In the design of complex products systematic methods for managing requirements and system architecture are used. Different analysis methods, such as system simulation, can be used to predict the behaviour and properties of a system for a point design. However, there is also a need for methods to establish relations in a design through quantitative analysis, where different aspect can be presented and visualized in such a way that the designer can understand the design space and the trade-off between requirements, as a support for design decisions. In this paper an overview of a range of computationally efficient methods that can be used on underlying models of the system. These include well known methods such as system optimization and sensitivity analysis. Here is also introduced methods for visualizing functional correlation.The methods are demonstrated on an small electric commuter aircraft.