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question

boufogre avatar image
boufogre asked boufogre commented

[BUG] VStab and HStab shaping algorithm

Hello,


How are exactly calculated the root and tip chord of both the horizontal and vertical stabilizers?


Seeing that no root chord is set in the config file, I understand the algorithm is different than the one given for the wing in the Flight Model Physics section of the SDK.

However, when using real dimensions, the shape is wrongly interpreted and give as a result two triangles opposed by a common point, as can be seen in the screenshot below:

1649151759591.png

In red, the leading edge, in yellow, the trailing edge.


The same happens with the VStab (same colour coding):

1649151974803.png


Could we get better control on the shape of these surfaces?

It could in the form of specifying their taper ratio for example, using hstab_taper_ratio and vstab_taper_ratio parameters, and specifying their root chords.


At least, could the above behaviour get fixed so that we have the proper shape of the stabilizers?

Thank you!

aircraftflightmodelbug
1649151759591.png (3.9 MiB)
1649151974803.png (3.0 MiB)
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boufogre avatar image
boufogre answered

Am I the only one here being bothered by this?

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boufogre avatar image
boufogre answered

So, if this is of interest to anyone at some point, it turns out the shape is NOT based on the Hstab or Vstab areas, but on the rudder and elevator areas.

Here is another screenshot showing the Vstab of the 747 with the area of the rudder to the one the full stab and as you can see, the shape is now correct:

1649405913491.png

To summarise: set the the rudder and elevator areas to the area of the full corresponding stabilizer to get the correct shapes.


1649405913491.png (3.4 MiB)
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GrimPhoenix9349 avatar image
GrimPhoenix9349 answered boufogre commented

So the question really is, do we use the correct areas for the elevator and rudder or do we artificially inflate them to get the shape correctly in the sim?

I did raise this quite a while back with Asobo and never got an answer.

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I'm using the effectiveness scalars to "reduce" the areas to real ones. But I think the SDK is wrong as it indicates we should use real dimensions, and this clearly does not work as described.
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Yep - real dimensions at least would give us a solid base and we could then 'nudge' things as required using coefficients / effectiveness scalars. A large part of the problem is that, if we do not use real dimensions and then put scalars on top, the whole thing becomes just a random guess. If each random guess only affected one thing you could get away with it but that's far from the case here.
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boufogre avatar image boufogre GrimPhoenix9349 ·
Hopefully, we can soon get a feedback from on of the devs.
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