Re: 1900d

Date:         26 Apr 98 03:44:12 
From:         David Lednicer <dave@amiwest.com>
Organization: Analytical Methods, Inc.
References:   1 2
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J. David Dishman wrote:
>
> Tony Paton wrote in message ...
> >Beech state that the stabilons and tailets on the 1900d eliminate the
> >the need for a stability augmentation system. Can someone explain what
> >a SAS is?

	In the case of the Beech 1900, one goal of the design was to use as
many parts from the King Air 200 as possible.  In the wind tunnel, the
aircraft was found to lack directional stability and to have a limited
CG range.  The things hanging down from the horizontal stabilizer
increased the directional stability to acceptable levels and the
stabilons which project horizontally from the rear fuselage increased
the static longitudinal stability and allowed the CG to have acceptable
range.  When the fuselage was deepened, going from the 1900C to the
1900D, the directional stability decreased due to the added side area of
the fuselage ahead of the CG.  To counter this, strakes were added to
the lower rear fuselage.  These strakes restored the aircraft's
directional stability.

	A SAS does what the name implies - it augments the aircraft's
stability.  On commercial aircraft, this is just what it does - augment.
On recent military aircraft, such as the F-16, F-18, X-29, etc., the
aircraft would be unflyable but for the computer that provides artifical
stability.

-------------------------------------------------------------------
David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
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Redmond, WA  98052  USA    |   fax:     (206) 746-1299