Control surfaces seem to deflect opposite to indicated direction

[Jasper]

Hello all,

It seems to me that the control surface deflections are opposite of what is indicated in OpenVSP. To test this I made a simple model and analysis with deflected control surfaces: a simple wing, with ailerons on both sides, and vertical tail with rudder. The control surfaces are grouped and all have a positive deflection gain of 1, such that the deflection should correspond to the indicator direction. Following right hand rule, root to tip, the aileron of the right wing should then deflect down as is indicated, and the rudder should deflect TE towards the right wing as is indicated. However, from the path of the trailing wakes in the viewer it seems that both the ailerons and rudder are deflected in the opposite direction. Also the forces (positive CFy) seem to confirm this.

Is something going wrong in VSPAERO, or am I misunderstanding/misinterpreting something?

Thanks!

Jasper

[Rob McDonald]

Are you looking at the model from the rear, or from the front?

Rob

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[corp...@gmail.com]

Hi,

although I'm still find some problems with control surfaces, I solved the problem you are referring about, grouping each control surfase separately and not together. At overview tab under Control Group Angles you will find two surfaces to manage. Give one surface positive angle and second surface negative angle, they will deflect in the same direction.

Hope this helps

Regards
Corrado

[corp...@gmail.com]

In this way I found more easy to manage the control surfaces deflected also in opposite direction.

But honestly it's not clear to me if this is the right way, i made many attempts and tried different combinations and up to now this is what seems to me working better.

Corrado

[Jasper]

Hi Rob and Corrado,

Rob, the wakes screenshot was taken from the front - sorry, unclear indeed- . Attached an isometric view, where you can still see the same trends of the wake lines.

Corrado, what problem do you have exactly when grouping them together? Normally the control surface deflection gain is the preferred method to set the default deflection direction. I grouped my ailerons together, and left both gains to 1 and 1, and set a positive deflection angle (see screenshot). This way the ailerons deflect opposite, due to the root to tip direction being opposite for each wing and the right hand rule following this direction. When changing the gains to 1 and -1, they move in the same direction with the same angle. So for me the grouping system and gains seems to be working as expected.

So both changing gain sign and changing deflection angle sign allow the ailerons and rudder to move in the correct direction.The only issue is that it seems that a negative gain is required to meet the indicated direction in OpenVSP. 

[corp...@gmail.com]

Hi Jasper,

thank you for your advice.
My problem is actually related to the use of flaps and ailerons together, as I explained in a previous post, where I could'nt  work  with two kind of surfaces at the same time and I could'nt manage the angle of deflection in a proper way.  Had you never problems in using flaps and ailerons all deflected in the same analysis ?

By the way: I was using models created in previous releases of OpenVsp (some model probably started in release 3.9) and I had crashes of VSP both with VLM and Panel method, quite all with control surfaces enabled.

Just to have an idea, and waiting for comments from Rob, I enclose one picture taken in Viewer during one of the unsuccessful analysis, where the position of ailreons are altered in a very strange way.

Corrado

[Jasper]

Corrado,

I have replied on your other topic, to keep the threads (and problems) separate - but yes, I can reproduce your problem as well.