Validation of Helicopter Mathematical Models by Comparison of Data from Nap-of-the-Earth Flight Tests and Inverse Simulation

In this paper it is shown that conventional validation techniques, based on comparison of responses after the application of standard control inputs to real and simulated vehicles, are not appropriate for models used in NOE studies. It is further shown that when control inputs measured during NOE flight tests are used to drive simulations, the simulated data quickly diverges from the measured data, even for minor modelling errors, giving little information on the validity of the model. The development of a new, more appropriate technique employing inverse simulations is described and its ability to identify inadequacies in mathematical models is demonstrated