src/FDM/JSBSim/FGAtmosphere.cpp

   1 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2
   3  Module:       FGAtmosphere.cpp
   4  Author:       Jon Berndt
   5                Implementation of 1959 Standard Atmosphere added by Tony Peden
   6  Date started: 11/24/98
   7  Purpose:      Models the atmosphere
   8  Called by:    FGSimExec
   9
  10  ------------- Copyright (C) 1999  Jon S. Berndt (jsb@hal-pc.org) -------------
  11
  12  This program is free software; you can redistribute it and/or modify it under
  13  the terms of the GNU General Public License as published by the Free Software
  14  Foundation; either version 2 of the License, or (at your option) any later
  15  version.
  16
  17  This program is distributed in the hope that it will be useful, but WITHOUT
  18  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  19  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  20  details.
  21
  22  You should have received a copy of the GNU General Public License along with
  23  this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  24  Place - Suite 330, Boston, MA  02111-1307, USA.
  25
  26  Further information about the GNU General Public License can also be found on
  27  the world wide web at http://www.gnu.org.
  28
  29 FUNCTIONAL DESCRIPTION
  30 --------------------------------------------------------------------------------
  31 Models the atmosphere. The equation used below was determined by a third order
  32 curve fit using Excel. The data is from the ICAO atmosphere model.
  33
  34 HISTORY
  35 --------------------------------------------------------------------------------
  36 11/24/98   JSB   Created
  37 07/23/99   TP    Added implementation of 1959 Standard Atmosphere
  38                  Moved calculation of Mach number to FGPropagate
  39                  Later updated to '76 model
  40 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  41 COMMENTS, REFERENCES,  and NOTES
  42 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  43 [1]   Anderson, John D. "Introduction to Flight, Third Edition", McGraw-Hill,
  44       1989, ISBN 0-07-001641-0
  45
  46 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  47 INCLUDES
  48 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  49
  50 #include "FGAtmosphere.h"
  51 #include "FGState.h"
  52 #include "FGFDMExec.h"
  53 #include "FGAircraft.h"
  54 #include "FGPropagate.h"
  55 #include "FGInertial.h"
  56 #include "FGPropertyManager.h"
  57
  58 namespace JSBSim {
  59
  60 static const char *IdSrc = "$Id$";
  61 static const char *IdHdr = ID_ATMOSPHERE;
  62
  63 /*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  64 CLASS IMPLEMENTATION
  65 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/
  66
  67
  68 FGAtmosphere::FGAtmosphere(FGFDMExec* fdmex) : FGModel(fdmex)
  69 {
  70   Name = "FGAtmosphere";
  71   lastIndex = 0;
  72   h = 0.0;
  73   psiw = 0.0;
  74   htab[0]=0;
  75   htab[1]=36089.239;
  76   htab[2]=65616.798;
  77   htab[3]=104986.878;
  78   htab[4]=154199.475;
  79   htab[5]=170603.675;
  80   htab[6]=200131.234;
  81   htab[7]=259186.352; //ft.
  82
  83   MagnitudedAccelDt = MagnitudeAccel = Magnitude = 0.0;
  84 //   turbType = ttNone;
  85   turbType = ttStandard;
  86 //   turbType = ttBerndt;
  87   TurbGain = 0.0;
  88   TurbRate = 1.0;
  89
  90   bind();
  91   Debug(0);
  92 }
  93
  94 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  95
  96 FGAtmosphere::~FGAtmosphere()
  97 {
  98   unbind();
  99   Debug(1);
 100 }
 101
 102 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 103
 104 bool FGAtmosphere::InitModel(void)
 105 {
 106   FGModel::InitModel();
 107
 108   Calculate(h);
 109   SLtemperature = intTemperature;
 110   SLpressure    = intPressure;
 111   SLdensity     = intDensity;
 112   SLsoundspeed  = sqrt(SHRatio*Reng*intTemperature);
 113   rSLtemperature = 1.0/intTemperature;
 114   rSLpressure    = 1.0/intPressure;
 115   rSLdensity     = 1.0/intDensity;
 116   rSLsoundspeed  = 1.0/SLsoundspeed;
 117   temperature=&intTemperature;
 118   pressure=&intPressure;
 119   density=&intDensity;
 120
 121   useExternal=false;
 122
 123   return true;
 124 }
 125
 126 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 127
 128 bool FGAtmosphere::Run(void)
 129 {
 130   if (!FGModel::Run()) {                 // if false then execute this Run()
 131     //do temp, pressure, and density first
 132     if (!useExternal) {
 133       h = Propagate->Geth();
 134       Calculate(h);
 135     }
 136
 137     if (turbType != ttNone) {
 138       Turbulence();
 139       vWindNED += vTurbulence;
 140     }
 141
 142     if (vWindNED(1) != 0.0) psiw = atan2( vWindNED(2), vWindNED(1) );
 143
 144     if (psiw < 0) psiw += 2*M_PI;
 145
 146     soundspeed = sqrt(SHRatio*Reng*(*temperature));
 147
 148     Debug(2);
 149
 150     return false;
 151   } else {                               // skip Run() execution this time
 152     return true;
 153   }
 154 }
 155
 156 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 157 //
 158 // See reference 1
 159
 160 void FGAtmosphere::Calculate(double altitude)
 161 {
 162   double slope, reftemp, refpress;
 163   int i = 0;
 164
 165   i = lastIndex;
 166   if (altitude < htab[lastIndex]) {
 167     if (altitude <= 0) {
 168       i = 0;
 169       altitude=0;
 170     } else {
 171        i = lastIndex-1;
 172        while (htab[i] > altitude) i--;
 173     }
 174   } else if (altitude > htab[lastIndex+1]) {
 175     if (altitude >= htab[7]) {
 176       i = 7;
 177       altitude = htab[7];
 178     } else {
 179       i = lastIndex+1;
 180       while (htab[i+1] < altitude) i++;
 181     }
 182   }
 183
 184   switch(i) {
 185   case 1:     // 36089 ft.
 186     slope     = 0;
 187     reftemp   = 389.97;
 188     refpress  = 472.452;
 189     //refdens   = 0.000706032;
 190     break;
 191   case 2:     // 65616 ft.
 192     slope     = 0.00054864;
 193     reftemp   = 389.97;
 194     refpress  = 114.636;
 195     //refdens   = 0.000171306;
 196     break;
 197   case 3:     // 104986 ft.
 198     slope     = 0.00153619;
 199     reftemp   = 411.57;
 200     refpress  = 8.36364;
 201     //refdens   = 1.18422e-05;
 202     break;
 203   case 4:     // 154199 ft.
 204     slope     = 0;
 205     reftemp   = 487.17;
 206     refpress  = 0.334882;
 207     //refdens   = 4.00585e-7;
 208     break;
 209   case 5:     // 170603 ft.
 210     slope     = -0.00109728;
 211     reftemp   = 487.17;
 212     refpress  = 0.683084;
 213     //refdens   = 8.17102e-7;
 214     break;
 215   case 6:     // 200131 ft.
 216     slope     = -0.00219456;
 217     reftemp   = 454.17;
 218     refpress  = 0.00684986;
 219     //refdens   = 8.77702e-9;
 220     break;
 221   case 7:     // 259186 ft.
 222     slope     = 0;
 223     reftemp   = 325.17;
 224     refpress  = 0.000122276;
 225     //refdens   = 2.19541e-10;
 226     break;
 227   case 0:
 228   default:     // sea level
 229     slope     = -0.00356616; // R/ft.
 230     reftemp   = 518.67;    // R
 231     refpress  = 2116.22;    // psf
 232     //refdens   = 0.00237767;  // slugs/cubic ft.
 233     break;
 234
 235   }
 236
 237   if (slope == 0) {
 238     intTemperature = reftemp;
 239     intPressure = refpress*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 240     //intDensity = refdens*exp(-Inertial->SLgravity()/(reftemp*Reng)*(altitude-htab[i]));
 241     intDensity = intPressure/(Reng*intTemperature);
 242   } else {
 243     intTemperature = reftemp+slope*(altitude-htab[i]);
 244     intPressure = refpress*pow(intTemperature/reftemp,-Inertial->SLgravity()/(slope*Reng));
 245     //intDensity = refdens*pow(intTemperature/reftemp,-(Inertial->SLgravity()/(slope*Reng)+1));
 246     intDensity = intPressure/(Reng*intTemperature);
 247   }
 248   lastIndex=i;
 249   //cout << "Atmosphere:  h=" << altitude << " rho= " << intDensity << endl;
 250 }
 251
 252 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 253 // Return the pressure at an arbitrary altitude and then restore the internal state
 254
 255 double FGAtmosphere::GetPressure(double alt) {
 256   Calculate(alt);
 257   double p = *pressure;
 258   // Reset the internal atmospheric state
 259   Run();
 260   return(p);
 261 }
 262
 263 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 264 // square a value, but preserve the original sign
 265
 266 static inline double square_signed (double value)
 267 {
 268     if (value < 0)
 269         return value * value * -1;
 270     else
 271         return value * value;
 272 }
 273
 274 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 275
 276 void FGAtmosphere::Turbulence(void)
 277 {
 278   switch (turbType) {
 279   case ttStandard: {
 280     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 281     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 282     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 283
 284     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 285                                 // Scale the magnitude so that it moves
 286                                 // away from the peaks
 287     MagnitudedAccelDt = ((MagnitudedAccelDt - Magnitude) /
 288                          (1 + fabs(Magnitude)));
 289     MagnitudeAccel    += MagnitudedAccelDt*rate*TurbRate*State->Getdt();
 290     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 291
 292     vDirectiondAccelDt.Normalize();
 293
 294                                 // deemphasise non-vertical forces
 295     vDirectiondAccelDt(eX) = square_signed(vDirectiondAccelDt(eX));
 296     vDirectiondAccelDt(eY) = square_signed(vDirectiondAccelDt(eY));
 297
 298     vDirectionAccel += vDirectiondAccelDt*rate*TurbRate*State->Getdt();
 299     vDirectionAccel.Normalize();
 300     vDirection      += vDirectionAccel*rate*State->Getdt();
 301
 302     vDirection.Normalize();
 303
 304                                 // Diminish turbulence within three wingspans
 305                                 // of the ground
 306     vTurbulence = TurbGain * Magnitude * vDirection;
 307     double HOverBMAC = Auxiliary->GetHOverBMAC();
 308     if (HOverBMAC < 3.0)
 309         vTurbulence *= (HOverBMAC / 3.0) * (HOverBMAC / 3.0);
 310
 311     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 312
 313     vBodyTurbGrad = Propagate->GetTl2b()*vTurbulenceGrad;
 314
 315     if (Aircraft->GetWingSpan() > 0) {
 316       vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 317     } else {
 318       vTurbPQR(eP) = vBodyTurbGrad(eY)/30.0;
 319     }
 320 //     if (Aircraft->GetHTailArm() != 0.0)
 321 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 322 //     else
 323 //       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 324
 325     if (Aircraft->GetVTailArm() > 0)
 326       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 327     else
 328       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 329
 330                                 // Clear the horizontal forces
 331                                 // actually felt by the plane, now
 332                                 // that we've used them to calculate
 333                                 // moments.
 334     vTurbulence(eX) = 0.0;
 335     vTurbulence(eY) = 0.0;
 336
 337     break;
 338   }
 339   case ttBerndt: {
 340     vDirectiondAccelDt(eX) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 341     vDirectiondAccelDt(eY) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 342     vDirectiondAccelDt(eZ) = 1 - 2.0*(double(rand())/double(RAND_MAX));
 343
 344
 345     MagnitudedAccelDt = 1 - 2.0*(double(rand())/double(RAND_MAX)) - Magnitude;
 346     MagnitudeAccel    += MagnitudedAccelDt*rate*State->Getdt();
 347     Magnitude         += MagnitudeAccel*rate*State->Getdt();
 348
 349     vDirectiondAccelDt.Normalize();
 350     vDirectionAccel += vDirectiondAccelDt*rate*State->Getdt();
 351     vDirectionAccel.Normalize();
 352     vDirection      += vDirectionAccel*rate*State->Getdt();
 353
 354                                 // Diminish z-vector within two wingspans
 355                                 // of the ground
 356     double HOverBMAC = Auxiliary->GetHOverBMAC();
 357     if (HOverBMAC < 2.0)
 358         vDirection(eZ) *= HOverBMAC / 2.0;
 359
 360     vDirection.Normalize();
 361
 362     vTurbulence = TurbGain*Magnitude * vDirection;
 363     vTurbulenceGrad = TurbGain*MagnitudeAccel * vDirection;
 364
 365     vBodyTurbGrad = Propagate->GetTl2b()*vTurbulenceGrad;
 366     vTurbPQR(eP) = vBodyTurbGrad(eY)/Aircraft->GetWingSpan();
 367     if (Aircraft->GetHTailArm() > 0)
 368       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/Aircraft->GetHTailArm();
 369     else
 370       vTurbPQR(eQ) = vBodyTurbGrad(eZ)/10.0;
 371
 372     if (Aircraft->GetVTailArm() > 0)
 373       vTurbPQR(eR) = vBodyTurbGrad(eX)/Aircraft->GetVTailArm();
 374     else
 375       vTurbPQR(eR) = vBodyTurbGrad(eX)/10.0;
 376
 377     break;
 378   }
 379   default:
 380     break;
 381   }
 382 }
 383
 384 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 385
 386 void FGAtmosphere::UseExternal(void) {
 387   temperature=&exTemperature;
 388   pressure=&exPressure;
 389   density=&exDensity;
 390   useExternal=true;
 391 }
 392
 393 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 394
 395 void FGAtmosphere::UseInternal(void) {
 396   temperature=&intTemperature;
 397   pressure=&intPressure;
 398   density=&intDensity;
 399   useExternal=false;
 400 }
 401
 402 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 403
 404 void FGAtmosphere::bind(void)
 405 {
 406   typedef double (FGAtmosphere::*PMF)(int) const;
 407   PropertyManager->Tie("atmosphere/T-R", this,
 408                        &FGAtmosphere::GetTemperature);
 409   PropertyManager->Tie("atmosphere/rho-slugs_ft3", this,
 410                        &FGAtmosphere::GetDensity);
 411 //  PropertyManager->Tie("atmosphere/P-psf", this,
 412 //                       &FGAtmosphere::GetPressure);
 413   PropertyManager->Tie("atmosphere/a-fps", this,
 414                        &FGAtmosphere::GetSoundSpeed);
 415   PropertyManager->Tie("atmosphere/T-sl-R", this,
 416                        &FGAtmosphere::GetTemperatureSL);
 417   PropertyManager->Tie("atmosphere/rho-sl-slugs_ft3", this,
 418                        &FGAtmosphere::GetDensitySL);
 419   PropertyManager->Tie("atmosphere/P-sl-psf", this,
 420                        &FGAtmosphere::GetPressureSL);
 421   PropertyManager->Tie("atmosphere/a-sl-fps", this,
 422                        &FGAtmosphere::GetSoundSpeedSL);
 423   PropertyManager->Tie("atmosphere/theta-norm", this,
 424                        &FGAtmosphere::GetTemperatureRatio);
 425   PropertyManager->Tie("atmosphere/sigma-norm", this,
 426                        &FGAtmosphere::GetDensityRatio);
 427   PropertyManager->Tie("atmosphere/delta-norm", this,
 428                        &FGAtmosphere::GetPressureRatio);
 429   PropertyManager->Tie("atmosphere/a-norm", this,
 430                        &FGAtmosphere::GetSoundSpeedRatio);
 431   PropertyManager->Tie("atmosphere/psiw-rad", this,
 432                        &FGAtmosphere::GetWindPsi);
 433   PropertyManager->Tie("atmosphere/p-turb-rad_sec", this,1,
 434                        (PMF)&FGAtmosphere::GetTurbPQR);
 435   PropertyManager->Tie("atmosphere/q-turb-rad_sec", this,2,
 436                        (PMF)&FGAtmosphere::GetTurbPQR);
 437   PropertyManager->Tie("atmosphere/r-turb-rad_sec", this,3,
 438                        (PMF)&FGAtmosphere::GetTurbPQR);
 439 }
 440
 441 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 442
 443 void FGAtmosphere::unbind(void)
 444 {
 445   PropertyManager->Untie("atmosphere/T-R");
 446   PropertyManager->Untie("atmosphere/rho-slugs_ft3");
 447 //  PropertyManager->Untie("atmosphere/P-psf");
 448   PropertyManager->Untie("atmosphere/a-fps");
 449   PropertyManager->Untie("atmosphere/T-sl-R");
 450   PropertyManager->Untie("atmosphere/rho-sl-slugs_ft3");
 451   PropertyManager->Untie("atmosphere/P-sl-psf");
 452   PropertyManager->Untie("atmosphere/a-sl-fps");
 453   PropertyManager->Untie("atmosphere/theta-norm");
 454   PropertyManager->Untie("atmosphere/sigma-norm");
 455   PropertyManager->Untie("atmosphere/delta-norm");
 456   PropertyManager->Untie("atmosphere/a-norm");
 457   PropertyManager->Untie("atmosphere/psiw-rad");
 458   PropertyManager->Untie("atmosphere/p-turb-rad_sec");
 459   PropertyManager->Untie("atmosphere/q-turb-rad_sec");
 460   PropertyManager->Untie("atmosphere/r-turb-rad_sec");
 461 }
 462
 463 //%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 464 //    The bitmasked value choices are as follows:
 465 //    unset: In this case (the default) JSBSim would only print
 466 //       out the normally expected messages, essentially echoing
 467 //       the config files as they are read. If the environment
 468 //       variable is not set, debug_lvl is set to 1 internally
 469 //    0: This requests JSBSim not to output any messages
 470 //       whatsoever.
 471 //    1: This value explicity requests the normal JSBSim
 472 //       startup messages
 473 //    2: This value asks for a message to be printed out when
 474 //       a class is instantiated
 475 //    4: When this value is set, a message is displayed when a
 476 //       FGModel object executes its Run() method
 477 //    8: When this value is set, various runtime state variables
 478 //       are printed out periodically
 479 //    16: When set various parameters are sanity checked and
 480 //       a message is printed out when they go out of bounds
 481
 482 void FGAtmosphere::Debug(int from)
 483 {
 484   if (debug_lvl <= 0) return;
 485
 486   if (debug_lvl & 1) { // Standard console startup message output
 487     if (from == 0) { // Constructor
 488     }
 489   }
 490   if (debug_lvl & 2 ) { // Instantiation/Destruction notification
 491     if (from == 0) cout << "Instantiated: FGAtmosphere" << endl;
 492     if (from == 1) cout << "Destroyed:    FGAtmosphere" << endl;
 493   }
 494   if (debug_lvl & 4 ) { // Run() method entry print for FGModel-derived objects
 495   }
 496   if (debug_lvl & 8 ) { // Runtime state variables
 497   }
 498   if (debug_lvl & 16) { // Sanity checking
 499   }
 500   if (debug_lvl & 32) { // Turbulence
 501     if (frame == 0 && from == 2) {
 502       cout << "vTurbulence(X), vTurbulence(Y), vTurbulence(Z), "
 503            << "vTurbulenceGrad(X), vTurbulenceGrad(Y), vTurbulenceGrad(Z), "
 504            << "vDirection(X), vDirection(Y), vDirection(Z), "
 505            << "Magnitude, "
 506            << "vTurbPQR(P), vTurbPQR(Q), vTurbPQR(R), " << endl;
 507     } else if (from == 2) {
 508       cout << vTurbulence << ", " << vTurbulenceGrad << ", " << vDirection << ", " << Magnitude << ", " << vTurbPQR << endl;
 509     }
 510   }
 511   if (debug_lvl & 64) {
 512     if (from == 0) { // Constructor
 513       cout << IdSrc << endl;
 514       cout << IdHdr << endl;
 515     }
 516   }
 517 }
 518
 519 } // namespace JSBSim