Sub-Scale Flight Testing of Drag Reduction Features for Amphibious Light Sport Aircraft

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper explores Sub-Scale Flight Testing of Drag Reduction Features for Amphibious Light Sport Aircraft.

1. In Section 1,the state parameter diagram of the flight testing process needs to be provided, such as speed, altitude, thrust, etc.
2. In Section 4, supplementary analysis of flight parameters, providing the relationship between flight parameters and aerodynamic forces.
3. It is recommended to delete Section 6, with the relevant content adjusted and incorporated into Section 4.
4. Comparison of supplementary flight test results with early aerodynamic simulationresults.
5. In the conclusion section, the research results need to be presented concisely in bullet points.

Author Response

1. In Section 1, the state parameter diagram of the flight testing process needs to be provided, such as speed, altitude, thrust, etc.
2. In Section 4, supplementary analysis of flight parameters, providing the relationship between flight parameters and aerodynamic forces.

Comment 1 & 2: Thank you for your recommendation. We have added section 3.7.1 with a diagram to show the state parameters and demonstrate their relationship. The expected effects of associated limitations and assumptions are then covered at the end of the method in the new assumptions and limitations section.

3. It is recommended to delete Section 6, with the relevant content adjusted and incorporated into Section 4.

Comment 3: Thank you for the suggestion; this has been implemented.

4. Comparison of supplementary flight test results with early aerodynamic simulation results.

Comment 4: This would be a great next step in research direction; however, time and resources were not available to complete this valuable addition. We have highlighted your suggestion in the recommended future research.

5. In the conclusion section, the research results need to be presented concisely in bullet points.

Comment 5: Thank you for your suggestion; this has been implemented.

Reviewer 2 Report

Comments and Suggestions for Authors

Review Questions on the Article " Sub-Scale Flight Testing of Drag Reduction Features for Amphibious Light Sport Aircraft ".

 

I think it is an interesting work. However, the authors should address the following questions before further decision.

1. Please make the specific technical novelty explicit in the last paragraph of Introduction and again in the first paragraph (what is new compared with the latest published papers?).
2. Your results are interesting, but the measurements (thrust/GPS/battery) aren’t solid enough. Please redo key runs with reliable sensors and fresh batteries or say clearly that the results are only preliminary.
3. In the Seamax part, you mix two different aspect ratios. Use the same one throughout and update the numbers that depend on it.
4. Put all test limits and caveats in one short “Limitations” section before the Results. In figures and tables, add units, label error bars, and point to each figure in the text.
5. Minor English and format fixes required.
6. Quick language clean-ups:
   • “the effectiveness … is assessed” (not “are”).
   • Use one speed format (e.g., KTAS) and write “5%” (no space).
   • Keep symbols italic, align decimal places, and shorten repeated caption/template boilerplate.

 

 

Comments for author File: Comments.pdf

Author Response

1. Please make the specific technical novelty explicit in the last paragraph of Introduction and again in the first paragraph (what is new compared with the latest published papers?).

Comment 1: Thank you for your suggestion. We have added discussion clearly stating the technical novelty at the end of the introduction.

2. Your results are interesting, but the measurements(thrust/GPS/battery) aren’t solid enough. Please redo key runs with reliable sensors and fresh batteries, or say clearly that the results are only preliminary.

Comment 2:  Unfortunately, we do not have access to the DAQ system anymore, and we are unable to repeat testing; a product of unfunded research. We have stated in the discussion and conclusions the test results are preliminary and require further confirmation research.

3. In the Seamax part, you mix two different aspect ratios. Use the same one throughout and update the numbers that depend on it.

Comment 3: Thank you for spotting this, we have corrected the aspect ratios and checked the follow-on calculations.

 

4. Put all test limits and caveats in one short “Limitations” section before the Results. In figures and tables, add units, label error bars, and point to each figure in the text.

Comment 4: Limitations have been stated in a section before results and figures and tables have been checked/edited to include units, labelled error bars and references in text. Hopefully, these are to standard, please advise if you were requiring something more.

5. Minor English and format fixes required.
6. Quick language clean-ups:“the effectiveness … is assessed” (not “are”). Use one speed format (e.g., KTAS) and write “5%” (no space). Keep symbols italic, align decimal places, and shorten repeated caption/template boilerplate.

Comments 5 and 6: These items have been addressed, thank you for pointing them out.

Reviewer 3 Report

Comments and Suggestions for Authors

1) The value of this paper lies in the SFT. Indeed it is a technique not widely used, although in the past there were somme cases. For instance, during the design stage of the Swedish fighter SAAB J 35 DRAKEN, a halfscale MANNED model, named LILDRAKEN was flown to gather data and confirm the adopted design. The SFT technique is valuable becase it permits to gather data from the real world.

2) Due to their small dimensions, the LSAs can be easily transported, especially if they have foldable wings. They also can be used  for special military operations.

3) There was at least one (as far as i know)  amphibian plane with retractable tip floats, the BLACKBURN B-20.

4) The use of a marine hull and a step is not mandatory. The French LSA LIZA AKOYA has a perfectly smooth fuselage. Transit from the displacement mode to the hydroplaning one is achievet by two main hydrofoils near the front end of the fuselage and two smaller ones near the tail. These hydrofoils have also a contribution to lift in flight. Due to their small areas, their contribution to the total drag of the aircraft is small. They don't have any significant aerodynamic interference with the main wing and the horizontal stabilizer.

5) Since an amphibian plane, operates mainly in a highly salted environment, any mechanism to move devices like retractable tip floats e.t.c. must be frequently very well washed.

 

Author Response

1. The value of this paper lies in the SFT. Indeed it is a technique not widely used, although in the past there were some cases. For instance, during the design stage of the Swedish fighter SAAB J 35 DRAKEN, a half-scale MANNED model, named LILDRAKEN was flown to gather data and confirm the adopted design. The SFT technique is valuable because it permits to gather data from the real world.
2. Due to their small dimensions, the LSAs can be easily transported, especially if they have foldable wings. They also can be used for special military operations.
3. There was at least one (as far as i know) amphibian plane with retractable tip floats, the BLACKBURN B-20.
4. The use of a marine hull and a step is not mandatory. TheFrench LSA LIZA AKOYA has a perfectly smooth fuselage. Transit from the displacement mode to the hydroplaning one is achieved by two main hydrofoils near the front end of the fuselage and two smaller ones near the tail. These hydrofoils have also a contribution to lift in flight. Due to their small areas, their contribution to the total drag of the aircraft is small. Theydon't have any significant aerodynamic interference with the main wing and the horizontal stabilizer.
5. Since an amphibian plane, operates mainly in a highly salted environment, any mechanism to move devices like retractable tip floats etc. must be frequently very well washed.

Comments 1-5: Thank you for your feedback and insights, it is a very fascinating concept! The LSA LIZA AKOYA is a particularly interesting aircraft, we did come across it in our research. Those hydrofoils certainly would make much less drag than a step, and the small, downturned wingtips must perform great, too.

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors,

Fig. 9 – correct the caption

A small corrections refers to the angle of the motor shaft versus the flight path angle.

Maybe a better thrust cell can be used for the future.

Author Response

1. 9 – correct the caption

Thank you for your feedback. On reflection, Figures 8 and 9 have been removed as a non-essential pictures.

2. A small corrections refers to the angle of the motor shaft versus the flight path angle.

Discussion has been included in Sections 3.7.1 and 3.9, addressing the motor vs flight path angle detail. Thank you for pointing this out.

3. Maybe a better thrust cell can be used for the future.

We have improved the discussion section to encourage future research and funding on this important approach.