transferring loads that applied at different times and under different loading cases; minimizing disruption of the load flow caused by different stress concentrators (cuts, holes, acute angles, abrupt changes of cross section area) that lead to increase of structural weight and decrease of airplane life span.
79 The criterion of general design rationality for separate units and for the whole airframe is the load-carrying factor that takes into accounts the internal stress value and the length of its action. It should be mentioned that all joints and cuts increase the airframe weight. The airplane structural and load-carrying scheme should define ways of load-transfer and specify elements that take part in load-transfer and balancing of the loads that applied to the airplane: aerodynamic forces, mass forces, forces of engine thrust, land reaction forces. The airplane structural and load-carrying scheme should provide the simplest and the most efficient methods of manufacturing airplane parts, junctions and units. This scheme together with the spatial-weight layout should provide the best airframe operating performance owing to the convenient access to all units and systems for their maintenance and repair. All decisions made when choosing the load-carrying scheme should be listed in the explanatory notes with the specification of the chosen load-carrying scheme for each unit, the main construction material, the type and the dimensions of raw materials, the type of the load-carrying elements that carry large concentrated loads, the principle of strengthening for big cut-offs in the fuselage and in the wing. 8.3 Specifying the aerodynamic scheme Development of the spatial-weight and the structural and load-carrying layouts and solution to problems of correlating space required for placing payload with locations of the load-carrying elements yield changes of some parameters and dimensions of the airplane units and also their relative position. Thus the final stage of the layout is to update and finalize the choice of all parameters and dimensions that define the aerodynamic scheme and the external
80 shape of the airplane. These changes and specifications lead to the necessity of updating the drawing of the airplane that was made in section 6. Nowadays all three stages of layout development are carried out in parallel- sequential way with the aid of three-dimensional mathematic models (3D models) and software that automate this process or some of its stages. 8.4 The airplane layout drawing The result of airplane layouts development is the airplane layout drawing that should exactly define the airplane design. The main drawing projection is the airplane longitudinal section along the symmetry plane or the planes that are parallel to the symmetry plane. It is supplemented by plan view (with reduced scaling) at which the starboard wing can be shown partially. Additionally, the drawing should contain several large-scale fuselage cross sections.
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- Summer '17
- Aerodynamics, ........., Requirements analysis, Takeoff