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> If a person is, like, lifting off from the ground, and moving through the air in a controlled fashion driven by jet engines, isn't that pretty exactly flying?

It depends, are they reaching a height where the Wing-in-ground effect is negligible? If they have to stay below that, then no, not really flying. Unless you'd say that a hovercraft or ekranoplan also flies.

Or they could just be staying low because it might be insanely dangerous if the operator loses control at even slight altitude.



Terminology nit: the effect is the ground effect; the vehicle might be a wing-in-ground-effect craft.


The wing-in-ground effect adds a great deal of drag, and is avoided in typical applications.


Ground effect reduces drag.


And the effect of putting your wing IN the ground is what?

The wing-in-ground effect. It’s a dumb little joke.


A hovercraft doesn’t fly not because the wing in ground effect but because it doesn’t have 6 degrees of freedom which constitutes flying.

A sub or a torpedo can fly through the water just like an airplane or a missile do through air.


Where did you get this idea of flying? I wondered if I had a misconception there but any source I could quickly find on the web disagrees with the "can move with six degrees of freedom" definition and uses a definition like "doesn't touch ground or sea while moving through the air" instead. (Wikipedia on "Flight" / "Ekranoplan" / "Ground-effect vehicle", Merriam Webster on the word "Flight", and search for "what is flight" if that's not enough).


Flight is typically 4DOF: (throttle, pitch, roll, yaw). There is no horizontal or vertical 'strafing' ability.


Helicopters and hummingbirds fly. And flies, they fly too. And there are a lot more flies flying than planes.


The platform can move in the vertical and horizontal, e.g by exploiting a crosswind.


Does an ekranoplan "fly" then ?


Can it move in 6 degrees of freedom?


I have no idea what that means, that's why I asked.


https://en.wikipedia.org/wiki/Six_degrees_of_freedom

If not it isn't really flying. I don't know if it moves around with forces in 6DOF or not either.


Up to a max altitude of 7 meters (at best), sure, an Ekranoplan has got all the degrees of freedom that other aircraft have, Which as was pointed out here https://news.ycombinator.com/item?id=24629545 , is not 6

Imho no, an Ekranoplan does not fly freely. Nothing to do with a bogus DOF count though


The only reason an Ekranoplan can't fly higher is it's wings don't generate enough lift out of ground effect. Load a 747 up high enough, and it too wouldn't be able to get out of ground effect, but I'd still say it was flying.


You can't just say that "because it's a 747, it can fly":

A 747 with no fuel can't take off and fly.

A 747 with so much load that it never takes off at all, can't fly.

And IMHO, a 747 with just so much load that it can barely take off but can't get out of ground effect, also can't fly. It's borderline, but not really.

It's an academic distinction though. Give the 747 a while, and it will burn enough fuel to lighten and ascend.


> Nothing to do with a bogus DOF count though

It seems that you don't understand the implication of the DOF count. Flying means moving freely through the air. That, colloquially, means 6degree of freedom movement through space. It means looping a, it means barrel rolls, it means it can run circles and go backwards and move upside down. You know, flying.

Ekranoplans fly as much as an hovercraft does, which mean they don't. Case in point: they are unable to do 6dof movement. An ekranoplan doesn't do barrel rolls for example.


I guess I'm confused. If an aircraft can't go backwards or do a loop, does that mean it's not flying? Because as far as I know, every fixed wing aircraft is incapable of going in reverse, and most can't do a loop. Not trying to pick on your defenition of flight based on degrees of freedom, but that doesn't seem to match any definition of flight I've run across.




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