The current predictive capability for modal frequencies, particularly in the presence of frequency coalescence and branching, merits significant improvement. No different is the current appreciation of the role and effectiveness of fast- Floquet, generalized-Floquet and generalized-fast-Floquet methods as feasible alternatives to regular Floquet method. Accordingly, this paper gives an assessment of how these three methods compare with conventional Floquet method and how the Fourier series expansion of periodic eigenvectors can be adapted to foolproof identification of modes, say in the treatment of models with 100 plus states. For rotorcraft with identical blades, fast-Floquet method is always better than Floquet method when full state-space modeling is available, so is the case between generalized-fast-Floquet and generalized-Floquet methods when such a full state-space modeling is not available. Generalized-Floquet and generalized-fast-Floquet methods provide a means of performing the stability analysis baed on Floquet theory with an arbitrary set of state excitations and measurements; the Floquet transition matrix and, in turn, damping and frequencies of RLM and such important modes are predicted in the least squares sense; the converged values of damping and frequencies are comparable to those from Floquet and fast-Floquet methods.© 2010 by the American Helicopter Society International, Inc.