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Kỹ thuật máy bay chiến đấu Episode 1 Part 8

Tham khảo tài liệu 'kỹ thuật máy bay chiến đấu episode 1 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 162 AIRCRAFT DESIGN Fig. 8.7 Structural concepts for fuselage loads. of the engine. The resulting weight penalty compared to a podded engine must be balanced against the reduced drag of a buried engine installation. Figure 8.5 illustrates another important concept in structural arrangement. Large concentrated loads such as the wing and landing gear attachments must be carried by a strong heavy structural member such as a major fuselage bulkhead. The number of such heavy bulkheads can be minimized by arranging the aircraft so that the bulkheads each carry a number of concentrated loads rather than requiring a separate bulkhead for each concentrated load. In Fig. 8.5 the two bulkheads in the aft fuselage carry the loads for the engines tails and arresting hook. Had the tails and engine been located without this in mind the structural designer would have had to provide four or five heavy bulkheads rather than the two shown. The lift force on the wing produces a tremendous bending moment where the wing attaches to the fuselage. The means by which this bending moment is carried across the fuselage is a key parameter in the structural arrangement and will greatly influence both the structural weight and the aerodynamic drag of the aircraft. Figure 8.8 illustrates the four major types of wing carrythrough structure. The box carrythrough is virtually standard for high-speed transports and general-aviation aircraft. The box carrythrough simply continues the wing box through the fuselage. The fuselage itself is not subjected to any of the bending moment of the wing which minimizes fuselage weight. However the box carrythrough occupies a substantial amount of fuselage volume and tends to add cross-sectional area at the worst possible place for SPECIAL CONSIDERATIONS 163 Fig. 8.8 Wing carrythrough structure. wave drag as discussed above. Also the box carrythrough interferes with the longeron load-paths. The ring-frame approach relies upon large heavy bulkheads to carry the .