In stability analysis from Floquet theory, the current predictive capability for mode identification merits significant improvement, particularly in rotor-fuselage or aeromechanical stability of hingeless and bearingless helicopters. Accordingly, this mode identification is addressed under ground contact, hovering and forward flight conditions from complex Fourier series expansion of periodic modal vectors. A simplified hingeless-rotor helicopter model with Peters-He dynamic inflow is used, and it involves periodically varying coefficients even under ground-contact and hovering conditions. The Floquet mode identification results are compared with those from a widely used approximate method based on constant-coefficient approximation in multiblade coordinates. Moreover, Floquet mode identification results are correlated with the experimental results under ground-contact conditions, which include resonance and mode-to-mode similarity. In this ongoing study, the emphasis is on identifying the regressing lag, and body roll and pitch modes; these mode identifications from constant-coefficient approximation and Floquet approach agree. Copyright © 2011 by the American Helicopter Society International, Inc. All rights reserved.