T7 Stability Analysis, Elevator Tilt not displayed

[AirMarshal222]

Hi,

I am trying to reproduce a stability analysis I've done in XFLR5, to see if it can also be done in FLOW5. Currently, I am trying to access the elevator tilt option in AVL-Type Controls append control set option. For more context, I'd like to use the elevator tilt option to find the best incident angle for my elevator. However, all I see is this:

I've read through the stability analysis step-by-step guide and to my understanding that feature should be there, although in the few images I see, it's instead placed in a section called Surface Angles, which I do not see at all in the T7 Polar analysis setup, so I might be misinterpreting. Is the solution to instead just set the flap gains both to 1? I have read through some of the discussions and I see based on responses here: https://github.com/techwinder/flow5/discussions/29, that I might have to change the elevator tilt manually in the plane definition, and run a separate analysis each time?

Thank you in advance for any help.

[Flying-Geek]

Hi,
I believe the option to have the lifting surface's tilt angle as a control parameter has been deprecated since v7.13.

Since your elevator is probably not the same size as your horizontal tail, unless you have an all-moving tail of course, using it as the control parameter is not equivalent to tilting the entire tail. The differences between using it instead of the incidence angle are likely very small compared to the overall uncertainties though.

Alternatively you can either use the T6 analysis, in which case you will need to set a static elevator tilt angle if you want to investigate the effects over the entire flight envelope, or you'll need to modify the plane itself and perform separate stability analyses for each plane.

A possible workaround might be to set the flap hinge forward of the airfoil leading edge itself, in which case the entire horizontal tail (or any lifting surface) should start behaving like a flap (elevator in this case). Then it should be possible to control the incidence angle of the entire tail in the stability analysis, the same you would be doing now with just your elevator. I have never tried that though, so it might not work or produce unexpected results.

Cheers,
Stefan

[AirMarshal222]

Hi Stefan,

That makes sense, thanks for the advice, I'll try to set the flap hinge at the airfoil leading edge and see what happens.