Flight Dynamic Modeling and Stability Analysis of Flexible Wing Generic Transport Aircraft

Abstract

This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a new aerodynamic control surface for active wing shaping control for drag reduction. This aerodynamic surface is referred to as a Variable Camber Continuous Trailing Edge Flap (VCCTEF). A vortex-lattice aerodynamic model of the ESAC is developed for coupling with the aeroelastic finite-element model via an automated geometry generation tool. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients which are used for the flight dynamic model. Two different methods for a state-space formulation for coupled aeroelastic-flight dynamics are considered to address the dependency on the reduced frequency parameter. The first method is to formulate the equations of motion which are dependent on the exact Theodorsen’s unsteady aerodynamic model. The second method is to approximate the Theodorsen’s complex-valued function as a second-order transfer function proposed by R. T. Jones. This approximation eliminates the reduced frequency dependency, but also results into two additional states for each of the structural deflection state. Both methods will be described in the study. A vehicle stability analysis will be conducted to assess the effect of aeroelasticity on rigid-body aircraft modes.