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Airplane design 5 - component weight estimation - part 3

Nó được sử dụng các dữ liệu thống kê từ các thiết kế trước đây để ngoại suy thông tin cho một thiết kế mới. Tôi recomemnd cuốn sách này cho bất cứ ai từ một nhà thiết kế máy bay homebuilt để một kỹ sư hành nghề. -A cao cấp trong Kỹ thuật hàng không vũ trụ từ Đại học bang Iowa. | 4.2 METHODS FOR CONSTRUCTING y-n DIAGRAMS In this section a step-by-step procedure is presented for constructing v-n diagrams for the following types of airplanes 4.2.1 FAR 23 Certified Airplanes 4.2.2 FAR 25 Certified Airplanes 4.2.3 Military Airplanes Example applications for three airplanes are provided in sub-section 4.2.4. The v-n diagrams are used to determine design limit and design ultimate load factors as well as the corresponding speeds to which airplane structures are designed. As will be seen ỉn the Class II weight equations of Chapters 5-7 many require as input a design load factor and or a design speed. Important tiQtfig 1. The v-n diagrams given here are simplified versions of those defined in Refs 15-17. They should be used only in conjunction with Class II weight estimation methods. 2. In the Class II method only flaps-up cases are considered. 4.2.1 v-n Diagram for FAR 23 Certified Airplanes Reference 15 in Part 23.335 presents the v-n diagram shown in Figure 4.1. The following definitions apply to the various speeds given in the diagram Note all speeds are normally given in KEAS. Vg lg stall speed or the minimum speed at which the airplane is controllable vc design cruising speed VD - design diving speed VA design maneuvering speed Determination of these speeds and determination of the critical points A c D E F and G in Figure 4.1 is discussed in sub-sub-sections 4.2.1.1 through 4.2.1.7. Part V Chapter 4 Page 31 Figure 4.1 v-n Diagram According to FAR 23 4.2.1.1 Determination of lq stall speedi_vs vc 2 GW S pCM 1 2 4.4 5 wmax where GW - flight design gross weight in lbs . 2 s - wing area in ft 3 p air density in slugs ft c maximum normal force coefficient. Nmax 7 The maximum normal force coefficient follows from CN CT. 2 cn 2 1 2 4.5 N La u _ max max at Cr Bmax In preliminary design it is acceptable to set CN l.lCr 4.6 max max 4.2.1.2 Determination of design cruising speed _vc Vp k GW S 1 2 4.7 where the constant kc takes on the following values k