Engine magnetos

[bomber64]

engine magnetos according to the manual is the property

propulsion/magneto_cmd

In flightgear it's not exposed in the property tree.

I have a 4 engines heavy bomber where I need to test each engines left right and both magneto functionality

Now I mentioned flightgear above but it's not for that simulation it's for another.

Is there anyway in the future I could have access to individual engines magnetos

regards

Simon

[seanmcleod]

Taking a look at the source code there is the ability to set the active engine.

jsbsim/src/models/FGPropulsion.cpp

Lines 817 to 818 in c867cc7

	PropertyManager->Tie("propulsion/active_engine", this, &FGPropulsion::GetActiveEngine,
	&FGPropulsion::SetActiveEngine);

Which is then used for magnetos, starter etc. Although there is no modelling of multiple magnetos per engine.

jsbsim/src/models/FGPropulsion.cpp

Lines 592 to 607 in c867cc7

	void FGPropulsion::SetMagnetos(int setting)
	{
	if (ActiveEngine < 0) {
	for (auto& engine: Engines) {
	// ToDo: first need to make sure the engine Type is really appropriate:
	// do a check to see if it is of type Piston. This should be done for
	// all of this kind of possibly across-the-board settings.
	if (engine->GetType() == FGEngine::etPiston)
	static_pointer_cast<FGPiston>(engine)->SetMagnetos(setting);
	}
	} else {
	auto engine = dynamic_pointer_cast<FGPiston>(Engines[ActiveEngine]);
	if (engine)
	engine->SetMagnetos(setting);
	}
	}

[bomber64]

Hi Sean, I'm not familiar with how that active engine code works as it's non functional in fightgear

Within the engine file exists this

sparkfaildrop 0.1 /sparkfaildrop
this is the percentage drop in horsepower for single magneto operation, 10% equaals 0.1

within the propulsion properties exists this property...... active_engine (as you identified in the code)

If I set its value to 1, can I assume it's working on engine 1 only ?
How does magneto_cmd property then work ?
If I set it to 3 does that put both magentos on...

If I then change active_engine to 2 whilst magneto_cmd is at 3 would that then turn engine 2 magneto both on. ?

Sorry to be a pain, but struggling to visualise this and flightgears property tree doesn't help in this particular case

Simon

[seanmcleod]

So given the following property binding:

jsbsim/src/models/FGPropulsion.cpp

Line 814 in c867cc7

PropertyManager->Tie("propulsion/magneto_cmd", this, (iPMF)nullptr, &FGPropulsion::SetMagnetos);

That means anytime the property propulsion/magneto_cmd is written to with an integer value, whether from a JSBSim XML based script, via the Python interface etc. the method FGPropulsion::SetMagnetos(int) is called.

And as shown in the code snippet I posted in the earlier post you'll see that if the ActiveEngine < 0 then the value written to the property is forwarded to all engines. Otherwise it's only forwarded to the active engine.

And by default:

jsbsim/src/models/FGPropulsion.cpp

Line 77 in c867cc7

ActiveEngine = -1; // -1: ALL, 0: Engine 1, 1: Engine 2 ...

Ignore the following statement I made, I assumed SetMagnetos(int) was really a boolean, 0 or 1.

Although there is no modelling of multiple magnetos per engine.

Whereas it's really:

jsbsim/src/models/propulsion/FGPiston.cpp

Lines 564 to 568 in c867cc7

	// Magneto positions:
	// 0 -> off
	// 1 -> left only
	// 2 -> right only
	// 3 -> both