A very basic question

On Sat, 06 Nov 2004 22:22:22 GMT, Mike Rhodes
wrote:


A banked aircraft will not turn if, and only if, the wing is not
generating lift. A wing will not generate lift if its angle of attack
is so controlled by the horizontal stabilizer.

I was not quite right with the "if and only if". Of course the rudder
can also stop the turn, as in a side-slip. And the side-slip Peter
mentioned is what pushes the nose around in the turn by its push on
vertical stabilizer. I did not point directly at the vert stabilizer
as Peter did in his reply.

Because the banked aircraft is aligned less with gravity, it would
then want to accelerate 'up', as 'up' is relative to the aircraft.
But this would immediately change the angle-of-attack of the both the
wing and the horizontal stab. So the wing loses some lift, while the
horizontal stab increases its already downward push. This would tend
to push the nose 'up', and restore the angle of attack of the wing.

The turn is a relatively slow process (the pilot has time to make
adjustments), and maybe the mechanics are not so simple as I think my
post implied.

--Mike

On Mon, 08 Nov 2004 19:30:24 GMT, Mike Rhodes
wrote:

On Sat, 06 Nov 2004 22:22:22 GMT, Mike Rhodes
wrote:



Because the banked aircraft is aligned less with gravity, it would
then want to accelerate 'up', as 'up' is relative to the aircraft.
But this would immediately change the angle-of-attack of the both the
wing and the horizontal stab. So the wing loses some lift, while the
horizontal stab increases its already downward push. This would tend
to push the nose 'up', and restore the angle of attack of the wing.


Oops. I got this wrong. If both wing and horizontal stab are pushed
down then the net effect is no change in angle of attack.

--Mike

Ramapriya wrote:
Hi guys,

Unlike the elevators and rudder that change an aircraft's pitch and
yaw with no other secondary effect,

None of the controls really operate without producing secondary
effects. Rudder-only will produce Yaw, of course, but the yaw
accelerates one wing forward and one wing back, which changes
the airflow over the wings - the forward-accelerating wing
produces additional lift, the aft-accellerating wing less,
producing a roll. Its a sloppy turn, but it can be done.

Elevator changes the pitch, which typically will affect the
angle of attack and thus the lift produced by the wings, and
may produce a climb or descent which will affect the airspeed, ...

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?

The wings produce Lift. In straight and level flight, the lift
vector is straight up. When you bank, you change the direction of the
lift vector - the bank introduces a lateral component that accelerates
the aircraft in that direction - the turn. The rudder is used in
this case only to counteract any adverse yaw produced by the ailerons in
commanding the bank. And the 'tail feathers' (vertical stabilizer) tend
to keep the aircraft aligned with the airflow.

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

There are many. But try: http://www.av8n.com/how/

Yes, my understanding is that a bank causes an airplane to slip, which
then causes it to weathervane into the wind. Why do you ask? Is there
something I am missing?



"Hilton" wrote in news:lUGjd.8614$O11.3080
@newsread3.news.pas.earthlink.net:

Andrew,

Andrew Sarangan wrote:
Hilton wrote:

Andrew Sarangan wrote:

Sure, but that still does not explain why the airplane turns. A
horizontal component of lift will make the airplane side-slip, not
turn. It is the stability (weathervane effect) that makes the
airplane turn.

By definition, the 'weathervane effect' occurs because air exerts
more
pressure on one side of the object (aircraft) than the other - same
definition as slipping. Therefore, are you are asserting that an
aircraft turns because it is slipping? More over, it will only
turn
if it is slipping?

Hilton


Think of the space shuttle. If you fire rockets horizontal to the
flight
path, the shuttle will slide sideways. It will not turn the nose
towards
the direction of travel. An airplane turns because it wants to point
the
nose into the relative wind.

I understand that, but you never answered my question: "Are you
asserting
that an aircraft turns because it is slipping (weathervaning)?"

Hilton








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That is exatly what I said in a previous post on this thread. A bank causes
an airplane to side-slip, which in turn makes it point into the wind.



soxinbox wrote in
. 165:

I don't think anyone has hit on what is really going on here. The
explanations about the sideways force created by lift when the AC is
banked cause it to move ( accelerate ) to the side, but not rotate.
The dihedral wing explanation doesn't work either, because the raised
wing's horizontal force is applied aft of the CG, thus causing
rotation in the opposite direction of the turn. The major reason that
a plane rotates about the vertical axis during a turn is wind vaning.

You bank the plane, the lift is broken into horizontal and vertical
components. The horizontal force causes the plane to accelerate to the
side, but not rotate as others have stated. Now with the plane picking
up speed in the lateral direction, the relative wind is now coming
from one side of the plane, a forward quartering headwind! As anyone
who has taxied on a windy day knows, planes have a natural tendency to
face into the wind. This is caused by the big wind vane we call a
tail. This rotates the plane into the wind. The relative wind is thus
always leading the plane by a few degrees, causing a continued
rotation. And as a side benefit, the horizontal acceleration is
countered by the centripetal force of the turn, so we don't continue
to accelerate to faster and faster horizontal speeds.


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(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?

Think about the direction of lift from the wings. When the ailerons
roll the plane, the direction of lift points partly sideways. That
will pull the plane to the side. It's not quite that simple, but
that's the nut of the matter.

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

Well, a newsgroup is for posting questions. But, you might want to
check out: a href="http://www.av8n.com/how/"See How It Flies/a as
well.

-Malcolm Teas