Augmentation Method 0

[papygreg]

Hi folks !
I have tried to tie the augmentation method 0 to the FCS using the following lines :

<!-- engine 1 augmentation -->
			<switch name="names/throttle/augmentation">
				<default value="0"/>
					<test logic="AND" value="1">
					  fcs/throttle-pos-norm ge 75
					  propulsion/engine/n2 ge 84
					  /engines/engine/running == 1
				  </test>
				<output>/engines/engine/augmentation</output>
			</switch>
			<!-- engine 2 augmentation -->
			<switch name="names/throttle1/augmentation">
				<default value="0"/>
					<test logic="AND" value="1">
					  fcs/throttle-pos-norm ge 75
					  propulsion/engine[1]/n2 ge 84
					  /engines/engine[1]/running == 1
				  </test>
				<output>/engines/engine[1]/augmentation</output>
			</switch>

Unfortunnatly nothing happens. I think I use a wrong path but i am unable to find the correct one.
Is anyone familiar with this issue ?
many thanks !

[dpculp]

Throttle-pos-norm is a value in the normalized range, 0.0 to 1.0, so it will never get to 75.

…

On Mon, 2022-10-17 at 08:06 -0700, papygreg wrote: Hi folks ! I have tried to tie the augmentation method 0 to the FCS using the following lines : <!-- engine 1 augmentation --> <switch name="names/throttle/augmentation"> <default value="0"/> <test logic="AND" value="1"> fcs/throttle-pos-norm ge 75 propulsion/engine/n2 ge 84 /engines/engine/running == 1 </test> <output>/engines/engine/augmentation</output> </switch> <!-- engine 2 augmentation --> <switch name="names/throttle1/augmentation"> <default value="0"/> <test logic="AND" value="1"> fcs/throttle-pos- norm ge 75 propulsion/engine[1]/n2 ge 84 /engines/engine[1]/running == 1 </test> <output>/engines/engine[1]/augmentation</output> </switch> Unfortunnatly nothing happens. I think I use a wrong path but i am unable to find the correct one. Is anyone familiar with this issue ? many thanks ! — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: <JSBSim-Team/jsbsim/repo- ***@***.***>

[papygreg]

Yes, i have tried also with values between 0.0 and 1.0 without any results

[bomber64]

Are the output properties correct ?

[papygreg]

Yes, we track the throttle-pos-norm value as well as the augmentation bool value. The throttle-pos-norm evolves correctly and is consistent with the throttle position we send to jsbsim. The augmentation bool stays at 0 at all times even if the conditions in the switch are reached

[bomber64]

I've not done augmentation before but I must admit I'd have expected JSBsim to have put the augmentation property in propulsion/engine[0] but of you say it's in engines/engine[0]..... Then who am I to say otherwise.

[papygreg]

The path is given in the FGTurbine source

[seanmcleod]

You haven't specified which engine you're using or shown the relevant snippet from your engine file around the augmentation method.

jsbsim/src/models/propulsion/FGTurbine.h

Lines 133 to 139 in f13d015

	augmented
	0 = afterburner not installed
	1 = afterburner installed
	augmethod
	0 = afterburner activated by property /engines/engine[n]/augmentation
	1 = afterburner activated by pushing throttle above 99% position
	2 = throttle range is expanded in the FCS, and values above 1.0 are afterburner range

So depending on the augmentation method specified the FGTurbine code could be updating it on each time step.

jsbsim/src/models/propulsion/FGTurbine.cpp

Lines 231 to 252 in f13d015

	if (AugMethod == 1) {
	if ((ThrottlePos > 0.99) && (N2 > 97.0)) {Augmentation = true;}
	else {Augmentation = false;}
	}
	if ((Augmented == 1) && Augmentation && (AugMethod < 2)) {
	thrust = MaxThrustLookup->GetValue() * MaxThrust;
	FuelFlow_pph = Seek(&FuelFlow_pph, thrust * ATSFC->GetValue(), 5000.0, 10000.0);
	NozzlePosition = Seek(&NozzlePosition, 1.0, 0.8, 0.8);
	}
	if (AugMethod == 2) {
	if (AugmentCmd > 0.0) {
	Augmentation = true;
	double tdiff = (MaxThrust * MaxThrustLookup->GetValue()) - thrust;
	thrust += (tdiff * AugmentCmd);
	FuelFlow_pph = Seek(&FuelFlow_pph, thrust * ATSFC->GetValue(), 5000.0, 10000.0);
	NozzlePosition = Seek(&NozzlePosition, 1.0, 0.8, 0.8);
	} else {
	Augmentation = false;
	}
	}

So the first thing to confirm is what augmentation method you have specified in your engine file. You have mentioned in your original post that you're trying to use augmentation method 0, but seeing is believing 😉

[papygreg]

There you go

-- File: F119-PW-100.xml Author: Aero-Matic v 0.8 Inputs: name: F119-PW-100 type: turbine thrust: 37000.8 lb augmented? yes injected? no -->

<turbine_engine name="F119-PW-100">

<milthrust> 26950.0 </milthrust>

<maxthrust> 37000.0 </maxthrust>

<bypassratio> 0.2 </bypassratio>

<tsfc> 0.8 </tsfc>

<atsfc> 1.95 </atsfc>

<idlen1> 40.0 </idlen1>

<idlen2> 53.0 </idlen2>

<maxn1> 100.0 </maxn1>

<maxn2> 100.0 </maxn2>

<augmented> 1 </augmented>

<augmethod> 0 </augmethod>

<injected> 0 </injected>

It is a turbine engine set with the good parameters. I have put the switch function in the throttle Control part

[papygreg]

In fact, I just realised augmentation methods 0 & 1 are all or nothing. So I'm digging into the augmentation method 2. Then, the question is how to expand the throttle-pos range in the fcs. Digging through the code get me to realize only value between 0 and 1 are allowed for the throttle-pos

[dpculp]

The T-38 model in the aircraft repository is an example of how to use augmentation method 2. In this case the throttle command (0.0-1.0) is multiplied by 2 using a pure_gain FCS element. So the value is now mapped to the throttle position in the range 0.0-2.0. The turbine model will now treat the range 0.0-1.0 as unaugmented, and the range

1.0-2.0 as augmented.

You can change the multiplier value in step one above to alter the proportion of your physical throttle range that will be allotted for afterburner use.

[papygreg]

Thanks, I will check that tomorrow!