Re: [Jsbsim-devel] Rascal 110 FDM, Datcom and Datcom-modeler

[Bill G. <bi...@be...>]

 

> -----Original Message-----
> From: Ron Jensen [mailto:wi...@je...] 
> Sent: Friday, October 16, 2009 11:46 PM
> To: JSBSim development issues
> Subject: [Jsbsim-devel] Rascal 110 FDM, Datcom and Datcom-modeler
> 
> I'm moving this thread over to the JSBSim list hoping Anders, 
> Bill G and Dave will jump in! :)
> 
> While searching the web on an unrelated topic, I came across 
> a 2006 thesis paper on the Rascal 110 RC aircraft:
> 
> http://handle.dtic.mil/100.2/ADA451288
> 
> It has a lot of potentially good data on the Rascal to allow 
> us to fine-tune the FDM.
> 
> DATCOM-MODELER:
> Starting around page 84 of the PDF are 3D line drawings 
> called "Input to Digital Datcom."  When comparing these line 
> drawings to my datcom-modeler program I see the line drawings 
> are ovals while datcom-modeler renders diamonds.  
> Datcom-modeler is supposed to approximate the area S, 
> specified for each station while using ZU, ZL and R.  Does 
> anyone know what software generated the 3D line drawings and 
> if it also tries to take S and/or P into account?
> 
> On page 160 is the DATCOM model.  Its flight conditions 
> section lists an array notion that datcom-modeler doesn't 
> like.  That is the ALPHA(17) notation.  I'm not a FORTRAN 
> guy, does that mean we start at the 17th element of that array?
> 
>  $FLTCON NMACH=1.,MACH=0.061,NALPHA=20.,NALT=1.,ALT=1000.,
>   
> WT=17.,ALPHA=-10.,-8.,-6.,-4.,-2.,0.,2.,4.,6.,8.,10.,12.,14.,1
> 6.,18.,20.,
>   ALPHA(17)=22.,24.,26.,28.,$
> 
> DATCOM+ errors out on this model, even though the .out file only shows
> two minor  ** ERROR ** NO NAMELIST NAME FOLLOWING $ errors
> 
> 
> Ron
> 
> P.S.
> Look, I spelled Rascal right in the subject!  :)
> 



Okay, I'm up early on a Saturday, so I'll throw in first.

I d/l'ed the report, and took a peek at the input file. I put it into a .DCM file, but the AC3D picture that Datcom+ generated looked proper as far as the fuselage goes. However, it didn't have a tail on it. Looking at the .dcm file, it defines the tail section, then in the next case, goes back and defines the ailerons (I'm assuming at this point those are ailerons). DATCOM places any moveable surfaces on the aft-most horizontal surface, so are these differential elevators?  I'll have to study the report and the aircraft some more before I have a clearer understanding.

Concerting the lines:
   ALPHA=-10.,-8.,-6.,-4.,-2.,0.,2.,4.,6.,8.,10.,12.,14.,16.,18.,20.,
      ALPHA(17)=22.,24.,26.,28.,$

Yeah, that's Fortran. It is acceptable to input it that way, just not the nicest. It could have been done without the "ALPHA(17)=" completely, and the subsequent elements would have been loaded correctly.

I'll look into this some more when I have some time, but that might not be for a while, as my plate is full right now.

Bill