BT wrote:
Isn't interesting that entry level RC Aircraft only have rudder and elevator
controls.. and then turn just fine.

When the rudder is applied, a skid and a turn follow. The skid is of no
consequence, but any turn rate at all is of great consequence, since tht
makes the outside wing fly faster, creating more lift, and a bank is the
result; a two-stage event where succession is important.

Sort of like turning a bicycle, where a small jink to the outside of
the intended turn is required to establish the bank needed for the turn.

In a stall, you pick up the low wing with rudder, not aileron, that only
adds adverse yaw, more drag on the low wing, and fights the rudder.

Aileron action, following the wright Brothers wing warping, was
intentionally symmetrical (same magnitude both sides) and all pilot
training through and after WWII were taught "Coordination"; one applied
rudder and aileron simultaneously. After WWII, civil airplane designers
acted to make life simpler for the pilot by tweaking aileron action.

The adverse yaw is caused by the extra induced* drag of a wing that is
obliged to lift more ends up also dragging more, The inbord wing is
casued to drop by an up-aileron, and any increase in parasite (non-lift)
drag is exceeded by the lack of induced drag. One day the light came on
and it was deduced that if only the inbirad aileron deflected up, the
adverse yaw would ve greately reduced if not eliminated. Sa ther wwas
born "differential movement" and belcrakx and levers were rigged such
that the inbord aileron deflected up a lot, while the outboard aileron
deflected very little.

[*"Induced" means that it is not real friction or turbulence drag, but
a new rearward force that results from a wing or aileron that is
creating extra lift.]

So today, most civit aircraft can be put into and out of gentle turns
with aileron alone, and that's what makes single-axis autopilots
(aileron only) so successful.

Angelo Campanella