Please see my attached PDF.

The article describes a validation of two aeroservoelastic models using a unique dataset obtained in the field from a 4.3MW wind turbine where one blade is equipped with a trailing edge flap. The work is novel and very relevant. The article is fairly well written and I recommend the publication of the article. Before publication, I think the authors could improve the article further by following some suggestions:

1) Although slightly out of scope, it would be nice and relevant to read about the intended use of such flap system. Both the abstract and the introduction say that the ATEF system is promising. Why is that? Promising for what?

2) The authors use acronyms heavily. In my current job we have a communications department that oversees our manuscripts, and I’ve learnt that the use of acronyms should be minimized to improve readability

3) The document relies heavily on the word “transient”, which I found fairly confusing. What does a “maximum difference for the blade-to-blade MBrM transients below 1%” mean? Isn’t enough to say  “maximum difference for the blade-to-blade MBrM below 1%”. We know MBrM varies in time/azimuth/wind speed. This is only one of the many uses of the word transient that I found confusing.

4) you’ve split the validation in three steps: first the flap deflections, second the lift coefficients, third the full aeroelastic model. Although this is said multiple times, it doesn’t always come out clearly. Maybe a scheme could help, or a clear numbered list in the intro?

5) HAWC2 and BHAWC are similar models and indeed the results match very well between the two. Would it help to only report results from the former?

6) Several paragraphs are very dense and not always clear. Maybe some schemes would help quick readers glance through the document.

And some additional minor suggestions:

- Line 1: Why is “Wind Turbine” capitalized?

- Line 25: it would be interesting to read more about the “potential benefits”

- Line 107: parenthesis seems missing wrapping Bergami and Gaunaa, 2012

- Line 112: typo, initial vs indicial

- Lines 120-124: I don’t follow this paragraph. Can you please rephrase it?

- Line 131: mainly 4 million. Why mainly?

- Line 139: lift and drag coefficients don’t depend on the chord. Why were they adjusted to the chord? And how?

- Line 165-170: I find this paragraph somewhat hard to follow

- Figure 4: I was surprised to see a transient of 3 seconds. Isn’t the pitch actuator faster that that? Again a little out of scope, but the value of a “slow” ATEF becomes harder to justify.

- Line 191: how can you target one wind speed experimentally?

- Line 217: 60s+60s=120s (not 90)?

- Line 235: this issue should be discussed further up or the previous paragraphs are confusing

- Line 237: if you average across azimuth, shouldn’t the azimuth-variation be gone entirely?

- Lines 248: I would put this paragraph first, and then the analysis.

- Figure 6: the legend covers the label

- Figures 12/13/14: include the grey band in the legend

- Line 480: I see a good match in Figure 15, what am I missing?

- Line 494: example of excessive use of acronyms, what’s o2o

- Line 515: typo, affect

- Line 517: typo, improves

- Line 518: typo, overestimates

- Line 537: isn’t a DT of 0.04 s excessively large?

- Line 565: thank you for the acknowledgment, even before reviews were in! To be seen if they improve the paper ;)