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,
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
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
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.
HYDRAULIC DROOP AILERON SYSTEM
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
EMERGENCY FLAP SYSTEM
If electrical and hydraulic power fails, the flaps
can be lowered by the emergency system. An
emergency flap extension bottle with a
300-cubic-inch capacity and charged to 3,000 psi
provides a power source. Emergency extension is
controlled by the emergency flap control handle,
which is mechanically linked to the emergency flap
air selector valve. Pulling the handle aft, the piston
inside the air selector valve shifts, alIowing
high-pressure air to flow through a separate set of
lines to shuttle valves in the flap system. The shuttle
valves reposition, and air pressure extends the flap
Air pressure also repositions the flap
system dump valve, dumping return side hydraulic