C. Section 44 extends from station 1000 to 1480 and contains the main deck, upper deck aft to Sta 1100, main gear wheel well, and provisions for the wing center section. Major structural members in this area include five bulkheads, keel beam, a torque box, the wing landing gear bulkhead, and the surface under the main deck floor beams. Structural openings in section 44 landing gear wheel well, and provisions for the wing center section.
D. Section 46 is the longest and most uniform of the five sections. It reaches from body station 1480 to 2360, and encloses the main deck and lower lobe. The lower lobe accommodates the aft containerized cargo compartment and the bulk cargo compartment. Attached to the lower lobe of section 46 is the aft end of the wing-to-body fairing. Structural openings include two cargo compartment doors, the observation windows, one on the left and one on the right.
E. There is a side cargo door on the left side of the airplane.
5. Fuselage Tail Section
_____________________
A. Section 48 is the nonpressurized tail section extending aft from body station 2360 to 2792. The smooth dome-shaped aft pressure bulkhead is part of the fuselage frame at body station 2360. The APU is also located in section 48. This section provides attachments for the vertical and horizontal tail structures. Major structural openings in section 48 are the actuator access and pressure relief door, the APU access door, APU air inlet, APU exhaust outlet, and the APU battery access door.
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A
747-400 MAINTENANCE MANUAL
MAIN FRAME - DESCRIPTION AND OPERATION
______________________________________
1. General (Fig. 1)_______
A. The main frame of the fuselage includes those members which form the basic shell exclusive of the skin and most skin reinforcements. It includes frames, bulkheads, stringers, floor-to-skin shear ties, the keel beam, wheel well structures, reinforcement structure around fuselage openings, and floor beams. All of the aforementioned is primary structure essential to the structural integrity of the airplane.
2. Main Frame Components_____________________
A. Frames are circumferential channel section or Z-section members generally spaced at 20-inch intervals along the length of the fuselage. They stabilize the skin and stringers and distribute concentrated loads (detail A, sheet 2).
B. Bulkheads consist of heavy frames with chords which fit all or part of the sectional contour of the airplane. Some bulkheads are reinforced by beams attached to the webs.
C. Stringers are longitudinal members spaced around the fuselage circumference and extending the full length of the fuselage. They are attached to the inboard face of the skin and the frame webs and chords. The stringers are typically hat-section or Z-section as required by location (detail A, sheet 2).
D. The floor-to-skin shear ties are those ties which extend longitudinally along the intersections of floor beams and frames (detail B, sheet 2).
E. The keel beam is the major longitudinal fuselage component in the main landing gear wheel well and wing center section areas. It extends along the fuselage centerline through the wheel well and under the wing center section.
F. The primary wheel well structures include bulkheads, beams, and torque boxes which contribute to fuselage integrity and support the landing gear attach fittings (Ref 53-15-00).
G. The floor beams attach to the frames except section 44 main deck floor beams where they run longitudinally and attach to the center wing box upper surface (detail B, sheet 2).
H. Additional stringers, frames, and/or skin doublers reinforce the
structural fuselage openings (Fig. 2).
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