At 14:24 02 February 2004, Chris Ocallaghan wrote:
Pete,


Every now and then, I like to keep my hand in with
sidesliping on finals. One airfield I fly at has a
real narrow tarmac strip, like 5 meters. When I am
in a nice balanced, wings level sideslip, how come
I maintain a striaght path all the way down to my reference
point where I kick it off to round out?



Unfortunately, you are wrong on this one. You can,
in fact, use rudder to change direction, much to the
aerodynamicist's
chagrin.

especially if you have and engine up front.

It is very
inefficient, but by holding wings level and ruddering
(a skid)

side slip actually

you
create an inward pointing force caused by the fuselage
(along with a
rearward componenet -- drag). It is this force that
allows you to slip
by counteracting the turning force of the wing with
an opposite force
from the fuselage. (Again, much to the chagrin of the
aerodynamicist.)

Please, expand on this 'force', from an aerodynamics
point of veiw. I'd love to know what law of physics
you have created this thrust vector from.


You need rethink your model. Remember, things only
go straight if in
equilibrium.

actually, all objects in motion exhibit a natual tendancy
to go in a straight line, unless an external force
is applied to upset that equilibrium. One of Mr Newtons
laws I think!

An aircraft flying sideways through the air wings level
won't be in equilibrium, therefore either speed or
direction
must change.

I did loads of sideways flying this weekend soaring
on our hill!
Wings level, straight line constant 60knots, crabbing
along at 40 odd degrees.

in order to keep the wings level while applying yaw,
you have to apply a roll moment to counter the secondary
roll moment caused by the yaw. This puts the aircraft
back into equilibrium by force. If you release the
aileron, the secondary roll moment caused by the yaw
will eventually bank the aircraft into a turn. Stick
an engine into the equation, and it all changes.