JSBSim.cxx

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/*
 * SPDX-FileName: JSBsim.cxx
 * SPDX-FileComment: interface to the JSBsim flight model
 * SPDX-FileCopyrightText: Copyright (C) 1999  Curtis L. Olson  - curt@flightgear.org
 * SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif
 
#include <simgear/compiler.h>
#include <simgear/sg_inlines.h>
 
#include <cstdlib>    //    size_t
#include <string>
 
#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
#include <simgear/math/sg_geodesy.hxx>
#include <simgear/misc/sg_path.hxx>
#include <simgear/structure/commands.hxx>
#include <simgear/bvh/BVHMaterial.hxx>
 
#include <FDM/flight.hxx>
#include <FDM/groundreactions.hxx>
 
#include <Aircraft/controls.hxx>
#include <Main/globals.hxx>
#include <Main/fg_props.hxx>
 
#include "JSBSim.hxx"
#include <FDM/JSBSim/FGFDMExec.h>
#include <FDM/JSBSim/FGJSBBase.h>
#include <FDM/JSBSim/initialization/FGInitialCondition.h>
#include <FDM/JSBSim/initialization/FGTrim.h>
#include <FDM/JSBSim/models/FGModel.h>
#include <FDM/JSBSim/models/FGAircraft.h>
#include <FDM/JSBSim/models/FGFCS.h>
#include <FDM/JSBSim/models/FGPropagate.h>
#include <FDM/JSBSim/models/FGAuxiliary.h>
#include <FDM/JSBSim/models/FGInertial.h>
#include <FDM/JSBSim/models/FGMassBalance.h>
#include <FDM/JSBSim/models/FGAerodynamics.h>
#include <FDM/JSBSim/models/FGLGear.h>
#include <FDM/JSBSim/models/FGGroundReactions.h>
#include <FDM/JSBSim/models/FGPropulsion.h>
#include <FDM/JSBSim/models/FGAccelerations.h>
#include <FDM/JSBSim/models/atmosphere/FGStandardAtmosphere.h>
#include <FDM/JSBSim/models/atmosphere/FGWinds.h>
#include <FDM/JSBSim/models/propulsion/FGEngine.h>
#include <FDM/JSBSim/models/propulsion/FGPiston.h>
#include <FDM/JSBSim/models/propulsion/FGTurbine.h>
#include <FDM/JSBSim/models/propulsion/FGTurboProp.h>
#include <FDM/JSBSim/models/propulsion/FGRocket.h>
#include <FDM/JSBSim/models/propulsion/FGElectric.h>
#include <FDM/JSBSim/models/propulsion/FGNozzle.h>
#include <FDM/JSBSim/models/propulsion/FGPropeller.h>
#include <FDM/JSBSim/models/propulsion/FGRotor.h>
#include <FDM/JSBSim/models/propulsion/FGTank.h>
#include <FDM/JSBSim/input_output/FGPropertyManager.h>
#include <FDM/JSBSim/input_output/FGGroundCallback.h>
 
using namespace JSBSim;
 
static inline double
FMAX (double a, double b)
{
  return a > b ? a : b;
}
 
class FGFSGroundCallback : public FGGroundCallback {
public:
  FGFSGroundCallback(FGJSBsim* ifc) : mInterface(ifc) {}
  virtual ~FGFSGroundCallback() {}

  virtual double GetAltitude(const FGLocation& l) const {
    double pt[3] = { SG_FEET_TO_METER*l(FGJSBBase::eX),
                     SG_FEET_TO_METER*l(FGJSBBase::eY),
                     SG_FEET_TO_METER*l(FGJSBBase::eZ) };
    double lat, lon, alt;
    sgCartToGeod( pt, &lat, &lon, &alt);
    return alt * SG_METER_TO_FEET;
  }

  double GetAGLevel(double t, const FGLocation& l, FGLocation& cont,
                    FGColumnVector3& n, FGColumnVector3& v, FGColumnVector3& w)
      const override {
    double contact[3], normal[3], vel[3], angularVel[3];
    double agl = mInterface->get_agl_ft(t, l, SG_METER_TO_FEET*2, contact,
                                        normal, vel, angularVel);
    n = FGColumnVector3( normal[0], normal[1], normal[2] );
    v = FGColumnVector3( vel[0], vel[1], vel[2] );
    w = FGColumnVector3( angularVel[0], angularVel[1], angularVel[2] );
    cont = FGColumnVector3( contact[0], contact[1], contact[2] );
    return agl;
  }
 
private:
  FGJSBsim* mInterface;
};
 
// FG uses a squared normalized magnitude for turbulence
// this lookup table maps fg's severity levels
// none(0), light(1/3), moderate(2/3) and severe(3/3)
// to the POE table indexes 0, 3, 4 and 7
class FGTurbulenceSeverityTable : public FGTable {
public:
  FGTurbulenceSeverityTable() : FGTable(4) {
    *this << (0.0/9.0) << 0.0;
    *this << (1.0/9.0) << 3.0;
    *this << (4.0/9.0) << 4.0;
    *this << (9.0/9.0) << 7.0;
  }
};
 
/******************************************************************************/
std::map<std::string,int> FGJSBsim::TURBULENCE_TYPE_NAMES;
 
static FGTurbulenceSeverityTable TurbulenceSeverityTable;
 
FGJSBsim::FGJSBsim( double dt )
  : FGInterface(dt)
{
    bool result;
    if( TURBULENCE_TYPE_NAMES.empty() ) {
        TURBULENCE_TYPE_NAMES["ttNone"]     = FGWinds::ttNone;
        TURBULENCE_TYPE_NAMES["ttStandard"] = FGWinds::ttStandard;
        TURBULENCE_TYPE_NAMES["ttCulp"]     = FGWinds::ttCulp;
        TURBULENCE_TYPE_NAMES["ttMilspec"]  = FGWinds::ttMilspec;
        TURBULENCE_TYPE_NAMES["ttTustin"]   = FGWinds::ttTustin;
    }
 
    // Set up the debugging level
    // FIXME: this will not respond to
    // runtime changes
 
    if ((sglog().get_log_classes() & SG_FLIGHT) != 0) {
 
                                // do a rough-and-ready mapping to
                                // the levels documented in FGFDMExec.h
        switch (sglog().get_log_priority()) {
        case SG_BULK:
            FGJSBBase::debug_lvl = 0x1f;
            break;
        case SG_DEBUG:
            FGJSBBase::debug_lvl = 0x1f;
        case SG_INFO:
        case SG_WARN:
        case SG_ALERT:
        case SG_POPUP:
            FGJSBBase::debug_lvl = 0x00;
            break;
 
        default:
            // silence warning about unhandled cases
            FGJSBBase::debug_lvl = 0x00;
            break;
        }
    } else {
                                // if flight is excluded, don't bother
            FGJSBBase::debug_lvl = 0x00;
    }
 
    PropertyManager = new FGPropertyManager( (FGPropertyNode*)globals->get_props() );
    fdmex = new FGFDMExec( PropertyManager );
    fdmex->Hold();
 
    Atmosphere      = fdmex->GetAtmosphere();
    Winds           = fdmex->GetWinds();
    FCS             = fdmex->GetFCS();
    MassBalance     = fdmex->GetMassBalance();
    Propulsion      = fdmex->GetPropulsion();
    Aircraft        = fdmex->GetAircraft();
    Propagate       = fdmex->GetPropagate();
    Auxiliary       = fdmex->GetAuxiliary();
    Inertial        = fdmex->GetInertial();
    Aerodynamics    = fdmex->GetAerodynamics();
    GroundReactions = fdmex->GetGroundReactions();
    Accelerations   = fdmex->GetAccelerations();
 
    // Register ground callback.
    Inertial->SetGroundCallback( new FGFSGroundCallback(this) );
 
    fgic=fdmex->GetIC();
    needTrim=true;
 
    SGPath aircraft_path( fgGetString("/sim/aircraft-dir") );
 
    SGPath engine_path( fgGetString("/sim/fg-root") );
    engine_path.append( "Aircraft/Generic/JSBSim/Engines" );
 
    SGPath systems_path( fgGetString("/sim/fg-root") );
    systems_path.append( "Aircraft/Generic/JSBSim/Systems" );
 
// deprecate sim-time-sec for simulation/sim-time-sec
// remove alias with increased configuration file version number (2.1 or later)
    SGPropertyNode * node = fgGetNode("/fdm/jsbsim/simulation/sim-time-sec");
    fgGetNode("/fdm/jsbsim/sim-time-sec", true)->alias(node, false);
    // end of sim-time-sec deprecation patch
 
    _ai_wake_enabled = fgGetNode("fdm/ai-wake/enabled", true);
 
    terrain = fgGetNode("/sim/fdm/surface", true);
 
    fdmex->Setdt( dt );
 
    result = fdmex->LoadModel( aircraft_path, engine_path, systems_path,
                               fgGetString("/sim/aero"), false );
 
    if (result) {
      SG_LOG( SG_FLIGHT, SG_INFO, "  loaded aero.");
    } else {
      SG_LOG( SG_FLIGHT, SG_INFO,
              "  aero does not exist (you may have mis-typed the name).");
      throw(-1);
    }
 
    SG_LOG( SG_FLIGHT, SG_INFO, "" );
    SG_LOG( SG_FLIGHT, SG_INFO, "" );
    SG_LOG( SG_FLIGHT, SG_INFO, "After loading aero definition file ..." );
 
    int Neng = Propulsion->GetNumEngines();
    SG_LOG( SG_FLIGHT, SG_INFO, "num engines = " << Neng );
 
    if ( GroundReactions->GetNumGearUnits() <= 0 ) {
        SG_LOG( SG_FLIGHT, SG_ALERT, "num gear units = "
                << GroundReactions->GetNumGearUnits() );
        SG_LOG( SG_FLIGHT, SG_ALERT, "This is a very bad thing because with 0 gear units, the ground trimming");
        SG_LOG( SG_FLIGHT, SG_ALERT, "routine (coming up later in the code) will core dump.");
        SG_LOG( SG_FLIGHT, SG_ALERT, "Halting the sim now, and hoping a solution will present itself soon!");
        exit(-1);
    }
 
    init_gear();
 
    // Set initial fuel levels if provided.
    for (unsigned int i = 0; i < Propulsion->GetNumTanks(); i++) {
      double d;
      SGPropertyNode * node = fgGetNode("/consumables/fuel/tank", i, true);
      FGTank* tank = Propulsion->GetTank(i);
      SGPropertyNode * prop = node->getNode( "density-ppg", true );
 
      d = prop->getDoubleValue();
      if( d > 0.0 ) {
        tank->SetDensity( d );
      } else {
        prop->setDoubleValue( SG_MAX2<double>(tank->GetDensity(), 0.1) );
      }
 
      prop = node->getNode( "level-lbs", true );
      d = prop->getDoubleValue();
      if( d > 0.0 ) {
        tank->SetContents( d );
      } else {
        prop->setDoubleValue( tank->GetContents() );
      }
 
      prop = node->getNode( "unusable-gal_us", true );
      d = prop->getDoubleValue();
      if ( d > 0.0 ) {
        tank->SetUnusableVolume( d );
      } else {
        prop->setDoubleValue(tank->GetUnusableVolume());
      }
      /* Capacity is read-only in FGTank and can't be overwritten from FlightGear */
      node->getNode("capacity-gal_us", true )->setDoubleValue( tank->GetCapacityGallons() );
    }
    Propulsion->SetFuelFreeze((fgGetNode("/sim/freeze/fuel",true))->getBoolValue());
 
    fgSetDouble("/fdm/trim/pitch-trim", FCS->GetPitchTrimCmd());
    fgSetDouble("/fdm/trim/throttle",   FCS->GetThrottleCmd(0));
    fgSetDouble("/fdm/trim/aileron",    FCS->GetDaCmd());
    fgSetDouble("/fdm/trim/rudder",     FCS->GetDrCmd());
 
    startup_trim = fgGetNode("/sim/presets/trim", true);
 
    trimmed = fgGetNode("/fdm/trim/trimmed", true);
    trimmed->setBoolValue(false);
 
    pitch_trim = fgGetNode("/fdm/trim/pitch-trim", true );
    throttle_trim = fgGetNode("/fdm/trim/throttle", true );
    aileron_trim = fgGetNode("/fdm/trim/aileron", true );
    rudder_trim = fgGetNode("/fdm/trim/rudder", true );
 
    stall_warning = fgGetNode("/sim/alarms/stall-warning",true);
    stall_warning->setDoubleValue(0);
 
 
    flap_pos_pct=fgGetNode("/surface-positions/flap-pos-norm",true);
    elevator_pos_pct=fgGetNode("/surface-positions/elevator-pos-norm",true);
    left_aileron_pos_pct
        =fgGetNode("/surface-positions/left-aileron-pos-norm",true);
    right_aileron_pos_pct
        =fgGetNode("/surface-positions/right-aileron-pos-norm",true);
    rudder_pos_pct=fgGetNode("/surface-positions/rudder-pos-norm",true);
    speedbrake_pos_pct
        =fgGetNode("/surface-positions/speedbrake-pos-norm",true);
    spoilers_pos_pct=fgGetNode("/surface-positions/spoilers-pos-norm",true);
    tailhook_pos_pct=fgGetNode("/gear/tailhook/position-norm",true);
    wing_fold_pos_pct=fgGetNode("surface-positions/wing-fold-pos-norm",true);
 
    elevator_pos_pct->setDoubleValue(0);
    left_aileron_pos_pct->setDoubleValue(0);
    right_aileron_pos_pct->setDoubleValue(0);
    rudder_pos_pct->setDoubleValue(0);
    flap_pos_pct->setDoubleValue(0);
    speedbrake_pos_pct->setDoubleValue(0);
    spoilers_pos_pct->setDoubleValue(0);
 
    override_fg_brake_prop = fgGetNode("/fdm/jsbsim/systems/override-fg-brake-properties", true);
    override_fg_brake_prop->setBoolValue(false);
    ab_brake_engaged = fgGetNode("/autopilot/autobrake/engaged", true);
    ab_brake_left_pct = fgGetNode("/autopilot/autobrake/brake-left-output", true);
    ab_brake_right_pct = fgGetNode("/autopilot/autobrake/brake-right-output", true);
 
    arrestor_wire_engaged_hook = fgGetNode("/fdm/jsbsim/systems/hook/arrestor-wire-engaged-hook", true);
    release_hook = fgGetNode("/fdm/jsbsim/systems/hook/tailhook-release-cmd", true);
 
    altitude = fgGetNode("/position/altitude-ft");
    precipitation = fgGetNode("/environment/rain-norm", true);
    temperature = fgGetNode("/environment/temperature-degc",true);
    pressure = fgGetNode("/environment/pressure-inhg",true);
    pressureSL = fgGetNode("/environment/pressure-sea-level-inhg",true);
    dew_point = fgGetNode("/environment/dewpoint-degc", true);
    ground_wind = fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt",true);
    turbulence_gain = fgGetNode("/environment/turbulence/magnitude-norm",true);
    turbulence_rate = fgGetNode("/environment/turbulence/rate-hz",true);
    turbulence_model = fgGetNode("/environment/params/jsbsim-turbulence-model",true);
 
    wind_from_north= fgGetNode("/environment/wind-from-north-fps",true);
    wind_from_east = fgGetNode("/environment/wind-from-east-fps" ,true);
    wind_from_down = fgGetNode("/environment/wind-from-down-fps" ,true);
 
    slaved = fgGetNode("/sim/slaved/enabled", true);
 
    for (unsigned int i = 0; i < Propulsion->GetNumEngines(); i++) {
      SGPropertyNode * node = fgGetNode("engines/engine", i, true);
      Propulsion->GetEngine(i)->GetThruster()->SetRPM(node->getDoubleValue("rpm") /
                     Propulsion->GetEngine(i)->GetThruster()->GetGearRatio());
    }
 
    hook_root_struct = FGColumnVector3(
        fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-offset-x-in", 196),
        fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-offset-y-in", 0),
        fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-offset-z-in", -16));
    last_hook_tip[0] = 0; last_hook_tip[1] = 0; last_hook_tip[2] = 0;
    last_hook_root[0] = 0; last_hook_root[1] = 0; last_hook_root[2] = 0;
 
    crashed = false;
 
    mesh = new AircraftMesh(fgGetDouble("/fdm/jsbsim/metrics/bw-ft"),
                            fgGetDouble("/fdm/jsbsim/metrics/cbarw-ft"),
                            fdmex->GetModelName());
 
    // Trim once to initialize all output parameters
    FGTrim *fgtrim = new FGTrim(fdmex,tFull);
    fgtrim->DoTrim();
    delete fgtrim;
 
    std::string directive_file = fgGetString("/sim/jsbsim/output-directive-file");
    if (!directive_file.empty())
      fdmex->SetOutputDirectives(directive_file);
}
 
/******************************************************************************/
FGJSBsim::~FGJSBsim(void)
{
  delete fdmex;
  delete PropertyManager;
}
 
/******************************************************************************/
 
// Initialize the JSBsim flight model, dt is the time increment for
// each subsequent iteration through the EOM
 
void FGJSBsim::init()
{
    SG_LOG( SG_FLIGHT, SG_INFO, "Starting and initializing JSBsim" );
 
    // Explicitly call the superclass's
    // init method first.
 
    if (fgGetBool("/environment/params/control-fdm-atmosphere")) {
      Atmosphere->SetTemperature(temperature->getDoubleValue(), get_Altitude(), FGAtmosphere::eCelsius);
      Atmosphere->SetPressureSL(FGAtmosphere::eInchesHg, pressureSL->getDoubleValue());
      // initialize to no turbulence, these values get set in the update loop
      Winds->SetTurbType(FGWinds::ttNone);
      Winds->SetTurbGain(0.0);
      Winds->SetTurbRate(0.0);
      Winds->SetWindspeed20ft(0.0);
      Winds->SetProbabilityOfExceedence(0.0);
    }
 
    fgic->SetWindNEDFpsIC(0.0, 0.0, 0.0);
 
    SG_LOG(SG_FLIGHT,SG_INFO,"T,p,rho: " << Atmosphere->GetTemperature()
     << ", " << Atmosphere->GetPressure()
     << ", " << Atmosphere->GetDensity() );
 
    FCS->SetDfPos( ofNorm, globals->get_controls()->get_flaps() );
 
    needTrim = startup_trim->getBoolValue();
    common_init();
 
    copy_to_JSBsim();
    fdmex->Resume();
    fdmex->RunIC();     //loop JSBSim once w/o integrating
    if (fgGetBool("/sim/presets/running")) {
      Propulsion->InitRunning(-1);
      for (unsigned int i = 0; i < Propulsion->GetNumEngines(); i++) {
        FGPiston* eng = (FGPiston*)Propulsion->GetEngine(i);
        globals->get_controls()->set_magnetos(i, eng->GetMagnetos());
        globals->get_controls()->set_mixture(i, FCS->GetMixtureCmd(i));
      }
    }
 
    if ( needTrim ) {
      const FGLocation& cart = fgic->GetPosition();
      double contact[3], d[3], vel[3];
      update_ground_cache(cart, 0.01);
 
      get_agl_ft(fdmex->GetSimTime(), cart, SG_METER_TO_FEET*2, contact, d, vel,
                 d);
      double terrain_alt = sqrt(contact[0]*contact[0] + contact[1]*contact[1]
                                + contact[2]*contact[2]) - cart.GetSeaLevelRadius();
 
      SG_LOG(SG_FLIGHT, SG_INFO, "Ready to trim, terrain elevation is: "
                                 << terrain_alt );
 
      if (fgGetBool("/sim/presets/onground")) {
        FGColumnVector3 gndVelNED = cart.GetTec2l()
                                  * FGColumnVector3(vel[0], vel[1], vel[2]);
        fgic->SetVNorthFpsIC(gndVelNED(1));
        fgic->SetVEastFpsIC(gndVelNED(2));
        fgic->SetVDownFpsIC(gndVelNED(3));
      }
      do_trim();
      needTrim = false;
    }
 
    copy_from_JSBsim(); //update the bus
 
    _fmag = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/magnitude", false);
    _fbx = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/x", false);
    _fby = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/y", false);
    _fbz = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/z", false);
    _mmag = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/magnitude-lbsft", false);
    _mbx = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/l", false);
    _mby = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/m", false);
    _mbz = fgGetNode("/fdm/jsbsim/external_reactions/ai-wake/n", false);
 
    SG_LOG( SG_FLIGHT, SG_INFO, "  Initialized JSBSim with:" );
 
    switch(fgic->GetSpeedSet()) {
    case setned:
        SG_LOG(SG_FLIGHT,SG_INFO, "  Vn,Ve,Vd= "
               << Propagate->GetVel(FGJSBBase::eNorth) << ", "
               << Propagate->GetVel(FGJSBBase::eEast) << ", "
               << Propagate->GetVel(FGJSBBase::eDown) << " ft/s");
    break;
    case setuvw:
        SG_LOG(SG_FLIGHT,SG_INFO, "  U,V,W= "
               << Propagate->GetUVW(1) << ", "
               << Propagate->GetUVW(2) << ", "
               << Propagate->GetUVW(3) << " ft/s");
    break;
    case setmach:
        SG_LOG(SG_FLIGHT,SG_INFO, "  Mach: "
               << Auxiliary->GetMach() );
    break;
    case setvc:
    default:
        SG_LOG(SG_FLIGHT,SG_INFO, "  Indicated Airspeed: "
               << Auxiliary->GetVcalibratedKTS() << " knots" );
    break;
    }
 
    stall_warning->setDoubleValue(0);
 
    SG_LOG( SG_FLIGHT, SG_INFO, "  Bank Angle: "
            << Propagate->GetEuler(FGJSBBase::ePhi)*RADTODEG << " deg" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  Pitch Angle: "
            << Propagate->GetEuler(FGJSBBase::eTht)*RADTODEG << " deg" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  True Heading: "
            << Propagate->GetEuler(FGJSBBase::ePsi)*RADTODEG << " deg" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  Latitude: "
            << Propagate->GetLocation().GetLatitudeDeg() << " deg" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  Longitude: "
            << Propagate->GetLocation().GetLongitudeDeg() << " deg" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  Altitude: "
            << Propagate->GetAltitudeASL() << " feet" );
    SG_LOG( SG_FLIGHT, SG_INFO, "  loaded initial conditions" );
 
    SG_LOG( SG_FLIGHT, SG_INFO, "  set dt" );
 
    SG_LOG( SG_FLIGHT, SG_INFO, "Finished initializing JSBSim" );
 
    SG_LOG( SG_FLIGHT, SG_INFO, "FGControls::get_gear_down()= " <<
                                  globals->get_controls()->get_gear_down() );
}
 
/******************************************************************************/
 
void FGJSBsim::unbind()
{
  fdmex->Unbind();
  FGInterface::unbind();
}
 
/******************************************************************************/
 
// Run an iteration of the EOM (equations of motion)
void FGJSBsim::update( double dt )
{
    if(crashed) {
      if(!fgGetBool("/sim/crashed"))
        fgSetBool("/sim/crashed", true);
      return;
    }
 
    if (is_suspended())
      return;
 
    int multiloop = _calc_multiloop(dt);
    FGLocation cart = Auxiliary->GetLocationVRP();
 
    update_ground_cache(cart, dt);
 
    copy_to_JSBsim();
 
    trimmed->setBoolValue(false);
 
    for ( int i=0; i < multiloop; i++ ) {
      if (!fdmex->Run()) {
        // The property fdm/jsbsim/simulation/terminate has been set to true
        // by the user. The sim is considered crashed.
        crashed = true;
        break;
      }
      update_external_forces(fdmex->GetSimTime() + i * fdmex->GetDeltaT());
    }
 
    FGJSBBase::Message* msg;
    while ((msg = fdmex->ProcessNextMessage()) != NULL) {
//      msg = fdmex->ProcessNextMessage();
      switch (msg->type) {
      case FGJSBBase::Message::eText:
        if (msg->text == "Crash Detected: Simulation FREEZE.")
          crashed = true;
        SG_LOG( SG_FLIGHT, SG_INFO, msg->messageId << ": " << msg->text );
        break;
      case FGJSBBase::Message::eBool:
        SG_LOG( SG_FLIGHT, SG_INFO, msg->messageId << ": " << msg->text << " " << msg->bVal );
        break;
      case FGJSBBase::Message::eInteger:
        SG_LOG( SG_FLIGHT, SG_INFO, msg->messageId << ": " << msg->text << " " << msg->iVal );
        break;
      case FGJSBBase::Message::eDouble:
        SG_LOG( SG_FLIGHT, SG_INFO, msg->messageId << ": " << msg->text << " " << msg->dVal );
        break;
      default:
        SG_LOG( SG_FLIGHT, SG_INFO, "Unrecognized message type." );
        break;
      }
    }
 
    reset_wake_group();
 
    // translate JSBsim back to FG structure so that the
    // autopilot (and the rest of the sim can use the updated values
    copy_from_JSBsim();
}
 
/******************************************************************************/
 
void FGJSBsim::suspend()
{
  fdmex->Hold();
  SGSubsystem::suspend();
}
 
/******************************************************************************/
 
void FGJSBsim::resume()
{
  fdmex->Resume();
  SGSubsystem::resume();
}
 
/******************************************************************************/
 
// Convert from the FGInterface struct to the JSBsim generic_ struct
 
bool FGJSBsim::copy_to_JSBsim()
{
    unsigned int i;
 
    // copy control positions into the JSBsim structure
 
    FCS->SetDaCmd( globals->get_controls()->get_aileron());
    FCS->SetRollTrimCmd( globals->get_controls()->get_aileron_trim() );
    FCS->SetDeCmd( globals->get_controls()->get_elevator());
    FCS->SetPitchTrimCmd( globals->get_controls()->get_elevator_trim() );
    FCS->SetDrCmd( -globals->get_controls()->get_rudder() );
    FCS->SetDsCmd( globals->get_controls()->get_rudder() );
    FCS->SetYawTrimCmd( -globals->get_controls()->get_rudder_trim() );
    FCS->SetDfCmd( globals->get_controls()->get_flaps() );
    FCS->SetDsbCmd( globals->get_controls()->get_speedbrake() );
    FCS->SetDspCmd( globals->get_controls()->get_spoilers() );
 
    if (!override_fg_brake_prop->getBoolValue()) {
        // Parking brake sets minimum braking
        // level for mains.
        double parking_brake = globals->get_controls()->get_brake_parking();
        double left_brake = globals->get_controls()->get_brake_left();
        double right_brake = globals->get_controls()->get_brake_right();
 
        if (ab_brake_engaged->getBoolValue()) {
            left_brake = ab_brake_left_pct->getDoubleValue();
            right_brake = ab_brake_right_pct->getDoubleValue();
        }
 
        FCS->SetLBrake(FMAX(left_brake, parking_brake));
        FCS->SetRBrake(FMAX(right_brake, parking_brake));
 
        FCS->SetCBrake( 0.0 );
        // FCS->SetCBrake( globals->get_controls()->get_brake(2) );
    }
 
    FCS->SetGearCmd( globals->get_controls()->get_gear_down());
    for (i = 0; i < Propulsion->GetNumEngines(); i++) {
      SGPropertyNode * node = fgGetNode("engines/engine", i, true);
 
      FCS->SetThrottleCmd(i, globals->get_controls()->get_throttle(i));
      FCS->SetMixtureCmd(i, globals->get_controls()->get_mixture(i));
      FCS->SetPropAdvanceCmd(i, globals->get_controls()->get_prop_advance(i));
      FCS->SetFeatherCmd(i, globals->get_controls()->get_feather(i));
 
      switch (Propulsion->GetEngine(i)->GetType()) {
      case FGEngine::etPiston:
        { // FGPiston code block
        FGPiston* eng = (FGPiston*)Propulsion->GetEngine(i);
        eng->SetMagnetos( globals->get_controls()->get_magnetos(i) );
        break;
        } // end FGPiston code block
      case FGEngine::etTurbine:
        { // FGTurbine code block
        FGTurbine* eng = (FGTurbine*)Propulsion->GetEngine(i);
        eng->SetAugmentation( globals->get_controls()->get_augmentation(i) );
        eng->SetReverse( globals->get_controls()->get_reverser(i) );
        //eng->SetInjection( globals->get_controls()->get_water_injection(i) );
        eng->SetCutoff( globals->get_controls()->get_cutoff(i) );
        eng->SetIgnition( globals->get_controls()->get_ignition(i) );
        break;
        } // end FGTurbine code block
      case FGEngine::etRocket:
        { // FGRocket code block
//        FGRocket* eng = (FGRocket*)Propulsion->GetEngine(i);
        break;
        } // end FGRocket code block
      case FGEngine::etTurboprop:
        { // FGTurboProp code block
        FGTurboProp* eng = (FGTurboProp*)Propulsion->GetEngine(i);
        eng->SetReverse( globals->get_controls()->get_reverser(i) );
        eng->SetCutoff( globals->get_controls()->get_cutoff(i) );
        // eng->SetIgnition( globals->get_controls()->get_ignition(i) );
 
        eng->SetGeneratorPower( globals->get_controls()->get_generator_breaker(i) );
        eng->SetCondition( globals->get_controls()->get_condition(i) );
        break;
        } // end FGTurboProp code block
      default:
        break;
      }
 
      { // FGEngine code block
      FGEngine* eng = Propulsion->GetEngine(i);
 
      eng->SetStarter( globals->get_controls()->get_starter(i) );
      eng->SetRunning( node->getBoolValue("running") );
      } // end FGEngine code block
    }
 
    Atmosphere->SetTemperature(temperature->getDoubleValue(), get_Altitude(), FGAtmosphere::eCelsius);
    Atmosphere->SetPressureSL(FGAtmosphere::eInchesHg, pressureSL->getDoubleValue());
    static_cast<FGStandardAtmosphere*>(Atmosphere)->SetDewPoint(FGAtmosphere::eCelsius,
                                                                dew_point->getDoubleValue());
 
    Winds->SetTurbType((FGWinds::tType)TURBULENCE_TYPE_NAMES[turbulence_model->getStringValue()]);
    switch( Winds->GetTurbType() ) {
        case FGWinds::ttStandard:
        case FGWinds::ttCulp: {
            double tmp = turbulence_gain->getDoubleValue();
            Winds->SetTurbGain(tmp * tmp * 100.0);
            Winds->SetTurbRate(turbulence_rate->getDoubleValue());
            break;
        }
        case FGWinds::ttMilspec:
        case FGWinds::ttTustin: {
            // milspec turbulence: 3=light, 4=moderate, 6=severe turbulence
            // turbulence_gain normalized: 0: none, 1/3: light, 2/3: moderate, 3/3: severe
            double tmp = turbulence_gain->getDoubleValue();
            Winds->SetProbabilityOfExceedence(
              SGMiscd::roundToInt(TurbulenceSeverityTable.GetValue( tmp ) )
            );
            Winds->SetWindspeed20ft(ground_wind->getDoubleValue());
            break;
        }
 
        default:
            break;
    }
 
    Winds->SetWindNED( -wind_from_north->getDoubleValue(),
                       -wind_from_east->getDoubleValue(),
                       -wind_from_down->getDoubleValue() );
//    SG_LOG(SG_FLIGHT,SG_INFO, "Wind NED: "
//                  << get_V_north_airmass() << ", "
//                  << get_V_east_airmass()  << ", "
//                  << get_V_down_airmass() );
 
    for (i = 0; i < Propulsion->GetNumTanks(); i++) {
      SGPropertyNode * node = fgGetNode("/consumables/fuel/tank", i, true);
      FGTank * tank = Propulsion->GetTank(i);
      double fuelDensity = node->getDoubleValue("density-ppg");
 
      if (fuelDensity < 0.1)
        fuelDensity = 6.0; // Use average fuel value
 
      tank->SetDensity(fuelDensity);
      tank->SetContents(node->getDoubleValue("level-lbs"));
    }
 
    Propulsion->SetFuelFreeze((fgGetNode("/sim/freeze/fuel",true))->getBoolValue());
    fdmex->SetChild(slaved->getBoolValue());
 
    return true;
}
 
/******************************************************************************/
 
// Convert from the JSBsim generic_ struct to the FGInterface struct
 
bool FGJSBsim::copy_from_JSBsim()
{
    unsigned int i, j;
/*
    _set_Inertias( MassBalance->GetMass(),
                   MassBalance->GetIxx(),
                   MassBalance->GetIyy(),
                   MassBalance->GetIzz(),
                   MassBalance->GetIxz() );
*/
    _set_CG_Position( MassBalance->GetXYZcg(1),
                      MassBalance->GetXYZcg(2),
                      MassBalance->GetXYZcg(3) );
 
    _set_Accels_Body( Accelerations->GetBodyAccel(1),
                      Accelerations->GetBodyAccel(2),
                      Accelerations->GetBodyAccel(3) );
 
    _set_Accels_CG_Body_N ( Auxiliary->GetNcg(1),
                            Auxiliary->GetNcg(2),
                            Auxiliary->GetNcg(3) );
 
    _set_Accels_Pilot_Body( Auxiliary->GetPilotAccel(1),
                            Auxiliary->GetPilotAccel(2),
                            Auxiliary->GetPilotAccel(3) );
 
    _set_Nlf( Auxiliary->GetNlf() );
 
    // Velocities
 
    _set_Velocities_Local( Propagate->GetVel(FGJSBBase::eNorth),
                           Propagate->GetVel(FGJSBBase::eEast),
                           Propagate->GetVel(FGJSBBase::eDown) );
 
    _set_Velocities_Body( Propagate->GetUVW(1),
                          Propagate->GetUVW(2),
                          Propagate->GetUVW(3) );
 
    // Make the HUD work ...
    _set_Velocities_Ground( Propagate->GetVel(FGJSBBase::eNorth),
                            Propagate->GetVel(FGJSBBase::eEast),
                            -Propagate->GetVel(FGJSBBase::eDown) );
 
    _set_V_rel_wind( Auxiliary->GetVt() );
 
    _set_V_equiv_kts( Auxiliary->GetVequivalentKTS() );
 
    _set_V_calibrated_kts( Auxiliary->GetVcalibratedKTS() );
 
    _set_V_ground_speed( Auxiliary->GetVground() );
 
    _set_Omega_Body( Propagate->GetPQR(FGJSBBase::eP),
                     Propagate->GetPQR(FGJSBBase::eQ),
                     Propagate->GetPQR(FGJSBBase::eR) );
 
    _set_Euler_Rates( Auxiliary->GetEulerRates(FGJSBBase::ePhi),
                      Auxiliary->GetEulerRates(FGJSBBase::eTht),
                      Auxiliary->GetEulerRates(FGJSBBase::ePsi) );
 
    _set_Mach_number( Auxiliary->GetMach() );
 
    // Positions of Visual Reference Point
    FGLocation l = Auxiliary->GetLocationVRP();
    _updatePosition(SGGeoc::fromRadFt( l.GetLongitude(), l.GetLatitude(),
                                       l.GetRadius() ));
 
    _set_Altitude_AGL( Propagate->GetDistanceAGL() );
    {
      double contact[3], d[3], sd, t;
      is_valid_m(&t, d, &sd);
      get_agl_ft(t, l, SG_METER_TO_FEET*2, contact, d, d, d);
      double rwrad
        = FGColumnVector3( contact[0], contact[1], contact[2] ).Magnitude();
      _set_Runway_altitude( rwrad - get_Sea_level_radius() );
    }
 
    _set_Euler_Angles( Propagate->GetEuler(FGJSBBase::ePhi),
                       Propagate->GetEuler(FGJSBBase::eTht),
                       Propagate->GetEuler(FGJSBBase::ePsi) );
 
    _set_Alpha( Auxiliary->Getalpha() );
    _set_Beta( Auxiliary->Getbeta() );
 
 
    _set_Gamma_vert_rad( Auxiliary->GetGamma() );
 
    _set_Earth_position_angle( Propagate->GetEarthPositionAngle() );
 
    _set_Climb_Rate( Propagate->Gethdot() );
 
    const FGMatrix33& Tl2b = Propagate->GetTl2b();
    for ( i = 1; i <= 3; i++ ) {
        for ( j = 1; j <= 3; j++ ) {
            _set_T_Local_to_Body( i, j, Tl2b(i,j) );
        }
    }
 
    // Copy the engine values from JSBSim.
    for ( i=0; i < Propulsion->GetNumEngines(); i++ ) {
      SGPropertyNode * node = fgGetNode("engines/engine", i, true);
      SGPropertyNode * tnode = node->getChild("thruster", 0, true);
      FGThruster * thruster = Propulsion->GetEngine(i)->GetThruster();
 
      switch (Propulsion->GetEngine(i)->GetType()) {
      case FGEngine::etPiston:
        { // FGPiston code block
        FGPiston* eng = (FGPiston*)Propulsion->GetEngine(i);
        node->setDoubleValue("egt-degf", eng->getExhaustGasTemp_degF());
        node->setDoubleValue("oil-temperature-degf", eng->getOilTemp_degF());
        node->setDoubleValue("oil-pressure-psi", eng->getOilPressure_psi());
        node->setDoubleValue("mp-osi", eng->getManifoldPressure_inHg());
        // NOTE: mp-osi is not in ounces per square inch.
        // This error is left for reasons of backwards compatibility with
        // existing FlightGear sound and instrument configurations.
        node->setDoubleValue("mp-inhg", eng->getManifoldPressure_inHg());
        node->setDoubleValue("cht-degf", eng->getCylinderHeadTemp_degF());
        node->setDoubleValue("rpm", eng->getRPM());
        } // end FGPiston code block
        break;
      case FGEngine::etRocket:
        { // FGRocket code block
//        FGRocket* eng = (FGRocket*)Propulsion->GetEngine(i);
        } // end FGRocket code block
        break;
      case FGEngine::etTurbine:
        { // FGTurbine code block
        FGTurbine* eng = (FGTurbine*)Propulsion->GetEngine(i);
        node->setDoubleValue("n1", eng->GetN1());
        node->setDoubleValue("n2", eng->GetN2());
        node->setDoubleValue("egt-degf", 32 + eng->GetEGT()*9/5);
        node->setBoolValue("augmentation", eng->GetAugmentation());
        node->setBoolValue("water-injection", eng->GetInjection());
        node->setBoolValue("ignition", eng->GetIgnition() != 0);
        node->setDoubleValue("nozzle-pos-norm", eng->GetNozzle());
        node->setDoubleValue("inlet-pos-norm", eng->GetInlet());
        node->setDoubleValue("oil-pressure-psi", eng->getOilPressure_psi());
        node->setBoolValue("reversed", eng->GetReversed());
        node->setBoolValue("cutoff", eng->GetCutoff());
        node->setDoubleValue("epr", eng->GetEPR());
        globals->get_controls()->set_reverser(i, eng->GetReversed() );
        globals->get_controls()->set_cutoff(i, eng->GetCutoff() );
        globals->get_controls()->set_water_injection(i, eng->GetInjection() );
        globals->get_controls()->set_augmentation(i, eng->GetAugmentation() );
        } // end FGTurbine code block
        break;
      case FGEngine::etTurboprop:
        { // FGTurboProp code block
        FGTurboProp* eng = (FGTurboProp*)Propulsion->GetEngine(i);
        node->setDoubleValue("n1", eng->GetN1());
        //node->setDoubleValue("n2", eng->GetN2());
        node->setDoubleValue("itt_degf", 32 + eng->GetITT()*9/5);
        // node->setBoolValue("ignition", eng->GetIgnition() != 0);
        // node->setDoubleValue("nozzle-pos-norm", eng->GetNozzle());
        // node->setDoubleValue("inlet-pos-norm", eng->GetInlet());
        node->setDoubleValue("oil-pressure-psi", eng->getOilPressure_psi());
        node->setBoolValue("reversed", eng->GetReversed());
        node->setBoolValue("cutoff", eng->GetCutoff());
        node->setBoolValue("starting", eng->GetEngStarting());
        node->setBoolValue("generator-power", eng->GetGeneratorPower());
        node->setBoolValue("damaged", eng->GetCondition() != 0);
        node->setBoolValue("ielu-intervent", eng->GetIeluIntervent());
        node->setDoubleValue("oil-temperature-degf", eng->getOilTemp_degF());
//        node->setBoolValue("onfire", eng->GetFire());
        globals->get_controls()->set_reverser(i, eng->GetReversed() );
        globals->get_controls()->set_cutoff(i, eng->GetCutoff() );
        } // end FGTurboProp code block
        break;
      case FGEngine::etElectric:
        { // FGElectric code block
        FGElectric* eng = (FGElectric*)Propulsion->GetEngine(i);
        node->setDoubleValue("rpm", eng->getRPM());
        } // end FGElectric code block
        break;
      case FGEngine::etUnknown:
        break;
      }
 
      { // FGEngine code block
      FGEngine* eng = Propulsion->GetEngine(i);
      node->setDoubleValue("fuel-flow-gph", eng->getFuelFlow_gph());
      node->setDoubleValue("thrust_lb", thruster->GetThrust());
      node->setDoubleValue("fuel-flow_pph", eng->getFuelFlow_pph());
      node->setBoolValue("running", eng->GetRunning());
      node->setBoolValue("starter", eng->GetStarter());
      node->setBoolValue("cranking", eng->GetCranking());
      globals->get_controls()->set_starter(i, eng->GetStarter() );
      } // end FGEngine code block
 
      switch (thruster->GetType()) {
      case FGThruster::ttNozzle:
        { // FGNozzle code block
//        FGNozzle* noz = (FGNozzle*)thruster;
        } // end FGNozzle code block
        break;
      case FGThruster::ttPropeller:
        { // FGPropeller code block
        FGPropeller* prop = (FGPropeller*)thruster;
        tnode->setDoubleValue("rpm", thruster->GetRPM());
        tnode->setDoubleValue("pitch", prop->GetPitch());
        tnode->setDoubleValue("torque", prop->GetTorque());
        tnode->setBoolValue("feathered", prop->GetFeather());
        } // end FGPropeller code block
        break;
      case FGThruster::ttRotor:
        { // FGRotor code block
//        FGRotor* rotor = (FGRotor*)thruster;
        } // end FGRotor code block
        break;
      case FGThruster::ttDirect:
        { // Direct code block
        } // end Direct code block
        break;
      }
 
    }
 
    // 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 ) );
      }
    }
 
    update_gear();
 
    stall_warning->setDoubleValue( Aerodynamics->GetStallWarn() );
 
    elevator_pos_pct->setDoubleValue( FCS->GetDePos(ofNorm) );
    left_aileron_pos_pct->setDoubleValue( FCS->GetDaLPos(ofNorm) );
    right_aileron_pos_pct->setDoubleValue( FCS->GetDaRPos(ofNorm) );
    rudder_pos_pct->setDoubleValue( -1*FCS->GetDrPos(ofNorm) );
    flap_pos_pct->setDoubleValue( FCS->GetDfPos(ofNorm) );
    speedbrake_pos_pct->setDoubleValue( FCS->GetDsbPos(ofNorm) );
    spoilers_pos_pct->setDoubleValue( FCS->GetDspPos(ofNorm) );
    tailhook_pos_pct->setDoubleValue( FCS->GetTailhookPos() );
    wing_fold_pos_pct->setDoubleValue( FCS->GetWingFoldPos() );
 
    // force a sim crashed if crashed (altitude AGL < 0)
    if (get_Altitude_AGL() < -100.0) {
         fdmex->SuspendIntegration();
         crashed = true;
    }
 
    return true;
}
 
 
bool FGJSBsim::ToggleDataLogging(void)
{
  // ToDo: handle this properly
  fdmex->DisableOutput();
  return false;
}
 
 
bool FGJSBsim::ToggleDataLogging(bool state)
{
    if (state) {
      fdmex->EnableOutput();
      return true;
    } else {
      fdmex->DisableOutput();
      return false;
    }
}
 
 
//Positions
void FGJSBsim::set_Latitude(double lat)
{
  double alt = altitude->getDoubleValue();
  double sea_level_radius_meters, lat_geoc;
 
  if ( alt < -9990 ) alt = 0.0;
 
  SG_LOG(SG_FLIGHT,SG_INFO,"FGJSBsim::set_Latitude: " << lat );
  SG_LOG(SG_FLIGHT,SG_INFO," cur alt (ft) =  " << alt );
 
  if (needTrim)
    fgic->SetGeodLatitudeRadIC( lat );
  else {
    sgGeodToGeoc( lat, alt * SG_FEET_TO_METER,
                  &sea_level_radius_meters, &lat_geoc );
 
    double sea_level_radius_ft = sea_level_radius_meters * SG_METER_TO_FEET;
    _set_Sea_level_radius( sea_level_radius_ft );
 
    Propagate->SetLatitude(lat_geoc);
  }
 
  FGInterface::set_Latitude(lat);
}
 
 
void FGJSBsim::set_Longitude(double lon)
{
  SG_LOG(SG_FLIGHT,SG_INFO,"FGJSBsim::set_Longitude: " << lon );
 
  if (needTrim)
    fgic->SetLongitudeRadIC(lon);
  else
    Propagate->SetLongitude(lon);
 
  FGInterface::set_Longitude(lon);
}
 
// Sets the altitude above sea level.
void FGJSBsim::set_Altitude(double alt)
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Altitude: " << alt );
 
  if (needTrim)
    fgic->SetAltitudeASLFtIC(alt);
  else
    Propagate->SetAltitudeASL(alt);
 
  FGInterface::set_Altitude(alt);
}
 
void FGJSBsim::set_V_calibrated_kts(double vc)
{
    SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_V_calibrated_kts: " <<  vc );
 
  if (needTrim)
    fgic->SetVcalibratedKtsIC(vc);
  else {
    double p=pressure->getDoubleValue();
    double mach = FGJSBBase::MachFromVcalibrated(vc, p);
    double temp = 1.8*(temperature->getDoubleValue()+273.15);
    double soundSpeed = sqrt(1.4*1716.0*temp);
    FGColumnVector3 vUVW = Propagate->GetUVW();
    vUVW.Normalize();
    vUVW *= mach * soundSpeed;
    Propagate->SetUVW(1, vUVW(1));
    Propagate->SetUVW(2, vUVW(2));
    Propagate->SetUVW(3, vUVW(3));
  }
 
  FGInterface::set_V_calibrated_kts(vc);
}
 
void FGJSBsim::set_Mach_number(double mach)
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Mach_number: " <<  mach );
 
  if (needTrim)
    fgic->SetMachIC(mach);
  else {
    double temp = 1.8*(temperature->getDoubleValue()+273.15);
    double soundSpeed = sqrt(1.4*1716.0*temp);
    FGColumnVector3 vUVW = Propagate->GetUVW();
    vUVW.Normalize();
    vUVW *= mach * soundSpeed;
    Propagate->SetUVW(1, vUVW(1));
    Propagate->SetUVW(2, vUVW(2));
    Propagate->SetUVW(3, vUVW(3));
  }
 
  FGInterface::set_Mach_number(mach);
}
 
void FGJSBsim::set_Velocities_Local( double north, double east, double down )
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Velocities_Local: "
     << north << ", " <<  east << ", " << down );
 
  if (needTrim) {
    fgic->SetVNorthFpsIC(north);
    fgic->SetVEastFpsIC(east);
    fgic->SetVDownFpsIC(down);
  }
  else {
    FGColumnVector3 vNED(north, east, down);
    FGColumnVector3 vUVW = Propagate->GetTl2b() * vNED;
    Propagate->SetUVW(1, vUVW(1));
    Propagate->SetUVW(2, vUVW(2));
    Propagate->SetUVW(3, vUVW(3));
  }
 
  FGInterface::set_Velocities_Local(north, east, down);
}
 
void FGJSBsim::set_Velocities_Body( double u, double v, double w)
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Velocities_Body: "
     << u << ", " <<  v << ", " <<  w );
 
  if (needTrim) {
    fgic->SetUBodyFpsIC(u);
    fgic->SetVBodyFpsIC(v);
    fgic->SetWBodyFpsIC(w);
  }
  else {
    Propagate->SetUVW(1, u);
    Propagate->SetUVW(2, v);
    Propagate->SetUVW(3, w);
  }
 
  FGInterface::set_Velocities_Body(u, v, w);
}
 
//Euler angles
void FGJSBsim::set_Euler_Angles( double phi, double theta, double psi )
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Euler_Angles: "
     << phi << ", " << theta << ", " << psi );
 
  if (needTrim) {
    fgic->SetThetaRadIC(theta);
    fgic->SetPhiRadIC(phi);
    fgic->SetPsiRadIC(psi);
  }
  else {
    FGQuaternion quat(phi, theta, psi);
    FGMatrix33 Tl2b = quat.GetT();
    FGMatrix33 Ti2b = Tl2b*Propagate->GetTi2l();
    FGQuaternion Qi = Ti2b.GetQuaternion();
    Propagate->SetInertialOrientation(Qi);
  }
 
  FGInterface::set_Euler_Angles(phi, theta, psi);
}
 
//Flight Path
void FGJSBsim::set_Climb_Rate( double roc)
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Climb_Rate: " << roc );
 
  //since both climb rate and flight path angle are set in the FG
  //startup sequence, something is needed to keep one from cancelling
  //out the other.
  if( fabs(roc) > 1 && fabs(fgic->GetFlightPathAngleRadIC()) < 0.01 ) {
    if (needTrim)
      fgic->SetClimbRateFpsIC(roc);
    else {
      FGColumnVector3 vNED = Propagate->GetVel();
      vNED(FGJSBBase::eDown) = -roc;
      FGColumnVector3 vUVW = Propagate->GetTl2b() * vNED;
      Propagate->SetUVW(1, vUVW(1));
      Propagate->SetUVW(2, vUVW(2));
      Propagate->SetUVW(3, vUVW(3));
    }
 
    FGInterface::set_Climb_Rate(roc);
  }
}
 
void FGJSBsim::set_Gamma_vert_rad( double gamma)
{
  SG_LOG(SG_FLIGHT,SG_INFO, "FGJSBsim::set_Gamma_vert_rad: " << gamma );
 
  if( !(fabs(gamma) < 0.01 && fabs(fgic->GetClimbRateFpsIC()) > 1) ) {
    if (needTrim)
      fgic->SetFlightPathAngleRadIC(gamma);
    else {
      FGColumnVector3 vNED = Propagate->GetVel();
      double vt = vNED.Magnitude();
      vNED(FGJSBBase::eDown) = -vt * sin(gamma);
      FGColumnVector3 vUVW = Propagate->GetTl2b() * vNED;
      Propagate->SetUVW(1, vUVW(1));
      Propagate->SetUVW(2, vUVW(2));
      Propagate->SetUVW(3, vUVW(3));
    }
 
    FGInterface::set_Gamma_vert_rad(gamma);
  }
}
 
void FGJSBsim::init_gear(void )
{
    FGGroundReactions* gr=fdmex->GetGroundReactions();
    int Ngear=GroundReactions->GetNumGearUnits();
    double max = 1.0;
    for (int i=0;i<Ngear;i++) {
      FGLGear *gear = gr->GetGearUnit(i);
      SGPropertyNode * node = fgGetNode("gear/gear", i, true);
      // coordinates are in feet so convert
      node->setDoubleValue("xoffset-in", gear->GetBodyLocation()(1) * 12);
      node->setDoubleValue("yoffset-in", gear->GetBodyLocation()(2) * 12);
      node->setDoubleValue("zoffset-in", gear->GetBodyLocation()(3) * 12);
 
      node->setDoubleValue("xoffset-m", gear->GetBodyLocation()(1) * SG_FEET_TO_METER);
      node->setDoubleValue("yoffset-m", gear->GetBodyLocation()(2) * SG_FEET_TO_METER);
      node->setDoubleValue("zoffset-m", gear->GetBodyLocation()(3) * SG_FEET_TO_METER);
 
      node->setBoolValue("wow", gear->GetWOW());
      node->setDoubleValue("rollspeed-ms", gear->GetWheelRollVel() * SG_FEET_TO_METER);
      node->setBoolValue("has-brake", gear->GetBrakeGroup() > 0);
      node->setDoubleValue("position-norm", gear->GetGearUnitPos());
//    node->setDoubleValue("tire-pressure-norm", gear->GetTirePressure());
      max = node->getDoubleValue("max-compression-ft");
      if (max < 0.00001) {
        max = node->getDoubleValue("max-compression-m");
        if (max < 0.00001) max = 1.0;
        else max /= SG_FEET_TO_METER;
      }
      node->setDoubleValue("compression-norm", gear->GetCompLen() / max);
      node->setDoubleValue("compression-m", gear->GetCompLen() * SG_FEET_TO_METER);
      node->setDoubleValue("compression-ft", gear->GetCompLen());
      if ( gear->GetSteerable() )
        node->setDoubleValue("steering-norm", gear->GetSteerNorm());
    }
}
 
void FGJSBsim::update_gear(void)
{
    FGGroundReactions* gr=fdmex->GetGroundReactions();
    int Ngear=GroundReactions->GetNumGearUnits();
    double max = 1.0;
    for (int i=0;i<Ngear;i++) {
      FGLGear *gear = gr->GetGearUnit(i);
      SGPropertyNode * node = fgGetNode("gear/gear", i, true);
      node->getChild("wow", 0, true)->setBoolValue( gear->GetWOW());
      node->getChild("rollspeed-ms", 0, true)->setDoubleValue(gear->GetWheelRollVel() * SG_FEET_TO_METER);
      node->getChild("position-norm", 0, true)->setDoubleValue(gear->GetGearUnitPos());
//    gear->SetTirePressure(node->getDoubleValue("tire-pressure-norm"));
      max = node->getDoubleValue("max-compression-ft");
      if (max < 0.00001) {
        max = node->getDoubleValue("max-compression-m");
        if (max < 0.00001) max = 1.0;
        else max /= SG_FEET_TO_METER;
      }
      node->setDoubleValue("compression-norm", gear->GetCompLen() / max);
      node->setDoubleValue("compression-m", gear->GetCompLen() * SG_FEET_TO_METER);
      node->setDoubleValue("compression-ft", gear->GetCompLen());
      if ( gear->GetSteerable() )
        node->setDoubleValue("steering-norm", gear->GetSteerNorm());
    }
}
 
void FGJSBsim::do_trim(void)
{
  FGTrim *fgtrim;
 
  if ( fgGetBool("/sim/presets/onground") )
  {
    fgtrim = new FGTrim(fdmex,tGround);
  } else {
    fgtrim = new FGTrim(fdmex,tFull);
  }
 
  if ( !fgtrim->DoTrim() ) {
    fgtrim->Report();
    fgtrim->TrimStats();
  } else {
    trimmed->setBoolValue(true);
  }
  delete fgtrim;
 
  pitch_trim->setDoubleValue( FCS->GetPitchTrimCmd() );
  throttle_trim->setDoubleValue( FCS->GetThrottleCmd(0) );
  aileron_trim->setDoubleValue( FCS->GetDaCmd() );
  rudder_trim->setDoubleValue( -FCS->GetDrCmd() );
 
  globals->get_controls()->set_elevator_trim(FCS->GetPitchTrimCmd());
  globals->get_controls()->set_elevator(FCS->GetDeCmd());
  for( unsigned i = 0; i < Propulsion->GetNumEngines(); i++ )
    globals->get_controls()->set_throttle(i, FCS->GetThrottleCmd(i));
 
  globals->get_controls()->set_aileron(FCS->GetDaCmd());
  globals->get_controls()->set_rudder( -FCS->GetDrCmd());
 
  SG_LOG( SG_FLIGHT, SG_INFO, "  Trim complete" );
}
 
bool FGJSBsim::update_ground_cache(const FGLocation& cart, double dt)
{
  // Compute the radius of the aircraft. That is the radius of a ball
  // where all gear units are in. At the moment it is at least 10ft ...
  double acrad = 10.0;
  int n_gears = GroundReactions->GetNumGearUnits();
  for (int i=0; i<n_gears; ++i) {
    FGColumnVector3 bl = GroundReactions->GetGearUnit(i)->GetBodyLocation();
    double r = bl.Magnitude();
    if (acrad < r)
      acrad = r;
  }
 
  // Compute the potential movement of this aircraft and query for the
  // ground in this area.
  double groundCacheRadius = acrad + 2*dt*Propagate->GetUVW().Magnitude();
 
  double cart_pos[3] {cart(1), cart(2), cart(3)};
  double t0 = fdmex->GetSimTime();
  bool cache_ok = prepare_ground_cache_ft( t0, t0 + dt, cart_pos,
                                           groundCacheRadius );
  if (!cache_ok) {
    //SG_LOG(SG_FLIGHT, SG_WARN,
    //       "FGInterface is being called without scenery below the aircraft!");
 
    //SG_LOG(SG_FLIGHT, SG_WARN, "altitude         = "
    //                  << fgic->GetAltitudeASLFtIC());
 
    //SG_LOG(SG_FLIGHT, SG_WARN, "sea level radius = "
    //                  << get_Sea_level_radius());
 
    //SG_LOG(SG_FLIGHT, SG_WARN, "latitude         = "
    //                  << fgic->GetLatitudeRadIC());
 
    //SG_LOG(SG_FLIGHT, SG_WARN, "longitude        = "
    //                  << fgic->GetLongitudeRadIC());
  }
 
  return cache_ok;
}
 
double
FGJSBsim::get_agl_ft(double t, const FGColumnVector3& loc, double alt_off,
                     double contact[3], double normal[3], double vel[3],
                     double angularVel[3])
{
  const simgear::BVHMaterial* material = nullptr;
  simgear::BVHNode::Id id;
  double pt[3] {loc(1), loc(2), loc(3)};
 
  if (!FGInterface::get_agl_ft(t, pt, alt_off, contact, normal, vel,
                          angularVel, material, id))
    material = nullptr; // Discard the material data when FGInterface reports an problem.
 
  SGGeod geodPt = SGGeod::fromCart(SG_FEET_TO_METER*SGVec3d(pt));
  SGQuatd hlToEc = SGQuatd::fromLonLat(geodPt);
 
#ifdef JSBSIM_USE_GROUNDREACTIONS
  bool terrain_active = (terrain->getIntValue("override-level", -1) > 0) ? false : true;
  terrain->setBoolValue("active", terrain_active);
  terrain->setBoolValue("valid", (material && terrain_active) ? true : false);
  if (terrain_active)
  {
    static bool material_valid = false;
 
    if (updateGroundReactions(material)) {
      setPosition(pt);
      setHeading(Propagate->GetEuler(FGJSBBase::ePsi));
      GroundReactions->SetRollingFFactor(getRolingFrictionFactor());
      GroundReactions->SetStaticFFactor(getStaticFrictionFactor());
      GroundReactions->SetMaximumForce(getPressure()*0.00014503773800721815);
      GroundReactions->SetBumpiness(getBumpiness());
      GroundReactions->SetSolid(getSolid());
      GroundReactions->SetPosition(pt);
      material_valid = true;
    } else {
       if (material_valid) {
         GroundReactions->resetValues();
         material_valid = false;
      }
    }
  }
#else
  terrain->setBoolValue("valid", false);
#endif
  return dot(hlToEc.rotate(SGVec3d(0, 0, 1)), SGVec3d(contact) - SGVec3d(pt)) +
         getGroundDisplacement();
}
 
inline static double sqr(double x)
{
    return x * x;
}
 
static double angle_diff(double a, double b)
{
    double diff = fabs(a - b);
    if (diff > 180) diff = 360 - diff;
 
    return diff;
}
 
static void check_hook_solution(const FGColumnVector3& ground_normal_body, double E, double hook_length, double sin_fi_guess, double cos_fi_guess, double* sin_fis, double* cos_fis, double* fis, int* points)
{
    FGColumnVector3 tip(-hook_length * cos_fi_guess, 0, hook_length * sin_fi_guess);
    double dist = DotProduct(tip, ground_normal_body);
    if (fabs(dist + E) < 0.0001) {
        sin_fis[*points] = sin_fi_guess;
        cos_fis[*points] = cos_fi_guess;
        fis[*points] = atan2(sin_fi_guess, cos_fi_guess) * SG_RADIANS_TO_DEGREES;
        (*points)++;
    }
}
 
 
static void check_hook_solution(const FGColumnVector3& ground_normal_body, double E, double hook_length, double sin_fi_guess, double* sin_fis, double* cos_fis, double* fis, int* points)
{
    if (sin_fi_guess >= -1 && sin_fi_guess <= 1) {
        double cos_fi_guess = sqrt(1 - sqr(sin_fi_guess));
        check_hook_solution(ground_normal_body, E, hook_length, sin_fi_guess, cos_fi_guess, sin_fis, cos_fis, fis, points);
        if (fabs(cos_fi_guess) > SG_EPSILON) {
            check_hook_solution(ground_normal_body, E, hook_length, sin_fi_guess, -cos_fi_guess, sin_fis, cos_fis, fis, points);
        }
    }
}
 
void FGJSBsim::update_external_forces(double t_off)
{
    const FGMatrix33& Tb2l = Propagate->GetTb2l();
    const FGMatrix33& Tl2b = Propagate->GetTl2b();
    const FGLocation& Location = Propagate->GetLocation();
    const FGMatrix33& Tec2l = Location.GetTec2l();
 
    double hook_area[4][3];
 
    FGColumnVector3 hook_root_body = MassBalance->StructuralToBody(hook_root_struct);
    FGColumnVector3 hook_root = Location.LocalToLocation(Tb2l *   hook_root_body);
    hook_area[1][0] = hook_root(1);
    hook_area[1][1] = hook_root(2);
    hook_area[1][2] = hook_root(3);
 
    hook_length = fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-length-ft", 6.75);
    double fi_min = fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-pos-min-deg", -18);
    double fi_max = fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-pos-max-deg", 30);
    double fi = fgGetDouble("/fdm/jsbsim/systems/hook/tailhook-pos-norm") * (fi_max - fi_min) + fi_min;
    double cos_fi = cos(fi * SG_DEGREES_TO_RADIANS);
    double sin_fi = sin(fi * SG_DEGREES_TO_RADIANS);
 
    FGColumnVector3 hook_tip_body = hook_root_body;
    hook_tip_body(1) -= hook_length * cos_fi;
    hook_tip_body(3) += hook_length * sin_fi;
    if (!arrestor_wire_engaged_hook->getBoolValue()) {
      double contact[3];
      double ground_normal[3];
      double ground_vel[3];
      double ground_angular_vel[3];
      double root_agl_ft = get_agl_ft(t_off, hook_root, 0, contact,
                                      ground_normal, ground_vel,
                                      ground_angular_vel);
        if (root_agl_ft > 0 && root_agl_ft < hook_length) {
            FGColumnVector3 ground_normal_body = Tl2b * (Tec2l * FGColumnVector3(ground_normal[0], ground_normal[1], ground_normal[2]));
            FGColumnVector3 contact_body = Tl2b * Location.LocationToLocal(FGColumnVector3(contact[0], contact[1], contact[2]));
            double D = -DotProduct(contact_body, ground_normal_body);
 
            // check hook tip agl against same ground plane
            double hook_tip_agl_ft = DotProduct(hook_tip_body, ground_normal_body) + D;
            if (hook_tip_agl_ft < 0) {
 
                // hook tip: hx - l cos, hy, hz + l sin
                // on ground:  - n0 l cos + n2 l sin + E = 0
 
                double E = D + DotProduct(hook_root_body, ground_normal_body);
 
                // substitue x = sin fi, cos fi = sqrt(1 - x * x)
                // and rearrange to get a quadratic with coeffs:
                double a = sqr(hook_length) * (sqr(ground_normal_body(1)) + sqr(ground_normal_body(3)));
                double b = 2 * E * ground_normal_body(3) * hook_length;
                double c = sqr(E) - sqr(ground_normal_body(1) * hook_length);     
 
                double disc = sqr(b) - 4 * a * c;
                if (disc >= 0) {
                    double delta = sqrt(disc) / (2 * a);
                
                    // allow 4 solutions for safety, should never happen
                    double sin_fis[4];
                    double cos_fis[4];
                    double fis[4];
                    int points = 0;
                
                    double sin_fi_guess = -b / (2 * a) - delta;
                    check_hook_solution(ground_normal_body, E, hook_length, sin_fi_guess, sin_fis, cos_fis, fis, &points);
                    check_hook_solution(ground_normal_body, E, hook_length, sin_fi_guess + 2 * delta, sin_fis, cos_fis, fis, &points);
                
                    if (points == 2) {
                        double diff1 = angle_diff(fi, fis[0]);
                        double diff2 = angle_diff(fi, fis[1]);
                        int point = diff1 < diff2 ? 0 : 1;
                        fi = fis[point];
                        sin_fi = sin_fis[point];
                        cos_fi = cos_fis[point];
                        hook_tip_body(1) = hook_root_body(1) - hook_length * cos_fi;
                        hook_tip_body(3) = hook_root_body(3) + hook_length * sin_fi;
                    }
                }
            }
        }
    } else {
        if (release_hook->getBoolValue()) {
            release_wire();
            fgSetDouble("/fdm/jsbsim/external_reactions/hook/magnitude", 0.0);
            arrestor_wire_engaged_hook->setBoolValue(false);
            release_hook->setBoolValue(false);
        } else {
            FGColumnVector3 hook_root_vel = Propagate->GetVel() + (Tb2l * (Propagate->GetPQR() *  hook_root_body));
            double wire_ends_ec[2][3];
            double wire_vel_ec[2][3];
            get_wire_ends_ft(t_off, wire_ends_ec, wire_vel_ec);
            FGColumnVector3 wire_vel_1 = Tec2l * FGColumnVector3(wire_vel_ec[0][0], wire_vel_ec[0][1], wire_vel_ec[0][2]);
            FGColumnVector3 wire_vel_2 = Tec2l * FGColumnVector3(wire_vel_ec[1][0], wire_vel_ec[1][1], wire_vel_ec[1][2]);
            FGColumnVector3 rel_vel = hook_root_vel - (wire_vel_1 + wire_vel_2) / 2;
            if (rel_vel.Magnitude() < 3) {
                release_wire();
                fgSetDouble("/fdm/jsbsim/external_reactions/hook/magnitude", 0.0);
                arrestor_wire_engaged_hook->setBoolValue(false);
                release_hook->setBoolValue(false);
            }
            else {
                FGColumnVector3 wire_end1_body = Tl2b * Location.LocationToLocal(FGColumnVector3(wire_ends_ec[0][0], wire_ends_ec[0][1], wire_ends_ec[0][2])) - hook_root_body;
                FGColumnVector3 wire_end2_body = Tl2b * Location.LocationToLocal(FGColumnVector3(wire_ends_ec[1][0], wire_ends_ec[1][1], wire_ends_ec[1][2])) - hook_root_body;
                FGColumnVector3 force_plane_normal = wire_end1_body * wire_end2_body;
                force_plane_normal.Normalize();
                cos_fi = DotProduct(force_plane_normal, FGColumnVector3(0, 0, 1));
                if (cos_fi < 0) cos_fi = -cos_fi;
                sin_fi = sqrt(1 - sqr(cos_fi));
                fi = atan2(sin_fi, cos_fi) * SG_RADIANS_TO_DEGREES;
 
                fgSetDouble("/fdm/jsbsim/external_reactions/hook/x", -cos_fi);
                fgSetDouble("/fdm/jsbsim/external_reactions/hook/y", 0);
                fgSetDouble("/fdm/jsbsim/external_reactions/hook/z", sin_fi);
                fgSetDouble("/fdm/jsbsim/external_reactions/hook/magnitude", fgGetDouble("/fdm/jsbsim/systems/hook/force"));
            }
        }
    }
 
    FGColumnVector3 hook_tip = Location.LocalToLocation(Tb2l * hook_tip_body);
 
    hook_area[0][0] = hook_tip(1);
    hook_area[0][1] = hook_tip(2);
    hook_area[0][2] = hook_tip(3);
 
    if (!arrestor_wire_engaged_hook->getBoolValue()) {
        // The previous positions.
        hook_area[2][0] = last_hook_root[0];
        hook_area[2][1] = last_hook_root[1];
        hook_area[2][2] = last_hook_root[2];
        hook_area[3][0] = last_hook_tip[0];
        hook_area[3][1] = last_hook_tip[1];
        hook_area[3][2] = last_hook_tip[2];
 
        // Check if we caught a wire.
        // Returns true if we caught one.
        if (caught_wire_ft(t_off, hook_area)) {
                arrestor_wire_engaged_hook->setBoolValue(true);
        }
    }
 
    // save actual position as old position ...
    last_hook_tip[0] = hook_area[0][0];
    last_hook_tip[1] = hook_area[0][1];
    last_hook_tip[2] = hook_area[0][2];
    last_hook_root[0] = hook_area[1][0];
    last_hook_root[1] = hook_area[1][1];
    last_hook_root[2] = hook_area[1][2];
 
    fgSetDouble("/fdm/jsbsim/systems/hook/tailhook-pos-deg", fi);
 
    if (_ai_wake_enabled->getBoolValue()) {
      FGColumnVector3 uvw = Propagate->GetUVW();
      FGQuaternion ql2b = Propagate->GetQuaternion();
      FGLocation l = Auxiliary->GetLocationVRP();
      SGVec3d cartPos(l(1), l(2), l(3));
      // The scalar component is the first component in FGQuaternion but
      // the last component in SGQuat.
      SGQuatd orient(ql2b(2), ql2b(3), ql2b(4), ql2b(1));
 
      mesh->setPosition(cartPos * SG_FEET_TO_METER, orient);
 
      SGVec3d f = mesh->GetForce(get_wake_group(),
                                 SGVec3d(uvw(1), uvw(2), uvw(3)),
                                 Atmosphere->GetDensity());
      const SGVec3d& m = mesh->GetMoment();
 
      if (_fmag) _fmag->setDoubleValue(1.0);
      if (_fbx) _fbx->setDoubleValue(f[0]);
      if (_fby) _fby->setDoubleValue(f[1]);
      if (_fbz) _fbz->setDoubleValue(f[2]);
 
      if (_mmag) _mmag->setDoubleValue(1.0);
      if (_mbx) _mbx->setDoubleValue(m[0]);
      if (_mby) _mby->setDoubleValue(m[1]);
      if (_mbz) _mbz->setDoubleValue(m[2]);
    }
    else {
      if (_fmag) _fmag->setDoubleValue(0.0);
      if (_mmag) _mmag->setDoubleValue(0.0);
    }
}
 
 
// Register the subsystem.
#if 0
SGSubsystemMgr::Registrant<FGJSBsim> registrantFGJSBsim;
#endif