The second annual Electric Aircraft Symposium (EAS) held late last month offered a lot of theory and some progress. For now, the tone at EAS may suggest development of electric aircraft could follow the path of electric cars, and see their most immediate practical incarnations take the form of gas/electric hybrids. Boeing, which this year flew a small fuel cell aircraft, has one research group targeting a hybrid that could fly 300 miles per charge. That initiative is connected with a navigational control package that aims to take the work (fun?) out of flying and make it accessible to individuals without special training. That offering may appear sometime in the next few decades. Later this year, however, expect Pipistrel to offer its "world's first two seater self launching glider powered by electrical means." In August the CAFE (Comparative Aircraft Flight Efficiency) foundation will host a contest to test the practical application of current designs and award $50,000 to the most efficient aircraft.
As a near-term offering, Pipistrel's Taurus Electro aircraft (which has already flown) will be limited in range by the thermal seeking skills of its pilot. Its motor is intended for launch to 6,000 feet, but you can order one today for about $132,000, expect a 40:1 glide ratio, and delivery perhaps late this year. Pipistrel is hoping to work as an airframe supplier for the Stuttgart Institute of Aircraft Design's proposed fuel cell aircraft.
Current electric motors commonly peak at over ninety percent efficiency, which compares favorably to internal combustion engines that rarely achieve much better than 20 percent and are generally less efficient as they are scaled down. On the contrary, electric motors are efficient regardless of size, which encourages unique engine placement -- like inside the wing to blow air over the lifting surface and promote lower stall speeds. The challenge is storage. The battery systems promoted today -- Sonex E-Flight Initiative, Pipistrel Taurus Electro, and others -- generally only provide enough storage capacity for low-power flights of less than one hour while carrying more than 200 pounds of batteries. Batteries, unlike fossil fuels, do not get lighter as their energy is expended. For now, that makes flight planning easier and load carrying harder. And nanotechnology may be the future of battery structure, allowing it to move away from cells toward flexible mats of silicon nanowires that could theoretically hold up to ten times the lithium ions of conventional batteries.