Not When It Is A Vorten Tip!

By ANN Correspondent Juan Jimenez

One of the things we like about the regional fly-ins is that there is always some cool product that doesn't make it to the larger shows. The SWRFI show was no exception, and this time we got a look at the Vorten Tip.

The Vorten Tip is a patented wingtip vortex attenuating device developed from a concept tested in the Purdue University wind tunnel. It was designed by Ed Johnstone of Johnstone Aero out of San Antonio, TX. We all know that a lifting surface always has an associated induced drag which produces a vortex that trails behind it. Student pilots are taught about wingtip vortices, and those of us who fly in and out of airports servicing larger aircraft hear about them from ATC all the time.

The Vorten Tip takes air into an inlet located at the highest pressure point  on the airfoil, forces that high energy air through an aerodynamically designed plenum chamber and extrudes it through a reduced-area opening at the trailing edge. If you are familiar with the design of the P-51 Mustang cooling air scoop, you know what happens at the exit point - the air leaves at a much higher velocity than when it came in. With the Vorten Tip, this effect modifies the "helix angle" associated with the vortex by stretching it out. This has the effect of reducing induced drag, which is of course "a good thing."

So what does this all mean? The way Mr. Johnstone explains it, the Vorten Tip, which can be adapted to just about any "Hershey Bar" style wing, improves climb and short field performance. It also improves cruise speed at higher altitudes. Flight testing has been performed so far on a modified Piper Cherokee PA28-140. The testing has documented a 100 FT/MIN increase in rate of climb. Continued testing is being performed in order to optimize the inlet and outlet configurations.

An application for an STC has already been filed with the FAA to install the Vorten Tip on Piper Cherokees, and STC's for other aircraft are planned once the first one is completed.

FMI: Ed Johnstone, (210) 496-3847, ehjjaco@aol.com