# Variable airfoils using the MulTabLoc USER function

**URL:** <https://forums.nlr.gov/t/variable-airfoils-using-the-multabloc-user-function/1006>\
**Category:** Computer-Aided Engineering Software Tools\
**Created:** [October 1, 2014, 9:18am UTC](https://forums.nlr.gov/t/variable-airfoils-using-the-multabloc-user-function/1006 "2014-10-01T09:18:11Z")\
**Posts on this page:** 1\
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**Author:** ![Niklas.Theilig](https://avatars.discourse-cdn.com/v4/letter/n/7bcc69/32.png) [@Niklas.Theilig](https://forums.nlr.gov/u/Niklas.Theilig)\
**Post date:** [October 1, 2014, 9:18am UTC](https://forums.nlr.gov/t/variable-airfoils-using-the-multabloc-user-function/1006/1 "2014-10-01T09:18:11Z")

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Hello,

I’m using Fast v8.08 and I would like to activate the Aerodyn MulTabLoc function. Since I want to control the airfoil selection for some blade elements actively I chose the MulTabLoc “USER” option.  
I had a look at the source code but I could not figure out on my own how I have to modify the source code to provide a control signal (eg from a dll controller). Also I did not find where I have to fill in my own routine how it is mentioned in the AeroDyn manual on page 13 (“Use USER only if you supply your own algorithm  
in the dynamics code to move between airfoil tables during a Simulation.”).

Could you please give me a few hints for the necessary modifications.

Thank you in advance.

Niklas

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