Applied Composite Materials (2005) 12: 3–11 © Springer 2005 Multi-Disciplinary Design Philosophy for Aircraft Fuselages. Part I A. BEUKERS, M. J. L. VAN TOOREN and TH. DE JONG Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, PO Box 5058, 2629 HS Delft, The Netherlands. e-mail: ebeukers@LR.TUDelft.nl (Received and accepted 30 September 2004) Abstract. A short discussion is given to show the potential to improve aircraft fuselages with the application of a multi-disciplinary design philosophy. Key words: multi-disciplinary design, aircraft fuselages. 1. Introduction At the end of the thirties, light aluminium started to take over the role of wood and steel as primary materials in aircraft. The all-metal, stressed skin structure became the standard in the aircraft industry. Simultaneously, the airplane configuration was adapted to the new structural concept, as were the fabrication methods. The results of the introduction of aluminium were rather spectacular. Within a relatively short period it became possible to transport more passengers over greater distances, faster, at higher altitudes and, therefore, with more comfort. The first steps to modern air traffic were taken. These steps marked the beginning of a long lasting evolution of the aluminium airplane structure. This evolution has lead to the current (over)-optimized stiffened skin structure, for which only extensive protection measures, inspection programs and mainte- nance programs, can guarantee the required comfort, reliability and durable safety level. Still, it is tried to further optimize the aluminium stiffened skin structures at the cost of large investments by, among other ways, applying new alloys without a clear improvement of the cost efficiency. This is illustrated in Figure 1. Herein it is shown that airliners are facing a continuous decrease in profit per aircraft seat. Reasons for this are, among others, the increase in competition due to the open- skies-policy and the increased cost of personnel, airports and fuel. The second curve in Figure 1 shows the increased cost per aircraft passenger seat. One of the main reasons for the cost increase is the increase of manufacturing costs. This is highly in contrast with the development of manufacturing costs of most other tech- nical products like cars and consumer electronics, for which the price/performance ratio is continuously improving.