Flight Loads Evaluation and Airworthiness Compliance for the V-Tail of a Medium-Altitude Long-Endurance Unmanned Platform

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript presents a methodology for V-tail load evaluation of a medium-altitude long-endurance UAV. The V-tail configuration is increasingly used in current UAVs, but its load evaluation is seldom presented in published literatures. The methodology presented in this manuscript can be useful in V-tail structural design of UAVs. There are several suggestions that might be improve the manuscript.

Comments:

1. Regarding the title of the manuscript: The title of the manuscript seems not specific enough. Since the manuscript addresses flight loads for the V-tail, not for entire components of the UAV, the title of the manuscript could be modified slightly. It is suggested that the title of the manuscript could be changed into “Flight Loads Evaluation and Airworthiness Compliance for the V-tail of a Medium-Altitude Long-Endurance Unmanned Platform”.
2. Line 104: It seems better that Subsection 1.1 “Vehicle Description” is separated from Section 1 of “Introduction”. “Vehicle Description” could be a single section that describes the UAV in this work. Also, more description on the V-tail of the UAV should be added. It is not clear from the text whether the V-tail is an all-moving tail or it consists of a stabilizer and a ruddervator.
3. Regarding “Methodology” in Section 2: Organization of Section 2 could be improved. It will make the methodology much easier to understand if a procedure for the methodology is described using a step-by-step manner. It is suggested that the authors should reorganize the Section 2 in a more logical way.
4. In the Section 2: The authors should add a more detail description on the aerodynamic database that comes from the high-fidelity CFD simulation. Drag polar, lift curve and pitching moment coefficient curve are described already in this Section. But it seems that those aerodynamic coefficients are not enough for the V-tail load evaluation. All the aerodynamic coefficients that are needed for the V-tail load evaluation should be listed. Do all these aerodynamic coefficients come from the CFD simulation?
5. In the line of 173, “0.1 deg” is incorrect, and it should be “0.1 deg^-1”.
6. In Figure 2, there is a typing error for “0.0.08069”.
7. In Figure 5: the meaning of each point (such as point AF, etc.) should be given.
8.  Regarding the title for Section 3: I wonder why the authors use “Structural Loads Analysis” rather than “Flight Loads Analysis” (or “Aerodynamic Loads Analysis”).  What is the meaning of “Structural Loads” in the manuscript?

Author Response

The reply point by point is in the file attached. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors I would like to congratulate the authors for their work. The article presents very interesting results when applying the load cases included in UAV certification standards to a V-tail configuration. The models are well implemented and reasonably well described. However, the novel contribution of this work is not evident. What research was conducted to carry out this study? What relevant conclusions were reached? Were any novel methodologies applied? What technical or methodological difficulties were encountered? What contribution from the state of the art does this work represent? In my opinion, at least as the article is written, there doesn't seem to be a high degree of innovation or research, beyond the calculation of load cases for a V-tail UAV, which, as I said, were carried out rigorously.

Author Response

The reply point by point is in the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

I have a minor suggestion for the authors: please include a brief description of the CFD methods used, such as numerical schemes, software, and turbulence models, as the main conclusions are highly dependent on these choices.

Author Response

The reply point by point is in the attached file.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

DRONES REVIEW-3936779

 

Title: Flight Loads Evaluation and Airworthiness Compliance for a
Medium-Altitude Long-Endurance Unmanned Platform.
Journal: Drones
Authors: Pierluigi Della Vecchia *, Vincenzo Cusati, Claudio Mirabella

The issue considered in the reviewed article is very relevant and important for the aerospace industry. Currently, there are very few studies devoted to the assessment of flight loads and there is no methodology for such an assessment for medium-class UAVs with unconventional geometric configurations, V-tail. The authors use the industry military standard NATO STANAG 4671, which provides a high level of reliability, necessary and very important for certification purposes. A comparison is made with traditional aircraft configurations, regulatory references are provided to USAR.423,…425etc.
Recommendations and comments for authors:

1) The work would benefit greatly if a comparison were made with similar studies for T or H-tail configurations.

2) We think that it makes sense to also consider the wing load. It would be interesting to know why the authors decided to exclude the wing load from this analysis. Perhaps this will be the topic of the authors' next article?

3) The section on fatigue life and cumulative loads could be supplemented with numerical examples.

In general, the article makes a positive impression. The work has scientific novelty, practical value that corresponds to the topic of the journal. I recommend accepting it for publication after making small clarifications regarding the above-mentioned points.

 

Author Response

The reply point by point is in the attached file.

Author Response File: Author Response.pdf