Does anyone happen to have a reference or such that explains the naming convention used by Prof. Wortmann for his airfoils?

Usually it follows that for symmetrical ones, the first 2 digits are to indicate the planned transition location at zero alfa and the last 3 for for the thickness.

ex: fx76-120 -> fx (prefix for FX.Wortmann) 76 (transition) 120 (12%)

would like to double confirm this with a reference if available and also the meaning of the middle letters used in some foils.

Ex: FX76-MP-150 (MP for man-powered in this case but there are many more) 2 is known thanks to Peter Kampf. Any idea on remaining?

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1 Answer 1


FX stands for Franz Xaver, Professor Wortmann's given names.

The next two digits stand for the year this airfoil has been designed. Add '19' in front and you have the full year.

Then may follow one or two optional letters which specify a dedicated use, but they can be missing for general purpose airfoils. For example, the 'L' in FX 71-L-150/30 stands for "Leitwerk" which in German is the name for the combination of the horizontal and vertical tail surfaces.

The next three digits denote the relative thickness times one thousand. So the "150" in FX 71-L-150/30 tells us that this airfoil is 15% thick.

The last digits are again optional and denote the relative flap chord in cases of control surfaces, this times in percent. The FX 71-L-150/30 is optimized for a 30% chord control surface.

Reference: Stuttgarter Profilkatalog ISBN 3-528-08464-2, 1981.

  • $\begingroup$ Thanks @Peter Kampf, I will double-check your first pointer on the year. I am not 100% sure on this. If you happen to have a reference handy for this and willing to share, that is highly appreciated. $\endgroup$
    – user46017
    Mar 18, 2020 at 2:26
  • $\begingroup$ Also, may I kindly request you to have a look at this question as well. aviation.stackexchange.com/questions/75385/… $\endgroup$
    – user46017
    Mar 18, 2020 at 2:27
  • $\begingroup$ The Althaus airfoil use the same convention for the year?, It could be that yes (e.g. AH 93-K-132/15) $\endgroup$
    – andy
    Nov 5, 2023 at 16:08
  • 1
    $\begingroup$ @andy Yes, Althaus continued the work of Wortmann and used the same convention. K stands for Klappe, so this is an airfoil of 13.2% thickness and optimized for a 15% flap. $\endgroup$ Nov 5, 2023 at 18:19

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