, and reflected load of the springs should be verified in accordance with the values provided in the applicable MIM. 3. Inspect mated surfaces for excessive wear, separation of plating, and evidence of nicks or scratches. All parts that show signs of excessive scoring, pitting, or other surface irregularities should be replaced. Minor imperfections can sometimes be removed with fine crocus cloth or lapping compound, depending on the design and tolerance specifications of the part. 4. Be sure that all passages and chambers of the part under repair are clean and free from obstructions. NOTE: During the complete repair process, cleanliness of the work area, as well as the external and internal parts, is a prime consideration. The close tolerance mated surfaces within most hydraulic components are extremely susceptible to damage by contamination regardless of the manner of introduction. 9-50