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 | | From: | Jim | | Subject: | Wings-level "skid" or "slip"? | | Date: | Wed, 12 Jan 2005 12:16:02 -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.
Thank you for your clear descriptions of these situations. They help
me visualize what is happening. I agree too that coordinated is
better!
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