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 | | From: | Todd Pattist | | Subject: | Wings-level "skid" or "slip"? | | Date: | Tue, 11 Jan 2005 18:26:50 -0800 |
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>Can a wings-level, rudder-induced, yawed but stable (the yawing
>motion has stopped) orientation be called a "skid" or a "slip", or do
>"skid" and "slip" only apply to a banked orientation?
The correct term to use ("slip" or "skid") doesn't depend
on whether your wings are level or banked, nor does it
depend on the rudder usage. The correct term to use
depends on whether your track through the air mass is
straight or curved, and if curved, the relative direction of
the airflow. When your track is straight, it is never
called a "skid," it's a "slip." If your track is curved,
it is a "skid" when the relative airflow is from the outside
of the curve and a "slip" when it's from the inside.
Here are some examples:
Your wings are level, you've kicked in right rudder, so your
yaw string is off to the right side but your track through
the air mass is still straight. Technically, you are
slipping.
The above situation is unstable, since your fuselage is at a
slight angle to the airflow and produces a sideways lift
force. You can't really have wings level AND a straight
track. There are two possibilities:
1 - you keep your wings exactly level, as above and the
sideways lift force on the fuselage produces a yaw-only slow
turn to the right. Now you are not flying a straight track.
You are flying a skidding turn. Note that this is only
slightly different from the slipping case above.
2 - you put in some left bank to counteract the
fuselage-produced force to the right. Now your track is
straight, but you are banked left with right rudder. This
is called a forward slip.
Assume you have some right rudder in and don't change that.
Assume you also have your left wing down and only vary your
bank angle. At one specific left bank angle, your track
through the air mass will be straight and you will be in the
forward slip described above.
With more left bank, your track will curve left and it's
called a slipping left turn. With less left bank, no left
bank or a small amount of right bank, your track will curve
right, but the airflow over the fuselage will continue to
come from outside the turn and it's called a skidding right
turn. (Too much right rudder.)
As you increase the right bank, depending on the aircraft
design, you may eventually pass through a coordinated turn,
leave the skidding right turn and begin a slipping right
turn. (Too little right rudder.)
Fly coordinated, it's better.
Todd Pattist
(Remove DONTSPAMME from address to email reply.)
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