"True Scientist" hah!
I don't think you would want to fly on an airplane designed by what you are calling a "true scientist".
You're confused at the difference between science and engineering.
Engineering applies and tests designs based on scientific knowledge, but science itself is the process of exploring and refining tentative knowledge to gain more evidence for overweighing and critically analyzing/assessing.
With science, knowledge is always tentative, no matter how good it gets. With engineering, you take scientific knowledge and apply it and then test the applications.
So when you design an airplane, for example, you engineer it using principles derived from scientific theories, but then you build prototypes, etc. to test and refine before finally arriving at a version that you send people up in.
Engineering can be done in a scientific way, but when you finally send people up in the finished airplane, that is an act of faith in an engineering design based on scientific principles, not science itself. Make sense?