Aircraft Design: Synthesis and Analysis - part 6

Một số điểm cần được thực hiện về các kết quả trên đây. 1. Kết quả sidewash trên winglet (trong mặt phẳng Trefftz) là không cho kéo gây ra tối thiểu có nghĩa là kéo tự do của winglet chỉ hủy bỏ winglet lực đẩy liên kết với sidewash cánh. Tối ưu tải cánh nhỏ do đó làm giảm kéo gây ra bằng cách hạ thấp các downwash bình quân trên cánh, | Several points should be made about the preceding results. 1. The result that the sidewash on the winglet in the Trefftz plane is zero for minimum induced drag means that the self-induced drag of the winglet just cancels the winglet thrust associated with wing sidewash. Optimally-loaded winglets thus reduce induced drag by lowering the average downwash on the wing not by providing a thrust component. 2. The results shown here deal with the inviscid flow over nonplanar wings. There is a slight difference in optimal loading in the viscous case due to lift-dependent viscous drag. Moreover for planar wings the ideal chord distribution is achieved with each section at its maximum Cl Cd and the inviscid optimal lift distribution. For nonplanar wings this is no longer the case and the optimal chord and load distribution for minimum drag is a bit more complex. 3. Other considerations of primary importance include Stability and control Structures Other pragmatic issues More details on the design of nonplanar wings may be found in a recent paper Highly Nonplanar Lifting Systems accessible here. Wing Layout Having decided on initial estimates for wing area sweep aspect ratio and taper an initial specification of the wing planform is possible. Three additional considerations are important High and Low Wings High wing aircraft have the following advantages The gear may be quite short without engine clearance problems. This lowers the floor and simplifies loading especially important for small aircraft or cargo aircraft that must operate without jet-ways. High wing designs may also be appropriate for STOL aircraft that make use of favorable engine-flap interactions and for aircraft with struts. Low wing aircraft are usually favored for passenger aircraft based on considerations of ditching water landing safety reduced interference of the wing carry-through structure with the cabin and convenient landing gear attachment. Wing Location on the Fuselage The wing position on the .

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