Or at least an approach to provide angst-free cross-country flying, as Michael Friend explained in his Electric Aircraft Symposium presentation last April at Rohnert Park, California. Friend, a Boeing engineer closely tied to the company’s early fuel cell work, is the owner and pilot of N787M, one of the earliest production kit Silence Twisters. The Twister is a Spitfire-like, retractable-gear light aircraft capable of cruising 146 on its Jabiru 80-horsepower engine. It’s capable of full aerobatic flight, and was converted to electric power in Germany for possible airshow demonstrations. The Twister’s designers also plan a lengthened wing that would make motor gliding possible. Friend noted the difference in energy density between available batteries and gasoline, explaining that 10 kilograms of gasoline (22 pounds – or about 3.75 gallons) had the energy of 450 kilograms (990 pounds) of lithium batteries. The gasoline cost $10 (April prices) while the battery pack cost $36,000. Despite the fact that the batteries will run through …