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SWS-AlexVletsas avatar image
SWS-AlexVletsas asked SWS-AlexVletsas commented

Setting combustion off forces engine RPM to 0

When setting combustion to OFF using the A:var (reciprocal engine), engine RPM instantaneously goes to 0 on the next frame. When combustion is stopped through "regular means" such as turning the magnetos to OFF, the combustion flag goes to 0 but the engine smoothly decelerates.

Is it possible to make the propeller behaviour consistent?

aircraft
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FlyingRaccoon avatar image
FlyingRaccoon answered FlyingRaccoon commented

Hello @SWS-AlexVletsas

I think you will have this behaviour if you write to GENERAL ENG COMBUSTION EX1 instead of GENERAL ENG COMBUSTION

Regards,
Sylvain

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I tried it and it did not work. The EX1 variable turns to 0 and is reset to 1 on the next cycle.
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FlyingRaccoon avatar image FlyingRaccoon ♦♦ SWS-AlexVletsas ·
Are you not writing to it somewhere else? I ran my tests on the Asobo TBM and it worked.
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SWS-AlexVletsas avatar image SWS-AlexVletsas FlyingRaccoon ♦♦ ·
There are no other instances where I'm setting the combustion variable, only there. The aircraft uses a piston engine. When setting the magnetos to off, either by code or using the switch, the engine decelerates smoothly. Cutting fuel using the mixture lever or fuel selector also stops it smoothly.

Setting the combustion to 0 by code freezes it. Setting Combustion EX1 doesn't do anything and it resets back to 1 on the next frame.

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B21 avatar image
B21 answered FlyingRaccoon edited

SWS-AlexVletsas can you be more specific about your sequence, so I could reproduce it? There is no SimVar called A:var. I'm guessing your aircraft is on the ground during this test. Can you reproduce this with a stock aircraft, e.g. the Cessna 152? If so can you let me know the simplest plane? I think you have an issue with the ENGINE behaviour, not the propeller behaviour, although I accept those things appear bolted together in the model.

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You can try with the Asobo TBM. Writing 0 to GENERAL ENG COMBUSTION will instantly stop the propeller while writing 0 to GENERAL ENG COMBUSTION EX1 will have it decelerate smoothly.

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B21 avatar image
B21 answered FlyingRaccoon commented

I've realised this thread assumes the plane is on the ground, so my hope someone might have found a way to stop the propeller rotating more generally (i.e. including in the air) doesn't apply.

Raccoon is that a typo in your comment? i.e. your "1" would be a zero hence 0 (>GENERAL ENG COMBUSTION:1, Bool).

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This is an area were I am also struggling , both the slow down of the prop at the end of a cranking start failure, as well as matching associated appropriate sound, to that slowdown to stop transition.


So watching with interest to see how this develops :)
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Yes, I meant 0 obviously.
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FlyingRaccoon avatar image
FlyingRaccoon answered SWS-AlexVletsas commented

@SWS-AlexVletsas Some additional details:

The GENERAL ENG COMBUSTION EX1 simvar depends on other factors.

On turbines, if auto_ignition is enabled and ignition_auto_type is set to always on (empty string or omitted parameter), the combustion will logically be reset to 1 instantly.

On piston engines, if you set the simvar to 0 but magnetos are on and engines are running fast enough to restart, combustion will be set to 1 as well.

May I ask what are you trying to achieve?
If you're trying to stop combustion on a piston engine, I'd say using the magnetos simvars is more appropriate.

Regards,
Sylvain

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@flyingRaccoon I tried using the magneto simvars as well, but this resulted in the key being turned with them. As the current engine/electrical systems do not support PMAGs, the only way to do it is to null the combustion Simvar.


To explain a bit further: the plane with said problem is the RV-14 which is equipped with P-MAGs and a test switch for them. Setting the switch to TEST will disconnect the P-MAGs from the electrical system. If the engine has sufficient speed to maintain a combustion it will, but if it drops below 1000rpm the engine will stop, regardless of the magneto position.

As I cannot set the rpm threshold through the engine file and setting the magnetos triggers the animation, turning off the engine with one of the combustion flags is the only way I can think of to shut down the engine.

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