Jose wrote:
Do you agree that the net momentum transfered to the Earth by the
air molecules is equal and opposite to the net momentum transferred
to the wing by the air molecules?

Yes.

Do you agree, therefor that there is no net momentum transfered to
the air?

Overall, yes. Similarly, there is no net momentum transferred to the
basketball when it is being used to support a (very fast) dribbler. But
that is not to say that there is no momentum transfer. The basketball
certainly moves around. I do agree that the net overall is zero. The
air does not pile up permanently.

Good. That was my point all along. There is no net momentum
transfered
to the air. There is a net transfer of energy to the air..


At which ponit the Earth throws the air molecule back up so that the
net momemtum transferred to the air molecule is zero (averaged over
the entire atmosphere)

Yes.

[it hits the wing on the way up]
Which again transferes an equal and opposite momentum to the
molecule which again is transferrred to the Earth leaving no net
transfer of momentum to the air.

Yes.

Overall, there is no net (or "permanent") transfer of momentum to the
air. The air is an intermediary, keeping the wing and the earth apart.
There is certainly =energy= transfer to the air (mv^2/2), and there is
a lot of momentum transfer =back=and=forth= with the air, but I will
agree that the net is zero. The air is sort of a catalyst - ending up
unchanged as it transfers momentum to the earth and then transfers it
back from the earth to the wing.

Yes, although we do not yet agree on the details of the mechanism.


So.. after all that, I think we are in agreement - there is no =net=
(permanent) vertical momentum transfer to the air, but there is locally
momentum transferred to the air, which carries it to the earth and uses
it to neutralize the momentum the earth has acquired being attracted to
the plane, in doing so it acquires momentum in the opposite direction
and transfers it to the wing, ending the cycle and leavint the air ready
to act as momentum messenger again.


No. Being attracted to something does not cause momentum. There
must be relative motion for momentum.

It carries momentum messages both ways, they (overall) cancel out, but
do keep the earth and the wing separated.

No, it is not momentum that keeps the aircraft from falling, it is
lift. The lift is produced by a pressure difference through the
wing.


===

In addition, the wing is throwing air forwards, due to its AOA and its
own forward motion. (this acts as drag, counteracted by the engine).
The air thrown forwards increases the pressure in front of the wing,
that plus the air thrown down makes the air pressure in front of and
below the wing higher, causing the air to rise in front of the wing.
This rising air helps lift the wing; this is the source of induced drag.
Some of the rising air spills around the wingtips, causing vortices.
The vortices are not the cause of lift, they are an inescapable side
effect of lift.

Concur?

No.

--

FF