Among the various causes of bearing damage and failure, metal fatigue of the rolling contact surface is the dominant failure mechanism. The fatigue life is associated with the load conditions under which wind turbines operate in the field [1]. Therefore, it is important to understand the long-term distribution of the bearing loads under various environmental conditions. The National Renewable Energy Laboratory’s 750 kilowatt (kW) Gearbox Reliability Collaborative wind turbine was studied in this work. A decoupled analysis using several computer codes was carried out. The global aero-elastic simulations were performed using HAWC2. The time series of the drivetrain loads and motions from the global dynamic analysis were fed to a drivetrain model in SIMPACK. The timevarying internal pressure distribution along the raceway was obtained analytically [2]. A series of probability distribution functions were then used to fit the long-term statistical distribution at different locations along raceways. The long-term distribution of the bearing raceway loads were estimated under different environmental conditions. Finally, the bearing fatigue lives of the bearings were calculated. Objectives During the study, research objectives included: • Characterizing the bearing contact load zone distribution of the inner and outer raceways • Investigating the validity of different probability distribution functions in fitting the long-term radial contact force and in estimating the basic rating life • Comparing the effect of wind conditions on fatigue life estimation • Understanding the effects of misalignment/tilting on fatigue life