Dan Winterland said......"None of the LE devices in the 747s are slotted."
Well, I beg your pardon, if your Honour shall allow me to object!
Come on guys. None of this stuff is rocket science! This aircraft type (or shall I say derivative so as to include -100, -200, -300, -400, SP, E4B, VC-25, Combi, Freighter, Shuttle transport etc, etc, etc, etc, etc) first flew on the 9-FEB-1969 and entered service on 22-JAN-1970. This was over 27 years ago and none of this design is state secret any more (if ever it was). If I may quote from the Boeing "description and operation" section of the 747 maintenance manual:
Krueger Flaps.
Operation
The krueger flaps are positioned by rotary actuators which drive
mechanical linkages attached to the flap. The flaps retain a flat
surface when they extend and there is no gap created to allow
airflow between the leading edge flap and the wing leading edge.
Each flap has a folding nose which is unfolded when the flap is
extended, and restowed above the flap panel when the flap is
retracted. The nose is hinged to the flap and positioned by the flap
linkage.
The flap is supported by two hinges which attach to the wing leading
edge.
Bulb seals are provided at the sides and forward and aft edges of
each flap panel for aerodynamic sealing.
Variable Camber Leading Edge Flaps
Operation
The flaps are positioned by rotary actuators connected to drive arms.
Mechanical linkages curve the flexible fiber glass panels as they
drive. The area of each flap is increased by a folding nose which is
positioned at the flap leading edge as the flap is extended. A slot is
also formed between the flap and the wing leading edge to increase
aerodynamic efficiency. The folding nose section is stowed and the
panel returned to a flat shape when the flap is retracted.
As for retraction when symetrical reverse is applied:
Automatic Leading Edge Flap Retraction
Group A leading edge flaps are automatically retracted during ground
reverse thrust operation in order to improve structural life of the flap
panels. The function is armed when the airplane is on the ground and
the flaps are operating in the pneumatic mode.
Group A leading edge flaps retract when armed and engines 1 and 4
are placed in reverse thrust or engines 2 and 3 are placed in reverse
thrust. The flaps re-extended when the reverse thrust signals are
removed.
NOTE:
Thrust reverser operation is defined as reverse thrust
selected or airmotor brake released or gearbox unlocked
on a symmetrical pair of engines.