threaded power screw. The actuator is manually controlled through inputs from the trim switch on the control stick grip. When the stabilizer is in automatic trim, the actuator receives inputs from the AFCS. High speed is used during manual trim, and low speed during automatic trim. The stabilizer shifting mechanism, shown in figure 9-7, consists of a shift sector and its linkage, plus cable that runs from the flap drive gearbox and the rudder cam shift mechanism. A spin recovery cylinder is also attached to the shifting mechanism, and provides an alternate method of shifting the stabilizer and rudder from the “clean” configu- ration to the “dirty,”   or increased throw con- figuration. In normal operation, when flaps are extended, a cable running from a drum on top of the flap drive gearbox to the sector assembly of the shifting mechanism rotates the sector. Linkage connecting the sector assembly and the control stick linkage is shifted. Linkage shifting increases control stick travel. Stabilizer down travel is increased to a 24-degree maximum. A cable is also connected from the sector assembly to the rudder cam stop shifting mechanism, which increases rudder travel from 4 to 35 degrees each side of neutral. The pilot, at his/her option, may obtain increased stabilizer and rudder throw by actuation of the spin recovery assist switch, eliminating the necessity of lowering the flaps. This action ports hydraulic pressure through the spin recovery selector valve and its flow regulators and check valve to the spin recovery cylinder, causing it to extend and shift the mechanism in the same manner as provided by the cable action. The two nonbypass-type filters in the system protect the intricate valving mechanisms of the actuator from contamination, and are vitally important to proper stabilizer operation. They are checked with the requirements listed in the maintenance requirements card deck, and should not be overlooked when troubleshooting stabilizer system malfunctions. The stabilizer power package, used on various Navy aircraft, is linked to the approach power compensator system (APC). This system aids the pilot in maintaining optimum angle of attack for approach and landing. An APC potentiometer is mechanically linked to the power package, and provides electrical inputs to the APC system to compensate for changes in pitch attitude required during landing approaches. The APC system regulates the throttle position to provide the engine thrust required to establish and maintain the desired angle of attack. The potentiometer provides inputs relative to the position of the horizontal stabilizer. Horizontal Stabilizer Control System (Double Axis) Because of the complexity and interrelationships of the flight control systems of newer model aircraft, only a brief description of a representative stabilizer control (pitch/roll. axis) follows. This system allows pitch about the aircraft’s lateral axis and roll about the aircraft’s longitudinal axis. Stabilizer control, which affects both the pitch and roll axis, is provided by forward or aft and/or left or right movement of the control stick grip. Forward or aft movement provides pitch-axis control; left or right movement, roll-axis control. The control, stick grip movement is mechanically transferred to the left and right stabilizer servo cylinders through the pitch and roll command summing network, the feel assemblies, and the summing network. These servo cylinders, which are normally powered by the flight and combined hydraulic power systems, move the stabilizers. If both hydraulic systems fail, the stabilizer servo cylinders automatically receive hydraulic power from the backup system. The trim switch on the control stick grip enables trimming of the aircraft in pitch and roll. LATERAL CONTROL SYSTEMS Lateral control systems control roll about the longitudinal axis of the aircraft. In this section, several of the different system arrangements used by aircraft manufacturers are described, and general maintenance requirements systems are discussed. for primary flight control 9-9