Several types of naval aircraft are equipped with flap systems that feature both leading edge and trailing edge flap panels. On some aircraft these leading edge panels are referred to as slats. Figure 9-34 shows a leading edge and trailing edge flap arrangement. The figure shows flap operation with aileron drooping and boundary layer control. These features create even greater lift and stability than with flaps alone.

This flap system consists of three leading edge and one trailing edge flap panels for each wing, with each panel having its own actuator. A three-position flap control switch in the cockpit is labeled "UP, 1/2, and DN."

The leading edge flaps operate by a manifold-mounted selector valve and dual actuating cylinders. Trailing edge flaps use this same selector valve plus a wing-mounted selector valve and dual tandem actuating cylinders. 

When the flap control switch is placed in the 1/2 position, the manifold-mounted selector valve directs utility system pressure through the shuttle valves. Pressure is sent into the down lines of the leading edge flap actuators. The leading edge flaps are lowered to the full down position. The inboard leading edge flap deflection is 30 +0, 2 degrees. The center flap deflection is 60 +0, 2 degrees. The outboard flap deflection is 55 1/2 degrees 1/2 degree.

At the same time, hydraulic fluid flows through the fuselage-mounted flow divider and into the extend side of the dual tandem trailing edge flap actuating cylinder. This action moves the trailing edge flaps to the 1/2 position with a deflection of 30, 2 degrees. The cockpit flap position indicator indicates barber poles while the flaps are in transit and flap position at the completion of selected movement. The limit switches are connected into the control circuit in series to provide an indication of flap position and to continuously energize the electrical circuits to maintain hydraulic pressure when the flaps are down. Moving the flap control switch to the full down position actuates the wing-mounted selector valve, porting pressure through a second flow divider. Pressure is sent into the down side of the retracted half of the trailing edge flap cylinder, moving the flaps from the 1/2 to the full down position. Full down position is 60 +1, 2 degrees. Both flap position indicators will indicate DN when the cycle is completed.

Placing the flap control switch to the UP position allows hydraulic pressure to be directed to the retract side of all flap actuators. Position indicators indicate UP. The electrical control circuits and solenoids of both selector valves are de-energized. The leading edge flaps are locked in the UP position by the overcenter locking mechanism. The trailing edge flaps are locked up by internal locks within the trailing edge actuating cylinders.

When the flap switch is placed in 1/2 or DN position, with PC 1, PC 2, and utility hydraulic power applied, the ailerons will extend 16 1/2 degrees down. The control stick will remain centered. The droop aileron actuating cylinder (fig. 9-34), one in each wing, extends by flap down utility hydraulic pressure. The droop aileron is retracted by springs in the cylinder when extend pressure is removed. The droop cylinder connects between the aircraft structure and an idler bell crank in the aileron power package linkage. With flaps up, the droop cylinder acts as a solid link. When the flap control switch is placed in the 1/2 or DN position, the droop aileron extend relay energizes. This relay completes the extend electrical circuit to the droop aileron actuators. As the actuators extend, the aileron power cylinder input levers reposition, and both ailerons droop as before. The actuators are de-energized by the integral extend limit switch. The ailerons are free to operate normally. When the flap control switch is placed to UP, the droop aileron extend relay is de-energized. The droop actuator reposition the aileron power cylinder input levers. Both ailerons move back to their normal position. The droop actuators are de-energized at the completion of the retract cycle by the integral limit switch.