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Why we don’t understand heavier-than-air flight

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Re: Why we don’t understand heavier-than-air flight

#51

Post by hamilyon2 »

Cogito wrote: post #40
hamilyon2 wrote: post #35

Earlier quoted context omitted.

Not an expert or anything. Never studied aerodynamic or flight in depth. As far as I understand, for helicopter to fly, it definitely has to have thrust to weight ratio greater than one. Flying things that have thrust to weight ratio > 0 are intuitive to me. They generate force and stay in the air indefinitely. Planes obviously don't require that to fly. So, they're different type of beast. They somehow squeeze more…

It's the exact same principle for planes and helicopters. If a plane isn't producing more lift than weight it will fall, just like a helicopter. Planes work by pushing a wing through the air, helicopters by spinning it. In both cases the wing has to push down enough air to keep the aircraft in flight.

So, people answering on quora for example, are wrong? https://www.quora.com/Can-a-helicopter-having-a-power-to-wei...

I am even more confused now.

Re: Why we don’t understand heavier-than-air flight

#52

Post by k__ »

garmaine wrote: post #16
Sniffnoy wrote: post #6

Earlier quoted context omitted.

Hm, I was hoping this article would explain in what sense we don't understand flight, or in what sense people think we don't understand flight, but it didn't seem to answer that question...

We understand flight perfectly well. Although the common explanations are often BS.

Reminds me of learning what electricity is.

I learned it multiple times. In middle school, in high school, in university, on youtube explained by a quantum physicist.

Everytime I understood less of it.

Re: Why we don’t understand heavier-than-air flight

#54

Post by gpm »

AstralStorm wrote: post #20
NickNameNick wrote: post #12

Earlier quoted context omitted.

Why does the air move faster on the upper side of the wing? It's not because there's a magic force that requires air particles parted be the leading edge to rejoin thier partner at the trailing edge. The air particles on the upper surface reach the trailing edge much sooner than the ones under the wing.

Does not move faster either. Otherwise, a flat wing would not work, and they do. Gravity or force creates the pressure differential. Wing pushes on air below it. (Why birds fly.) Additionally, for moving wing, edges create vortices that create local pressure differentials. (Why helicopters and planes and birds work better than floating pieces of paper.) Wings work very similarly to performance ship hulls in this rega…

Surely it does move faster, because it's lower pressure/you're putting less resistance on it?

If I have a wing shaped like ∖, air going in -> direction, which is what you need to generate lift with a flat wing, then the air on the bottom is running into the wing and slowing down, while the air on the top is being pulled into the region the wing swept clear of particles and speeding up.

Re: Why we don’t understand heavier-than-air flight

#55

Post by DangitBobby »

hamilyon2 wrote: post #51
Cogito wrote: post #40

Earlier quoted context omitted.

It's the exact same principle for planes and helicopters. If a plane isn't producing more lift than weight it will fall, just like a helicopter. Planes work by pushing a wing through the air, helicopters by spinning it. In both cases the wing has to push down enough air to keep the aircraft in flight.

So, people answering on quora for example, are wrong? https://www.quora.com/Can-a-helicopter-having-a-power-to-wei... I am even more confused now.

No, I have to conclude that the previous commenter didn't understand your point, which was the observation that heavy aircraft with very low sustained forward thrust (thrust that would not be sufficient for a helicopter to hover) results in sufficient upward lift to suspend the aircraft indefinitely, which is very surprising.

Re: Why we don’t understand heavier-than-air flight

#56

Post by lowkey »

Can confirm. I worked at Pratt & Whitney testing jet engines early in my career. At the time I read a similar article and spread it amongst my colleagues - the cognitive dissonance was palpable.

As engineers we had been taught that lift was due to air above the wing traveling faster than air below the wing and thus creating lift by way of a pressure differential. The more accurate answer as seen in the article is that the effect is better explained through Newton’s laws as a re-vectoring of horizontal thrust in a downward direction. Literally the engine pushes horizontally accelerated air downward and the action-reaction mechanic causes an equal but opposite upward force lifting the plane.

Amazing how so many experts could be so wrong in their understanding while the planes continue to fly.

It reminds me of how hummingbirds don’t know that they violate the known laws of physics when they fly.

Re: Why we don’t understand heavier-than-air flight

#57

Post by handrous »

k__ wrote: post #52
garmaine wrote: post #16

Earlier quoted context omitted.

We understand flight perfectly well. Although the common explanations are often BS.

Reminds me of learning what electricity is. I learned it multiple times. In middle school, in high school, in university, on youtube explained by a quantum physicist. Everytime I understood less of it.

I once read a book called "There Are No Electrons". I'm not sure I'd recommend it, but its approach was interesting: the author reasons that unless you're in grad school studying physics (and perhaps even then), everything you've been taught about electricity is a lie anyway, so the author attempts to present a framework of easier to understand lies intended to make the reader able to better reason about and predict the behavior of electrical systems, than if the reader had only the lies that are usually taught.

Re: Why we don’t understand heavier-than-air flight

#58

Post by yiyus »

progfix wrote: post #37
oolonthegreat wrote: post #31

I didn't understand what we don't understand about hta flight but maybe that's just me.

We don't know how to calculate turbulence, we can only predict it. It is the turbulence that create the uplift on a wing, so the author says we don't understand it.

> It is the turbulence that create the uplift on a wing

You can have lift with laminar flow. In fact, the article includes an explanation of the usage of the Reynolds number to characterize laminar and turbulent flow and how the flow around plane wings is clearly laminar (called "smooth" in the article).

Re: Why we don’t understand heavier-than-air flight

#59

Post by ghosty141 »

lowkey wrote: post #56

Can confirm. I worked at Pratt & Whitney testing jet engines early in my career. At the time I read a similar article and spread it amongst my colleagues - the cognitive dissonance was palpable. As engineers we had been taught that lift was due to air above the wing traveling faster than air below the wing and thus creating lift by way of a pressure differential. The more accurate answer as seen in the article is tha…

As a layman this explanation makes more sense than the "fast air over the top of the wing" one.

Re: Why we don’t understand heavier-than-air flight

#60

Post by anvandare »

lowkey wrote: post #56

Can confirm. I worked at Pratt & Whitney testing jet engines early in my career. At the time I read a similar article and spread it amongst my colleagues - the cognitive dissonance was palpable. As engineers we had been taught that lift was due to air above the wing traveling faster than air below the wing and thus creating lift by way of a pressure differential. The more accurate answer as seen in the article is tha…

I usually just answer Socratically: "So how can (some) planes fly upside-down?" whenever I encounter the Bernoulli-adherents.
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