Flap System
applied, the ailerons will extend 16 1/2 degrees down.
The control stick will remain centered. The droop
The flaps divide into two panels per wing at the
aileron actuating cylinder (fig. 16-34), one in each
wing-fold joint. Each panel is supported by two sets of
wing, extends by flap down utility hydraulic pressure.
tracks and rollers that are driven by two ball screw
The droop aileron is retracted by springs in the cylinder
actuators. Pressure from the combined hydraulic
when extend pressure is removed. The droop cylinder
system powers the flap drive motor and gearbox
connects between the aircraft structure and an idler bell
assembly, shown in figure 16-35.
crank in the aileron power package linkage. With flaps
up, the droop cylinder acts as a solid link. When the
If the combined hydraulic system fails, a hydraulic
flap control switch is placed in the 1/2 or DN position,
brake locks the hydraulic motor, and an emergency
the droop aileron extend relay energizes. This relay
electric motor provides continued operation.
completes the extend electrical circuit to the droop
Emergency flap extension and retraction is controlled
by placing the EMERG FLAP switch on the throttle
aileron actuators. As the actuators extend, the aileron
quadrant at either UP or DN. Cam-operated switches
power cylinder input levers reposition, and both
within the flap drive gearbox provide input signals to
ailerons droop as before. The actuators are
show the flap position on the cockpit-integrated
de-energized by the integral extend limit switch. The
position indicator.
ailerons are free to operate normally. When the flap
control switch is placed to UP, the droop aileron extend
Operation of the flap control handle energizes the
relay is de-energized. The droop actuator reposition
solenoid-operated flap selector valve, directing
the aileron power cylinder input levers. Both ailerons
hydraulic pressure to the extend or retract lines of the
move back to their normal position. The droop
flap drive motor. The wings must be spread and locked
actuators are de-energized at the completion of the
to provide a complete electrical circuit through the
retract cycle by the integral limit switch.
wing unlock relay to the selector valve.
Placing the flap control handle to the TAKEOFF
EMERGENCY FLAP SYSTEM
position completes the electrical circuit through the
30-degree switch and cam-operated flap drive gearbox
If electrical and hydraulic power fails, the flaps can
limit switch to the selector valve. Pressure ports to the
be lowered by the emergency system. An emergency
down side of the high-speed hydraulic motor, which
flap extension bottle with a 300-cubic-inch capacity
drives the gearbox. The flap drive gearbox, through a
and charged to 3,000 psi provides a power source.
series of torque tubes and offset gearboxes, drives all
Emergency extension is controlled by the emergency
eight flap actuators.
flap control handle, which is mechanically linked to
The flap actuators, shown in figure 16-34, drive the
the emergency flap air selector valve. Pulling the
carriage and attaching flaps out and down to the
handle aft, the piston inside the air selector valve shifts,
30-degree position. The limit switch in the flap drive
allowing high-pressure air to flow through a separate
gearbox opens, de-energizing the selector valve
set of lines to shuttle valves in the flap system. The
circuit, allowing the valve shuttle to return to neutral,
shuttle valves reposition, and air pressure extends the
blocking flow to the motor, and preventing further flap
flap actuators. Air pressure also repositions the flap
extension.
system dump valve, dumping return side hydraulic
fluid overboard. The leading edge flaps extend to the
full down position and trailing edge flaps to the 1/2
down position. The aileron drooping feature does not
operate when the flaps are lowered by the emergency
flap system.
SEMI-INDEPENDENT FLAP AND SLAT
SYSTEM
This system consists of semi-independent flap and
slat systems, which raise and lower using hydraulic
motors drive units, torque tubes, and screw jack-type
Figure 16-35.--Flap drive gearbox.
actuators.
16-40
