[ColinWright]

I suspect we are really not far from each other, but we might have different ideas of what is "intuitive", or "obvious", or "complete", or "well understood".

I've spoken with several aerodynamicists over many years, and they all say that the "conservation of momentum" idea, and the "downwash" explanation are only part of the story, and when you run the numbers the lift you get is not completely explained by those alone.

But at this point I need to go back to work, and I'll come back when I can to see how the overall discussion is going. It does feel unlikely that I'll have anything useful to add.

[mansoor_]

Ok.

To clarify the physics, the "conservation of momentum" idea explains all of the lift, not just some of it.

If you draw a bounding box around the wing and measure the momentum at either end, the lost momentum will be because of the wing, some of that will be lift generation (there is also drag + other turbulent losses).

[wbeaty]

If it's a 3D wing with finite span, then you're well into vortex-shedding and momentum-carrying plumes of gas.

The usual way to avoid this is to make the wingspan be infinite, with no wingtips. But this is dishonest, because it transforms the problem into a "venturi effect," where the airfoil is producing an instant-force against the ground. Then, the Newtonian force-pair exists between wing and ground. (Yet real, non-infinite wings don't need any ground surface to react against. Their force-pair is between the wing and the vortices being launched downwards.)

To simplify: first explain a hovering helicopter. Wings work the same, acting as air-pumps, pulling in air from all directions, then creating a momentum-carrying plume launched downwards. (Helicopters and wings, both are examples of fluid propulsion, where Bernoulli doesn't apply.)