747-400 AMM 飞机维护手册 机身 FUSELAGE(14)

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 A.  The floor-to-skin shear ties extend along both sides of the fuselage, lever with the floor at each deck. Two types of shear ties are used. A punched and formed sheet metal type is most common but a truss-type is used where decompression venting provisions are required. The shear ties are attached to fuselage skin stringers, floor beams, and body frame.
 B.  The floor-to-skin shear ties of sections 42 and 46 are the same. There are no floor-to-skin shear ties in section 44.
 6.  Keel Beam (Fig. 2)
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 A.  The keel beam consists of two main assemblies, the underwing keel beam from the forward to the rear wing center section spar, and the keel beam dividing the main landing gear wheel wells from station 1241 (rear spar) to 1480.
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 53-12-00
 ALL  ú ú 01 Page 5 ú Feb 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 B.  The underwing keel beam consists of a pair of high strength aluminum alloy compression chords 18.0 inches apart stabilized by shear webs from the chords to T-chords attached to the lower surface of the center wing section. Additional stabilization is acquired by 0.25 inch thick diagonal tie braces from the compression chords to the T-chords. Horizontal stabilization is attained by a shear web attaching the two compression chords.
 C.  The keel beam from stations 1241 to 1480 consists of a pair of high strength aluminum alloy compression chords spliced to the keel beam chords from the underwing keel beam and stabilized by a rectangular box structure. The box structure consists of shear webs, stiffeners, and diaphragm bulkheads. A shear web containing stiffeners to prevent buckling is installed between the main deck floor and the top of the keel beam aft of the wing rear spar to station 1480.
 7.  Window Opening Reinforcements
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 A.  The upper deck window openings in the skin are reinforced by doublers and high strength forged window frames. Extruded T-section stiffeners are attached to the upper and lower edges of the window frames.
 B.  The window opening reinforcements in sections 42, 44, and 46 on the main deck are basically the same. Doubler and window frame thickness increase with appropriate increases in stress level where adjacent to large cutouts or bulkheads.
 8.  Door Opening Reinforcements
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 A.  The main deck door openings are surrounded by doublers and skins machined from aluminum plate which are bonded or fay sealed and riveted together. Openings surrounding the cargo doors are similarly reinforced. A fay sealed doubler also surrounds the center electrical/electronic equipment access hatch.
 B.  Additional stringers, sills, straps, and frames have been added to these openings as required by local load conditions.
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 53-12-00
 ALL  ú ú 05 Page 6 ú Oct 10/94
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
 KEEL BEAM - INSPECTION/CHECK
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 1.  General_______
 A.  This procedure contains one task. The task is the inspection of the keel beam.
 B.  You get access to the keel beams through the wheel wells for the landing gear and the fuselage access panels.
 TASK 53-12-01-206-001
 2.  The Keel Beam Inspection (Fig. 601)________________________
 A.  References
 (1) 32-00-30/201, Landing Gear Door Locks
 B.  Access
 (1)  
Location Zone
 135 Wing Landing Gear Well, Left
 136 Wing Landing Gear Well, Right
 137 Body Landing Gear Well, Left
 138 Body Landing Gear Well, Right
 129 Keel Beam
 139 Keel Beam
 149 Keel Beam

 (2)  
Access Panel
 191GG Panel - Access - Keel Beam
 191JJ Panel - Access - Keel Beam
 191KK Panel - Access - Keel Beam
 193J Panel - Access - Keel Beam
 193K Panel - Access - Keel Beam
 193L Panel - Access - Keel Beam
　
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