Ryan C. Paul, Joseba Murua, Ashok Gopalarathnam
DOI Number: N/A
Conference number: IFASD-2015-070
By extending an unsteady vortex lattice method with a decambering approach to handle stall, a modeling environment has been developed for flight dynamics analysis of rigid aircraft in preand post-stall conditions, with possible future extensions to include structural flexibility. The combined equations for vortex-lattice analysis, rigid-body flight dynamics, and decambering stall model are integrated for semi-analytical analysis of the coupled system. The resulting framework allows for performing aircrafttrim calculations in both pre-stall and post-stall conditions. Linearization about the trim condition leads to a state-space form, with states including vortex-lattice and flightdynamic variables. The decambering variable for each section is introduced in the system matrices as a control variable, whose value is linearly related to the changes in flight velocities. Eigenvalue analysis of the resulting system matrix yields the flight dynamic modes. Results for loss of roll damping with increase in angle of attack beyond stall show excellent agreement with high-alpha data from flight-test results in the literature. Full-aircraft results for all flight modes are verified for pre-stall conditions. At post-stall conditions, the full-aircraft predictions for some modes are in broad agreement with the limited general trends that could be found in the literature.