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What does /payload/weight/arm-in do ?

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Re: What does /payload/weight/arm-in do ?

Postby wlbragg » Fri Jan 21, 2022 5:19 pm

Ah, okay, that is a "standard" pointmass definition I am using in the addon to allow anyone to easily add a payload point to their aircraft and have it work in the addon. I originally copied that structure from who knows where, maybe the c172p. I assumed it to be a standard property in any pointmass definition and didn't give it a second thought. I have no idea what it is for or if it is needed or used by jsbsim. I searched the jsbsim pdf for it and it wasn't in there.

If it isn't recognised by anyone and not commonly used in other aircraft, i would suspect it might be a dead property that is no longer used? Otherwise maybe something internal to jsbsim?
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Re: What does /payload/weight/arm-in do ?

Postby wkitty42 » Fri Jan 21, 2022 7:59 pm

it seems to me that arm-in is aliased to a jsbsim property for some sort of calculations... probably related to the craft's CoG depending on things added to the craft (eg: other passengers, baggage, more fuel, etc...)...

why it is named "arm-in" i have no idea... it could probable be named something other name as long as any other code that needs it is also adjusted...
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Re: What does /payload/weight/arm-in do ?

Postby wlbragg » Fri Jan 21, 2022 8:55 pm

The only reference to it in jsbsim FDM was in JSBSim.cxx line 995. I didn't search any other source code.

Code: Select all
    // Copy the fuel levels from JSBSim if fuel
    // freeze not enabled.
    if ( ! Propulsion->GetFuelFreeze() ) {
      for (i = 0; i < Propulsion->GetNumTanks(); i++) {
        SGPropertyNode * node = fgGetNode("/consumables/fuel/tank", i, true);
        FGTank* tank = Propulsion->GetTank(i);
        double contents = tank->GetContents();
        double temp = tank->GetTemperature_degC();
        double fuelDensity = tank->GetDensity();

        if (fuelDensity < 0.1)
          fuelDensity = 6.0; // Use average fuel value

        node->setDoubleValue("density-ppg" , fuelDensity);
        node->setDoubleValue("level-lbs", contents);
        if (temp != -9999.0) node->setDoubleValue("temperature_degC", temp);

        node->setDoubleValue("arm-in", tank->GetXYZ(FGJSBBase::eX ) );
      }
    }


Curt also gave an explanation on the mailing list.
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Re: What does /payload/weight/arm-in do ?

Postby S&J » Fri Jan 21, 2022 9:39 pm

Wooopy do ....... Curt should post in here if he wants vision of it.
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Re: What does /payload/weight/arm-in do ?

Postby S&J » Fri Jan 21, 2022 9:41 pm

Armature in inches.
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Re: What does /payload/weight/arm-in do ?

Postby wlbragg » Fri Jan 21, 2022 10:35 pm

Curt should post in here if he wants vision of it.


I asked the question there, so he answered there.
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Re: What does /payload/weight/arm-in do ?

Postby S&J » Sat Jan 22, 2022 11:09 am

Sorry, I'd had a couple and was thinking it was a silly place to answer a question asked here
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Re: What does /payload/weight/arm-in do ?

Postby wlbragg » Sat Jan 22, 2022 4:44 pm

Only a couple? Well then, that is the problem, you didn't have enough! :)
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