1. General
A. The primary flight controls are the ailerons, elevators, and rudder(Fig. 1). These hydraulically-powered control surfaces provide flight control in roll, pitch, and yaw. The auxiliary flight controls are the trailing edge flaps, leading edge flaps and slats, the spoilers, and an adjustable horizontal stabilizer. B. Lateral (roll) trim is provided by repositioning the aileron null detent to deflect the ailerons. Longitudinal (pitch) trim is provided by positioning the adjustable horizontal stabilizer. Directional (yaw) trim
is provided by repositioning rudder neutral to deflect the rudder.
2. Roll Control System
A. The roll (lateral) control surfaces consist of the two ailerons and the four flight spoilers. These surfaces are controlled by rotation of the captain's and first officer's control wheels (Fig. 2). With hydraulic power on, the control wheel forces are provided by an artifical feel mechanism as all these surfaces are fully hydraulic powered. Control signals from the pilots' control wheels are transmitted through the aileron control system to the control valves on the two aileron power control units (Fig. 3). These power control units are supplied with
hydraulic power, one from system A and the other from system B. Aileron hydraulic supplies are controlled by the flight controls shutoff valve in each flight controls hydraulic modular package (Fig. 4 and 5). Switches for these valves are on the pilots' overhead panel. The aileron power control units are interchangeable with the elevator power control units and are located in the left wheel well. The aileron power control units drive a bus cable system connected to the ailerons by quadrants and pushrods. Balance tabs and balance panels aerodynamically reduce the
forces required for aileron movement. In the event of hydraulic failure,motion of the pilots' control wheels mechanically positions the ailerons.B. Lateral (roll) trim is accomplished by the aileron trim control switches (Fig. 2) located on the control stand. An electrical actuator in the
left wheel well repositions the artificial feel and centering mechanism null detent. This shift of aileron control system null detent provides trim correction by positioning the ailerons.C. Flight spoilers and ground spoilers are located on the upper surface of the wing. Two flight spoilers are outboard of each nacelle. Two ground spoilers are outboard of the flight spoilers, and one ground spoiler is inboard of each nacelle. The flight spoilers are hydraulically actuated in response to inputs from the aileron control system. The flight spoilers raise on the wing with up aileron and remain faired on the wing with down aileron. Flight spoiler motion is in proportion to aileron movement. One spoiler actuator hydraulically positions each flight spoiler panel. Hydraulic system A provides power for spoilers 3 and 6.Hydraulic system B provides power for spoilers 2 and 7. The flight spoilers may be deactivated by the spoiler shutoff valves in the flight controls hydraulic modular packages (Fig. 4). These valves are controlled by spoiler system A and B switches on the pilots' overhead panel (Fig. 5). All flight spoilers may also be used as speed brakes by aft movement of the speed brake control lever (Fig. 2). The speed brake control lever actuates the spoiler control system to cause all the flight spoiler panels to raise in unison. The flight spoilers will still respond to aileron inputs when being used as speed brakes. With speed brakes on and the airplane on the ground, hydraulic system A will power the ground spoilers 0, 1, 4, 5, 8, and 9 to full up position.
3. Pitch Control System
A. The elevators provide primary response of the airplane in pitch control.Fore and aft movement of the captain's and first officer's control columns (Fig. 2) is transmitted through the elevator control system to the control valves of the two elevator power control units. These power control units are supplied with hydraulic power, one from system A and the other from system B. Elevator hydraulic supplies are controlled by the flight controls shutoff valve in each flight controls hydraulic modular package (Fig. 4). Switches for these valves are located on the pilots' overhead panel (Fig. 5). The power control units are interchangeable with the aileron power control units and are located in the empennage aft of the stabilizer rear spar. These power control units drive the elevator through pushrods and a torque tube. Balance panels and tabs aerodynamically reduce the forces required for elevator movement. In the event of hydraulic failure, motion of the pilots'control columns mechanically positions the elevators. Also, the elevator balance tabs reduce the forces required to operate the elevator.B. The adjustable horizontal stabilizer provides pitch (longitudinal) trim. The stabilizer is controlled by stabilizer trim control switches (Fig. 2)located on the outboard horn of both the captain's and first officer's control wheels. Manual operation of the stabilizer is accomplished by rotating the stabilizer trim control wheels located on the control stand. The stabilizer trim control wheels operate a forward mechanism which drives the stabilizer trim indicator and are connected to the stabilizertrim actuator by cables. The trim actuator is a gearbox, jackscrew, and ballnut assembly which drives the stabilizer front spar to provide stabilizer motion. The gearbox is driven by an electric actuator, an autopilot actuator, and a cable drum. The autopilot actuator and main trim actuator is powered by a two-speed reversible electric motor.Stabilizer trim cutout switches located on the control stand electrically
4. Rudder Control
A. The hydraulically-powered rudder is controlled by the captain's and firstofficer's rudder pedals (Fig. 2). The rudder pedals are bussed together and are adjustable fore and aft by use of pedal adjustment cranks. The pedals provide input to the rudder power control unit through the rudder control system. The power control unit moves the rudder with hydraulic power from both hydraulic systems A and B. Rudder hydraulic supplies are controlled by the flight controls shutoff valve in the flight controls hydraulic modular packages (Fig. 4). Switches for these valves are on the pilots' overhead panel (Fig. 5). In the event of hydraulic system A or B failure, the standby hydraulic system will drive a rudder standby power unit to move the rudder. Control of the standby hydraulic system power is by a shutoff valve on the standby modular package. The flight control switches on the pilots' overhead panel and the automatic standby function controls this valve. These switches and the automatic standby function also provide control for pressurizing the standby hydraulic system.B. Rudder trim is controlled by a rudder trim control switch (Fig. 2)located on the control stand. Motion from the trim control unit shifts rudder control system neutral providing trim correction by positioning the rudder.
5. Lift Devices
A. The lift devices consist of two pairs of triple slotted trailing edge flaps, three pairs of leading edge slats, and two pairs of leading edge flaps. Fore and aft movement of the flap control lever on the control stand is transmitted by the flap control system to the flap control valve in the main wheel well. The flap control valve directs power from hydraulic system B to actuate the flap power unit. The rotary motion of the flap power unit is transmitted by the flap drive system to retract or extend the trailing edge flaps. The trailing edge flaps can be located at intermediate angles depending on the positions of the flap control lever. In the event of hydraulic system failure, the trailing edge flaps may be operated electrically. In this case, control of the flaps is accomplished by two switches on the pilot's overhead panel (Fig. 5); one switch arms the electric flap drive system and the other switch activates the system to extend or retract the flaps. The trailing edge flap system is protected from excessive airloads by a flap load limiter system. The load limiter system automatically retracts the flaps from 40 to 30 units at airspeeds in excess of 162 knots.B. The leading edge slats are located outboard of the engines and extend forward from the wing leading edge. The leading edge flaps are located inboard of the engines and extend by rotating downward from the lower surface of the wing leading edge. Motion of the trailing edge flap drive system actuates the leading edge flap and slat control valve. This valve directs system B hydraulic power to drive the leading edge flap and slat actuators. The hydraulic system power transfer unit will automatically activate and supply system B hydraulic power if system B engine driven pump fails, airplane is in the air mode, and trailing edge flaps are not up. In the event of system B hydraulic failure, the leading edge flaps and slats may be driven to the fully extended position using power from the standby hydraulic system. In this case, the leading edge flaps and slats extend when the electric flap drive system is armed and the control switch is placed in the down position. An autoslat system automatically extends the leading edge slats from the intermediate position to the fully extended position at a predetermined angle of attack. The slats automatically retract to the intermediate position when angle of attack is reduced.
