JSBSim Flight Dynamics Model  1.2.0 (05 Nov 2023)
An Open Source Flight Dynamics and Control Software Library in C++
FGAuxiliary Class Reference

Detailed Description

Encapsulates various uncategorized scheduled functions.

Pilot sensed accelerations are calculated here. This is used for the coordinated turn ball instrument. Motion base platforms sometimes use the derivative of pilot sensed accelerations as the driving parameter, rather than straight accelerations.

The theory behind pilot-sensed calculations is presented:

For purposes of discussion and calculation, assume for a minute that the pilot is in space and motionless in inertial space. She will feel no accelerations. If the aircraft begins to accelerate along any axis or axes (without rotating), the pilot will sense those accelerations. If any rotational moment is applied, the pilot will sense an acceleration due to that motion in the amount:

[wdot X R] + [w X (w X R)] Term I Term II

where:

wdot = omegadot, the rotational acceleration rate vector w = omega, the rotational rate vector R = the vector from the aircraft CG to the pilot eyepoint

The sum total of these two terms plus the acceleration of the aircraft body axis gives the acceleration the pilot senses in inertial space. In the presence of a large body such as a planet, a gravity field also provides an accelerating attraction. This acceleration can be transformed from the reference frame of the planet so as to be expressed in the frame of reference of the aircraft. This gravity field accelerating attraction is felt by the pilot as a force on her tushie as she sits in her aircraft on the runway awaiting takeoff clearance.

In JSBSim the acceleration of the body frame in inertial space is given by the F = ma relation. If the vForces vector is divided by the aircraft mass, the acceleration vector is calculated. The term wdot is equivalent to the JSBSim vPQRdot vector, and the w parameter is equivalent to vPQR.

Author
Tony Peden, Jon Berndt

Definition at line 100 of file FGAuxiliary.h.

#include <FGAuxiliary.h>

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+ Collaboration diagram for FGAuxiliary:

Classes

struct  Inputs
 

Public Member Functions

 FGAuxiliary (FGFDMExec *Executive)
 Constructor. More...
 
 ~FGAuxiliary ()
 Destructor.
 
double Getadot (int unit) const
 
double Getadot (void) const
 
double GetAeroPQR (int axis) const
 
const FGColumnVector3GetAeroPQR (void) const
 
double GetAeroUVW (int idx) const
 
const FGColumnVector3GetAeroUVW (void) const
 
double Getalpha (int unit) const
 
double Getalpha (void) const
 
double Getbdot (int unit) const
 
double Getbdot (void) const
 
double Getbeta (int unit) const
 
double Getbeta (void) const
 
double GetDistanceRelativePosition (void) const
 
double GetEulerRates (int axis) const
 
const FGColumnVector3GetEulerRates (void) const
 
double GetGamma (int unit) const
 
double GetGamma (void) const
 
double GetGroundTrack (void) const
 
double GetHOverBCG (void) const
 
double GetHOverBMAC (void) const
 
double GetLatitudeRelativePosition (void) const
 
const FGLocationGetLocationVRP (void) const
 
double GetLongitudeRelativePosition (void) const
 
double GetMach (void) const
 Gets the Mach number.
 
double GetMachU (void) const
 The mach number calculated using the vehicle X axis velocity.
 
double GetMagBeta (int unit) const
 
double GetMagBeta (void) const
 
double GetNcg (int idx) const
 
const FGColumnVector3GetNcg (void) const
 
double GetNlf (void) const
 
double GetNpilot (int idx) const
 
const FGColumnVector3GetNpilot (void) const
 
const FGColumnVector3GetNwcg (void) const
 
double GetNx (void) const
 The longitudinal acceleration in g's of the aircraft center of gravity.
 
double GetNy (void) const
 The lateral acceleration in g's of the aircraft center of gravity.
 
double GetNz (void) const
 The vertical acceleration in g's of the aircraft center of gravity.
 
double GetPilotAccel (int idx) const
 
const FGColumnVector3GetPilotAccel (void) const
 
double Getqbar (void) const
 
double GetqbarUV (void) const
 
double GetqbarUW (void) const
 
double GetReynoldsNumber (void) const
 
double GetTAT_C (void) const
 
const FGMatrix33GetTb2w (void) const
 Calculates and returns the body-to-wind axis transformation matrix. More...
 
double GetTotalPressure (void) const
 Returns the total pressure. More...
 
double GetTotalTemperature (void) const
 Returns the total temperature. More...
 
const FGMatrix33GetTw2b (void) const
 Calculates and returns the wind-to-body axis transformation matrix. More...
 
double GetVcalibratedFPS (void) const
 Returns Calibrated airspeed in feet/second.
 
double GetVcalibratedKTS (void) const
 Returns Calibrated airspeed in knots.
 
double GetVequivalentFPS (void) const
 Returns equivalent airspeed in feet/second.
 
double GetVequivalentKTS (void) const
 Returns equivalent airspeed in knots.
 
double GetVground (void) const
 Gets the ground speed in feet per second. More...
 
double GetVt (void) const
 Gets the magnitude of total vehicle velocity including wind effects in feet per second.
 
double GetVtrueFPS () const
 Returns the true airspeed in feet per second.
 
double GetVtrueKTS () const
 Returns the true airspeed in knots.
 
bool InitModel (void) override
 
double MachFromImpactPressure (double qc, double p) const
 Compute the Mach number from the differential pressure (qc) and the static pressure. More...
 
double MachFromVcalibrated (double vcas, double pressure) const
 Calculate the Mach number from the calibrated airspeed.Based on the formulas in the US Air Force Aircraft Performance Flight Testing Manual (AFFTC-TIH-99-01). More...
 
double PitotTotalPressure (double mach, double pressure) const
 Compute the total pressure in front of the Pitot tube. More...
 
bool Run (bool Holding) override
 Runs the Auxiliary routines; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold. More...
 
void SetAeroPQR (const FGColumnVector3 &tt)
 
double VcalibratedFromMach (double mach, double pressure) const
 Calculate the calibrated airspeed from the Mach number. More...
 
- Public Member Functions inherited from FGModel
 FGModel (FGFDMExec *)
 Constructor.
 
 ~FGModel () override
 Destructor.
 
virtual SGPath FindFullPathName (const SGPath &path) const
 
FGFDMExecGetExec (void)
 
const std::string & GetName (void)
 
unsigned int GetRate (void)
 Get the output rate for the model in frames.
 
bool InitModel (void) override
 
virtual bool Load (Element *el)
 
void SetPropertyManager (std::shared_ptr< FGPropertyManager > fgpm)
 
void SetRate (unsigned int tt)
 Set the ouput rate for the model in frames.
 
- Public Member Functions inherited from FGModelFunctions
std::string GetFunctionStrings (const std::string &delimeter) const
 Gets the strings for the current set of functions. More...
 
std::string GetFunctionValues (const std::string &delimeter) const
 Gets the function values. More...
 
std::shared_ptr< FGFunctionGetPreFunction (const std::string &name)
 Get one of the "pre" function. More...
 
bool Load (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void PostLoad (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void PreLoad (Element *el, FGFDMExec *fdmex, std::string prefix="")
 
void RunPostFunctions (void)
 
void RunPreFunctions (void)
 
- Public Member Functions inherited from FGJSBBase
 FGJSBBase ()
 Constructor for FGJSBBase.
 
virtual ~FGJSBBase ()
 Destructor for FGJSBBase.
 
void disableHighLighting (void)
 Disables highlighting in the console output.
 

Public Attributes

struct JSBSim::FGAuxiliary::Inputs in
 

Additional Inherited Members

- Public Types inherited from FGJSBBase
enum  { eL = 1 , eM , eN }
 Moments L, M, N.
 
enum  { eP = 1 , eQ , eR }
 Rates P, Q, R.
 
enum  { eU = 1 , eV , eW }
 Velocities U, V, W.
 
enum  { eX = 1 , eY , eZ }
 Positions X, Y, Z.
 
enum  { ePhi = 1 , eTht , ePsi }
 Euler angles Phi, Theta, Psi.
 
enum  { eDrag = 1 , eSide , eLift }
 Stability axis forces, Drag, Side force, Lift.
 
enum  { eRoll = 1 , ePitch , eYaw }
 Local frame orientation Roll, Pitch, Yaw.
 
enum  { eNorth = 1 , eEast , eDown }
 Local frame position North, East, Down.
 
enum  { eLat = 1 , eLong , eRad }
 Locations Radius, Latitude, Longitude.
 
enum  {
  inNone = 0 , inDegrees , inRadians , inMeters ,
  inFeet
}
 Conversion specifiers.
 
- Static Public Member Functions inherited from FGJSBBase
static const std::string & GetVersion (void)
 Returns the version number of JSBSim. More...
 
static constexpr double KelvinToFahrenheit (double kelvin)
 Converts from degrees Kelvin to degrees Fahrenheit. More...
 
static constexpr double CelsiusToRankine (double celsius)
 Converts from degrees Celsius to degrees Rankine. More...
 
static constexpr double RankineToCelsius (double rankine)
 Converts from degrees Rankine to degrees Celsius. More...
 
static constexpr double KelvinToRankine (double kelvin)
 Converts from degrees Kelvin to degrees Rankine. More...
 
static constexpr double RankineToKelvin (double rankine)
 Converts from degrees Rankine to degrees Kelvin. More...
 
static constexpr double FahrenheitToCelsius (double fahrenheit)
 Converts from degrees Fahrenheit to degrees Celsius. More...
 
static constexpr double CelsiusToFahrenheit (double celsius)
 Converts from degrees Celsius to degrees Fahrenheit. More...
 
static constexpr double CelsiusToKelvin (double celsius)
 Converts from degrees Celsius to degrees Kelvin. More...
 
static constexpr double KelvinToCelsius (double kelvin)
 Converts from degrees Kelvin to degrees Celsius. More...
 
static constexpr double FeetToMeters (double measure)
 Converts from feet to meters. More...
 
static bool EqualToRoundoff (double a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, float b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (float a, double b)
 Finite precision comparison. More...
 
static bool EqualToRoundoff (double a, float b)
 Finite precision comparison. More...
 
static constexpr double Constrain (double min, double value, double max)
 Constrain a value between a minimum and a maximum value.
 
static constexpr double sign (double num)
 
- Static Public Attributes inherited from FGJSBBase
static char highint [5] = {27, '[', '1', 'm', '\0' }
 highlights text
 
static char halfint [5] = {27, '[', '2', 'm', '\0' }
 low intensity text
 
static char normint [6] = {27, '[', '2', '2', 'm', '\0' }
 normal intensity text
 
static char reset [5] = {27, '[', '0', 'm', '\0' }
 resets text properties
 
static char underon [5] = {27, '[', '4', 'm', '\0' }
 underlines text
 
static char underoff [6] = {27, '[', '2', '4', 'm', '\0' }
 underline off
 
static char fgblue [6] = {27, '[', '3', '4', 'm', '\0' }
 blue text
 
static char fgcyan [6] = {27, '[', '3', '6', 'm', '\0' }
 cyan text
 
static char fgred [6] = {27, '[', '3', '1', 'm', '\0' }
 red text
 
static char fggreen [6] = {27, '[', '3', '2', 'm', '\0' }
 green text
 
static char fgdef [6] = {27, '[', '3', '9', 'm', '\0' }
 default text
 
static short debug_lvl = 1
 
- Protected Member Functions inherited from FGModel
bool Upload (Element *el, bool preLoad)
 Uploads this model in memory. More...
 
- Static Protected Member Functions inherited from FGJSBBase
static std::string CreateIndexedPropertyName (const std::string &Property, int index)
 
- Protected Attributes inherited from FGModel
unsigned int exe_ctr
 
FGFDMExecFDMExec
 
std::string Name
 
std::shared_ptr< FGPropertyManagerPropertyManager
 
unsigned int rate
 
- Protected Attributes inherited from FGModelFunctions
FGPropertyReader LocalProperties
 
std::vector< std::shared_ptr< FGFunction > > PostFunctions
 
std::vector< std::shared_ptr< FGFunction > > PreFunctions
 
- Static Protected Attributes inherited from FGJSBBase
static constexpr double radtodeg = 180. / M_PI
 
static constexpr double degtorad = M_PI / 180.
 
static constexpr double hptoftlbssec = 550.0
 
static constexpr double psftoinhg = 0.014138
 
static constexpr double psftopa = 47.88
 
static constexpr double fttom = 0.3048
 
static constexpr double ktstofps = 1852./(3600*fttom)
 
static constexpr double fpstokts = 1.0 / ktstofps
 
static constexpr double inchtoft = 1.0/12.0
 
static constexpr double m3toft3 = 1.0/(fttom*fttom*fttom)
 
static constexpr double in3tom3 = inchtoft*inchtoft*inchtoft/m3toft3
 
static constexpr double inhgtopa = 3386.38
 
static constexpr double slugtolb = 32.174049
 Note that definition of lbtoslug by the inverse of slugtolb and not to a different constant you can also get from some tables will make lbtoslug*slugtolb == 1 up to the magnitude of roundoff. More...
 
static constexpr double lbtoslug = 1.0/slugtolb
 
static constexpr double kgtolb = 2.20462
 
static constexpr double kgtoslug = 0.06852168
 
static const std::string needed_cfg_version = "2.0"
 
static const std::string JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__
 

Constructor & Destructor Documentation

◆ FGAuxiliary()

FGAuxiliary ( FGFDMExec Executive)
explicit

Constructor.

Parameters
Executivea pointer to the parent executive object

Definition at line 61 of file FGAuxiliary.cpp.

61  : FGModel(fdmex)
62 {
63  Name = "FGAuxiliary";
64  pt = FGAtmosphere::StdDaySLpressure; // ISA SL pressure
65  tat = FGAtmosphere::StdDaySLtemperature; // ISA SL temperature
66  tatc = RankineToCelsius(tat);
67 
68  vcas = veas = 0.0;
69  qbar = qbarUW = qbarUV = 0.0;
70  Mach = MachU = 0.0;
71  alpha = beta = 0.0;
72  adot = bdot = 0.0;
73  gamma = Vt = Vground = 0.0;
74  psigt = 0.0;
75  hoverbmac = hoverbcg = 0.0;
76  Re = 0.0;
77  Nx = Ny = Nz = 0.0;
78 
79  vPilotAccel.InitMatrix();
80  vPilotAccelN.InitMatrix();
81  vAeroUVW.InitMatrix();
82  vAeroPQR.InitMatrix();
83  vMachUVW.InitMatrix();
84  vEulerRates.InitMatrix();
85 
86  bind();
87 
88  Debug(0);
89 }
static constexpr double RankineToCelsius(double rankine)
Converts from degrees Rankine to degrees Celsius.
Definition: FGJSBBase.h:200
FGModel(FGFDMExec *)
Constructor.
Definition: FGModel.cpp:57
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Member Function Documentation

◆ GetTb2w()

const FGMatrix33& GetTb2w ( void  ) const
inline

Calculates and returns the body-to-wind axis transformation matrix.

Returns
a reference to the wind-to-body transformation matrix.

Definition at line 230 of file FGAuxiliary.h.

230 { return mTb2w; }

◆ GetTotalPressure()

double GetTotalPressure ( void  ) const
inline

Returns the total pressure.

Total pressure is freestream total pressure for subsonic only. For supersonic it is the 1D total pressure behind a normal shock.

Definition at line 176 of file FGAuxiliary.h.

176 { return pt; }

◆ GetTotalTemperature()

double GetTotalTemperature ( void  ) const
inline

Returns the total temperature.

The total temperature ("tat", isentropic flow) is calculated:

tat = in.Temperature*(1 + 0.2*Mach*Mach)

(where "in.Temperature" is standard temperature calculated by the atmosphere model)

Definition at line 186 of file FGAuxiliary.h.

186 { return tat; }

◆ GetTw2b()

const FGMatrix33& GetTw2b ( void  ) const
inline

Calculates and returns the wind-to-body axis transformation matrix.

Returns
a reference to the wind-to-body transformation matrix.

Definition at line 225 of file FGAuxiliary.h.

225 { return mTw2b; }

◆ GetVground()

double GetVground ( void  ) const
inline

Gets the ground speed in feet per second.

The magnitude is the square root of the sum of the squares (RSS) of the vehicle north and east velocity components.

Returns
The magnitude of the vehicle velocity in the horizontal plane.

Definition at line 245 of file FGAuxiliary.h.

245 { return Vground; }

◆ MachFromImpactPressure()

double MachFromImpactPressure ( double  qc,
double  p 
) const

Compute the Mach number from the differential pressure (qc) and the static pressure.

Based on the formulas in the US Air Force Aircraft Performance Flight Testing Manual (AFFTC-TIH-99-01).

Parameters
qcThe differential/impact pressure
pressurePressure in psf
Returns
The Mach number

Definition at line 267 of file FGAuxiliary.cpp.

268 {
269  constexpr double SHRatio = FGAtmosphere::SHRatio;
270  constexpr double a = 2.0/(SHRatio-1.0);
271  constexpr double b = (SHRatio-1.0)/SHRatio;
272  constexpr double c = 2.0/b;
273  constexpr double d = 0.5*a;
274  const double coeff = pow(0.5*(SHRatio+1.0), -0.25*c)
275  * pow(0.5*(SHRatio+1.0)/SHRatio, -0.5*d);
276 
277  double A = qc / pressure + 1;
278  double M = sqrt(a*(pow(A, b) - 1.0)); // Equation (4.12)
279 
280  if (M > 1.0)
281  for (unsigned int i = 0; i<10; i++)
282  M = coeff*sqrt(A*pow(1 - 1.0 / (c*M*M), d)); // Equation (4.17)
283 
284  return M;
285 }
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◆ MachFromVcalibrated()

double MachFromVcalibrated ( double  vcas,
double  pressure 
) const

Calculate the Mach number from the calibrated airspeed.Based on the formulas in the US Air Force Aircraft Performance Flight Testing Manual (AFFTC-TIH-99-01).

Parameters
vcasThe calibrated airspeed (CAS) in ft/s
pressurePressure in psf
Returns
The Mach number

Definition at line 297 of file FGAuxiliary.cpp.

298 {
299  constexpr double StdDaySLpressure = FGAtmosphere::StdDaySLpressure;
300  double qc = PitotTotalPressure(vcas / in.StdDaySLsoundspeed, StdDaySLpressure) - StdDaySLpressure;
301  return MachFromImpactPressure(qc, pressure);
302 }
double PitotTotalPressure(double mach, double pressure) const
Compute the total pressure in front of the Pitot tube.
double MachFromImpactPressure(double qc, double p) const
Compute the Mach number from the differential pressure (qc) and the static pressure.
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◆ PitotTotalPressure()

double PitotTotalPressure ( double  mach,
double  pressure 
) const

Compute the total pressure in front of the Pitot tube.

It uses the Rayleigh formula for supersonic speeds (See "Introduction to Aerodynamics of a Compressible Fluid - H.W. Liepmann, A.E. Puckett - Wiley & sons (1947)" ยง5.4 pp 75-80)

Parameters
machThe Mach number
pressurePressure in psf
Returns
The total pressure in front of the Pitot tube in psf

Definition at line 230 of file FGAuxiliary.cpp.

231 {
232  constexpr double SHRatio = FGAtmosphere::SHRatio;
233  constexpr double a = (SHRatio-1.0) / 2.0;
234  constexpr double b = SHRatio / (SHRatio-1.0);
235  constexpr double c = 2.0*b;
236  constexpr double d = 1.0 / (SHRatio-1.0);
237  const double coeff = pow(0.5*(SHRatio+1.0), b)
238  * pow((SHRatio+1.0)/(SHRatio-1.0), d);
239 
240  if (mach < 0) return pressure;
241  if (mach < 1) //calculate total pressure assuming isentropic flow
242  return pressure*pow((1.0 + a*mach*mach), b);
243  else {
244  // Shock in front of pitot tube, we'll assume its normal and use the
245  // Rayleigh Pitot Tube Formula, i.e. the ratio of total pressure behind the
246  // shock to the static pressure in front of the normal shock assumption
247  // should not be a bad one -- most supersonic aircraft place the pitot probe
248  // out front so that it is the forward most point on the aircraft.
249  // The real shock would, of course, take on something like the shape of a
250  // rounded-off cone but, here again, the assumption should be good since the
251  // opening of the pitot probe is very small and, therefore, the effects of
252  // the shock curvature should be small as well. AFAIK, this approach is
253  // fairly well accepted within the aerospace community
254 
255  // The denominator below is zero for Mach ~ 0.38, for which
256  // we'll never be here, so we're safe
257 
258  return pressure*coeff*pow(mach, c)/pow(c*mach*mach-1.0, d);
259  }
260 }
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◆ Run()

bool Run ( bool  Holding)
overridevirtual

Runs the Auxiliary routines; called by the Executive Can pass in a value indicating if the executive is directing the simulation to Hold.

Parameters
Holdingif true, the executive has been directed to hold the sim from advancing time. Some models may ignore this flag, such as the Input model, which may need to be active to listen on a socket for the "Resume" command to be given.
Returns
false if no error

Reimplemented from FGModel.

Definition at line 131 of file FGAuxiliary.cpp.

132 {
133  if (FGModel::Run(Holding)) return true; // return true if error returned from base class
134  if (Holding) return false;
135 
136  // Rotation
137 
138  vEulerRates(eTht) = in.vPQR(eQ)*in.CosPhi - in.vPQR(eR)*in.SinPhi;
139  if (in.CosTht != 0.0) {
140  vEulerRates(ePsi) = (in.vPQR(eQ)*in.SinPhi + in.vPQR(eR)*in.CosPhi)/in.CosTht;
141  vEulerRates(ePhi) = in.vPQR(eP) + vEulerRates(ePsi)*in.SinTht;
142  }
143 
144  // Combine the wind speed with aircraft speed to obtain wind relative speed
145  vAeroPQR = in.vPQR - in.TurbPQR;
146  vAeroUVW = in.vUVW - in.Tl2b * in.TotalWindNED;
147 
148  alpha = beta = adot = bdot = 0;
149  double AeroU2 = vAeroUVW(eU)*vAeroUVW(eU);
150  double AeroV2 = vAeroUVW(eV)*vAeroUVW(eV);
151  double AeroW2 = vAeroUVW(eW)*vAeroUVW(eW);
152  double mUW = AeroU2 + AeroW2;
153 
154  double Vt2 = mUW + AeroV2;
155  Vt = sqrt(Vt2);
156 
157  if ( Vt > 0.001 ) {
158  beta = atan2(vAeroUVW(eV), sqrt(mUW));
159 
160  if ( mUW >= 1E-6 ) {
161  alpha = atan2(vAeroUVW(eW), vAeroUVW(eU));
162  double Vtdot = (vAeroUVW(eU)*in.vUVWdot(eU) + vAeroUVW(eV)*in.vUVWdot(eV) + vAeroUVW(eW)*in.vUVWdot(eW))/Vt;
163  adot = (vAeroUVW(eU)*in.vUVWdot(eW) - vAeroUVW(eW)*in.vUVWdot(eU))/mUW;
164  bdot = (in.vUVWdot(eV)*Vt - vAeroUVW(eV)*Vtdot)/(Vt*sqrt(mUW));
165  }
166  }
167 
168  UpdateWindMatrices();
169 
170  Re = Vt * in.Wingchord / in.KinematicViscosity;
171 
172  double densityD2 = 0.5*in.Density;
173 
174  qbar = densityD2 * Vt2;
175  qbarUW = densityD2 * (mUW);
176  qbarUV = densityD2 * (AeroU2 + AeroV2);
177  Mach = Vt / in.SoundSpeed;
178  MachU = vMachUVW(eU) = vAeroUVW(eU) / in.SoundSpeed;
179  vMachUVW(eV) = vAeroUVW(eV) / in.SoundSpeed;
180  vMachUVW(eW) = vAeroUVW(eW) / in.SoundSpeed;
181 
182  // Position
183 
184  Vground = sqrt( in.vVel(eNorth)*in.vVel(eNorth) + in.vVel(eEast)*in.vVel(eEast) );
185 
186  psigt = atan2(in.vVel(eEast), in.vVel(eNorth));
187  if (psigt < 0.0) psigt += 2*M_PI;
188  gamma = atan2(-in.vVel(eDown), Vground);
189 
190  tat = in.Temperature*(1 + 0.2*Mach*Mach); // Total Temperature, isentropic flow
191  tatc = RankineToCelsius(tat);
192 
193  pt = PitotTotalPressure(Mach, in.Pressure);
194 
195  if (abs(Mach) > 0.0) {
196  vcas = VcalibratedFromMach(Mach, in.Pressure);
197  veas = sqrt(2 * qbar / FGAtmosphere::StdDaySLdensity);
198  }
199  else
200  vcas = veas = 0.0;
201 
202  vPilotAccel.InitMatrix();
203  vNcg = in.vBodyAccel/in.StandardGravity;
204  // Nz is Acceleration in "g's", along normal axis (-Z body axis)
205  Nz = -vNcg(eZ);
206  Ny = vNcg(eY);
207  Nx = vNcg(eX);
208  vPilotAccel = in.vBodyAccel + in.vPQRidot * in.ToEyePt;
209  vPilotAccel += in.vPQRi * (in.vPQRi * in.ToEyePt);
210 
211  vNwcg = mTb2w * vNcg;
212  vNwcg(eZ) = 1.0 - vNwcg(eZ);
213 
214  vPilotAccelN = vPilotAccel / in.StandardGravity;
215 
216  // VRP computation
217  vLocationVRP = in.vLocation.LocalToLocation( in.Tb2l * in.VRPBody );
218 
219  // Recompute some derived values now that we know the dependent parameters values ...
220  hoverbcg = in.DistanceAGL / in.Wingspan;
221 
222  FGColumnVector3 vMac = in.Tb2l * in.RPBody;
223  hoverbmac = (in.DistanceAGL - vMac(3)) / in.Wingspan;
224 
225  return false;
226 }
double VcalibratedFromMach(double mach, double pressure) const
Calculate the calibrated airspeed from the Mach number.
FGLocation LocalToLocation(const FGColumnVector3 &lvec) const
Conversion from Local frame coordinates to a location in the earth centered and fixed frame.
Definition: FGLocation.h:326
virtual bool Run(bool Holding)
Runs the model; called by the Executive.
Definition: FGModel.cpp:89
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◆ VcalibratedFromMach()

double VcalibratedFromMach ( double  mach,
double  pressure 
) const

Calculate the calibrated airspeed from the Mach number.

Based on the formulas in the US Air Force Aircraft Performance Flight Testing Manual (AFFTC-TIH-99-01).

Parameters
machThe Mach number
pressurePressure in psf
Returns
The calibrated airspeed (CAS) in ft/s

Definition at line 289 of file FGAuxiliary.cpp.

290 {
291  double qc = PitotTotalPressure(mach, pressure) - pressure;
292  return in.StdDaySLsoundspeed * MachFromImpactPressure(qc, FGAtmosphere::StdDaySLpressure);
293 }
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The documentation for this class was generated from the following files: