Aircraft Stability Analysis Including Unsteady Aerodynamic Effects

An Investigation of Unsteady Aerodynamic Multi-axisState-Space Formulations as a Tool for Wing RockRepresentationByPedro J. de Oliveira NetoCommittee Chairman: Dr. William H. MasonAerospace Engineering(ABSTRACT)The objective of the present research is to investigate unsteady aerodynamic models withstate equation representations that are valid up to the high angle of attack regime with thepurpose of evaluating them as computationally affordable models that can be used inconjunction with the equations of motion to simulate wing rock. The unsteadyaerodynamic models with state equation representations investigated are functionalapproaches to modeling aerodynamic phenomena, not directly derived from the physicalprinciples of the problem. They are thought to have advantages with respect to thephysical modeling methods mainly because of the lower computational cost involved inthe calculations. The unsteady aerodynamic multi-axis models with state equationrepresentations investigated in this report assume the decomposition of the airplane intolifting surfaces or panels that have their particular aerodynamic force coefficientsmodeled as dynamic state-space models. These coefficients are summed up to find thetotal aircraft force coefficients. The products of the panel force coefficients and theirmoment arms with reference to a given axis are summed up to find the global aircraftmoment coefficients. Two proposed variations of the state space representation of thebasic unsteady aerodynamic model are identified using experimental aerodynamic dataavailable in the open literature for slender delta wings, and tested in order to investigatetheir ability to represent the wing rock phenomenon. The identifications for the secondproposed formulation are found to match the experimental data well. The simulationsrevealed that even though it was constructed with scarce data, the model presented theexpected qualitative behavior and that the concept is able to simulate wing rock.