JSBSim Turboprop starting

[Soitanen]

I have problem - I cannot start my turboprop engine, if it is shutted down. I tried the same procedure, as on jet turbines:
- /controls/engine/starter=true
- wait some time
- /controls/engine/cutoff=false
and engine will start. On turboprop nothing happens when I set starter to true. How can I start engine using controls?

[erik]

I needed this too so I looked at the code:

- /controls/engine/starter=true
- bring /fdm/jsbsim/propulsion/engine/n1 above 15
- /controls/engine/cutoff=false

Erik

[dg-505]

Hi all,

I'm also trying to start the turboprop engine of the Twin Otter. I'm orientating on the Beechcraft 1900 because they have similar engines (both are PT6A)

I observed that the property engines/engine[0]/starting is set to true while the engine is starting, but in the code I didn't find an alias or a binding that sets this property to true, so I think this property is handled somehow internally by the FDM and there are ceratin requirements that have to be met to get the engine starting.

Can someone please tell my if my assumption is correct, and what these requirements are?

Thanks in advance
Jonathan

[Josh_grtuxteam]

I needed this too so I looked at the code:

- /controls/engine/starter=true
- bring /fdm/jsbsim/propulsion/engine/n1 above 15
- /controls/engine/cutoff=false

Erik

i confirm the engine related
using propulsion/engine/n1 = 20 do the job



Josh

[dg-505]

@Josh
Yeah, I've already understood that, but in my case n1 doesn't even rise.
Now I need to know under what conditions the engines actually spool up.

[Josh_grtuxteam]

@dg-505

Like Eric did say +> /controls/engine/starter=true => /controls/engine/cutoff=false should answer .
About the process, I would recommend
=> first /controls/engine/cutoff=false
and
then with multiple binding to do
=> /controls/engine/starter=true => /fdm/jsbsim/propulsion/engine/n1 = 20 ............. at the same moment

Josh

[dg-505]

Ah, thanks Josh, now we get closer

When setting fdm/jsbsim/propulsion/engine/n1 to 20 manually e.g. using the property browser and then switching engines/engine/cutoff to false, then the engine starts correctly!

That brings me to the next question: In systems.nas of the b1900d there is the following nasal block (lines 498 - 529):

Code: Select all

var update_engine = func(eng){
    if(FDM=="jsb")return;
    N1[eng] = getprop("engines/engine["~eng~"]/n1");
    var rn=getprop("engines/engine["~eng~"]/running");
    var cnd =getprop("controls/engines/engine["~eng~"]/condition");
    var cutoff =getprop("controls/engines/engine["~eng~"]/cutoff");
    var tm=getprop("sim/time/delta-sec");
        if(rn){
                setprop("instrumentation/eng-gauge/fuel-pph["~eng~"]",getprop("engines/engine["~eng~"]/fuel-flow-gph")* 6.72);
                setprop("controls/engines/engine["~eng~"]/condition-input",cnd);
                setprop("engines/engine["~eng~"]/n1",getprop("engines/engine["~eng~"]/n2"));
        }else{
            var ign= getprop("controls/engines/engine["~eng~"]/ignition");
            var strtr=getprop("controls/engines/engine["~eng~"]/starter");
                setprop("controls/engines/engine["~eng~"]/condition-input",0);
                if(strtr){
                N1[eng] = N1[eng] + (tm * 3);
                if(N1[eng]>15){
                    if(N1[eng]>30)N1[eng]=30;
                    if(ign==1){
                        if(cnd>0.01){
                            setprop("controls/engines/engine["~eng~"]/condition-input",cnd);
                        }
                    }
                }
            }else{
                N1[eng] = N1[eng] - (tm * 2);
                if(N1[eng]<0)N1[eng]=0;
            }
            setprop("engines/engine["~eng~"]/n1",N1[eng]);
    }
}


My question is specifically about the "if(FDM=="jsb")return;": What does "return;" do? In other words does this line cause that the code is executed only when the FDM is JSBSim or when the FDM is not JSBSim?

Thanks again for your help

[dg-505]

Another question:

The Engine file has a definition for n1

Code: Select all

<turboprop_engine name="PT6A-27">
    [...]
    <idlen1>                       60.0   </idlen1>
    <maxn1>                        96.0   </maxn1>
    [...]
</turboprop_engine>


But neither the wiki nor the JSBSim reference manual tell what exactly n1 is.

In Yasim, engine/n1 not defined, engine/n2 is the engine rpm, and engine/rpm is the propeller rpm.
In JSBSim, engine/n2 is not defined, as well as engine/rpm. engine/thruster/rpm seems to be the propeller rpm, so am I correct that engine/n1 is the engine rpm?

[dg-505]

Well, unfortunately not, but thanks

This page tells basically the same like the wiki (i.e. no clear statement what n1 exactly is.

[sanhozay]

Sorry, I deleted my post when I realised it didn't have any useful information.

For reference, it was a just a link to the FGTurboprop class reference:

http://jsbsim.sourceforge.net/JSBSim/cl ... oProp.html

[dg-505]

No problem, but thanks anyway

[wkitty42]

My question is specifically about the "if(FDM=="jsb")return;": What does "return;" do? In other words does this line cause that the code is executed only when the FDM is JSBSim or when the FDM is not JSBSim?

as i read it, it returns to whatever the caller was if the FDM equals jsb... in other words, that rest of that code block is for YASim... it is a jump out check in case we're not using the FDM it was written for...

FWIW: there is also work going on to move yasim properties into the same area along side the jsb properties... possibly also some aliasing to have properties show up in both places for those craft that expect them... there's been talk on the dev list about this in the last week or two...

[Josh_grtuxteam]

there is also work going on to move yasim properties into the same area along side the jsb properties... possibly also some aliasing to have properties show up in both places for those craft that expect them... there's been talk on the dev list about this in the last week or two...

@wkitty42 I don't understand, jsb has yet an alias feature which answer to most of the request, i have noticed it when maintaining the grtuxhangar.( you may check it with the models we are delivering )
To my opinion since jsb is powerful and flexible enough, it does NOT need any yasim property. (don't make me wrong i do not want open a fight jsb versus yasim)
Mixing both would be a crime
Well , i hope that project won't break the perfect enbedded jsbsim alias feature.


@dg-505
propulsion/engine/engine-rpm is the engine-rpm
n1 is a percentage

You may read carefully you Engines/XXXXX.xml file you will notice there is some reference to n1

Josh

[dg-505]

Okay, finally I think I figured it out:

To get a JSBSim Turboprop starting, there have to be met only two requirements:
1. /controls/electric/engine[~n~]/generator = 'true'
2. /engines/engine[~n~]/starter = ’true’

I.e. that seems to be completely independent from the electrical system or whatever...

Thanks all for your help!

[Josh_grtuxteam]

Good, you got it working

Though we ( our team ) don't use the same process, everything is done within JSBSim since , our AC can be flown stand alone, so not FG dependant

Josh