An investigation into an adaptable morphing concept for enhancing aircraft control and performance is described in this thesis. The impetus for the work was multi-legend. Initially, the work involved identifying and optimizing winglets on a swept wing baseline configuration to enhance the controllability and aerodynamic efficiency of unmanned aerial vehicles. Moreover, the other objective was to develop a realistic skin for a morphing aircraft concept that would allow subtle, more efficient shape changes to improve aircraft efficiency. In this regard, preliminary computations were performed with Athena Vortex Lattice modelling in which varying degrees of twist, swept and dihedral angle were considered. The results from this work indicated that if adaptable winglets were employed on small scale UAVs improvements in both aircraft control and performance could be achieved. Subsequent to this computational study, novel morphing wing and/or winglet mechanisms were developed to provide efficient shape changing as well as to develop a novel alternative method for a morphing skin. This new technique was numerically optimized in ANSYS Mechanical, experimentally investigated in a wind tunnel, and also compared with a baseline aileron configuration. Afterwards, flight testing was performed with an Extra 300 78 inch remote controller aircraft with the results being compared against existing fixed wing configurations. After evaluating numerical results, from various winglet configurations investigated in AVL, selected cases were found to provide good evidence that adaptable winglets, through morphing, could provide benefits for small scale aircraft control and performance as well as offering an acceptable alternative aircraft control methodology to the current discrete, 3-axis control philosophies. Using ANSYS Mechanical for structural analysis, rib configurations were also optimised in terms of weight, stress, and displacement, as well as required twist deformation magnitudes (±6° of twist achieved). Furthermore, the skin was found to be rigid with a low rate of surface wrinkling promoting a low drag surface. Ultimately, the viability of this novel concept mechanism was validated through flight testing with similar roll authority achieved compared to traditional aileron configuration. Finally, a morphing concept also provided potential shape changing performance with smooth aerodynamic surface finish. Leading to the possibility of the concept is being a viable skin for morphing application.

Harmonic oscillatory tests for a fighter aircraft using the Dynamic Plunge--Pitch--Roll model mount at Virginia Tech Stability Wind Tunnel are described. Corresponding data reduction methods are developed on the basis of multirate digital signal processing. Since the model is sting mounted, the frequencies associated with sting vibration are included in balance readings thus a linear filter must be used to extract out the aerodynamic responses. To achieve this, a Finite Impulse Response (FIR) is designed using the Remez exchange algorithm. Based on the reduced data, a state–space model is developed to describe the unsteady aerodynamic characteristics of the aircraft during roll oscillations. For this model, we chose to separate the aircraft into panels and model the local forces and moments. Included in this technique is the introduction of a new state variable, a separation state variable which characterizes the separation for each panel. This new variable is governed by a first order differential equation. Taylor series expansions in terms of the input variables were performed to obtain the aerodynamic coefficients of the model. These derivatives, a form of the stability derivative approach, are not constant but rather quadratic functions of the new state variable. Finally, the concept of the model was expanded to allow for the addition of longitudinal motions. Thus, pitching moments will be identified at the same time as rolling moments. The results show that the goal of modeling coupled longitudinal and lateral–directional characteristics at the same time using the same inputs is feasible. / Master of Science