Hello,

I try to figure out the behaviour of the different fdms. Here the results:

/sim/flight-model="yasim"
        /consumables/fuel/tank[i]/level-gal_us
                                  level-lbs
                                  density-ppg
                                  capacity-gal_us

        /yasim/gross-weight-lbs = Zero-Fuel-weight + level-lbs[i]

        Zero-fuel-weight = Parameter AC_EMPTYWT in <aircraft>.xml +/- ??


I checked the 747: Parameter AC_EMPTYWT in 747.xml = 370.000 lb. When I set all fuel to zero, /yasim/gross-weight-lbs = 400.000 lb

        I don't know,where the difference of 30.000 lb comes from.

/sim/flight-model="jsb"
        /consumables/fuel/tank[i]/level-gal_us
                                 level-lb

        /fdm/jsbsim/inertia/weight-lbs = Zero-Fuel-weight + level-lb[i]

        Zero-fuel-weight = Paramter AC_EMPTYWT in <aircraft>.xml +/- ???
        Fuel-Capacity =  <AC_TANK TYPE="FUEL" NUMBER="0">
                            CAPACITY 10200.0
                            But I can't find it in the property tree

        I checked the 737:
        Parameter AC_EMPTYWT in 737.xml = 83000 lb
        When I set all fuel to zero,
          /fdm/jsbsim/inertia/weight-lbs = 80.000
        I don't know, where the difference of 3.000 lb comes from


/sim/flight-model="larcsim"

        I checked ornithopter           : No fuel information
        I checked the wrightflyer       : No fuel information
        I check a4-uiuc                 : No fuel information

        Are there no fuel information ??


The solution could be:

1. yasim changes the property /consumables/fuel/tank[i]/level-lbs
                        to    /consumables/fuel/tank[i]/level-lb
                        or 2 property are filled with the same value

2. jsbsim sets /consumables/fuel/tank[i]/capacity-gal_us with
                        AC_TANK TYPE="FUEL" NUMBER="0">
                        CAPACITY 10200.0
                        from <aircraft>.xml

3. /yasim/gross-weight-lbs and  /fdm/jsbsim/inertia/weight-lbs
   are both fdm-related. May be we need a new property entry with
   weights like

        /weight/emptyweight
                zerofuelweight
                paxweight
                maxtakeoffweight
                maxlandingweight

    As a temporary solution in should be handle in the nasal-script


Hans-Georg










Jon Berndt wrote:
Hans-Georg Wunder wrote:

if try to set the fuel and payload with the menu-entry
EQUIPMENT/FUEL and PAYLOAD I get an error:

Nasal runtime error: nil used in numeric context
  at /Debian/Flightgear/FlightGear-0.9.5/data/Nasal/gui.nas, line 166
  called from: <command>, line 1

Yes, this dialog makes use of a bunch of YASim-only features, so it's really not portable to JSBSim, which lacks stuff like a gross weight output, runtime-settable weights and a per-tank fuel capacity value.

Basically: you can't fix this with Nasal; you need to add the
appropriate features to the FDM.

The right way to solve this would be to either support the existing
interface in JSBSim or to decide on a similar "standard" interface for
this stuff and support it in both FDMs.


Well ... we do have a per-tank fuel capacity value, as well as fuel tank contents at 
init
time. We have a way to set the weight and location of point masses, which is what I 
assume
you mean by payload, at init time. It would be pretty easy to set these items at 
runtime
by the addition of the appropriate setter, and whatever mechanism is available on the
flightgear side. Fuel setting has always been a bit of a problem, because that can be 
set
in the JSBSim config file as well (since we have to maintain the ability to run in a
standalone mode, we of course need a way to set some of these things on our own). When
integrated with FlightGear, these values for fuel can be overridden. Initially, that 
lead
to some confusion.

I haven't really followed this discussion closely, but we'd be happy to help figure 
out a
way to make this all work for both of us (and does this need to be fixed for LarcSIM 
and
LaRCSim/UIUC, too?). Can someone elaborate on what is needed?

Jon


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