From: loki@midgard.Sgi.COM (Peter DiPrete)
Newsgroups: rec.aviation.student
Subject: Re: Turning
Date: 2 Jan 93 07:32:53 GMT
Reply-To: loki@wpd.sgi.com
Organization: Silicon Graphics, Inc.

In article <1i37v4INN50e@pith.uoregon.edu>,
margolin@darkwing.uoregon.edu (Brian Margolin) writes:
|> I took my first lesson today and am now at home studying the FAA
|> Flight
|> Training Handbook.  Unfortunately the weather was terrible today 
|> (only a 1000' ceiling) and we had to come back in early.  Anyway, to
|> get to the point, I am unsure about the forces encountered during a
|> bank.  It seems that upon banking the plane there is a horizontal
|> force component exerted at the point where the wings reach the
|> fuselage.
|> I understand that this causes the plane to move sideways.  According
|> to
|> what I have read, the wings on most planes are positioned behind the
|> center of gravity.  The way I figure, the plane should therefore be
|> forced to pivot away from the turn.  Why therefore does the plane
|> actually pivot into the turn (as if the wings were in front of the
|> center of gravity)?  Thanks in advance for the info.

Well, maybe I should leave this to the experts, since I'm only a
student
with 4.3 hours under my belt. In any event, Geoff Peck and the true
experts
will correct my errors.

So, you're right, the center of gravity is ahead of the center of
lift/pressure. In straight and level flight, of course, all forces
are in equalibrium, though, so no turning forces are exerted on any
of our three favorite axes.

When you bank into a turn, 2 things happen as a result of the back:
	1) the "up" component of lift is reduced,
and	2) the "lateral" component is increased.

If all you, as the pilot, did nothing other than roll the airplane into
the
turn you would actually yaw away from your intended turning direction
then
it would slip into the turn. The adverse yaw is caused mostly by the
increase
in lift from the "down" airleron on the outer wing. More lift (from the
down
airleron) causes more drag which yaws the play *away* from the desired
turn.
The slip is caused by the lateral component of the wing's "lift" when in
the
bank.

The loss of lift is corrected with backpressure.

But the plane actually turn (yaws) into the turn in time, so I have two
theories. In the first place, you can cause the yaw by backpressure on
the
yoke increasing AOA deliberately (in fact, you must do this plus add
power
in steep turns). In the second case, it's also true that the horizontal
stabilizer itself loses lift increasing AOA (of the main wing) without
any additional action on the part of you, the pilot. It's also true that
the
airplane has a vertical stabilizer. The effect (in my theory) of the
vstab
is that as the plane slips into the turn, the tail will slip into the
turn
much MUCH more slowly because it has lower mass and much higher
aerodynamic
stability. Therefore, the nose of the plane is slipping into the turn
faster
than the tail, and you have the yaw that you desire.
+---------------------+-------------------------------------+-----------
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| What makes a mouse  | Peter DiPrete		            | loki@sgi.com   |
| king of his house?  | Manager, Software Quality           |
(415)390-1971  |
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