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Avoid propeller spinning in the wind (issue #2581)

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Some propellers could start windmilling very easily under mild wind conditions (11 kts). And in stronger wind the propeller could even generate some power and torque strong enough to turn the aircraft upside down.

This was due to the combination of:
- Propellers generating power (wind turbine) for advance ratio higher than 1.0 (is it plausible !?!)
- Powers and torques computed with ludicrously small RPMs.

So this commit basically filters out extremely small RPMs in order to avoid huge numbers resulting from division by small values.
This commit is contained in:
Bertrand Coconnier 2021-05-29 15:59:56 +02:00
parent 3bef9e7747
commit d310b84bdf
1 changed files with 9 additions and 3 deletions
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12
src/FDM/JSBSim/models/propulsion/FGPropeller.cpp
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@ -161,9 +161,15 @@ FGPropeller::FGPropeller(FGFDMExec* exec, Element* prop_element, int num)
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";
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);
}
@ -219,7 +225,7 @@ double FGPropeller::Calculate(double EnginePower)
double Vtip = RPS * Diameter * M_PI;
HelicalTipMach = sqrt(Vtip*Vtip + Vel*Vel) / in.Soundspeed;
if (RPS > 0.0) J = Vel / (Diameter * RPS); // Calculate J normally
if (RPS > 0.01) J = Vel / (Diameter * RPS); // Calculate J normally
else J = Vel / Diameter;
PowerAvailable = EnginePower - GetPowerRequired();
@ -278,7 +284,7 @@ double FGPropeller::Calculate(double EnginePower)
FGColumnVector3 vH(Ixx*omega*Sense*Sense_multiplier, 0.0, 0.0);
if (omega > 0.0) ExcessTorque = PowerAvailable / omega;
if (omega > 0.01) ExcessTorque = PowerAvailable / omega;
else ExcessTorque = PowerAvailable / 1.0;
RPM = (RPS + ((ExcessTorque / Ixx) / (2.0 * M_PI)) * in.TotalDeltaT) * 60.0;