At 4/25/02, you wrote:
>I have been seeing a strange difference between the view I get with the 
>same AC mode and the JSBSim and MagicCarpet FDMs.  The pilot view is 
>correct with JSBSim, but under the magic carpet, the pilot is buried up to 
>their eyeballs in the tarmac.  There are pictures that show both 
>situations, from the outside view.
>
>http://homepage.mac.com/eq_fidget/magic_ac.png
>
>is with the MagicCarpet FDM and
>
>http://homepage.mac.com/eq_fidget/JSBSim.png
>
>is with JSBSim
>
>Its been a problem for a while, it's just that I haven't been using 
>anything other than the MagicCarpet and thought it was a more general problem.

I speculate that the new problem running w/ the MagicCarpet FDM (buried 
aircraft) is related to the same problem running w/ the LaRCsim/UIUC FDM 
that I have reported.  All the while, this has not been a problem running 
w/ JSBSim FDM.  The problem started around the time that work on the viewer 
code began.

Here's my Beech 99 buried:
http://amber.aae.uiuc.edu/~m-selig/tmp/beech.gif

With this aircraft I used Dz_cg = 2.5 ft.  This is a LaRCsim variable which 
we can set from our code.  When I set Dz_cg = 0 ft, then the aircraft is 
above the ground.  I don't like this solution because it means that I 
cannot move the cg relative to the aero reference point anymore (unless I 
want to watch the aircraft takeoff from underground).  It also required me 
to change some of my configuration files (most were using Dz_cg = 0 by 
default).

I have not tried to dig deeper.  But it must relate to Dz_cg and w/ it 
d_cg_rp_body_v (see flight.hxx and ls_generic.h).  Getting closer to the 
problem might involved this part of code in flight.hxx

// This is based heavily on LaRCsim/ls_generic.h
class FGInterface : public FGSubsystem {
....

Much has changed here since 0.7.8

I would not have to speculate if I knew what I need to know about c++ ...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I wonder if you run JSBSim w/ Dz_cg not equal to zero, are the aircraft buried?

Regards,
Michael



>Thanks,
>
>Jonathan Polley
>
>
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>Flightgear-devel mailing list
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**************************************************
  Prof. Michael S. Selig
  Dept. of Aero/Astro Engineering
  University of Illinois at Urbana-Champaign
  306 Talbot Laboratory
  104 South Wright Street
  Urbana, IL 61801-2935
  (217) 244-5757 (o), (509) 691-1373 (fax)
  mailto:[EMAIL PROTECTED]
  http://www.uiuc.edu/ph/www/m-selig
  http://www.uiuc.edu/ph/www/m-selig/faq.html (FAQ)
**************************************************


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