747-400
FAULT ISOLATION/MAINT MANUAL

ALTERNATE SOLENOID VALVE, Y11LM01 PRESSURE
RECTIFIER AND REGULATOR PRIMARY DRIVE VALVE ASSEMBLY PNEUMATIC
INLET DUCT(REF)SOLENOID, (REF)Y11R001
ALTERNATE
ELECTRIC MOTOR,
Y11M002

SERVO MOTOR
AND SWITCH
ASSEMBLY,

OVERPRESSURE
Y11M001 SWITCH, Y11S001
ROTARY CONTROL VALVE
OUTPUT
(REF) DRIVE SPLINE
SENSITIVE ANNUNCIATOR
FEEDBACK SWITCH,
Y11S002

LE FLAP ELECTROPNEUMATIC DRIVE UNIT (TYPICAL)
E FROM SHT 3 P54 PANEL
FWD
CENTER EQUIPMENT CENTER SEE F
CENTER EQUIPMENT CENTER F
Lift Augmenting - Component Location
Figure 102 (Sheet 4)

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A

747-400
MAINTENANCE MANUAL

 LEADING EDGE FLAP SYSTEM - DESCRIPTION AND OPERATION
____________________________________________________
 1.  General
_______
 A.  Additional lift is provided during takeoff and landing by 28 leading edge (LE) flaps operating with the trailing edge (TE) flaps. Extension of the wing flaps changes wing camber to produce the desired lift. The 11 outboard and midwing flaps in each wing are variable camber flaps with the camber being changed as the flaps are extended. The remaining three flaps in each wing are Krueger flaps. Primary pneumatic power to position all LE flaps is provided by pneumatic motors. Electric motors provide power to position LE flaps in alternate or primary electrical operations.
 B.  For normal flap extension operation, the LE flaps are controlled automatically by the flap control units (FCU's). For normal flap retraction operation, the LE flaps are controlled by the FCU's and the TE flaps positions. Primary pneumatic power for the power drive units (PDU's) is provided by pneumatic motors; primary electric and alternate power by electric motors. The LE flaps are driven by the PDU's through a torque tube system. The flaps are then positioned by rotary actuators. All LE flaps are designed as two position surfaces, either full up or full down. In the non-normal flap configurations, the LE flap indication displays the flaps in full up, full down, disagree, or in transit position for inboard, midspan, or outboard LE flaps.
LE FLAP POSITION

Leading Edge Flap Control System Block Diagram
Figure 1

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL

 C.  The LE flaps are extended in two groups. Group A LE flaps, consisting of flaps No. 6 through 13 in the left wing and No. 14 through 21 in the right wing, will extend together when the flap control lever is moved to the 1 unit detent. The remaining LE flaps, group B, will extend when the flap control lever is moved to the 5 unit detent.
 D.  The LE flaps are sequenced to retract in two groups. Group A LE flaps will retract when the flap control lever is moved to the full UP detent and after the outboard TE flaps is fully retracted. Group B LE flaps will retract when the flap control lever is moved to the 1 unit or full UP detent and the inboard TE flaps are less than 5 units.
 E.  All LE flaps are two-position flaps, intended to be either full up or full down. Normal extension or retraction of either group of the LE flaps by pneumatic motors requires approximately 10 seconds. If the flaps fail to respond in the pneumatic mode, the affected group of flaps are automatically driven to the commanded position by electric motors. The primary electric operation requires approximately 75-100 seconds. During normal operation, the group A LE flaps will be automatically retracted after landing upon application of reverse thrust and extended when the reverse thrust levers are returned to normal.
 F.  Alternate operation of the LE flaps is accomplished by an electric motor installed on each of the flap PDU's. These motors are controlled by an ALTN FLAPS ARM switch and an ALTN FLAPS EXT/RET switch located on the pilots' center panel. The ALTN FLAPS ARM switch provides power to the electric drive motors. These motors automatically drive the LE flaps to the position selected on the ALTN FLAPS EXT/RET switch. The LE flaps are extended or retracted using the same drive components as used with the pneumatic system. Alternate extension or retraction of the LE flaps requires 75-100 seconds. The inboard TE flaps must be fully retracted for the LE flaps to retract in alternate mode.
　
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