Re: [Jsbsim-devel] Trim options in initialisation file

[Sean M. <se...@se...>]

Hi Dave

When I initially saw an example of <trim> 1 </trim> in an initialization file I assumed that I could enter any one the trim options, i.e.

integer equivalent to one of tLongitudinal (0), tFull (1), tGround (2), tPullup (3), tCustom (4), tTurn (5).

But the code in FGInitialCondition only returns a bool based on the trim value from the trim element.

  /** Does initialization file call for trim ?
      @return true if initialization file (version 1) called for trim. */
  bool NeedTrim(void) const { return needTrim == 0 ? false : true; }

Which is then used in JSBSim.cpp with DoTrim() defaulting to tGround.

  FDMExec->RunIC();

  if (FDMExec->GetIC()->NeedTrim()) {
    trimmer = new JSBSim::FGTrim( FDMExec );
    try {
      trimmer->DoTrim();
      delete trimmer;
    } catch (string& msg) {
      cerr << endl << msg << endl << endl;
      exit(1);
    }

Hence the reason that currently the only trim option available from the initialization file is tGround.

I’d like to be able to specify any of the trim options from the initialization file. One thing to consider though would be maintaining backwards compatibility for existing initialization files.

Cheers

From: David Culp <dp...@gm...>
Sent: Friday, July 13, 2018 9:57 PM
To: Development issues <jsb...@li...>
Subject: Re: [Jsbsim-devel] Trim options in initialisation file

As I recall, this was added by me to support QtJSBSim.  I'm away on vacation, so I can't look it up right now.

Dave

On Fri, Jul 13, 2018, 12:48 PM Sean McLeod <se...@se...<mailto:se...@se...>> wrote:
Hi

Is there a specific reason why the only trim options available in the initialization file are ‘ground trim’  and no trim?

- trim (0 for no trim, 1 for ground trim)

Cheers
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