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Considering the Gravity of the Situation


By  · December 25, 2018 ·

A physicist can become a pilot. But does a pilot have to become a physicist? I don’t think so.

In fact, I’m sure of it.

It’s perfectly okay for a pilot — a good pilot, a really good, safe, conscientious pilot — to have only a passing understanding of important scientific theories. Theories like, how does lift work?

I believe that with all my heart and soul. Let the fireworks begin.

The great and powerful Paul Bertorelli recently published a piece on AvWeb titled, “Wait, you mean Bernoulli had it all wrong?” This short article garnered quite a bit of attention.

Paul is demonstrably braver than I am, so I doff my hat to him in taking the lead on this issue.

Although, contrary to the title, the thrust of his piece is not that Bernoulli was mistaken. In point of fact, it’s not so much that Daniel Bernoulli blew it, as it is that a long line of well-intentioned flight instructors have explained his discovery…let’s say poorly. I include myself in that pool of unsophisticated scholars.

A week after Bertorlelli’s piece ran, Isabel Goyer published a supporting piece in Plane & Pilot Magazine that took up for Bertorelli. I shared that piece via social media and was intrigued by the responses. All were respectful, but they took various perspectives on the topic, which got me thinking.

What if the topic in question wasn’t lift, but was something else that directly affected aircraft in flight? Would we still believe that it’s essential for pilots to understand the subject down to the molecular level? Probably not, although that’s essentially what the hubbub is about when it comes to lift.

You’ve been taught, and I’ve been taught, and pretty much every pilot in existence has been taught, that lift occurs because an air molecule traveling over the upper, curved side of an airfoil has farther to go than a molecule of air traveling under the flatter side. Because it has further to go it has to move faster, and because it moves faster there is a drop in air pressure, resulting in lift.

That’s sort of true. At least in parts. But it’s also largely incorrect.

Still, it’s what we’ve been teaching and learning for the better part of a century. Which raises an interesting question. If it is indeed important that pilots learn about the science of lift to the molecular level, does it matter at all if the information they learn is correct? That would seem to be somewhat important, at least to my mind.

So as I said, I began to wonder if we should be encouraged to understand other forces that affect flight.

Gravity for instance. Now, I know it is weight, not gravity, that counters lift. It’s weight, along with lift, thrust, and drag that make up the all-important Four Forces of Flight.

But gravity certainly plays a role when we discuss weight. That being the case, how precisely do you suppose a pilot has to understand gravity to fly safely? Do we need to have a thorough understanding of what Einstein proposed about gravity and space/time, or is it sufficient to understand that gravity acts downward, toward the center of the earth?

Like the theory of lift we’ve been taught, the belief that gravity acts toward the center of the Earth is not entirely correct. At the very least it’s incomplete. But it is a way of viewing the phenomenon that is practical, understandable, and can reliably guide our actions to keep us safe.

Let me propose something radical. Brace yourself.

Perhaps it’s not so bad to be ignorant of the fine details of a topic, provided you have an understanding of how the topic in question will affect you in the pursuit of specific activities.

In other words, if you don’t understand how lift is created, but you know how to apply it to your aircraft – you win. If the movement and speed of individual air molecules eludes you, but the importance of Angle of Attack is deeply rooted in your psyche, then as a pilot, you’re in good shape.

Is that so wrong?

Jeff Goin is one of the smartest, most experienced pilots I know. He’s also absolutely gonzo nuts about sharing his knowledge with others. His day job has him plying the skies in transport category aircraft. But when he’s home he can often be found just a few dozen feet above the ground, swinging beneath the canopy of a powered paraglider.

The man flies fixed wing, rotor-wing, weight-shift, and pretty much anything he can lay his hands on that will get him airborne. He’s so thoroughly enthralled with flight, including the simplest and most basic machines that will get him there, he’s written the bible on them. Literally. He wrote The Powered Paragliding Bible.

Thanks to Paul, and Isabel, and Jeff, I believe I’ve changed my formerly errant ways when it comes to teaching about lift and drag and such. Yes, I’ve been converted and now subscribe to Goin’s exceedingly simple but easily supportable hypothesis regarding aerodynamics.

Which is this: “Everything you need to know about aerodynamics can be learned by sticking your hand out the window of a moving car.”

Now that’s teaching a practical level of knowledge I can get serious about.


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