| This research develops and implements a framework for the computation of the sensitivities of the handling qualities measured according to ADS-33. These tools enable the designer to immediately see the consequences of changes of the design parameters on several performance measures, and are easily inserted in formal design optimization procedures. It has been possible to perform the sensitivity analysis with only a small computational penalty compared with a traditional, baseline analysis. The sensitivities are calculated with respect to a fuselage parameter, a flight control system parameter and a set of rotor parameters that affect structural, inertia and aerodynamic rotor loads. A complex, state-of-the-art flight dynamic simulation model is used. Existing solution procedures are replaced with newer procedures that take advantage of advances made in numerical analysis in the last decade. To do this, significant part of the original code has been rewritten in order to use the new solver. The new formulation of the mathematical model of the helicopter is expressed as a non-linear differential equation in implicit form. This formulation allows simple analytical derivations of the equations of motion with respect to selected design parameters. Semi-analytical results are compared with finite difference results.; A new linearization procedure is developed, and a simultaneous sensitivity analysis is carried out. Since the most expensive portions of the analysis are already available from the baseline calculation, the sensitivity analysis is performed without substantial additional computational effort compared to the baseline analysis. Results show that the method is accurate, and finite difference step size issues need not to be considered.; The present research also describes a study in which the simulation model provides the sensitivities of quantities that are computed from the time marching solution of the coupled rotor-fuselage equations of motion. These include the maneuver hub loads and the transient response metrics needed to verify compliance with the Moderate Amplitude Criteria (also known as “Quickness criteria”) of ADS-33. For this specification, the computational efficiency of the semi-analytical method is comparable to finite difference approximation.; An optimization study is carried out at the end of the dissertation. The optimization is implemented by using the design-oriented analysis developed in this research. The objective function is the damping of the progressive lag mode, which must be increased from its baseline value. Design variables side constraints, handling qualities constraints, aeromechanical constraints and hub loads constraints are considered. Results show that the semi-analytical analysis developed in the present study can be successfully coupled with an optimization loop with substantial reduction of computational effort. The damping of the lag mode is increased by 41%. |
