Dave Perry wrote:
> I have continued to tweak the yasim dc3.xml.  Attached is what I have
> settled on.

Sorry, I didn't get a chance to get to this over the weekend (wedding
plans...).  If anyone else has flown it and feels comfortable, feel
free to check it in.  I promise to get to it tonight, really I do. :)

> The CG is at x=-8 meters (still 1 meter aft of the center of the root
> cord) via negative ballast in the tail.  I could not get to this CG
> w/o increasing the length of the hstab to 3.5 meters, as the trim for
> approach solution always failed.

I got the lengths off of a 3-view diagram that may or may not have
been correct.  This sounds fine to me.

> The hstab effectiveness="4.2" with a flap effectiveness="0.5".

That sounds kinda high, but then we should expect to have a more
effective surface in the absence of prop wash.  If it doesn't cause
any other weird effects, it should be fine.

> I notice I am holding a little right aleron all the time.  It may be
> my imagination, but when I use the external view from the rear, it
> looks to me like the right aleron is ever-so-slightly drooping and
> the left aleron is slightly up when my yoke is neutral.  And when I
> add the right aleron to keep the wings level, this goes away.  Has
> anyone else seen this in yasim?

Check the value of /controls/aileron-trim.  In the past, I've seen
this set at startup to a non-zero value (0.055, if I remember
correctly).  I believe this is a magic tuning value that was added to
the JSBSim 172 at one point, but I was never able to track down where
it is coming from.  Setting it to zero at runtime, on the command
line, or in the dc3-yasim-set.xml file should fix this.  Anyone else
have an idea of where this value comes from?

Andy

-- 
Andrew J. Ross                NextBus Information Systems
Senior Software Engineer      Emeryville, CA
[EMAIL PROTECTED]              http://www.nextbus.com
"Men go crazy in conflagrations.  They only get better one by one."
 - Sting (misquoted)


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