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Simbol avatar image
Simbol asked jcomm edited

Turbo Prop, how to make it feather in the air properly?

Dear Asobo,

I am tweaking an Turbo prop engine, despite of the engine being shutdown and the prop feathered at Beta angle 85, it keeps spinning in the air (engine debug shows prop RPM at 350).. this is not the behavior I am looking for, the RPMs should reduce and eventually just stop.

I am not using legacy tables (my understanding, this would prevent me from going full prop_modern later), I also found this on the SDK documentation, where it says, the turbo Prop engine friction table is not longer used by MSFS.

1656919783016.png


So how we tweak this? how we make the props for turbo-props stop in flight?

Best,
Raul

aircraft
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Simbol avatar image
Simbol answered FlyingRaccoon converted comment to answer

Update

It seem the following parameter is the cause,


  1. prop_cx_parabol=1;


Setting this to zero, makes it feather properly.. setting it to one, and the propeller keeps spinning in the air.

How this can be tweaked? my understanding is the CX_parabol = 1 is the more modern formulas, and yet it would not allow the engine to feather properly.

Thanks in advance.
Raul

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FlyingRaccoon avatar image
FlyingRaccoon answered

Hello @Simbol

You probably want to have a look at those parameters, especially the first one.
Their description is inaccurate in the current doc version but will be fixed with SU10.

1657203883749.png

Regards,
Sylvain


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Simbol avatar image
Simbol answered

Hi Sylvain,

I have those variables set, I played with multiple numbers and the issued remained unless prop_cx_parabol was set to zero.

I have power_absorbed_cf = 1.0 and power_propeller_absorbed_cf = 1.0, and yet the propeller was not feathering correctly, keeps spinning.. only solution was to set prop_cx_parabol =0.. which is odd.

The if I change to prop_user_modern.. and I set the prop_mod_use_absorbed_torque=1, The issue remains despite of having the prop_cx_parabol set to 1 or zero.. propeller keeps spinning..

Is an odd behavior..

Any more clues?


Regards,
Raul

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jcomm avatar image
jcomm answered jcomm edited

Further to the above, I wonder why when with the new prop model, and in say the B350, we fail an engine and the prop feathers, flying in a sideslip doesn't make it rotate again.

We can see it stands still if we perform some kind of aileron roll, supposedly due to the relative airflow, but as we sideslip the aircraft then the lateral component should be enough for the prop to start rotating again...

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