Confessions

We here list some of the many confessions by experts that there is no scientific theory of flight, which is the starting point of the present study.

This is a cumbersome truth for both aerodynamicists as scientists and airlines reassuring their passengers that air transportation is safe. The design of safe airplanes is facilitated by correct theory. If there is no correct theory available now, it is important to find one as soon as possible.

New York Times, Dec 9, 2003.

K. Chang in Staying Aloft; What Does Keep Them Up There?:

  • To those who fear flying, it is probably disconcerting that physicists and aeronautical engineers still passionately debate the fundamental issue underlying this endeavor: what keeps planes in the air?
  •  “Here we are, 100 years after the Wright brothers, and there are people who give different answers to that question,” said Dr. John D. Anderson Jr..

AIAA: State-of-the-Art

J Hoffren, Quest for an Improved Explanation of Lift, AIAA, 2001:

  • The basic physical principles tend to be buried and replaced by mystical jargon.
  • Classical explanations for the generation of lift do not make the essence of the subject clear, relying heavily on cryptical terminology and theorems from mathematics.
  • Many classical texts even appear to have a fundamental error in their underlying assumptions.
  • Although the subject of lift is old, it is felt that a satisfactory general but easily understandable explanation for the phenomenon (of lift), is still lacking, and consequently there is a genuine need for one.

AVweb

Few physical principles have ever been explained as poorly as the mechanism of lift:

  • It’s all one interconnected system. Unless the overall result of that system is for air to end up lower than it was before the plane flew by, there will be no lift. Wings move air downward, and react by being pushed upward. That’s what makes lift. All the rest is just interesting details.

Airfoil Lifting Force Misconception

How do airplane wings really work? Amazingly enough, this question is still argued in many places, from elementary school classrooms all the way up to major pilot schools, and even in the engineering departments of ma- jor aircraft companies. This is unexpected, since we would assume that aircraft physics was completely explored early this century. Obviously the answers must be spelled out in detail in numerous old dusty aerodynamics texts. However, this is not quite the case. Those old texts contain the details of the math, but it’s the interpretation of the math that causes the contro- versy. There is an ongoing Religious War over both the way we should understand the functioning of wings, and over the way we should explain them in children’s textbooks.

Live Science

Lift is a lot trickier:

  • In fact it is very controversial and often poorly explained and, in many textbooks, flat wrong. I know, because some readers informed me that the original version of this story was inaccurate. I’ve attempted to correct it after researching conflicting ”expert” views on all this….If you’re about fed up, rest assured that even engineers still argue over the details of how all this works and what terms to use.

The Straight Dope

How Do Airplanes Fly, Really?

  • You’d think that after a century of powered flight we’d have this lift thing figured out. Unfortunately, it’s not as clear as we’d like. A lot of half-baked theories attempt to explain why airplanes fly. All try to take the mysterious world of aerodynamics and distill it into something comprehensible to the lay audience–not an easy task. Nearly all of the common ”theories” are misleading at best, and usually flat-out wrong.
  • How can aviation be grounded in such a muddy understanding of the un- derlying physics? As with many other scientific phenomena, it’s not always necessary to understand why something works to make use of it. We en- gineers are happy if we’ve got enough practical knowledge to build flying aircraft. The rest we chalk up to magic.

Curator for aerodynamics at Smithsonian Space Museum

From Staying Aloft; What Does Keep Them Up There?:

  • Some of them get to be religious fervor.
  • The answer, the debaters agree, is physics, and not a long rope hanging down from space. But they differ sharply over the physics, especially when explaining it to nonscientists. 
  • There is no simple one-liner answer to this.
  • The simple Newtonian explanation also glosses over some of the physics, like how does a wing divert air downward? The obvious answer – air molecules bounce off the bottom of the wing – is only partly correct.
  • If air has to follow the wing surface, that raises one last question. If there were no attractive forces between molecules, would there be no flight? Would a wing passing through a superfluid like ultracold helium, a bizarre fluid that can flow literally without friction, produce no lift at all? That has stumped many flight experts. “I’ve asked that question to several peo- ple that understand superfluidity,” Dr. Anderson, the retired physicist, said. “Alas! They don’t understand flight.”

HowStuffWorks   

  • It is important to realize that, unlike in the two popular explanations described earlier (longer path and skipping stone), lift depends on significant contributions from both the top and bottom wing surfaces. While neither of these explanations is perfect, they both hold some nuggets of validity. Other explanations hold that the unequal pressure distributions cause the flow deflection, and still others state that the exact opposite is true. In either case, it is clear that this is not a subject that can be explained easily using sim- plified theories. Likewise, predicting the amount of lift created by wings has been an equally challenging task for engineers and designers in the past. In fact, for years, we have relied heavily on experimental data collected 70 to 80 years ago to aid in our initial designs of wing.

Youtube

Wikipedia Lift Force:

John D. Anderson, Curator of Aerodynamics at the National Air and Space Museum:

  • It is amazing that today, almost 100 years after the first flight of the Wright Flyer, groups of engineers, scientists, pilots, and others can gather together and have a spirited debate on how an airplane wing generates lift. Various explanations are put forth, and the debate centers on which explanation is the most fundamental. 

See also Lack of Theory of Flight and Theory of Flight on Wikipedia.

Desktop Aeronautics

Applied Aeronautics text book Preface:

  • The aerodynamics of bumble bees, disk heads, weather, and many other things is not a solved problem. While it is impressive that the methods in use today do so well, we are still not able to predict many flows.

AIAA Referee

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