Physical Modeling of Aircraft Upsets for Real-Time Simulation Applications

TLDR: A modeling approach based on nonlinear lifting line/strip theory analysis of the aerodynamic loads combined with an unsteady, freelyevolving vortex wake model for the induced velocity due to the lifting surfaces is described.

Abstract: Improving the understanding of flight dynamics and control response characteristics of aircraft in upset conditions has been the focus of extensive research and development in recent years. Aircraft may experience upsets due to a number factors, and without suitable corrective actions, upsets may ultimately lead to loss of control in-flight (LOC-I) accidents. To provide models for engineering analysis and pilot training, conventional simulation approaches have historically used multi-variable aerodynamic databases (look-up tables) derived from wind tunnel and/or flight test data, which are difficult to acquire and do not always encompass the desired flight envelope. An alternative approach for modeling aerodynamic and flight dynamic characteristics of aircraft in upset conditions has been investigated based on methods that are not data-driven but that are derived from physicallybased models. This paper describes a modeling approach based on nonlinear lifting line/strip theory analysis of the aerodynamic loads combined with an unsteady, freelyevolving vortex wake model for the induced velocity due to the lifting surfaces. The paper describes background work and recent developments toward a generic, physically-based model for aircraft upsets. Application of the modeling approach to unmanned aircraft is presented.