A very basic question

(Ramapriya) wrote in message . com...
Hi guys,

Unlike the elevators and rudder that change an aircraft's pitch and
yaw with no other secondary effect, why does the banking of wings by
the use of ailerons not just roll an aircraft but also produces a turn
(yaw)? Logically, one would expect an aircraft to keep going straight
ahead even if the pilot banked the aircraft left or right. Where does
the turning effect come from?

Is there a website you know of that can teach me such basics, without
having to bug you?

Cheers,

Ramapriya


Alas, Ramapriya, it is far more complex than that! First of all, the
rudder causes not only yaw, but by virtue of the yaw accelerating the
outside wing and effectively increasing lift, causes bank toward the
inside of the turn.

The ailerons cause both roll AND yaw...but counterintuitively, the yaw
is to the outside of the turn. That is because the creation of lift
also creates drag. And when you use the ailerons to bank, you are
increasing the lift on the outside wing...and therefore yawing toward
the "outside" of the turn. The rudder largely is used to counter that
force.

And none of that is why an airplane turns. The true cause of the turn
is...well, we need to look at an airplane in our mind's eye...picture
it in level flight. The force of gravity is offset by the force of
lift...generated by the wings. We can say that there is a downward
vector...gravity...and an upward vector...lift, which is perpendicular
to the airplane's wing. Now, let us bank the airplane. The lift vector
is still perpendicular to the airplane's wing, but now it is directed
somewhat toward the inside of the bank. And the airplane therefore
turns that way...is pulled that way, if you will. Oh, and yes, since
the lift vector is directed toward the inside of the turn, the amount
of lift to counteract gravity is decreased...and the airplane will
descend unless something is done...usually the addition of power or an
increase in the angle of attack...increases the antigravity portion of
the lift vector.

That will either help or totally confuse you. Feel free to email me
for a dialog.

Jim