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
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
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
simultaneously with emergency flap operation,
using the emergency flap switch. Slat position is
also displayed on the cockpit integrated position
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.
DIRECT LIFT CONTROL (DLC)
Direct lift control controls the spoilers and
horizontal stabilizers to increase aircraft vertical
descent rate during landings. This may be done
without changing engine power. Actuating the
DLC engage-chaff dispense push-button switch on
the control stick grip modifies the pitch and roll
Figure 9-38.Wing sweep control system.