control switch in the cockpit is labeled "UP, 1/2, and
energized, the valve permits return fluid to bypass the
DN."
restrictor in the down pressure line, permitting fast
retraction of the flaps and quicker wing-fold operation.
The leading edge flaps operate by a
manifold-mounted selector valve and dual actuating
A relief valve is located in the pressure line ahead
cylinders. Trailing edge flaps use this same selector
of the flap normal system selector valve. The valve
valve plus a wing-mounted selector valve and dual
relieves pressure from thermal expansion, which may
tandem actuating cylinders.
build up on the inlet side of the selector valve.
When the flap control switch is placed in the 1/2
An emergency system for flap down operation
position, the manifold-mounted selector valve directs
includes a selector valve and an emergency dump
utility system pressure through the shuttle valves.
valve. The emergency flap down selector valve is
Pressure is sent into the down lines of the leading edge
usually in the NORMAL position. In this position, the
flap actuators. The leading edge flaps are lowered to
cylinder emergency line to return is vented. When you
the full down position. The inboard leading edge flap
move the emergency selector valve handle to the
deflection is 30 +0, -2 degrees. The center flap
FLAPS DOWN position, you can lower the flaps by
deflection is 60 +0, -2 degrees. The outboard flap
operating the hand pump. This action directs hand
deflection is 55 1/2 degrees 1/2 degree.
pump pressure through the integral shuttle valve to the
actuating cylinder. At the same time, the emergency
At the same time, hydraulic fluid flows through the
dump valve is actuated. The emergency dump valve
fuselage-mounted flow divider and into the extend side
opens the up side of the cylinder directly to return and
of the dual tandem trailing edge flap actuating cylinder.
closes off its normal return line through the selector
This action moves the trailing edge flaps to the 1/2
valve.
position with a deflection of 30, 2 degrees. The
cockpit flap position indicator indicates barber poles
Once actuated, the dump valve must be reset
while the flaps are in transit and flap position at the
manually to restore the system to normal operation.
completion of selected movement. The limit switches
The emergency selector valve handle must first be
are connected into the control circuit in series to
returned to the NORMAL position, relieving the
p r ov i d e a n i n d i c a t i o n o f f l a p p o s i t i o n a n d t o
pressure in the emergency line. The dump valve is then
continuously energize the electrical circuits to
reset by pushing the button on the dump valve. The
maintain hydraulic pressure when the flaps are down.
button is marked PUSH TO RESET. With pressure in
the normal system, the normal selector handle must be
Moving the flap control switch to the full down
placed in the down position to reset the integral shuttle
position actuates the wing-mounted selector valve,
valve. The flaps will then raise using normal control,
porting pressure through a second flow divider.
provided the flap up portion of the system is operative.
Pressure is sent into the down side of the retracted half
There are no provisions for emergency retraction of the
of the trailing edge flap cylinder, moving the flaps from
flaps.
the 1/2 to the full down position. Full down position is
60 +1, -2 degrees. Both flap position indicators will
LEADING/TRAILING EDGE WING FLAP
indicate DN when the cycle is completed.
SYSTEMS
Placing the flap control switch to the UP position
allows hydraulic pressure to be directed to the retract
Several types of naval aircraft are equipped with
side of all flap actuators. Position indicators indicate
flap systems that feature both leading edge and trailing
UP. The electrical control circuits and solenoids of
edge flap panels. On some aircraft these leading edge
both selector valves are de-energized.
panels are referred to as slats.
The leading edge flaps are locked in the UP
Figure 16-34 shows a leading edge and trailing
position by the overcenter locking mechanism. The
edge flap arrangement. The figure shows flap
trailing edge flaps are locked up by internal locks
operation with aileron drooping and boundary layer
within the trailing edge actuating cylinders.
control. These features create even greater lift and
stability than with flaps alone.
HYDRAULIC DROOP AILERON SYSTEM
This flap system consists of three leading edge and
one trailing edge flap panels for each wing, with each
When the flap switch is placed in 1/2 or DN
panel having its own actuator. A three-position flap
position, with PC 1, PC 2, and utility hydraulic power
16-38
