Aircraft Conceptual Design

People involved: L.Marchetti, A.De Gaspari, L.Riccobene, F.Toffol

NeoCASS (Next generation Conceptual Aero Structural Sizing) is a tool initially developed by the Department of Aerospace Sciences and Technologies (DAER) of Politecnico di Milano in the framework of the EU-FP6 SimSAC Project, aiming at the preliminary sizing and aeroelastic analysis for fixed wing aircraft.

One of the first problems to be addressed during the conceptual design of a new aircraft consists in determining the structural weight, that is fundamental during all the phases of the project. Historically we rely on parametric formulas obtained from the statistical analysis of the aircraft already existing and whose structural mass is therefore known. This approach has always been used but has obvious limitations: being the formulas based on the characteristics of other existing aircraft, their applicability to unconventional configurations it is at least questionable. The other limit is represented by the fact that what is obtained is only the value of the structural masses together with the position of their center of gravity.

What is missing is a reasonable estimate of the stiffness which becomes increasingly important given the growing optimization of structures and therefore the lowering of their weight. Aeroelastic effects become increasingly important to estimate the effectiveness of the controls and therefore the behaviour of the aircraft in flight, for the optimization of aerodynamics that can no longer simply consider the aircraft rigid and for the evaluation of instabilities such as the flutter which, if identified in too advanced stages, could excessively affect the time and costs of the entire project. NeoCASS tries to solve all these issues aiming at:

• Using simplified but physically based structural models (FEM stick models)
• Correctly sizing the structure under a realistic set of load conditions, specified by the certification rules, so that  the structural weigh is the result of the sizing process
• Bringing the aeroelasticity at conceptual design phase so allowing to investigate aeroealastic responses together with possible application of controls since the initial phases of the project. 

Since 2012 NeoCASS is a standalone suite Matlab-based now available as an Open Source Software under GPL license able to cover the design phases ranging from the conceptual structural design, static and dynamic load envelope calculation, static and dynamic structural responses computation, state-space models definition for active controls implementation (see www.neocass.org). It includes a dedicated module, called NeoRESP, dedicated to the aeroelastic dynamic response due to gust and external excitations, as well ad hoc tools to generate ad manage State-Space models for time response and active controls implementations.

NeoCASS Suite customizations as well training and support are now managed by a recently founded POLIMI's Spinoff called A-Cubed Technology (see www.acubedtechnology.com).