Max Munk, student and protege of Ludwig Prandtl, was responsible for aerodynamic theory at NACA during its formative years 1921-26. In General Theory of Thin Wing Sections Munk presents a version of the Kutta-Zhukovsy Circulation Theory, with the following plead that theory is useful:
- It is useful to discuss this phenomenon (the action of a wing) from the theoretical point of view, however imperfect the result may be as a consequence of neglecting the viscosity of the air.
- A theorectical investigation may at least give the limit of what to expect.
- It enables the investigator to survey and keep in mind a great number of isolated experiences, whether the agreement between theory and experiment be more or less close.
- It induces him to reflect on the phenomenon and thus becomes a source of progress by guiding him to new observations and experiments.
- It has often occurred even that some relation was thought to be confirmed by experience till the progress of theory made the relation improbable. And only then the experiments confirmed the improved relation, contrary to what they were supposed to do before.
- But is it really necessary to plead for the usefulness of theoretical work?
- This is nothing but systematical thinking and is not useless as sometimes supposed, but the difficulty of theoretical investigations makes many people dislike it.
We read that Munk intended to educate the uneducated engineers at NACA by teaching difficult Kutta-Prandtl theory, which he exposed in a flood of articles (later collected into the book Fundamentals of Fluid Dynamics for Aircraft Designers). This became too much for NACA and Munk was forced out of office in 1927: American NACA engineers did not embrace German theory, which in the light of the New Theory of Flight was fully rational.