Matlab/JSBSim S-function: error while changing aircraft file

[MariaALJ]

Hello,

I am trying to change the aircraft in the JSBSim S-function under matlab but I always have the error : Aircraft file could not be loaded. For example, I'm going from the 737 (default) to the 787-8. I also tried to manually change the aircraft model in the configuration script that is called in the S-function besides the aircraft model, but it didn't help.

Any help on this matter would be really appreciated.

Thank you in adavance!

The error log:

JSBSim S-Function is initializing...

 JSBSim Flight Dynamics Model v1.1.12 [GitHub build 866/commit 133fcff53ae15abcbbbd4d06390e1b59ab76e5c6] Jun 26 2022 09:57:16
        [JSBSim-ML v2.0]

JSBSim startup beginning ...
Simulation dt set to 0.008333
Setting up JSBSim with standard 'aircraft', 'engine', and 'system' paths.
Loading aircraft '787-8' ...
Reading Aircraft Configuration File: 787-8
Version: 2.0
This aircraft model is a BETA release!!!
This aircraft model probably will not fly as expected.
Use this model for development purposes ONLY!!!
Description: Flight Dynamics Model for the Boeing 787-8
Model Author: Narendran Muraleedharan, Dwayne Gable and Nicky Ivy
Creation Date: 2011-12-29
Version: $Revision: 1.10 $
Aircraft Metrics:
WingArea: 3501.798400
WingSpan: 192.000000
Incidence: 0.034907
Chord: 38.940000
H. Tail Area: 343.360000
H. Tail Arm: 81.600000
V. Tail Area: 471.777280
V. Tail Arm: 0.000000
Eyepoint (x, y, z): 0.000000 , 0.000000 , 0.000000
Ref Pt (x, y, z): 0.000000 , 0.000000 , 0.000000
Visual Ref Pt (x, y, z): 0.000000 , 0.000000 , 0.000000
Mass and Balance:
baseIxx: 7675399.200088 slug-ft2
baseIyy: 6595543.304209 slug-ft2
baseIzz: 22197429.613715 slug-ft2
baseIxy: -0.015489 slug-ft2
baseIxz: 0.015489 slug-ft2
baseIyz: -0.000000 slug-ft2
Empty Weight: 239200.000000 lbm
CG (x, y, z): -16.000000 , 0.000000 , 22.597200
Point Mass Object: 350.000000 lbs. at X, Y, Z (in.): -898.320000 0.000000 51.220000
Point Mass Object: 1800.000000 lbs. at X, Y, Z (in.): -591.000000 0.000000 78.800000
Point Mass Object: 6400.000000 lbs. at X, Y, Z (in.): -216.700000 0.000000 78.800000
Point Mass Object: 25000.000000 lbs. at X, Y, Z (in.): 157.600000 0.000000 78.800000
Point Mass Object: 10000.000000 lbs. at X, Y, Z (in.): -394.000000 0.000000 -39.400000
Point Mass Object: 5000.000000 lbs. at X, Y, Z (in.): 157.600000 0.000000 -39.400000
Ground Reactions:
BOGEY NOSE_GEAR
Location: -809.500580 , 0.000000 , -143.368720
Spring Constant: 160000.000000
Damping Constant: 80000.000000 (linear)
Rebound Damping Constant: 80000.000000 (linear)
Dynamic Friction: 0.300000
Static Friction: 0.400000
Rolling Friction: 0.020000
Steering Type: STEERABLE
Grouping: NONE
Max Steer Angle: 70.000000
Retractable: 1
BOGEY LEFT_MAIN
Location: 77.105800 , -193.599780 , -153.632420
Spring Constant: 833000.000000
Damping Constant: 166600.000000 (linear)
Rebound Damping Constant: 166600.000000 (linear)
Dynamic Friction: 0.350000
Static Friction: 0.400000
Rolling Friction: 0.020000
Steering Type: FIXED
Grouping: LEFT
Max Steer Angle: 0.000000
Retractable: 1
BOGEY RIGHT_MAIN
Location: 77.105800 , 193.599780 , -153.632420
Spring Constant: 833000.000000
Damping Constant: 166600.000000 (linear)
Rebound Damping Constant: 166600.000000 (linear)
Dynamic Friction: 0.350000
Static Friction: 0.400000
Rolling Friction: 0.020000
Steering Type: FIXED
Grouping: RIGHT
Max Steer Angle: 0.000000
Retractable: 1
STRUCTURE LEFT_WING_TIP
Location: 549.236000 , -1173.481720 , 154.830180
Spring Constant: 100000.000000
Damping Constant: 20000.000000 (linear)
Rebound Damping Constant: 20000.000000 (linear)
Dynamic Friction: 0.400000
Static Friction: 0.500000
STRUCTURE RIGHT_WING_TIP
Location: 549.236000 , 1173.481720 , 154.830180
Spring Constant: 100000.000000
Damping Constant: 20000.000000 (linear)
Rebound Damping Constant: 20000.000000 (linear)
Dynamic Friction: 0.400000
Static Friction: 0.500000
STRUCTURE TAIL_STRIKE
Location: 924.938640 , 0.000000 , 3.419920
Spring Constant: 100000.000000
Damping Constant: 20000.000000 (linear)
Rebound Damping Constant: 20000.000000 (linear)
Dynamic Friction: 0.400000
Static Friction: 0.500000
STRUCTURE NOSE
Location: -984.290800 , 0.000000 , -29.845500
Spring Constant: 100000.000000
Damping Constant: 20000.000000 (linear)
Rebound Damping Constant: 20000.000000 (linear)
Dynamic Friction: 0.400000
Static Friction: 0.500000
External Reactions:
Frame: BODY
Location: (0.000000, 0.000000, 0.000000)
Propulsion:
FUEL tank holds 52000.000000 lbs. FUEL
currently at 63.594883% of maximum capacity
Tank location (X, Y, Z): 0.000000, -295.500000, 25.610000
Effective radius: 0.000000 inches
Initial temperature: -9999.000000 Fahrenheit
Priority: 1
FUEL tank holds 52000.000000 lbs. FUEL
currently at 63.594883% of maximum capacity
Tank location (X, Y, Z): 0.000000, 295.500000, 25.610000
Effective radius: 0.000000 inches
Initial temperature: -9999.000000 Fahrenheit
Priority: 1
FUEL tank holds 120000.000000 lbs. FUEL
currently at 55.115566% of maximum capacity
Tank location (X, Y, Z): 0.000000, 0.000000, -39.400000
Effective radius: 0.000000 inches
Initial temperature: -9999.000000 Fahrenheit
Priority: 1
Simulation completed.
Remember to reset the program by typing clearSF in the matlab command window!
Error reported by S-function 'JSBSim_SFunction' in 'ex737cruise/S-Function':
Aircraft file could not be loaded.

[bcoconni]

That's weird indeed. I can load the 787-7 model successfully using JSBSim Python interface (I don't have MATLAB installed on my computer). The error seems to occur while loading the tables IdleThrust in the file engine/trent_1000.xml: I'm getting some output from JSBSim for these tables that are now listed in your log.

      Tank location (X, Y, Z): 0, 0, -39.4
      Effective radius: 0 inches
      Initial temperature: -9999 Fahrenheit
      Priority: 1
    2 dimensional table with 6 rows, 8 columns.
                -10000.0000     0.0000  10000.0000      20000.0000      30000.0000      40000.0000      50000.0000      60000.0000
        0.0000  0.0430  0.0488  0.0528  0.0694  0.0899  0.1183  0.1467  0.0000
        0.2000  0.0500  0.0501  0.0335  0.0544  0.0797  0.1049  0.1342  0.0000
        0.4000  0.0040  0.0047  0.0020  0.0272  0.0595  0.0891  0.1203  0.0000
        0.6000  0.0000  0.0000  0.0000  0.0000  0.0276  0.0718  0.1073  0.0000
        0.8000  0.0000  0.0000  0.0000  0.0000  0.0474  0.0868  0.0900  0.0000
        1.0000  0.0000  0.0000  0.0000  0.0000  0.0000  0.0552  0.0800  0.0000
    Function: propulsion/engine[0]/IdleThrust
    2 dimensional table with 8 rows, 8 columns.
                -10000.0000     0.0000  10000.0000      20000.0000      30000.0000      40000.0000      50000.0000      60000.0000
        0.0000  1.2600  1.0000  0.7400  0.5340  0.3720  0.2410  0.1490  0.0000
        0.2000  1.1710  0.9340  0.6970  0.5060  0.3550  0.2310  0.1430  0.0000
        0.4000  1.1500  0.9210  0.6920  0.5060  0.3570  0.2330  0.1450  0.0000
        0.6000  1.1810  0.9510  0.7210  0.5320  0.3780  0.2480  0.1540  0.0000
        0.8000  1.2580  0.9000  0.7020  0.5220  0.3770  0.2750  0.1700  0.0000
        1.0000  1.3690  1.1000  0.8510  0.6410  0.4550  0.3050  0.1960  0.0000
        1.2000  1.4850  1.2300  0.9750  0.7440  0.5450  0.3640  0.2250  0.0000
        1.4000  1.5941  1.3400  1.0860  0.8450  0.6280  0.4240  0.2630  0.0000
    Function: propulsion/engine[0]/MilThrust

In file ../../../aircraft/787-8/787-8.xml: line 251
Engine location ignored, only thruster location is used.

In file ../../../aircraft/787-8/787-8.xml: line 256
Engine orientation ignored, only thruster orientation is used.
      X = -211.9208
      Y = -383.1571
      Z = -31.2915
      Pitch = 0.0000 degrees
      Yaw = 0.0000 degrees

@noah-curran, any ideas ?

[noah-curran]

Off the top of my head, no ideas. I've used the S-Function for multiple custom aircraft, so I'm certain it is capable of using other aircraft besides the default 737. Without more information, I'm inclined to believe there is an issue with the aircraft file itself:

Loading aircraft '787-8' ...
Reading Aircraft Configuration File: 787-8
Version: 2.0
This aircraft model is a BETA release!!!
This aircraft model probably will not fly as expected.
Use this model for development purposes ONLY!!!

These warning messages seem awfully ominous...

[bcoconni]

Loading aircraft '787-8' ...
Reading Aircraft Configuration File: 787-8
Version: 2.0
This aircraft model is a BETA release!!!
This aircraft model probably will not fly as expected.
Use this model for development purposes ONLY!!!

These warning messages seem awfully ominous...

Nothing sinister there: that's the standard disclaimer for WIP flight models.

Anyway as I mentioned previously I can load this model successfully using Python so it's unlikely the model itself is at fault. I'd rather bet for a setting in the S-Function that needs some adjustment ?

[noah-curran]

I think I'm confused. You said you loaded in the 787-7 and @MariaALJ said she used the 787-8. Are these two models not different?

[noah-curran]

Regardless, I'm also still confused why you believe the S-Function is at fault here. The S-Function does not meddle with the aircraft files loading, it just calls JSBSim to load it. If an error was thrown, then the S-Function captured that the aircraft file was not properly loaded by JSBSim and terminated execution.
See these lines of code:

        if (!JII->OpenAircraft(aircraft)){
            ssSetErrorStatus(S, "Aircraft file could not be loaded.\n");
            return;
        }

I can dive further later when I take my closer look at overhauling parts of the S-Function's error returns, but I don't think there is anything definitive here that the S-Function is at fault. If the problem is that the error messages aren't descriptive enough, I agree completely re the discussion in #774. I'd advise making sure the aircraft file is OK.

[bcoconni]

I think I'm confused. You said you loaded in the 787-7 and @MariaALJ said she used the 787-8. Are these two models not different?

Oops ! Sorry that was a typo, I meant that I have tested the "787-8" model.

I can dive further later when I take my closer look at overhauling parts of the S-Function's error returns, but I don't think there is anything definitive here that the S-Function is at fault.

I did not mean that the S-Function code was at fault but rather that may be one of the S-Function input needs to be modified in addition to changing the model name ? I was thinking to initial conditions for instance ?