Role of three dimensional dynamic stall in stability of rotorcraft is investigated here.Yawed flow and radial flow coupling between blade segments are included in the ON ERA dynamic stall model and predictions for lead-lag damping are correlated with experimental data.Effect of each component of 3D effects are investigated individually.Yawed flow effect improves the correlation with experimental data significantly while radial coupling between blade segments alone show very little effect on lead-lag damping results. Contribution of dynamic inflow modelling in lead-lag damping prediction is also investigated. Dynamic wake effects plays a significant role and the 3D dynamic stall model with dynamic wake effects provides an excellent correlation with available experimental lead-lag damping data. © 43rd European Rotorcraft Forum, ERF 2017. All rights reserved.