Detailed Description

FGPropeller models a propeller given the tabular data for Ct (thrust) and Cp (power), indexed by the advance ratio "J".

Configuration File Format

<sense> {1 | -1} </sense>
<p_factor> {number} </p_factor>
<propeller name="{string}" version="{string}">
  <ixx> {number} </ixx>
  <diameter unit="IN"> {number} </diameter>
  <numblades> {number} </numblades>
  <gearratio> {number} </gearratio>
  <minpitch> {number} </minpitch>
  <maxpitch> {number} </maxpitch>
  <minrpm> {number} </minrpm>
  <maxrpm> {number} </maxrpm>
  <constspeed> {number} </constspeed>
  <reversepitch> {number} </reversepitch>
  <ct_factor> {number} </ct_factor>
  <cp_factor> {number} </cp_factor>
 
  <table name="C_THRUST" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
  <table name="C_POWER" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
  <table name="CT_MACH" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
  <table name="CP_MACH" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
  <table name="CT_RPM_FACTOR" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
  <table name="CP_RPM_FACTOR" type="internal">
    <tableData>
      {numbers}
    </tableData>
  </table>
 
</propeller>

Configuration Parameters

    <ixx>           - Propeller rotational inertia.
    <diameter>      - Propeller disk diameter.
    <numblades>     - Number of blades.
    <gearratio>     - Ratio of (engine rpm) / (prop rpm).
    <minpitch>      - Minimum blade pitch angle.
    <maxpitch>      - Maximum blade pitch angle.
    <minrpm>        - Minimum rpm target for constant speed propeller.
    <maxrpm>        - Maximum rpm target for constant speed propeller.
    <constspeed>    - 1 = constant speed mode, 0 = manual pitch mode.
    <reversepitch>  - Blade pitch angle for reverse.
    <sense>         - Direction of rotation (1=clockwise as viewed from cockpit,
                        -1=anti-clockwise as viewed from cockpit). Sense is
                       specified in the parent tag of the propeller.
    <p_factor>      - P factor. It is specified in the parent tag of
                       the propeller.
    <ct_factor>     - A multiplier for the coefficients of thrust.
    <cp_factor>     - A multiplier for the coefficients of power.

Two tables are needed. One for coefficient of thrust (Ct) and one for coefficient of power (Cp).

Four tables are optional. CT_MACH and CP_MACH apply a factor to Ct and Cp based on helical tip Mach. CT_RPM_FACTOR and CP_RPM_FACTOR apply a Reynolds-number correction factor indexed by propeller RPM, normalised to 1.0 at the RPM for which the baseline C_THRUST/C_POWER data were measured.

The RPM-indexed Reynolds correction is intended for very small propellers, such as those used on UAVs and MAVs. It assumes that the air viscosity is effectively constant (as is generally reasonable for low-altitude operation) and that the blade-relative airflow is dominated by circumferential velocity, rather than the vehicle's translational velocity. RPM is therefore used as a proxy for the change in Reynolds number; the correction tables do not account for changes in atmospheric properties or flight speed. They should be calibrated for the propeller and operating atmosphere in question, and may need retuning when used in substantially different conditions, for example in the Martian atmosphere.

The parameters <sense> and <p_factor> must be specified at the parent level i.e. in the <thruster> element. This allows to specify different sense and P factor values for each propeller of the model while using the same definition file for all the propellers.

In addition to thrust, the propeller applies two moments to the aircraft:

The torque that tends to roll the aircraft in the direction opposite to the propeller rotation,
and the gyroscopic moment.

It should be noted that historically the gyroscopic moment had an incorrect sign. The correct sign can be obtained by specifying a version attribute higher than 1.0 to the propeller definition

<propeller name="a_prop" version="1.1">
  <!-- propeller definition -->
</propeller>

For backward compatibility, the absence of the version attribute will result in the gyroscopic moment to be computed with the legacy incorrect sign.

Several references were helpful, here:

Barnes W. McCormick, "Aerodynamics, Aeronautics, and Flight Mechanics", Wiley & Sons, 1979 ISBN 0-471-03032-5
Edwin Hartman, David Biermann, "The Aerodynamic Characteristics of Full Scale Propellers Having 2, 3, and 4 Blades of Clark Y and R.A.F. 6 Airfoil Sections", NACA Report TN-640, 1938 (?)
Various NACA Technical Notes and Reports

Author: Jon S. Berndt

See also: FGEngine; FGThruster

Definition at line 194 of file FGPropeller.h.

#include <FGPropeller.h>

Inheritance diagram for FGPropeller:

Collaboration diagram for FGPropeller:

Public Member Functions
	FGPropeller (FGFDMExec exec, Element el, int num=0)
	Constructor for FGPropeller.

	~FGPropeller ()
	Destructor for FGPropeller - deletes the FGTable objects.

double	Calculate (double EnginePower)
	Calculates and returns the thrust produced by this propeller.

int	GetConstantSpeed (void) const
	Returns a non-zero value if the propeller is constant speed.

double	GetCpFactor (void) const
	Retrieves the coefficient of power multiplier.

FGTable *	GetCpMachTable (void) const
	Retrieves propeller power Mach effects factor.

FGTable *	GetCPowerRPMTable (void) const
	Retrieves propeller power RPM correction factor table.

FGTable *	GetCPowerTable (void) const
	Retrieves propeller power table.

double	GetCtFactor (void) const
	Retrieves the coefficient of thrust multiplier.

FGTable *	GetCThrustRPMTable (void) const
	Retrieves propeller thrust RPM correction factor table.

FGTable *	GetCThrustTable (void) const
	Retrieves propeller thrust table.

FGTable *	GetCtMachTable (void) const
	Retrieves propeller thrust Mach effects factor.

double	GetDiameter (void) const
	Retrieves the propeller diameter.

double	GetEngineRPM (void) const
	Calculates the RPMs of the engine based on gear ratio.

bool	GetFeather (void) const
	Returns true if the propeller is in feathered position.

double	GetHelicalTipMach (void) const
	Retrieves the Mach number at the propeller tips.

double	GetInducedVelocity (void) const
	Get the propeller induced velocity.

double	GetIxx (void) const
	Retrieves the propeller moment of inertia.

FGColumnVector3	GetPFactor (void) const
	Retrieves the P-Factor constant.

double	GetPitch (void) const
	Retrieves the pitch of the propeller in degrees.

double	GetPowerRequired (void)
	Retrieves the power required (or "absorbed") by the propeller - i.e.

bool	GetReverse (void) const
	Returns true if the propeller is in reverse position.

double	GetReverseCoef (void) const
	Retrieves the reverse pitch command.

double	GetRPM (void) const
	Retrieves the RPMs of the propeller.

double	GetThrustCoefficient (void) const
	Retrieves the thrust coefficient.

std::string	GetThrusterLabels (int id, const std::string &delimeter)
	Generate the labels for the thruster standard CSV output.

std::string	GetThrusterValues (int id, const std::string &delimeter)
	Generate the values for the thruster standard CSV output.

double	GetTorque (void) const
	Retrieves the Torque in foot-pounds (Don't you love the English system?)

bool	IsVPitch (void) const
	Returns true of this propeller is variable pitch.

void	ResetToIC (void)
	Reset the initial conditions.

void	SetAdvance (double advance)
	Set the propeller pitch.

void	SetConstantSpeed (int mode)
	Sets propeller into constant speed mode, or manual pitch mode.

void	SetCpFactor (double cpf)
	Sets coefficient of power multiplier.

void	SetCtFactor (double ctf)
	Sets coefficient of thrust multiplier.

void	SetEngineRPM (double rpm)
	Sets the Revolutions Per Minute for the propeller using the engine gear ratio.

void	SetFeather (bool f)
	If true, sets the propeller in feathered position.

void	SetInducedVelocity (double Vi)
	Set the propeller induced velocity.

void	SetPFactor (double pf)
	Sets the P-Factor constant.

void	SetPitch (double pitch)
	This commands the pitch of the blade to change to the value supplied.

void	SetReverse (bool r)
	If true, sets the propeller in reversed position.

void	SetReverseCoef (double c)
	Set the propeller reverse pitch.

void	SetRPM (double rpm)
	Sets the Revolutions Per Minute for the propeller.

void	SetSense (double s)
	Sets the rotation sense of the propeller.

Public Member Functions inherited from FGThruster
	FGThruster (FGFDMExec FDMExec, Element el, int num)
	Constructor.

virtual	~FGThruster ()
	Destructor.

double	GetGearRatio (void)

std::string	GetName (void)

double	GetReverserAngle (void) const

double	GetThrust (void) const

eType	GetType (void)

void	SetName (std::string name)

void	SetReverserAngle (double angle)

Public Member Functions inherited from FGForce
	FGForce (FGFDMExec *FDMExec)
	Constructor.

virtual	~FGForce ()
	Destructor.

const FGColumnVector3 &	GetActingLocation (void) const

double	GetActingLocationX (void) const

double	GetActingLocationY (void) const

double	GetActingLocationZ (void) const

double	GetAnglesToBody (int axis) const

const FGColumnVector3 &	GetAnglesToBody (void) const

virtual const FGColumnVector3 &	GetBodyForces (void)

double	GetBodyXForce (void) const

double	GetBodyYForce (void) const

double	GetBodyZForce (void) const

const FGColumnVector3 &	GetLocation (void) const

double	GetLocationX (void) const

double	GetLocationY (void) const

double	GetLocationZ (void) const

const FGColumnVector3 &	GetMoments (void) const

double	GetPitch (void) const

TransformType	GetTransformType (void) const

double	GetYaw (void) const

void	SetActingLocation (const FGColumnVector3 &vv)

void	SetActingLocation (double x, double y, double z)
	Acting point of application.

void	SetActingLocationX (double x)

void	SetActingLocationY (double y)

void	SetActingLocationZ (double z)

void	SetAnglesToBody (const FGColumnVector3 &vv)

void	SetAnglesToBody (double broll, double bpitch, double byaw)

void	SetLocation (const FGColumnVector3 &vv)

void	SetLocation (double x, double y, double z)

void	SetLocationX (double x)

void	SetLocationY (double y)

void	SetLocationZ (double z)

void	SetPitch (double pitch)

void	SetTransformType (TransformType ii)

void	SetYaw (double yaw)

const FGMatrix33 &	Transform (void) const

void	UpdateCustomTransformMatrix (void)

Public Member Functions inherited from FGJSBBase
	FGJSBBase ()
	Constructor for FGJSBBase.

virtual	~FGJSBBase ()
	Destructor for FGJSBBase.

Additional Inherited Members
Public Types inherited from FGThruster
enum	eType { ttNozzle , ttRotor , ttPropeller , ttDirect }

Public Types inherited from FGForce
enum	TransformType { tNone , tWindBody , tLocalBody , tInertialBody , tCustom }

Public Types inherited from FGJSBBase
enum	{ eL = 1 , eM , eN }
	Moments L, M, N. More...

enum	{ eP = 1 , eQ , eR }
	Rates P, Q, R. More...

enum	{ eU = 1 , eV , eW }
	Velocities U, V, W. More...

enum	{ eX = 1 , eY , eZ }
	Positions X, Y, Z. More...

enum	{ ePhi = 1 , eTht , ePsi }
	Euler angles Phi, Theta, Psi. More...

enum	{ eDrag = 1 , eSide , eLift }
	Stability axis forces, Drag, Side force, Lift. More...

enum	{ eRoll = 1 , ePitch , eYaw }
	Local frame orientation Roll, Pitch, Yaw. More...

enum	{ eNorth = 1 , eEast , eDown }
	Local frame position North, East, Down. More...

enum	{ eLat = 1 , eLong , eRad }
	Locations Radius, Latitude, Longitude. More...

enum	{ inNone = 0 , inDegrees , inRadians , inMeters , inFeet }
	Conversion specifiers. More...

Static Public Member Functions inherited from FGJSBBase
static constexpr double	CelsiusToFahrenheit (double celsius)
	Converts from degrees Celsius to degrees Fahrenheit.

static constexpr double	CelsiusToKelvin (double celsius)
	Converts from degrees Celsius to degrees Kelvin.

static constexpr double	CelsiusToRankine (double celsius)
	Converts from degrees Celsius to degrees Rankine.

static constexpr double	Constrain (double min, double value, double max)
	Constrain a value between a minimum and a maximum value.

static bool	EqualToRoundoff (double a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (double a, float b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, double b)
	Finite precision comparison.

static bool	EqualToRoundoff (float a, float b)
	Finite precision comparison.

static constexpr double	FahrenheitToCelsius (double fahrenheit)
	Converts from degrees Fahrenheit to degrees Celsius.

static constexpr double	FeetToMeters (double measure)
	Converts from feet to meters.

static const std::string &	GetVersion (void)
	Returns the version number of JSBSim.

static constexpr double	KelvinToCelsius (double kelvin)
	Converts from degrees Kelvin to degrees Celsius.

static constexpr double	KelvinToFahrenheit (double kelvin)
	Converts from degrees Kelvin to degrees Fahrenheit.

static constexpr double	KelvinToRankine (double kelvin)
	Converts from degrees Kelvin to degrees Rankine.

static constexpr double	RankineToCelsius (double rankine)
	Converts from degrees Rankine to degrees Celsius.

static constexpr double	RankineToKelvin (double rankine)
	Converts from degrees Rankine to degrees Kelvin.

static constexpr double	sign (double num)

Public Attributes inherited from FGThruster
struct JSBSim::FGThruster::Inputs	in

Static Public Attributes inherited from FGJSBBase
static short	debug_lvl = 1

Static Protected Member Functions inherited from FGJSBBase
static std::string	CreateIndexedPropertyName (const std::string &Property, int index)

Protected Attributes inherited from FGThruster
int	EngineNum

double	GearRatio

std::string	Name

double	PowerRequired

double	ReverserAngle

double	Thrust

double	ThrustCoeff

eType	Type

Protected Attributes inherited from FGForce
FGFDMExec *	fdmex

std::shared_ptr< FGMassBalance >	MassBalance

FGMatrix33	mT

TransformType	ttype

FGColumnVector3	vActingXYZn

FGColumnVector3	vFn

FGColumnVector3	vMn

FGColumnVector3	vOrient

FGColumnVector3	vXYZn

Static Protected Attributes inherited from FGJSBBase
static constexpr double	degtorad = M_PI / 180.

static constexpr double	fpstokts = 1.0 / ktstofps

static constexpr double	fttom = 0.3048

static constexpr double	hptoftlbssec = 550.0

static constexpr double	in3tom3 = inchtoftinchtoftinchtoft/m3toft3

static constexpr double	inchtoft = 1.0/12.0

static constexpr double	inhgtopa = 3386.38

static const std::string	JSBSim_version = JSBSIM_VERSION " " __DATE__ " " __TIME__

static constexpr double	kgtolb = 2.20462

static constexpr double	kgtoslug = 0.06852168

static constexpr double	ktstofps = 1852./(3600*fttom)

static constexpr double	lbtoslug = 1.0/slugtolb

static constexpr double	m3toft3 = 1.0/(fttomfttomfttom)

static const std::string	needed_cfg_version = "2.0"

static constexpr double	psftoinhg = 0.014138

static constexpr double	psftopa = 47.88

static constexpr double	radtodeg = 180. / M_PI

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.

Constructor & Destructor Documentation

◆ FGPropeller()

FGPropeller	(	FGFDMExec *	exec,
		Element *	el,
		int	num = `0`
	)

Constructor for FGPropeller.

Parameters

exec	a pointer to the main executive object
el	a pointer to the thruster config file XML element
num	the number of this propeller

Definition at line 51 of file FGPropeller.cpp.

                       : FGThruster(exec, prop_element, num)
{
  Element *table_element, *local_element;
  string name="";
  auto PropertyManager = exec->GetPropertyManager();
 
  MaxPitch = MinPitch = P_Factor = Advance = MinRPM = MaxRPM = 0.0;
  Sense = 1; // default clockwise rotation
  ReversePitch = 0.0;
  Reversed = false;
  Feathered = false;
  Reverse_coef = 0.0;
  GearRatio = 1.0;
  CtFactor = CpFactor = 1.0;
  ConstantSpeed = 0;
  cThrust = cPower = CtMach = CpMach = cThrustRPM = cPowerRPM = 0;
 
  if (prop_element->FindElement("ixx"))
    Ixx = max(prop_element->FindElementValueAsNumberConvertTo("ixx", "SLUG*FT2"), 1e-06);
 
  Sense_multiplier = 1.0;
  if (prop_element->HasAttribute("version")
      && prop_element->GetAttributeValueAsNumber("version") > 1.0)
      Sense_multiplier = -1.0;
 
  if (prop_element->FindElement("diameter"))
    Diameter = max(prop_element->FindElementValueAsNumberConvertTo("diameter", "FT"), 0.001);
  if (prop_element->FindElement("numblades"))
    numBlades = (int)prop_element->FindElementValueAsNumber("numblades");
  if (prop_element->FindElement("gearratio"))
    GearRatio = max(prop_element->FindElementValueAsNumber("gearratio"), 0.001);
  if (prop_element->FindElement("minpitch"))
    MinPitch = prop_element->FindElementValueAsNumber("minpitch");
  if (prop_element->FindElement("maxpitch"))
    MaxPitch = prop_element->FindElementValueAsNumber("maxpitch");
  if (prop_element->FindElement("minrpm"))
    MinRPM = prop_element->FindElementValueAsNumber("minrpm");
  if (prop_element->FindElement("maxrpm")) {
    MaxRPM = prop_element->FindElementValueAsNumber("maxrpm");
    ConstantSpeed = 1;
    }
  if (prop_element->FindElement("constspeed"))
    ConstantSpeed = (int)prop_element->FindElementValueAsNumber("constspeed");
  if (prop_element->FindElement("reversepitch"))
    ReversePitch = prop_element->FindElementValueAsNumber("reversepitch");
  while((table_element = prop_element->FindNextElement("table")) != 0) {
    name = table_element->GetAttributeValue("name");
    try {
      if (name == "C_THRUST") {
        cThrust = new FGTable(PropertyManager, table_element);
      } else if (name == "C_POWER") {
        cPower = new FGTable(PropertyManager, table_element);
      } else if (name == "CT_MACH") {
        CtMach = new FGTable(PropertyManager, table_element);
      } else if (name == "CP_MACH") {
        CpMach = new FGTable(PropertyManager, table_element);
      } else if (name == "CT_RPM_FACTOR") {
        cThrustRPM = new FGTable(PropertyManager, table_element);
      } else if (name == "CP_RPM_FACTOR") {
        cPowerRPM = new FGTable(PropertyManager, table_element);
      } else {
        FGXMLLogging log(table_element, LogLevel::ERROR);
        log << "Unknown table type: " << name << " in propeller definition.\n";
      }
    } catch (BaseException& e) {
      XMLLogException err(table_element);
      err << "Error loading propeller table:" << name << ". " << e.what() << "\n";
      throw err;
    }
  }
  if( (cPower == nullptr) || (cThrust == nullptr)){
    XMLLogException err(prop_element);
    err << "Propeller configuration must contain C_THRUST and C_POWER tables!\n";
    throw err;
  }
 
  local_element = prop_element->GetParent()->FindElement("sense");
  if (local_element) {
    double Sense = local_element->GetDataAsNumber();
    SetSense(Sense >= 0.0 ? 1.0 : -1.0);
  }
  local_element = prop_element->GetParent()->FindElement("p_factor");
  if (local_element) {
    P_Factor = local_element->GetDataAsNumber();
  }
  if (P_Factor < 0) {
    XMLLogException err(local_element);
    err << "P-Factor value in propeller configuration file must be greater than zero\n";
    throw err;
  }
  if (prop_element->FindElement("ct_factor"))
    SetCtFactor( prop_element->FindElementValueAsNumber("ct_factor") );
  if (prop_element->FindElement("cp_factor"))
    SetCpFactor( prop_element->FindElementValueAsNumber("cp_factor") );
 
  Type = ttPropeller;
  vTorque.InitMatrix();
  D4 = Diameter*Diameter*Diameter*Diameter;
  D5 = D4*Diameter;
  InitDynamics();
 
  string property_name, base_property_name;
  base_property_name = CreateIndexedPropertyName("propulsion/engine", EngineNum);
  property_name = base_property_name + "/engine-rpm";
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetEngineRPM );
  property_name = base_property_name + "/advance-ratio";
  PropertyManager->Tie( property_name.c_str(), &J );
  property_name = base_property_name + "/blade-angle";
  PropertyManager->Tie( property_name.c_str(), &Pitch );
  property_name = base_property_name + "/thrust-coefficient";
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetThrustCoefficient );
  property_name = base_property_name + "/propeller-rpm";
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetRPM );
  property_name = base_property_name + "/helical-tip-Mach";
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetHelicalTipMach );
  property_name = base_property_name + "/constant-speed-mode";
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetConstantSpeed,
                      &FGPropeller::SetConstantSpeed );
  property_name = base_property_name + "/prop-induced-velocity_fps"; // [ft/sec]
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetInducedVelocity,
                      &FGPropeller::SetInducedVelocity );
  property_name = base_property_name + "/propeller-power-ftlbps"; // [ft-lbs/sec]
  PropertyManager->Tie( property_name.c_str(), &PowerRequired );
  property_name = base_property_name + "/propeller-torque-ftlb"; // [ft-lbs]
  PropertyManager->Tie( property_name.c_str(), this, &FGPropeller::GetTorque);
  property_name = base_property_name + "/propeller-sense";
  PropertyManager->Tie( property_name.c_str(), &Sense );
 
  Debug(0);
}

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◆ ~FGPropeller()

~FGPropeller ( )

Destructor for FGPropeller - deletes the FGTable objects.

Definition at line 185 of file FGPropeller.cpp.

{
  delete cThrust;
  delete cPower;
  delete CtMach;
  delete CpMach;
  delete cThrustRPM;
  delete cPowerRPM;
 
  Debug(1);
}

Member Function Documentation

◆ Calculate()

double Calculate ( double EnginePower )

virtual

Calculates and returns the thrust produced by this propeller.

Given the excess power available from the engine (in foot-pounds), the thrust is calculated, as well as the current RPM. The RPM is calculated by integrating the torque provided by the engine over what the propeller "absorbs" (essentially the "drag" of the propeller).

Parameters

PowerAvailable this is the excess power provided by the engine to accelerate the prop. It could be negative, dictating that the propeller would be slowed.

Returns: the thrust in pounds

Reimplemented from FGThruster.

Definition at line 225 of file FGPropeller.cpp.

{
  FGColumnVector3 vDXYZ = MassBalance->StructuralToBody(vXYZn);
  const FGMatrix33& mT = Transform();
  // Local air velocity is obtained from Stevens & Lewis' "Aircraft Control and
  // Simualtion (3rd edition)" eqn 8.2-1
  // Variables in.AeroUVW and in.AeroPQR include the wind and turbulence effects
  // as computed by FGAuxiliary.
  FGColumnVector3 localAeroVel = mT.Transposed() * (in.AeroUVW + in.AeroPQR*vDXYZ);
  double omega, PowerAvailable;
 
  double Vel = localAeroVel(eU);
  double rho = in.Density;
  double RPS = RPM/60.0;
 
  // Calculate helical tip Mach
  double Area = 0.25*Diameter*Diameter*M_PI;
  double Vtip = RPS * Diameter * M_PI;
  HelicalTipMach = sqrt(Vtip*Vtip + Vel*Vel) / in.Soundspeed;
 
  if (RPS > 0.01) J = Vel / (Diameter * RPS); // Calculate J normally
  else           J = Vel / Diameter;
 
  PowerAvailable = EnginePower - GetPowerRequired();
 
  if (MaxPitch == MinPitch) {    // Fixed pitch prop
    ThrustCoeff = cThrust->GetValue(J);
  } else {                       // Variable pitch prop
    ThrustCoeff = cThrust->GetValue(J, Pitch);
  }
 
  // Apply optional scaling factor to Ct (default value = 1)
  ThrustCoeff *= CtFactor;
 
  // Apply optional Mach effects from CT_MACH table
  if (CtMach) ThrustCoeff *= CtMach->GetValue(HelicalTipMach);
 
  // Apply optional Reynolds-number correction indexed by RPM
  if (cThrustRPM) ThrustCoeff *= cThrustRPM->GetValue(RPM);
 
  Thrust = ThrustCoeff*RPS*RPS*D4*rho;
 
  // Induced velocity in the propeller disk area. This formula is obtained
  // from momentum theory - see B. W. McCormick, "Aerodynamics, Aeronautics,
  // and Flight Mechanics" 1st edition, eqn. 6.15 (propeller analysis chapter).
  // Since Thrust and Vel can both be negative we need to adjust this formula
  // To handle sign (direction) separately from magnitude.
  double Vel2sum = Vel*abs(Vel) + 2.0*Thrust/(rho*Area);
 
  if( Vel2sum > 0.0)
    Vinduced = 0.5 * (-Vel + sqrt(Vel2sum));
  else
    Vinduced = 0.5 * (-Vel - sqrt(-Vel2sum));
 
  // P-factor is simulated by a shift of the acting location of the thrust.
  // The shift is a multiple of the angle between the propeller shaft axis
  // and the relative wind that goes through the propeller disk.
  if (P_Factor > 0.0001) {
    double tangentialVel = localAeroVel.Magnitude(eV, eW);
 
    if (tangentialVel > 0.0001) {
      // The angle made locally by the air flow with respect to the propeller
      // axis is influenced by the induced velocity. This attenuates the
      // influence of a string cross wind and gives a more realistic behavior.
      double angle = atan2(tangentialVel, Vel+Vinduced);
      double factor = Sense * P_Factor * angle / tangentialVel;
      SetActingLocationY( GetLocationY() + factor * localAeroVel(eW));
      SetActingLocationZ( GetLocationZ() + factor * localAeroVel(eV));
    }
  }
 
  omega = RPS*2.0*M_PI;
 
  vFn(eX) = Thrust;
  vTorque(eX) = -Sense*EnginePower / max(0.01, omega);
 
  // The Ixx value and rotation speed given below are for rotation about the
  // natural axis of the engine. The transform takes place in the base class
  // FGForce::GetBodyForces() function.
 
  FGColumnVector3 vH(Ixx*omega*Sense*Sense_multiplier, 0.0, 0.0);
 
  if (omega > 0.01) ExcessTorque = PowerAvailable / omega;
  else             ExcessTorque = PowerAvailable / 1.0;
 
  RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * in.TotalDeltaT) * 60.0;
 
  if (RPM < 0.0) RPM = 0.0; // Engine won't turn backwards
 
  // Transform Torque and momentum first, as PQR is used in this
  // equation and cannot be transformed itself.
  vMn = in.PQRi*(mT*vH) + mT*vTorque;
 
  return Thrust; // return thrust in pounds
}

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◆ GetConstantSpeed()

int GetConstantSpeed ( void ) const

inline

Returns a non-zero value if the propeller is constant speed.

Definition at line 335 of file FGPropeller.h.

335{return ConstantSpeed;}

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◆ GetCpFactor()

double GetCpFactor ( void ) const

inline

Retrieves the coefficient of power multiplier.

Definition at line 272 of file FGPropeller.h.

272{ return CpFactor; }

◆ GetCpMachTable()

FGTable * GetCpMachTable ( void ) const

inline

Retrieves propeller power Mach effects factor.

Definition at line 285 of file FGPropeller.h.

285{ return CpMach; }

◆ GetCPowerRPMTable()

FGTable * GetCPowerRPMTable ( void ) const

inline

Retrieves propeller power RPM correction factor table.

Definition at line 290 of file FGPropeller.h.

290{ return cPowerRPM; }

◆ GetCPowerTable()

FGTable * GetCPowerTable ( void ) const

inline

Retrieves propeller power table.

Definition at line 280 of file FGPropeller.h.

280{ return cPower; }

◆ GetCtFactor()

double GetCtFactor ( void ) const

inline

Retrieves the coefficient of thrust multiplier.

Definition at line 269 of file FGPropeller.h.

269{ return CtFactor; }

◆ GetCThrustRPMTable()

FGTable * GetCThrustRPMTable ( void ) const

inline

Retrieves propeller thrust RPM correction factor table.

Definition at line 288 of file FGPropeller.h.

288{ return cThrustRPM; }

◆ GetCThrustTable()

FGTable * GetCThrustTable ( void ) const

inline

Retrieves propeller thrust table.

Definition at line 278 of file FGPropeller.h.

278{ return cThrust;}

◆ GetCtMachTable()

FGTable * GetCtMachTable ( void ) const

inline

Retrieves propeller thrust Mach effects factor.

Definition at line 283 of file FGPropeller.h.

283{ return CtMach; }

◆ GetDiameter()

double GetDiameter ( void ) const

inline

Retrieves the propeller diameter.

Definition at line 275 of file FGPropeller.h.

275{ return Diameter; }

◆ GetEngineRPM()

double GetEngineRPM ( void ) const

inlinevirtual

Calculates the RPMs of the engine based on gear ratio.

Reimplemented from FGThruster.

Definition at line 263 of file FGPropeller.h.

263{ return RPM * GearRatio; }

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◆ GetFeather()

bool GetFeather ( void ) const

inline

Returns true if the propeller is in feathered position.

Definition at line 329 of file FGPropeller.h.

329{ return Feathered; }

◆ GetHelicalTipMach()

double GetHelicalTipMach ( void ) const

inline

Retrieves the Mach number at the propeller tips.

Definition at line 333 of file FGPropeller.h.

333{return HelicalTipMach;}

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◆ GetInducedVelocity()

double GetInducedVelocity ( void ) const

inline

Get the propeller induced velocity.

Definition at line 339 of file FGPropeller.h.

339{return Vinduced;}

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◆ GetIxx()

double GetIxx ( void ) const

inline

Retrieves the propeller moment of inertia.

Definition at line 266 of file FGPropeller.h.

266{ return Ixx; }

◆ GetPFactor()

FGColumnVector3 GetPFactor ( void ) const

Retrieves the P-Factor constant.

Definition at line 395 of file FGPropeller.cpp.

{
  // These are moments in lbf per ft : the lever arm along Z generates a moment
  // along the pitch direction.
  double p_pitch = Thrust * Sense * (GetActingLocationZ() - GetLocationZ()) / 12.0;
  // The lever arm along Y generates a moment along the yaw direction.
  double p_yaw = Thrust * Sense * (GetActingLocationY() - GetLocationY()) / 12.0;
 
  return FGColumnVector3(0.0, p_pitch, p_yaw);
}

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◆ GetPitch()

double GetPitch ( void ) const

inline

Retrieves the pitch of the propeller in degrees.

Definition at line 257 of file FGPropeller.h.

257{ return Pitch; }

◆ GetPowerRequired()

double GetPowerRequired ( void )

virtual

Retrieves the power required (or "absorbed") by the propeller - i.e.

the power required to keep spinning the propeller at the current velocity, air density, and rotational rate.

Reimplemented from FGThruster.

Definition at line 323 of file FGPropeller.cpp.

{
  double cPReq;
 
  if (MaxPitch == MinPitch) {   // Fixed pitch prop
    cPReq = cPower->GetValue(J);
 
  } else {                      // Variable pitch prop
 
    if (ConstantSpeed != 0) {   // Constant Speed Mode
 
      // do normal calculation when propeller is neither feathered nor reversed
      // Note:  This method of feathering and reversing was added to support the
      //        turboprop model.  It's left here for backward compatiblity, but
      //        now feathering and reversing should be done in Manual Pitch Mode.
      if (!Feathered) {
        if (!Reversed) {
 
          double rpmReq = MinRPM + (MaxRPM - MinRPM) * Advance;
          double dRPM = rpmReq - RPM;
          // The pitch of a variable propeller cannot be changed when the RPMs are
          // too low - the oil pump does not work.
          if (RPM > 200) Pitch -= dRPM * in.TotalDeltaT;
          if (Pitch < MinPitch)       Pitch = MinPitch;
          else if (Pitch > MaxPitch)  Pitch = MaxPitch;
 
        } else { // Reversed propeller
 
          // when reversed calculate propeller pitch depending on throttle lever position
          // (beta range for taxing full reverse for braking)
          double PitchReq = MinPitch - ( MinPitch - ReversePitch ) * Reverse_coef;
          // The pitch of a variable propeller cannot be changed when the RPMs are
          // too low - the oil pump does not work.
          if (RPM > 200) Pitch += (PitchReq - Pitch) / 200;
          if (RPM > MaxRPM) {
            Pitch += (MaxRPM - RPM) / 50;
            if (Pitch < ReversePitch) Pitch = ReversePitch;
            else if (Pitch > MaxPitch)  Pitch = MaxPitch;
          }
        }
 
      } else { // Feathered propeller
               // ToDo: Make feathered and reverse settings done via FGKinemat
        Pitch += (MaxPitch - Pitch) / 300; // just a guess (about 5 sec to fully feathered)
      }
 
    } else { // Manual Pitch Mode, pitch is controlled externally
 
    }
 
    cPReq = cPower->GetValue(J, Pitch);
  }
 
  // Apply optional scaling factor to Cp (default value = 1)
  cPReq *= CpFactor;
 
  // Apply optional Mach effects from CP_MACH table
  if (CpMach) cPReq *= CpMach->GetValue(HelicalTipMach);
 
  // Apply optional Reynolds-number correction indexed by RPM
  if (cPowerRPM) cPReq *= cPowerRPM->GetValue(RPM);
 
  double RPS = RPM / 60.0;
  double local_RPS = RPS < 0.01 ? 0.01 : RPS;
 
  PowerRequired = cPReq*local_RPS*local_RPS*local_RPS*D5*in.Density;
 
  return PowerRequired;
}

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◆ GetReverse()

bool GetReverse ( void ) const

inline

Returns true if the propeller is in reverse position.

Definition at line 325 of file FGPropeller.h.

325{ return Reversed; }

◆ GetReverseCoef()

double GetReverseCoef ( void ) const

inline

Retrieves the reverse pitch command.

Definition at line 321 of file FGPropeller.h.

321{ return Reverse_coef; }

◆ GetRPM()

double GetRPM ( void ) const

inlinevirtual

Retrieves the RPMs of the propeller.

Reimplemented from FGThruster.

Definition at line 260 of file FGPropeller.h.

260{ return RPM; }

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◆ GetThrustCoefficient()

double GetThrustCoefficient ( void ) const

inline

Retrieves the thrust coefficient.

Definition at line 331 of file FGPropeller.h.

331{return ThrustCoeff;}

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◆ GetThrusterLabels()

string GetThrusterLabels	(	int	id,
		const std::string &	delimeter
	)

virtual

Generate the labels for the thruster standard CSV output.

Reimplemented from FGThruster.

Definition at line 408 of file FGPropeller.cpp.

{
  std::ostringstream buf;
 
  buf << Name << " Torque (engine " << id << ")" << delimeter
      << Name << " PFactor Pitch (engine " << id << ")" << delimeter
      << Name << " PFactor Yaw (engine " << id << ")" << delimeter
      << Name << " Thrust (engine " << id << " in lbs)" << delimeter;
  if (IsVPitch())
    buf << Name << " Pitch (engine " << id << ")" << delimeter;
  buf << Name << " RPM (engine " << id << ")";
 
  return buf.str();
}

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◆ GetThrusterValues()

string GetThrusterValues	(	int	id,
		const std::string &	delimeter
	)

virtual

Generate the values for the thruster standard CSV output.

Reimplemented from FGThruster.

Definition at line 425 of file FGPropeller.cpp.

{
  std::ostringstream buf;
 
  FGColumnVector3 vPFactor = GetPFactor();
  buf << vTorque(eX) << delimeter
      << vPFactor(ePitch) << delimeter
      << vPFactor(eYaw) << delimeter
      << Thrust << delimeter;
  if (IsVPitch())
    buf << Pitch << delimeter;
  buf << RPM;
 
  return buf.str();
}

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◆ GetTorque()

double GetTorque ( void ) const

inline

Retrieves the Torque in foot-pounds (Don't you love the English system?)

Definition at line 293 of file FGPropeller.h.

293{ return vTorque(eX); }

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◆ IsVPitch()

bool IsVPitch ( void ) const

inline

Returns true of this propeller is variable pitch.

Definition at line 222 of file FGPropeller.h.

222{return MaxPitch != MinPitch;}

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◆ ResetToIC()

void ResetToIC ( void )

virtual

Reset the initial conditions.

Reimplemented from FGThruster.

Definition at line 199 of file FGPropeller.cpp.

{
  FGThruster::ResetToIC();
  InitDynamics();
}

◆ SetAdvance()

void SetAdvance ( double advance )

inline

Set the propeller pitch.

Parameters

advance the pitch command in percent (0.0 - 1.0)

Definition at line 236 of file FGPropeller.h.

236{Advance = advance;}

◆ SetConstantSpeed()

void SetConstantSpeed ( int mode )

inline

Sets propeller into constant speed mode, or manual pitch mode.

Definition at line 242 of file FGPropeller.h.

242{ConstantSpeed = mode;}

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◆ SetCpFactor()

void SetCpFactor ( double cpf )

inline

Sets coefficient of power multiplier.

Definition at line 248 of file FGPropeller.h.

248{CpFactor = cpf;}

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◆ SetCtFactor()

void SetCtFactor ( double ctf )

inline

Sets coefficient of thrust multiplier.

Definition at line 245 of file FGPropeller.h.

245{CtFactor = ctf;}

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◆ SetEngineRPM()

void SetEngineRPM ( double rpm )

inlinevirtual

Sets the Revolutions Per Minute for the propeller using the engine gear ratio.

Reimplemented from FGThruster.

Definition at line 219 of file FGPropeller.h.

219{RPM = rpm/GearRatio;}

◆ SetFeather()

void SetFeather ( bool f )

inline

If true, sets the propeller in feathered position.

Definition at line 327 of file FGPropeller.h.

327{ Feathered = f; }

◆ SetInducedVelocity()

void SetInducedVelocity ( double Vi )

inline

Set the propeller induced velocity.

Definition at line 337 of file FGPropeller.h.

337{Vinduced = Vi;}

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◆ SetPFactor()

void SetPFactor ( double pf )

inline

Sets the P-Factor constant.

Definition at line 239 of file FGPropeller.h.

239{P_Factor = pf;}

◆ SetPitch()

void SetPitch ( double pitch )

inline

This commands the pitch of the blade to change to the value supplied.

This call is meant to be issued either from the cockpit or by the flight control system (perhaps to maintain constant RPM for a constant-speed propeller). This value will be limited to be within whatever is specified in the config file for Max and Min pitch. It is also one of the lookup indices to the power and thrust tables for variable-pitch propellers.

Parameters

pitch the pitch of the blade in degrees.

Definition at line 231 of file FGPropeller.h.

231{Pitch = pitch;}

◆ SetReverse()

void SetReverse ( bool r )

inline

If true, sets the propeller in reversed position.

Definition at line 323 of file FGPropeller.h.

323{ Reversed = r; }

◆ SetReverseCoef()

void SetReverseCoef ( double c )

inline

Set the propeller reverse pitch.

Parameters

c	the reverse pitch command in percent (0.0 - 1.0)

Definition at line 319 of file FGPropeller.h.

319{ Reverse_coef = c; }

◆ SetRPM()

void SetRPM ( double rpm )

inlinevirtual

Sets the Revolutions Per Minute for the propeller.

Normally the propeller instance will calculate its own rotational velocity, given the Torque produced by the engine and integrating over time using the standard equation for rotational acceleration \(a\): \(a = Q/I\) , where \(Q\) is Torque and \(I\) is moment of inertia for the propeller.

Parameters

rpm	the rotational velocity of the propeller

Reimplemented from FGThruster.

Definition at line 215 of file FGPropeller.h.

215{RPM = rpm;}

◆ SetSense()

void SetSense ( double s )

inline

Sets the rotation sense of the propeller.

Parameters

s	this value should be +/- 1 ONLY. +1 indicates clockwise rotation as viewed by someone standing behind the engine looking forward into the direction of flight.

Definition at line 254 of file FGPropeller.h.

254{ Sense = s;}

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The documentation for this class was generated from the following files:

Detailed Description

Configuration File Format

Configuration Parameters

Public Member Functions

Additional Inherited Members

Constructor & Destructor Documentation

◆ FGPropeller()

◆ ~FGPropeller()

Member Function Documentation

◆ Calculate()

◆ GetConstantSpeed()

◆ GetCpFactor()

◆ GetCpMachTable()

◆ GetCPowerRPMTable()

◆ GetCPowerTable()

◆ GetCtFactor()

◆ GetCThrustRPMTable()

◆ GetCThrustTable()

◆ GetCtMachTable()

◆ GetDiameter()

◆ GetEngineRPM()

◆ GetFeather()

◆ GetHelicalTipMach()

◆ GetInducedVelocity()

◆ GetIxx()

◆ GetPFactor()

◆ GetPitch()

◆ GetPowerRequired()

◆ GetReverse()

◆ GetReverseCoef()

◆ GetRPM()

◆ GetThrustCoefficient()

◆ GetThrusterLabels()

◆ GetThrusterValues()

◆ GetTorque()

◆ IsVPitch()

◆ ResetToIC()

◆ SetAdvance()

◆ SetConstantSpeed()

◆ SetCpFactor()

◆ SetCtFactor()

◆ SetEngineRPM()

◆ SetFeather()

◆ SetInducedVelocity()

◆ SetPFactor()

◆ SetPitch()

◆ SetReverse()

◆ SetReverseCoef()

◆ SetRPM()

◆ SetSense()