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Very efficient large aircraft

Exploitable results

Airport congestion and increased passenger numbers are the primary drivers leading to the development of larger and larger aircraft. However as aircraft size increases, it becomes more and more difficult to achieve corresponding improvements in aircraft performance. It is believed that for large civil aircraft the 'flying wing' design may offer improvements in aircraft performance that are significantly greater than those achievable by conventional aircraft. There have been a number of successful flying wing aircraft designs developed for the military market, but no civil flying wing transports. This has been caused by the differing payload, mission and airworthiness requirements, which, in the past, have penalized the design of a civil 'flying wing' aircraft. Modern conventional aircraft are 'fly-by-wire' where the flight control computer produces an aircraft response to pilot control inputs that is tailored to give optimum handling characteristics. This alleviates the need to tailor the airframe shape to provide acceptable handling qualities, which may allow a more optimal aerodynamic solution. The VELA project aimed at the development of skills, capabilities and methodologies suitable for the design and the optimization of civil flying wing aircraft. For radically different configurations like the flying wing aircraft, validation data was needed. Low speed wind tunnel tests have been performed to measure static and dynamic derivatives. These test results have been compared with the predictions made in advance using preliminary design tools. Aerodynamic derivatives are used to develop flight control systems. They describe the effect of the static deflection of control surfaces and the dynamic damping characteristics of an aircraft configuration. Various optimisation techniques have been enhanced and applied to maximise the efficiency of flying wing configurations. Parameters like chord length, twist angle and airfoil section shape were varied. To achieve realistic results, constraints like cabin dimensions and floor angle as well as longitudinal stability have been taken into account. Alternative solutions for the flat pressure cabin have been developed and assessed with finite element models. These models were then used to derive more accurate estimates of the structural mass of the configurations. Issues of airport integration as well as ditching and passenger evacuation have been addressed by new simulation techniques.