Hi all!
I discover an opened letter about Mr. Riblett. (link: Riblett airfoils (Walter Lounsbery, David Lednicer, "highflyer"))
It's interesting, but I don't understand the point 2, why the induced drag doesn't depend from the airfoil? Maybe because the induced drag is the lift-generated drag, and the lift = weight so this is the point?
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From: David Lednicer <[email protected]> Newsgroups: rec.aviation.homebuilt Subject: Re: GA Airfoils Date: Thu, 02 Dec 1999 09:42:55 +0000 My experience with Riblett and his airfoils is this:
1) He does his airfoil design work with the Eppler code, a program with some serious shortcomings. I am not aware of his airfoils ever being wind tunnel tested. This is necessary to properly quantify their behavior.
2) He has claimed that the proper choice of airfoils can reduce induced drag. This is incorrect and shows a lack of knowledge of the subject.
3) I think he probably has improved the NACA 60-series airfoils a bit. His modifications probably do produce better stall characteristics.
4) The claim that his airfoils "lift better" is meaningless.
5) His claims about the harsh stall characteristics of the NACA 5-digit series are correct, but nothing new. His extrapolation of these claims, calling for the grounding of the ATR-42, show his ignorance of 3-D aerodynamics. There are a lot of aircraft with NACA 5-digit airfoils that stall just fine, because the stall behavior has been properly tailored. For more information, see the Incomplete Guide to Airfoil Usage at: http://amber.aae.uiuc.edu/~m-selig/ads/aircraft.html
6) His knowledge of US copyright and patent law is lacking. I wanted to include his airfoils in the UIUC airfoil database, but he claimed they were copyrighted, which is impossible. Airfoils can be patented (one of mine is) but not copyrighted. Because of his agitation, his airfoils are not in the database, but I have the coordinates in my own personal database. On the other hand, his "book" contains unapproved reprints of copyrighted material, which is illegal.
7) I am not aware of any rotorcraft airfoils he has designed. However, the UIUC database contains rotorcraft airfoils designed at Boeing and Sikorsky.
David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc.
--------------------------------------------------------------
Typhoon
I discover an opened letter about Mr. Riblett. (link: Riblett airfoils (Walter Lounsbery, David Lednicer, "highflyer"))
It's interesting, but I don't understand the point 2, why the induced drag doesn't depend from the airfoil? Maybe because the induced drag is the lift-generated drag, and the lift = weight so this is the point?
----------------
From: David Lednicer <[email protected]> Newsgroups: rec.aviation.homebuilt Subject: Re: GA Airfoils Date: Thu, 02 Dec 1999 09:42:55 +0000 My experience with Riblett and his airfoils is this:
1) He does his airfoil design work with the Eppler code, a program with some serious shortcomings. I am not aware of his airfoils ever being wind tunnel tested. This is necessary to properly quantify their behavior.
2) He has claimed that the proper choice of airfoils can reduce induced drag. This is incorrect and shows a lack of knowledge of the subject.
3) I think he probably has improved the NACA 60-series airfoils a bit. His modifications probably do produce better stall characteristics.
4) The claim that his airfoils "lift better" is meaningless.
5) His claims about the harsh stall characteristics of the NACA 5-digit series are correct, but nothing new. His extrapolation of these claims, calling for the grounding of the ATR-42, show his ignorance of 3-D aerodynamics. There are a lot of aircraft with NACA 5-digit airfoils that stall just fine, because the stall behavior has been properly tailored. For more information, see the Incomplete Guide to Airfoil Usage at: http://amber.aae.uiuc.edu/~m-selig/ads/aircraft.html
6) His knowledge of US copyright and patent law is lacking. I wanted to include his airfoils in the UIUC airfoil database, but he claimed they were copyrighted, which is impossible. Airfoils can be patented (one of mine is) but not copyrighted. Because of his agitation, his airfoils are not in the database, but I have the coordinates in my own personal database. On the other hand, his "book" contains unapproved reprints of copyrighted material, which is illegal.
7) I am not aware of any rotorcraft airfoils he has designed. However, the UIUC database contains rotorcraft airfoils designed at Boeing and Sikorsky.
David Lednicer | "Applied Computational Fluid Dynamics" Analytical Methods, Inc.
--------------------------------------------------------------
Typhoon
