How to add new JSBsim component in unreal engine 5?

[cxr001]

I want to set vUVW value after running the engine, but I don't know how to write these code in JSBsim, and transfer them into UE5.
I also not sure how to use the autopilot in UE.

[cxr001]

Is there any more detailed tutorial for the JSBsim UE project? I am new to JSBsim and UE, and it is a little hard to learn all of these things.

[seanmcleod]

I want to set vUVW value after running the engine

Do you want to set UVW just once during initialization or are you wanting to change it while the simulation is running?

UVW can't be changed during simulation, they're read-only.

  PropertyManager->Tie("velocities/u-aero-fps", this, eU, (PMF)&FGAuxiliary::GetAeroUVW);
  PropertyManager->Tie("velocities/v-aero-fps", this, eV, (PMF)&FGAuxiliary::GetAeroUVW);
  PropertyManager->Tie("velocities/w-aero-fps", this, eW, (PMF)&FGAuxiliary::GetAeroUVW);

But you can set UVW as part of the initial conditions during initialization.

[cxr001]

I wish the airplane can realize different take-off methods, for example, by ejection. So the airplane should have a zero speed at first, although it has started the engine and has had some RPM at that time. Then start the engine, the airplane would have a speed suddenly, and these speed will be used just once. Could this be realised?

[seanmcleod]

When you say ejection, which normally refers to a pilot ejecting from an aircraft, do you mean you want some sort of vertical take-off?

Give us some more information on what you're trying to model and then we'll have a better chance of suggesting useful solutions.

[cxr001]

I mean a type of take-off, it will have a 0 speed but have started the engine at first, and then it would be given a force along the nose

[seanmcleod]

So use the initial conditions to set the engine running and then set the throttle to it's maximum.

[cxr001]

That speed is not enough. and the running engine would let the aircraft have a speed. I find that there is a file named FGExternalForce, could I use that in UE?

[seanmcleod]

Are you trying to model something like a catapult launch from an aircraft carrier? Where the engine is run up to maximum power and then the catapult provides an additional force for a particular distance? More details will help.

[cxr001]

Yes, it is something like a catapult launch

[seanmcleod]

Yep then take a look at using an external force.

[cxr001]

Thank you, I get it. and how to initialize the aircraft velocities or forces in UE?

[bcoconni]

Thank you, I get it. and how to initialize the aircraft velocities or forces in UE?

@gallonmate any idea ?

[gallonmate]

@cxr001 would need to confirm what they are asking. I believe they are asking which property can be used to apply some External Force on an aircraft, to simulate a catapult or external force launching a vehicle. But I do not know External Force so I cannot help there.
@cxr001 now appears to successfully be setting properties in Unreal Engine, seen in #813. So they would only need to know the property name and value to be using.

[cxr001]

Yes, I need to know the name of property, which can be used to apply some External Force, or any property to set the initial conditions of the UAV's speed ,or let the engine be idling.

[bcoconni]

There are quite a number of examples in the aircraft models that are provided with JSBSim. Just search for <external_reactions> in the aircraft folder.

Below are a few examples (you'll need to scroll on some of them to review the whole code snippet) :

jsbsim/aircraft/787-8/787-8.xml

Lines 980 to 993 in 9a99b4b

	<external_reactions>
	<force name="pushback" frame="BODY">
	<location unit="IN">
	<x>-612.06718</x>
	<y>0</y>
	<z>-100</z>
	</location>
	<direction>
	<x>1</x>
	<y>0</y>
	<z>0</z>
	</direction>
	</force>
	</external_reactions>

jsbsim/aircraft/ball/ball.xml

Lines 100 to 132 in 9a99b4b

	<external_reactions>
	<!-- "Declare" the reefing term -->
	<property>fcs/parachute_reef_pos_norm</property>
	<force name="parachute" frame="WIND">
	<function>
	<product>
	<property>aero/qbar-psf</property>
	<property>fcs/parachute_reef_pos_norm</property>
	<value> 1.0 </value> <!-- Full drag coefficient -->
	<value> 20.0 </value> <!-- Full parachute area -->
	</product>
	</function>
	<!-- The location below is in structural frame (x positive
	aft), so this location describes a point 1 foot aft
	of the origin. In this case, the origin is the center. -->
	<location unit="FT">
	<x>1</x>
	<y>0</y>
	<z>0</z>
	</location>
	<!-- The direction describes a unit vector. In this case, since
	the selected frame is the WIND frame, the "-1" x component
	describes a direction exactly opposite of the direction
	into the wind vector. That is, the direction specified below
	is the direction that the drag force acts in. -->
	<direction>
	<x>-1</x>
	<y>0</y>
	<z>0</z>
	</direction>
	</force>
	</external_reactions>

jsbsim/aircraft/Boeing314/Boeing314.xml

Lines 1630 to 1646 in 9a99b4b

	<external_reactions>
	<documentation>
	anchor at nose tip.
	</documentation>
	<force name="anchor" frame="BODY">
	<location unit="IN">
	<x>0 </x>
	<y>0 </y>
	<z>0 </z>
	</location>
	<direction>
	<x>-1</x>
	<y>0</y>
	<z>-1</z>
	</direction>
	</force>
	</external_reactions>

jsbsim/aircraft/Concorde/Concorde.xml

Lines 1734 to 1747 in 9a99b4b

	<external_reactions>
	<force name="tractor" frame="BODY">
	<location unit="IN">
	<x> 736.2000 </x>
	<y> 0.0000 </y>
	<z> -100.0000 </z>
	</location>
	<direction>
	<x>1</x>
	<y>0</y>
	<z>0</z>
	</direction>
	</force>
	</external_reactions>

[seanmcleod]

You can have the engine running but with a zero value for the throttle, i.e. the engine just idling which would prevent the aircraft from starting to move until you increase the throttle and/or apply the external force from the catapult.

Or if you want to have the engine at full thrust then you'll need to apply the brakes to prevent any movement until you release the brakes.

[cxr001]

which function could I use to let the engine be idling?