Dear Malte,
For a rigid structure, I would expect the overturning moment from RNA weight to be -1,420,000 Nm, based on the RNA mass of 350,000 kg and center of mass overhang of -0.413775 m for the NREL 5-MW baseline turbine, from the following forum topic: Using Aggregate Mass in ADAMS to Check NREL CS_Monopile.bmi. Of course, this will be effected by the deflection of the support structure and blades if these DOFs are enabled.
How are you calculating the aerodynamic loads; is the rotor spinning? The wind turbine should not be operational until the cut-in wind speed of 3 m/s.
Are you plotting the mean loads or maximum loads?
Best regards,