27-50-00
ALL ú ú 01 Page 109 ú Apr 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 FAULT ISOLATION/MAINT MANUAL
PILOTS' CENTER P54 PANELINSTRUMENT PANEL, P2-3
P6 PANEL SEE O
HATCH P415
(125B) PANEL
CENTER EQUIPMENT CENTER
E2-2 ALTN FLAPS EXT/RET
PILOTS' CONTROL
SWITCH, S1709 STAND L,C,R FLAP CONTROL
SEE P UNITS, M7881,M7880,
ALTN FLAPS M7879
OFF ALTN FLAPS
RET
EXT ARM SWITCH,
E1-2
S1710
FLAP CONTROL
ARM LEVER
RETRACTUP
FLAP CONTROL
ALTN SEE Q
270K-.82M
LEVER HANDLE
w
P2-3 PILOTS' CENTER
A A
INSTRUMENT PANEL O
FLAP UP
1
FLAP CONTROL
5
LEVER RVDT
PILOTS' CONTROL STAND
ASSEMBLY
10
P
20
FLAP
25
30
FLAP CONTROL LEVER A-A Q Flaps - Component Location Figure 102 (Sheet 6)
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27-50-00
ALL ú ú 01 Page 110 ú Jun 10/89
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400 MAINTENANCE MANUAL
TRAILING EDGE FLAP SYSTEM - DESCRIPTION AND OPERATION
_____________________________________________________
1. General (Figs. 1 & 2)_______
A. Two triple-slotted trailing edge flaps on each wing provide additional lift during takeoff, approach, and landing. As the trailing edge flaps are progressively extended, wing geometry is changed by first extending the chord and then increasing camber. Wing area and camber are further increased by 28 leading edge flaps (Ref 27-81-00), which operate in conjunction with the trailing edge flaps.
B. The inboard and outboard trailing edge (TE) flaps are positioned by independent drive systems. In normal operation, the TE flaps are hydraulically powered. As a backup to hydraulically powered operation, the flaps may be positioned by electric motors.
C. The flaps are normally controlled from a flap control lever on the pilots' control stand. The lever is linked to a triple Rotary Variable Differential Transformer (RVDT) assembly. Each RVDT converts flap lever position to an electrical signal which is sent to the flap control units in the main electrical equipment center. The flap control units monitor flap lever position and other airplane systems to command the flap actuator to change flap position.
Trailing Edge Flap Control System Block Diagram
Figure 1
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27-51-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
D. The flap actuator in the left body gear wheel well moves the input cranks to the inboard and outboard flap power packages when commanded by the flap control units. The input cranks position a control valve in each power package to port hydraulic fluid to the hydraulic motors. Each hydraulic motor is joined to a reduction gearbox which drives a torque tube extending into each wing. Angle gearboxes are installed along the torque tubes to permit change of direction. The torque tubes connect to two transmissions at each flap. The transmissions position the midflap of each three-part TE flap set through ball screw drives. Foreflaps and aftflaps are positioned as the midflap is moved.
E. An electric motor in each power package drives the TE flaps as an alternate to hydraulically powered operation. If flaps fail to move under hydraulic power, the flap control units automatically activate the alternate electric motors to position the flaps. The motors can also be controlled independently of the flap control units with switches on the pilots' center instrument panel.
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