CIVIL JET AIRCRAFT DESIGN

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Preface
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Introduction

Excellence in design is one of the principal factors that enable a developed nation to stay competitive in a global economy. The ability of companies to ‘add value’ to a product or manufactured goods is highly regarded throughout the world. Within this context, aircraft manufacture and operation is regarded as a desirable commercial activity. Many countries who previously were not involved in aeronautics are now moving into the business. However, as aircraft are made technically more complex, involve increasing interdependence between component parts (airframe, engines and systems), there is an increasing challenge to the industry. The aircraft design team is in the forefront of this challenge.

Set against this scenario are the conflicts between the various objectives and requirements for new aircraft projects. The designer is concerned about increasing performance and quality, meeting production deadlines, promoting total-life product support, and satisfying customer and infrastructure requirements. Above all these aspects the designer is expected to meet established safety and environmental requirements and to anticipate the sociological and political impact of the design. Balancing all these aspects within an acceptable cost and timescales is what makes aircraft design such a professionally challenging and ultimately satisfying activity.

One of the educational objectives of an aeronautical engineering curriculum is to introduce students to the procedures and practices of aircraft design as a means of illustrating the often conflicting requirements mentioned above. This textbook describes the initial project stages of civil transport aircraft design as an example of such practices. Obviously, the methods used have had to be simplified from industrial practice in order to match the knowledge, ability and timescales available to students. However, this simplification is made in the level of specialisation and detail design and not in the fundamental principles. An example of this approach is the substitution of general purpose spreadsheet methods in place of the specialist procedural-based mainframe programs commonly used for aircraft analysis in industry.

Apart from a general introduction to aircraft project design, this book provides an extension to the classical ‘Flight Mechanics’ courses. It also bridges the gap between specialist lectures in aerodynamics, propulsion, structures and systems, and aircraft project coursework. The scope of the book has purposely been limited to meet the objectives of undergraduate study. In order to illustrate the basic principles, a simplified approach has had to be made. Where appropriate, reference is made to other texts for more detailed study. Some prior knowledge of conventional theories in aerodynamics, propulsion, structures and control is necessary but where possible the analysis presented in the book can be used without further study. The terminology and the significance of various parameters is explained at the point of application and the main notation listed at the end of the book.

The Chapters

The book is arranged in two parts. In Chapters 1–14 each of the significant influences on aircraft project design is described. This part starts with a broad introduction to civil air transport, followed by a detailed description of the design process and a description of aircraft layout procedures. The next set of chapters are concerned with detailed descriptions of the design methods and an introduction to the principal aircraft components. The concluding chapters deal with the parametric methods used to refine the design configuration and a description of the formal presentation of the baseline design.

The second part of the book (Chapters 15–19) includes an introduction to the use of spreadsheet methods in aircraft design work and four separate design studies. The studies illustrate the application of such spreadsheet methods. Each study deals with a separate design topic. The first shows how a simple design specification is taken through the complete design process. As a contrast the second study deals with non-passenger aircraft design, considering a transport aircraft. As both the previous studies deal with conventional configurations the third study shows how to assess unorthodox layouts. Finally, the last design study shows how you may use the methods to analyse topics other than pure aircraft technical aspects.

No book alone will provide the key to good design. You can only achieve this through the acquisition of knowledge, hard methodical work, broad experience on many different aircraft projects and an open and creative mind. However, we hope that this book will eliminate some of the minor stumbling blocks that young engineers find annoying, confusing and time-wasting at the start of their design work.

Wherever possible System International (SI) units have been used. However, in aeronautics several parameters continue to be used and quoted in non-SI units (for example altitude is normally in feet). It is therefore necessary to have an understanding of different systems of units. To allow conversion between different systems of units a conversion table offers help to both aspiring young designers and older engineers who struggle to convert their past experience into the new system of units.

Conclusion

Finally, it is impossible to make the book complete. The contents and data do not cover all the aspects of civil transport design required by every user. For example, we have not included anything on supersonic aircraft because it is still uncertain if we can solve the environmental problems (noise and emissions) associated with high and fast operations. By the same token we have not gone too far on the inclusion of advanced technologies and materials. Such developments will not affect the main design process and you could allow for them in future studies by establishing factors for use in the standard formulae (e.g. mass and drag reduction factors).

However, allowing for these omissions, we have made a genuine attempt to produce a book that is a starting point for students who want to know more about the fascinating process of commercial turbofan aircraft design.