OFFSET GEARBOXES. The eight offset gearboxes in the flap system transmit power produced by the flap drive gearbox around wing structure obstacles and compensate for wing angularity. They also reduce the flap drive gearbox speed of 1,080 rpm to about 550 rpm at the outboard actuators.

FLAP WING-FOLD SHAFT. A wing-fold shaft consists of two interlocking splined sections and two universal joints connected to quill shafts. It provides a telescoping fold joint in the flap drive system linkage between the inboard and outboard wing panels.

The slat system, shown in figure 9-37, provides additional lift and stability to the aircraft at lower speeds in the same manner as the leading edge flap

Figure 9-37.Slat drive system.

 system previously discussed. The flap control handle controls the movement of the slats. Moving the flap control handle to the TAKEOFF or LAND position causes the slats to extend to a 27.5-degree leading edge down position.

The slat panels, one inboard and one outboard, interlock by a pin when the wings are spread. When fully retracted, the slats align with the top and bottom wing contours to form the wing leading edge. Shim spacers between the slats and the slat tracks provide adjustment for proper aerodynamic fairing.

Components of the slat system arc similar to those in the flap system. The slats extend and retract by using six series-linked ball screw actuators. The actuators are powered by the hydraulic motor through gearboxes and torque tubes.

If combined hydraulic system pressure fails, the hydraulic motor is locked in the same manner as the flap hydraulic motor, permitting the emergency electric motor to move the slats. Emergency slat operation is accomplished simultaneously with emergency flap operation, using the emergency flap switch. Slat position is also displayed on the cockpit integrated position indicator.

Placing of the flap control handle to either the TAKEOFF or LAND position mechanically closes switches to provide electrical current to the slat selector valve. The selector valve ports hydraulic pressure to the extend side of the high-speed hydraulic motor. This action drives the center gearbox and extends the slats.

Two ball screw actuators drive each outboard slat, and one drives each inboard slat of each wing. Each actuator connects to its downstream actuator by torque tubes and gearboxes. The slats move as one unit. Limit switches in the center drive gearbox de-energize the slat selector valve, blocking flow to the drive motor when the slats fully extend (27.5 degrees) or retract. Placing the flap control handle to the UP position energizes the opposite solenoid of the selector valve and reverses slat motor direction, retracting the slats. 

SLAT WING FOLD GEARBOX. A wing fold gearbox disconnects slat drive linkage at the wing fold joint when the wings fold. The gearbox consists of two identical halves interconnected by a spring-loaded disconnect coupling when the wings are spread. As the disconnect coupling halves move away from each other during the wing folding operation, a spring-operated brake engages, preventing relative motion between the inboard and outboard sections.

SLAT ANGLE GEARBOXES. Four slat angle gearboxes are provided in the slat system for changing direction of the slat torque tube linkage from the center gearbox to the wing actuators.