Applications of Bifurcation Methods to F-181HARV Open-loop Dynamics in Landing Configuration

Over the past two decades, bifurcation and continuation methods have emerged as efficient tools for prediction, and control of flight instabilities. Bifurcation phenomena have been associated with nonlinear behaviour of aircraft in actual flight tests, and the critical control combinations, which signify onset of instabilities, have been identified for almost all generations of modern fighter aircraft. A standard bifurcation analysis procedure has been used in the past. In this paper, the bifurcation theory, relevant to preliminary bifurcation analysis of nonlinear aircraft dynamics, has been introduced, and a stepswise methodology used in a standard bifurcation analysis procedure has been illustrated with an application to open-loop dynamics of an F- 18/HARV model in landing configuration. Further, an example manoeuvre is constructed, and numerical time simulations of an F-18/HARV model in this manoeuvre is carried out to validate the predictions from the bifurcation analysis. Numerical time simulation results confirm the onset of nonlinear behaviour at critical control combinations identified in bifurcation analysis of the aircraft model. Thus, bifurcation methods, in conjunction with selective numerical simulations, can be extremely useful in the design, development, evaluation, and flight training phases of a fighter aircraft development programme