File talk:Wing profile nomenclature.svg

Possible error in definition of thickness

I am most worried that there might be an error in the file regarding the definition of thickness.

Unfortunately I cannot find the answer. There are basically two definitions around:

• Thickness is measured perpendicular to chord. That is what is implied in the text and explicitly shown in Fig 5.5 of Bertin & Cummings 2009 ("Aerodynamics for Engineers"). That is what is shown in this file.
• Thickness is measured perpendicular to the camber line. That is what is explicitly written and drawn in Phillips 2010 p.26 ("Mechanics of Flight") where the author insists very strongly on the definition.

I have about 6 or 7 other textbooks in Fluid mechanics, Aircraft design, technical aeronautics at hand, which mention airfoil thickness but fail to define it precisely enough to tell.

Only one of the above definitions can be true. I am inclined towards the second solution (meaning my drawing is wrong) because

• My experience (using the book thoroughly) is that Phillips is extremely, extremely rigorous in his definitions
• The first definition does not allow one to draw the front section of the airfoil with a thickness distribution if it is highly cambered (such as on a turbine blade airfoil, see for example File:Chord length definition (en).svg.

Advice would be greatly appreciated. Thanks, Ariadacapo (talk) 19:35, 8 December 2011 (UTC)

OK, I found an explanation/description of the two conventions in Houghton & al 2003. Will update shortly. Ariadacapo (talk) 09:51, 10 December 2011 (UTC)