Aeroelastic analysis of advanced tiltrotor aircraft.

摘要

The primary objective of this study is to provide a comprehensive validated analysis for advanced tiltrotor configurations. The first task is to identify the parameters and mechanisms causing tiltrotor instabilities this is accomplished using a simple rigid-blade analysis. The main task is to develop an analysis, from first principles, capable of modeling complex tiltrotor configurations. Main modeling features are the following: rotor, wing and fuselage modeled as elastic beams with axial, flapwise, lagwise and torsional degrees-of-freedom, large pylon tilts, highly-twisted composite blades including modeling of nonclassical structural effects such as warping and transverse shear, advanced geometry rotor blades and wing with arbitrary sweep, anhedral, twist and planform taper variation along span, modeling of gimballed hubs, and fuselage, full wing-span and twin-rotor modeling. Analysis is performed using the finite-element method in space and time. Solution includes aircraft trim controls, rotor response, blade and hub loads, and system aeroelastic stability. Tiltrotor flight conditions handled include helicopter, conversion, and airplane modes. The accuracy of this analysis is established by validating the predictions for trim controls, rotor response, vibratory loads and aeroelastic stability with predictions from other established tiltrotor analyses as well as with test data. Parametric studies are performed to investigate the effects of blade tip sweep, anhedral and planform taper on aeroelastic stability in airplane mode. Studies show that blade tip sweepback of 30