How Airplanes Fly, Does anyone truly know?

So, an old friend was asking me if the article entitled “The secret to airplane flight? No one really knows” was true or not… and while the author is engaging in clickbait tactics to bring in eyeballs, there is a lot more truth in the title than not. Obviously with over 15 million flight ops handled by the FAA in 2016, and 19,601 airports in the US… it seems someone, or maybe a whole ton of people should know, but truly no one does, at least not yet.

Granted, one can look at the authors statements, as well as mine and say… its just semantics, and there is an element of truth in that too. Certainly CFD(computational fluid dynamics) is a robust science, and as a tool ,its used daily, not only in aviation, but in a multitude of applications, where it gets us pretty darn close, and in most cases, more than close enough. But bottom line, due to aerodynamics crazy level of complexity, we have chosen to characterize flight physics as contrasted with truly knowing (nicely solvable equations which work under all circumstances) what causes an airplace to fly. This could change in a heartbeat though, should someone win the millenium prize by solving the Navier-Stokes equation.

From a flight instructor point of view though, it is way more than just a semantics issue. On the one hand, the fearful student doesn’t need to hear that no one truly knows how airplanes fly (when most certainly CFD can model things to bits even though technically we still don’t truly know). On the other hand, the future aerodynamics student, shouldn’t be stuck having to relearn material that they were taught incorrectly from the get go. Its all too easy to misapply Bernouli, or Newton, or some *oddball comingling tweaking of the two and get things totally hosed up….

Alas, NASA comes to the rescue in this

Lift is the force that holds an aircraft in the air. How is lift generated? There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments for many years.

https://www.grc.nasa.gov/www/k-12/airplane/bernnew.html

Where in NASA proceeds to go into the incorrect methods one by one.
https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
https://www.grc.nasa.gov/www/k-12/airplane/wrong2.html
https://www.grc.nasa.gov/www/k-12/airplane/wrong3.html

Flightwriter goes into some nice discussions of folks mangling theories of lift…
1. “Equal Transit Time” is wrong, therefore Bernoulli is wrong,
2. “Equal Transit Time” is right,
3. Bernoulli is “just a theory” and has never been proven,
4. If Bernoulli were right, it wouldn’t be possible to fly inverted, and
5. 80% of lift comes from Bernoulli, 20% comes from Newton.

And even more so, he approaches the theories of lift very pragmatically, being careful not to hamstring a future engineering student, and at the same time, being insightful enough for the interested student pilot. Alas, the math person who wants everything neatly packaged is likely to be frustrated… Many real world phenomena, are just too complicated to know with the rigor expected in the math domain.

One thought on “How Airplanes Fly, Does anyone truly know?”

  1. My oldest is planning to go into aerospace engineering. I’ll have to show him this and the links you reference. It’ll nerd-snipe him.

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