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The design process is an interactive feedback process where the performance of the design is compared with the performance specification. In aircraft design it is very important that the system is optimised with respect to different aspects such as performance and weight. Traditionally, and by necessity, the design procedure has began with some kind of performance specification followed by a conceptual design, and after that the system has been optimised (usually implicitly) with respect to the performance specification. Typically, aircraft design optimisation is characterised by a multitude of objectives that can be difficult to compare to each other, such as low fuel consumption, high speed and passenger comfort. Usually this is where the engineering judgement of the designer comes in. In traditional design it is often difficult to establish what was the result of design decisions and what was the result of pure optimisation.

In this paper modern optimization techniques are applied to an aircraft sizing problem. The paper starts by discussing how optimization could support the design activity and thereafter different methods of formulating the design problem as an optimization problem is discussed. Finally the problem of aircraft sizing is addressed by combining the presented optimization strategy with a simulation model of an aircraft based on mathematical models gathered from the literature. The outcome of the optimization is for example the optimal layout in order to minimize fuel consumption for a specific mission or the trade-off between the number of passengers and the fuel consumption per passenger.

The current work present a simple model to integrate non-linear aerodynamic in conceptual design phase, before wind tunnel testing. A presentation of a simple pitch up maneuver based on three different aerodynamic models is simulated. The simulation indicates different behaviors depending on the aerodynamic model, and shows the importance of including unsteady aerodynamic.

The design modern aircraft requires integration of multidisciplinary models for analysis in early design phase to increase the chances of a successful project. In this paper, a framework for distributed aircraft analysis in the conceptual design including several domains is presented. The framework is based on so-called Web service standards, allowing integration of distributed models for system simulation and optimization using standardized interfaces. The analysis is controlled by a so-called sequencer which manages the interaction between simulation modules and an XML-based design data repository. This repository includes all design data and an executable process description defining the sequence for execution of the modules. In the paper, the framework with underlying concepts is described. The approach is further illustrated using the design of an Unmanned Aerial Vehicle as an example.

Modelling and simulation is of crucial importance for the understanding of system dynamics. In aircraft, simulation has been strong in the area of flight control. Modelling and simulation of the hydraulic systems has also a long tradition. The rapid increase in computational power has now come to a point where complete modelling and simulation of all the sub systems in an aircraft is not far away. This means new challenges in dealing with very complex multi domain systems. Of all the systems in an aircraft fluid power systems is one of the most difficult to handle from a numerical point of view. They are characterised by difficulties such as discontinuities, very strong non-linearities, stiff differential equations and a high degree of complexity. A considerable effort has therefore been made to develop methods suitable for simulation of such systems.