FRAME-Sim: A Free-Software, Multibody-Based, Pilot in the Loop Rotorcraft Flight Simulator

In the context of a modern approach to the design of rotocraft, handling qualities should be the result of careful planning, rather than the output of a multitude of other choices, made primarily focusing on more immediate constraints. For a wide range of flight conditions and mission task elements, the test pilot feedback is the essential measure upon which the design choices are made. Thus, it is becoming of fundamental importance to be able to simulate a representative model of the vehicle in a pilot-in-the-loop environment as early as possible in the design stage. This work is intended to document the development process of one such system currently being realized at the facilities belonging to the Aerospace Science and Technology Department of Politecnico di Milano. Particular attention is given to the software architecture, based on the free and open-source multibody solver MBDyn. The development of a module specifically designed to exploit the environment visualization capabilities of FlightGear, also a free and open-source software, is presented.