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I'm a bit involved into building an actual airplane. And while the guys go conventional ways, I'm trying to look around to see other solutions.

One of that is to try and use and RC scale-down model (easier and cheaper to build) to test and find flaws in the design and also possibly to give pilots some training before flying the actual plane.

So the question is - what will and what will not be similar in a model's behavior (say 90 cm and 180 cm wingspan versions) compared to full scale airplane (about 9m wingspan). I've already found answers related to Reynolds number on Physics SE, so it seems aerodynamics test (if we do any on the model) should be run in a pressurized tube. It's also obvious that power-to-weight ration in a model will be much higher, but possibly that can be solved by depowering the engine.

So if I build a 1:10 or 1:5 scale RC model, will it in some way be useful for actual aircraft design, building and pilot training?

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You need to decide between geometric similarity, kinematic similarity and dynamic similarity.

You need to decide which have to be met, while allowing others to vary so you can get meaningful results.

One change used is to test shapes in water instead of air as there is about a factor of 1000 between the two... This can provide meaningful results while keeping the models small enough to control and keeping the costs down. The difficulties of testing full scale items is usually a challenge - anyone have a wind tunnel which will fit the Airbus A380?

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  • $\begingroup$ Hm... well, I have two main objectives: 1) test how this specific design works; this means geometric similarity; 2) give future pilot a feeling of how the aircraft will handle; this means having kinematic similarity (or dynamic? what's the difference?); I could have two (or more) different RC models supplying those. But can that be reached? E.g. if I have geometric similarity, will I have feasible options to test the design (given the smaller Reynolds number)? Or how do I change geometrics so that I get kinematic/dynamic similarity? $\endgroup$
    – Gleb
    Commented Nov 17, 2019 at 14:55
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For an overview look at https://www.sciencedirect.com/science/article/pii/S0376042121000981 and https://m-selig.ae.illinois.edu/pubs/AnandaVahoraDantskerSelig-2017-AIAA-Paper-2017-4077-DesMethodforDynScalingGA.pdf

Based on youtube, the flight behavior of even large RC models,3,4,5 m wingspan, looks very different to that of a real aircraft. I doubt the pilots would learn much.

But... What you can do is simulate the scale model in your various analytical methods, and compare it with the actual model's flight performance, and then use the same method with the full size design.

You can then drop its predicted performance into a flight simulator and use that to train pilots.

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