This is exactly my point! Why don't we all already know what makes an
aircraft turn? Many pilots feel they do, but if we sit several
professional pilots down, separately, and ask them how an aircraft
flies from a pilot's perspective, you'll get three substantively
related, though specifically different answers.

I can demonstrate with an equation (F=ma), a rectangular piece of stiff
paper, and a paper clip that an aircraft in a bank will turn (establish
a circular flight path) unless the pilot intentionally prevents it from
turning by applying rudder or reducing AoA. The point, for the sake of
this thread, isn't to define a theory of flight suitable for aviators.
Rather, it is to recognize how informal and untested many of our
theories really are. A theory that demands tail feathers to initiate
turns (as opposed to the wing just dragging the aircraft sideways
through the air) doesn't sufficiently explain the flight of hang
gliders, boomerangs, frisbees, or my paper clip ballasted flying wing.

Some might say, well, the model serves well enough.... but does it
really? How many accidents do we have each year that are preventable?
Why do competent pilots spin in? Why do well-trained pilots demonstrate
a lack of competency in basic flight skills like slipping and stall
recognition?

I'll return to slips: it's my favorite example becasue so few people
can do them well or describe them accurately. What factors need to be
considered during a slip? Are you aware that the ailorons contribute a
nose down pitching motion during a slip? Have you considered that
during a slip, you must increase the angle of attack because the lift
verctor is no longer antiparallel with graivity (as in a turn)? Are
you aware that the pitching moment of the elevator decreases with
increased beta? What effect on lift and drag does the effective
reduction of wing aspect ratio have? What differences in stick use can
be expected in a high performance versus a wide-body glider during
slipping? Is there any aerodynamic difference between a forward and a
side slip? If there isn't, why do we bother differentiating them? Have
you ever seen any of these ideas discussed in a flight primer? Why not?
I consider all these questions foundational. Yet it took me a long time
to start asking them. I learned to do slips by rote, but never did them
really well until I began to ask these questions. Hopefully, you'll
recognize I've only asked some of the less obvious questions. There are
plenty of others, some taught, some ignored, some simply not
recognized. An example of the latter... how do you measure airspeed in
a slip?

OK, I'm dancing on the head of pin, but I needed an example to drive
home what we don't know about something so "simple" as slipping. A good
pilot should be asking questions and looking for answers all the time.
A good instructor should be looking for new and better ways to pose and
answer such questions. One last example, if I asked "What is the
primary yaw control in a glider?" how would you react if I answered,
"its the ailerons?" And why might this be a better answer than "the
rudder?"

There's alot left to learn, and discuss, and apply. And alot of bright,
"mis-informed" people out there who have something to contribute. I'll
address myself to Burt again... if the RAS is misinformed, isn't the
source culpable? Isn't the first step to recognize that we're ALL, to a
greater or lesser degree, misinformed so we can get about the business
of improving our understanding?