A 6DOF Flight Simulation Environment for General Aviation Aircraft with Control Loading Reproduction

This paper presents the main features of a six-degree-of-freedom (6DOF) flight simulation laboratory operated by the authors at the University of Naples. The aim of the flight simulator is twofold: serving as a research tool for model characterization and for the investigation of flying qualities of very-light and ultra-light aircraft; and offering a training options to the pilots of such airplanes. For these reasons the simulator cockpit has been conceived and set up as a generic cabin of a general aviation aircraft. The software suite that guides the various components of the system is based mainly on the features of FlightGear, an open-source flight simulation software. The simulation of aircraft motion, the cockpit instrument panel and flight controls, the outside scenery are all managed by a number of instances of FlightGear. All FlightGear instances are appropriately executed on different machines and communicate with each other via net protocols. Simulations are also supported by two other software modules. The first one controls the 6DOF motion of the cockpit. The second module implements a force reproduction system on the cockpit controls. An overview of all these modules is given in the paper, along with the discussion of the advantages and potentialities given by the source code accessibility and the high configurability of FlightGear. The force feedback model is particularly important to the purposes that this flight simulation facility has being designed for. To obtain an enhanced realism in piloting efforts, particular care has been taken to implement hinge moment equations in the simulation software. The result is a reliable closed-loop force-feedback system on all aircraft commands. Two useful and noteworthy generalizations have been implemented in this context: the effect of the mechanical linkage dynamics on the control surface motion and the effects on the control displacement due to the mechanical friction and to the presence of springs. The geometric, mass, inertia characteristics of each control surface and the hinge moment coefficients are managed by the control loading software. All the details of this model are given in the paper.