Bob, Thank you for the mini-course in airfoils. We (certainly I) don't really know much about this aspect of the coupe; or, about airfoils in general. The few articles I've read on airfoils have been more technical than I wanted to read, and said very little about how the numbers affected specific aircraft. I've always just accepted airfoil numbers as just part of the magic that goes into flying.
Ken Doyle Springfield, Mo Alon N5477E ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <[email protected]> Sent: Thursday, June 15, 2000 9:07 PM Subject: Re: [COUPERS] Coupe airfoil > The airfoil is 43013. The only other aircraft to use the 43000 family of > airfoils is the ATR-42/72 air carrier turboprops. > > The airfoil is constructed by taking a symmetrical airfoil and bending the > leading edge down at the 15% point to form a 13% camber. The airfoil > achieves good low drag performance in cruise as would a symmetrical airfoil > and develops good lift coefficients at high angles of attack because of the > drooped leading edge. The airfoil has very little pitching moment which > lowers the trim drag, further reducing drag. > > The bad news is that the airfoil has a big problem with stall recovery and > must only be used in aircraft which are never allowed to stall. The problem > is that once stalled, the wing will not un-stall until a significantly > greater than stall speed is achieved. This would be considered undesirable > in a trainer or any service where good slow flight behavior is important. > > The unpleasant behavior of this series of airfoils worries me when someone > suggests trying to modify and improve the wing with vortex generators and > wing tip mods. This is an area to move very slowly in and, there are more > productive ways to improve performance. > > The five digit airfoils were very popular with NACA at the time of the > Ercoupes' development but they are easily improved upon by the six digit > airfoil series. When the Ercoupe was reincarnated as the Cherokee series a > six digit airfoil was chosen even though the wing could not be constructed > smoothly enough to achieve the benefits of laminar airflow. The more common > of the five digit airfoils are the 23000 series which are very common on > light twins and some singles although the airfoil shares the poor stall > behavior of the 43000 series. When you hear of a light twin loosing control > and rolling inverted after the failure of one engine, the airfoil is a big > contributor to the event. > > Is this more than you wanted to know about your wing? > > Good luck, > Bob Condon > __________________________________________________________________________ __ ____ > To unsubscribe from this list please send mailto:[EMAIL PROTECTED] > ___________________________________________________________ > T O P I C A The Email You Want. http://www.topica.com/t/16 > Newsletters, Tips and Discussions on Your Favorite Topics > __________________________________________________________________________ ______ To unsubscribe from this list please send mailto:[EMAIL PROTECTED] ___________________________________________________________ T O P I C A The Email You Want. http://www.topica.com/t/16 Newsletters, Tips and Discussions on Your Favorite Topics
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