The paper describes the design and aerodynamic characterisation of a thrust-scales IEA 15MW wind turbine model. The paper is well written and the single aspects are well motivated. The results are relevant to the community. Nevertheless, there are a few aspects that are not 100% clear to me that the authors should address.

In the introduction the authors mention other scaled experiments with e.g. the DTU 10 MW model turbine. There are also a few experiments with a model turbine scaled down from a 5MW reference turbine (https://doi.org/10.5194/wes-6-1341-2021). In these experiments they also use the method by Herreaz to determine the axial and tangential induction factor along the rotor blade.

Figure 3 can easily be removed since it doesn’t provide any extra information for the rest of the paper.

On page 9 line 150 the authors state that in the post-processing they stich together the results from the pressure and the suction side of the profile to get the total flow around the profile. Are these images averaged over several events or are they temporally highly resolved? In the later case, can the authors say anything about variations in the flow field on the upper and lower side for measurements between single rotations? 

Line 200, page 11: The model turbine was running at constant rotational speed. Was that actively controlled or is that given due to the fact that the inflow was constant ? I can image, that there might have been some fluctuations in the rotational speed also due to the fact that the blades were all different. Passing the tower will cause different aerodynamics for each of the blades which could be seen in fluctuations in the rotational speed. Did the authors observe something like that ?

In section 3.1 it is not quite clear if the authors corrected the mean offset on the pitch (twist) for each blade or if they just measured the offset. If they did not correct the mean offset, why not? The authors say that the turbine is equipped with a manual pitch system which should allow the correction of the offset, right?

I do not fully understand why the authors show figure 12. Here they compare the calculated lift coefficient for each blade and compare it to the one from a reference for a specific Reynolds number. Why not going the other way and calculating the normal and tangential forces for each radial position on the blades using the angle of attack, acting velocities and the corresponding lift and drag coefficients from figure 1 for the correct Reynolds number and ad the results to figure 11? That would minimise the effect of the Reynolds number in the end should show how well all methods agree — or maybe I misunderstood the intension of figure 12.

Line 316, page 18, the authors mention that in future research they would like to reduce the impact of blade deflection on the results. In the paper they never mentioned the problem or determined the deflection and the impact on the results. While you mentioned it here, what is the impact of blade deflection on the results presented in the paper?