I've noticed that a lot of JSBsim files got updated just the other
day, and today was the first time I've had
   a chance to try it out.

   I'm working on the A380 which does use JSBsim, and during the engine
start everything freezes just after
   the starter is turned false, the ignition is true and the cutoff is
turned false. This is around N2 = 27%

   Fortunately I had compiled everything with debug, so a quick look in
gdb reveals at stacktrace (on interrupt signal)

#0  0x000000000068aeb8 in JSBSim::FGTank::Drain (this=0xc4829a0,
used=1.0180511166896056e-315) at FGTank.cpp:196
#1  0x000000000066640f in JSBSim::FGEngine::ConsumeFuel (this=0xc47d4c0)
at FGEngine.cpp:212
#2  0x00000000006945aa in JSBSim::FGTurbine::Start (this=0xc47d4c0) at
FGTurbine.cpp:290
#3  0x0000000000699d61 in JSBSim::FGTurbine::Calculate (this=0xc47d4c0)
at FGTurbine.cpp:155
#4  0x00000000006069c4 in JSBSim::FGPropulsion::Run (this=0xbdf8550) at
FGPropulsion.cpp:147
#5  0x00000000005670bc in JSBSim::FGFDMExec::Run (this=0xc573220) at
FGFDMExec.cpp:362
#6  0x000000000055949d in FGJSBsim::update (this=0xc413fb0,
dt=0.041666666666666664) at JSBSim.cxx:487
#7  0x0000000000435ec8 in fgUpdateTimeDepCalcs () at main.cxx:159
#8  0x00000000004371df in fgMainLoop () at main.cxx:449
#9  0x000000000049e1ac in fgOSMainLoop () at fg_os_osgviewer.cxx:172
#10 0x0000000000433e07 in fgMainInit (argc=9, argv=0x7fffffffda58) at
main.cxx:900
#11 0x00000000004332e1 in main (argc=9, argv=0x7fffffffda58) at
bootstrap.cxx:228


196     double FGTank::Drain(double used)                    
197     {                                                    
198       double remaining = Contents - used;                
199                                                          
200       if (remaining >= 0) { // Reduce contents by amount used.
201                                                               
202         Contents -= used;                                     
203         PctFull = 100.0*Contents/Capacity;                    
204                                  

the value for 'used' is 0   (which doesn't seem right)
the values for 'Contents' and 'remaining' are > 0 (they are correct
values)
'Drain' is called for each tank 

It seems this loop in FGEngine.cpp is executed repeatedly with no way
out;

183       while (FuelToBurn > 0.0) {
184                                 
185         // Count how many fuel tanks with the current priority level
have fuel.
186         // If none, then try next lower priority.  Build the feed
list.        
187         while ((TanksWithFuel == 0.0) && (CurrentPriority <=
Propulsion->GetNumTanks())) {
188           for (i=0; i<Propulsion->GetNumTanks(); i++)
{                                   
189             Tank =
Propulsion->GetTank(i);                                                
190             if (Tank->GetType() == FGTank::ttFUEL)
{                                      
191               if ((Tank->GetContents() > 0.0) && ((unsigned
int)Tank->GetPriority() == CurrentPriority)) {
192                  ++TanksWithFuel;
193                  FeedList.push_back(i);
194                }
195             } else {
196                cerr << "No oxidizer tanks should be used for this
engine type." << endl;
197             }
198           }
199           if (TanksWithFuel == 0.0) CurrentPriority++;
200         }
201
202         // No fuel found at any priority!
203         if (TanksWithFuel == 0.0) {
204           Starved = true;
205           return;
206         }
207
208         // Remove equal amount of fuel from each feed tank.
209         FuelNeeded = FuelToBurn/TanksWithFuel;
210         for (i=0; i<FeedList.size(); i++) {
211           Tank = Propulsion->GetTank(FeedList[i]);
212           Tank->Drain(FuelNeeded);
213           FuelToBurn -= FuelNeeded;
214         }
215
216         // check if we were not able to burn all the fuel we needed
to at this priority level
217         if (FuelToBurn > 0.001) {


The value of FuelToBurn is  = 1.4821969375237396e-323
The value of CurrentPriority = 1 and never changes.
once I step past line 217, it goes back to line 183 and never seems to
stop.


I'm not a C++ coder, and not much of a gdb debugger, but I hope that
helps enough if someone else is seeing similar problems.
    Scott.

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