Text 1 Phases of Aircraft DesignConceptual Design Aircraft design can be broken into three major phases, Conceptual Design, Preliminary Design and Detail Design. Conceptual design is the primary focus of this book. It is in conceptual design that the basic questions of configuration arrangement, size and weight, and performance are answered. The first question is, “Can an affordable aircraft be built that meets the requirements?” If not, the customer may wish to relax the requirement. Conceptual design is a very fluid process. New ideas and problems emerge as a design is investigated in ever-increasing detail. Each time the latest design is analyzed and sized, it must be redrawn to reflect the new gross weight, fuel weight, wing size, engine size, and other changes. Early wing-tunnel tests often reveal problems requiring some changes to the configuration. The steps of conceptual design are described later in more detail. 飞机设计可以分成三个主要的阶段：概念设计、初步设计和详细设计。本书主要讨论概念设计。飞机外形，尺寸和重量以及性能等基本问题在概念设计阶段都将得到答案。第一个问题是：“能否生产出经济上可以承受，性能上满足要求的飞机？”如果答案是否定的，那么订购商应该考虑放宽要求。概念设计是一个灵活多变的过程。新的想法和新的问题都会随着设计的进一步细化而出现。每一次最新的设计经过分析和定尺寸后，都要重新绘制草图以体现出新的总重，油料重量，机翼尺寸，发动机尺寸和其它变化。早期的风动测试通常会反应出很多的问题，需要对飞机的外形进行改进。我们将在后面更加详细的讨论概念设计的步骤。Preliminary Design Preliminary design can be said to begin when the major changes are over. The big questions such as whether to use a canard or an aft tail have been resolved. The configuration arrangement can be expected to remain about as shown on current drawings, although minor revisions may occur. At some point late in preliminary design, even minor changes are stopped when a decision is made to freeze the configuration. During preliminary design the specialists in areas such as structures, landing gear, and control systems will design and analyze their portion of the aircraft. Testing is initiated in areas such as aerodynamics, propulsion, structures, and stability and control. A mockup may be constructed at this point. 初步设计可以说在主要的改进结束后就开始了。像要采用鸭翼还是尾翼等的重要问题已经被确定下来了。虽然会有小的修改，但飞机的外形布局仍然希望以现有设计图纸主。在初步设计后期的某个时候，当飞机外形布局被确定的时候，即使很小的修改也是不允许的。在初步设计阶段，来自不同领域的专家，如结构、起落架和控制系统等，将设计和分析飞机上与他们相关的那一部分。气动、推力、结构、稳定性和控制测试就开始了。样机可能会在这一阶段建造出来。 A key activity during preliminary design is “lofting”. Lofting is the mathematical modeling of the outside skin of the aircraft with sufficient accuracy to insure proper fit between its different parts, even if they are designed by different designers and possibly fabricated in different locations. Lofting originated in shipyards and was originally done with long flexible rulers called “splines”. This work was done in a loft over the shipyard; hence the name. The ultimate objective during preliminary design is to ready the company for the detail design stage, also called full-scale development. Thus, the end of preliminary design usually involves a full-scale development proposal. In todays environment, this can result in a situation jokingly referred to as “you-bet-your-company”. The possible loss on an overrun contract or from lack of scales can exceed the net worth of the company! Preliminary design must establish confidence that the airplane can be built on time and at the estimated cost. 初步设计阶段一个重要的活动就是放样。放样就是有足够的准确度的飞机蒙皮外形的数字化模型，它用来保证飞机不同部分之间能够很好的配合，即使这些组件或配件来自不同的设计部门，或者由不同的工厂生产。放样源于船坞，最初是用一根被称为样条的长软尺来完成的。这项工作是在船坞上面的阁楼中完成的，因此就获到了这个名字。初步设计阶段的目标是让企业为详细设计，或者是说零件设计阶段做好准备。因此，初步设计通常会给出一个完整规模发展的计划书。在现在的环境下，这将陷进这样的一个被戏称为“你将赌注压在你公司身上”这样的一个情形中。合同上的超支或缺乏衡量尺度引起的损失会超过公司的净产值。初步设计必须相信飞机制造能按预期费用并准时完工。 Detail Design Assuming a favorable decision for entering full-scale development, the detail design phase begins in which the actual pieces to be fabricated are designed. For example, during conceptual and preliminary design the wing box will be designed and analyzed as a whole. During detail design, that whole will be broken down into individual ribs, spars, and skins, each of which must be separately designed and analyzed. Another important part of detail design is called production design. Specialists determine how the airplane will be fabricated, starting with the smallest and simplest subassemblies and building up to the final assembly process. Production designers frequently wish to modify the design for ease of manufacture; that can have a major impact on performance or weight. Compromises are inevitable, but the design must still meet the original requirements. 当支持做出进入大量生产的决定的时候，详细设计阶段就开始了。在详细设计阶段，每一个将要加工生产的具体零件都会被设计出来。例如，在概念设计和初步设计阶段翼盒是作为一个整体设计和分析的。在详细设计阶段，翼盒将分成独立的翼肋、桁条和蒙皮，并分别进行设计和分析。详细设计另一个重要的部分是生产设计。专业人员决定如何去制造飞机，从最小最简单的组件开始，然后在最后的总装配中进行组装。生产设计人员会经常想改变一些设计以达到简化制造，但这些改变会对飞机性能和重量都有很大的影响。难免要进行协调工作，但设计必须满足最初的设计要求。 It is interesting to note that in the Soviet Union, the production design is done by a completely different design bureau than conceptual and preliminary design, resulting in superior producibility at some expense in performance and weight. During detail design, the testing effort inten