(June 2011) In the February issue, Robert Goyer reported on a project to convert Cessna Skyhawks to electric power. Many Skyhawks are used as trainers, and training flights seldom last more than 90 minutes; so batteries, though notoriously lacking in stamina, might be an adequate power source for this application.
Parenthetically, Robert mentioned that wingtip turbines — little windmills just behind the wingtips — could capture some of the energy of the tip vortices and return it to the batteries. I soon received an e-mail from a friend who objected that this sounded like some sort of harebrained perpetual-motion scheme. After all, your battery had to supply the energy that moved the airplane and created the tip vortex in the first place; wasn’t this something like charging the battery of an electric car with a rooftop windmill driven by the car’s own motion?
