Leading Edge Devices
The secondary flight controls, high lift devices consisting of trailing edge (TE)
flaps and leading edge (LE) flaps and slats (LE devices), are powered by hydraulic system
B. Under certain conditions the power transfer unit (PTU) automatically powers the LE
devices. They can also be extended using standby hydraulic pressure.
LE devices consist of four flaps and eight slats: two flaps inboard and four slats outboard of
each engine. Slats extend to form a sealed or slotted leading edge depending on the TE
flap setting. The TE devices consist of double slotted flaps inboard and outboard of each
engine.
When the FLAP lever is moved from the UP position to the 1, 2, or 5 position, the TE flaps
extend to the commanded position and the LE:
- Flaps extend to the full extended position and
- Slats extend to the extend position.
When the FLAP lever is moved beyond the 5 position the TE flaps extend to the
commanded position and the LE:
- Flaps remain at the full extended position and
- Slats extend to the full extended position.
The LE devices sequence is reversed upon retraction.
Indicator lights on the center instrument panel provide overall LE devices position status.
The LE DEVICES annunciator panel on the aft overhead panel indicates the positions of
the individual flaps and slats.