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747-400
MAINTENANCE MANUAL

Figure 1 (Sheet 2)
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747-400
MAINTENANCE MANUAL

 B.  The center wing rear spar consists of a constant depth vertical web and angle chords which also serve as a structural part of the fuselage bulkhead at body station 1241. Vertical stiffeners attached to the web and chords provide additional rigidity. The outboard rear spars are beams which consist of a web and upper and lower angle chords. The spar tapers down in depth toward the wingtip. Vertical stiffeners, attached to both faces of the web, provide a means of attaching the wing inspar and trailing edge ribs.
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 1.

2.

3.

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747-400 MAINTENANCE MANUAL
 WING RIBS - DESCRIPTION AND OPERATION
_____________________________________General
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 A.  The wing ribs consist of three basic types: join ribs, standard ribs, and special ribs. Join ribs are provided where the wing joins the body, forming the inboard end of the wing box, and where the wing extensions join the wing box, forming the outboard end of the wing box. Outboard of the wing-to-body ribs, the standard wing ribs, which extend from the front spar to the rear spar, are located normal to the rear spar. The special ribs are located as required to carry various wing loads.
 B.  The wing ribs in the integral fuel tanks act as baffles to prevent excessive fuel surges resulting from airplane attitude changes. Full baffle ribs are provided with check valves to contain fuel around the fuel boost pumps and still permit free flow of fuel when the airplane is in level flight.
Join Ribs (Fig. 1)
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 A.  Join ribs are used where the wing joins the body and where the wing extensions join the wing box.
 (1)  
The two wing-to-body ribs, one each on the left and right side of fuselage, basically consist of chords, stiffened webs, and straps. The rib is attached to the front, mid, and rear spars, and No. 1, 2, and 3 spanwise beams. The rib is sealed to form the closure rib for the wing integral fuel tank.

 (2)  
The two wing-extension-to-wing-box ribs, one each at the outboard end of the left and right wing boxes, are constructed differently than any other rib. The upper chord, web, and stiffeners are made of a single aluminum casting. The lower chord, which is made by forming and machining an aluminum extrusion, is attached to the casting. The stringers, spars and skin of the wing box and wing extension are attached to the rib assembly.

Standard Ribs (Fig. 1)
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 A.  Standard ribs are of two basic types: those used inboard of wing station 1224 and those used outboard of wing station 1224.
 (1)  Inboard of wing station 1224, the rib consists of a forward section, located between the front and mid spars, and aft section, located between the mid and rear spars. Each rib section is formed by an upper angle chord, stiffened web, and lower angle chord. Along the upper and lower edges of the web, an angle chord attaches the rib to the wing stringers; and at the forward and aft ends, the rib web is attached to spars.
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747-400 MAINTENANCE MANUAL
BBL 127.75
BBL 0.0
WING-TO-BODY RIB
SEE  A  FRONT SPAR 
SPANWISE 
NACELLE  B  A  BEAM NO. 3 SPANWISE 
　
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