Re: Dutch Roll

From:         Don Stokes <Don.Stokes@vuw.ac.nz>
Organization: Victoria University of Wellington
Date:         18 Sep 95 12:06:53 
References:   1 2
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dorfman@netcom.com writes:
>Andrew Goldfinger (Andy.Goldfinger@aplmail.jhuapl.edu) wrote:
>that the name Dutch Roll is used because the motion of the aircraft seems
>similar to that of an ice skater slowly gliding down the frozen canals of
>the Netherlands.
>     I was not aware that the motion occurs only on swept wing aircraft.

I think the term predates swept wing aircraft, but swept wings are prone
to Dutch roll more than straight wings.  If a swept wing aircraft yaws,
one wing gets a lot more lift and drag than the other, where the airflow
is running down the leading edge rather then over the wing.  The result
is a roll on the "forward" wing, and a tendency to yaw back, setting up
an oscillation.  If you don't have enough directional stability (read:
a good big tail) the yaw back can be greater than the initial yaw, and
the plane can quickly go out of control.

With a straight wing, the both wings stay at more or less the same angle
to the airflow, and apart from factors such as the "wind shadow" of the
fuselage, you don't get the same asymmetry in airflow as with a swept
wing.

--
Don Stokes, Network Manager, Victoria University of Wellington, New Zealand.
don@vuw.ac.nz(work) don@zl2tnm.gen.nz(home) +64 4 495-5052 Fax+64 4 471-5386