A Preliminary Evaluation of Morphing Horizontal Tail Design for UAVs

Round 1

Reviewer 1 Report

The problem statement is relatively weak.

It is recommended to add a more comprehensive literature review survey to make your statement more compelling.

Overall, the paper has a good flow and easy to understand.

It is recommended that our of the morphing technologies, what is missing, and what area of work has not been seriously done in the research.

Then, please narrow down your statement of why you solved this problem and why this is a significant problem.

Also, please specify what approaches you used and why you chose that approach.

Please proofread the entire article to improve minor grammatical errors and context-wise nonsense.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper performs an investigation of the potential savings in drag and changes to flight dynamics that would arise if a conventional elevator were replaced by a camber morphing mechanism in the horizontal tailplane. The methods used; xfoil and eigenvalue analysis are fine. The paper is clearly written and the literature review is reasonable although it perhaps could refer to more papers.

However, I think there is a problem in the design of the study which if remedied could lead to a more conclusive paper, this is my point #1 below. I list a couple of other comments as well.

1.       To make the morphed tailplane equivalent to the tailplane with elevator deflected, the authors seek to match the Cl-alpha slope. However, as figure 7 shows, this slope is broadly similar even to the unmorphed NACA 0012 airfoil. This leads to a problem later on, that in order to get the same down force for trim, the morphed airfoil must also change incidence. (basically, the fact that morphing changes the zero lift incidence of the airfoil has been overlooked). This seems a bit ridiculous, as the elevator has now been replaced by both a camber morphing device and whole-tail incidence adjustment, which seems like a lot of mass and complexity in practice. (or do the authors propose to statically alter the incidence? This seems quite intrusive to the original aircraft). Would it not be much simpler to match the overall downforce of the camber morphed device to the deflected elevator configuration?

2.       Some diagrams and possibly a nomenclature to illustrate some of the terms used would be helpful. In particular, what is E, BPG, Wn? Also illustrations of the three morphed sections would be illuminating to the reader.

3.       I don’t see that the plotting of range parameters such as (Cl^3/2)/Cd has any relevance, the range parameter is really a property of the whole aircraft not just the tail.

The English seems fine. 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Unfortuately I do not think this revision has improved the paper.

The introduction now mentions a ' gust rejection procedure' but gust response is not referred to in the rest of the paper, so this just makes it more confusing.

I am not satisfied with the response to my comments. For comment 2, BPG has been defined as 'Basic Performance Graphic', but this term is one I have not heard before and appears to simply mean 'a graph'.  E has been defined as efficiency, but there are countless ways to define efficiency , which one is being used here? For point 3, the graph still seems to be present in figure 15, and the response mentions a 'height index' but I can't find this anywhere in the pape.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf