With the cost of aviation fuel soaring, I'm not surprised to see engineering efforts to find alternatives to conventional aircraft fuel, either jet or piston-powered. Previously I wrote on this blog about efforts to find replacement aviation fuels, either by Virgin Atlantic looking at biofuel as an alternative for jet fuel, or a small start-up company, Swift Enterprises, working on a synthetic substitute for general aviation gas. While it will be interesting to watch these efforts to see if they ever become practical fuel replacements, some folks are looking at completely different power sources for aircraft, including hydrogen and electric power.

With technology allowing for lighter, more powerful and longer-lasting batteries (thanks to the general public's appetite for ever-smaller portable electronics, such as laptops, cell phones and music players), you are starting to see the fledgling attempts to power a light aircraft with electric power alone. The radio controlled scaled aircraft industry has been building electric powered aircraft for a number of years, as has the UAV industry. Of course the technology is nowhere near advanced enough to allow large aircraft such as airliners to fly on electric power, but some smaller companies are attempting to see if electric power is practical for light general aviation airplanes. Though human-carrying electric aircraft have flown before, they have basically been experimental, very unique aircraft. The successful ones have used aircraft-mounted solar cells to provide power to the electrical motor instead of on board batteries. Such aircraft include the Solar Challenger, developed by pioneering aeronautical engineer Dr. Paul MacCready, that successfully flew across the English Channel in 1981. Another solar powered aircraft is the SunSeeker, which used solar panels and soaring flight techniques to fly across the U.S. successfully in 1991. Taking the design of a piloted solar powered aircraft to the extreme, a European team is developing an aircraft, called Solar Impulse, that they hope to fly non-stop around the world. Since this effort will take several days, the aircraft will require some type of on board batteries that can be charged during the day so they can power the electric motor during nighttime.

Although these solar-powered aircraft are great aerospace engineering achievements, the cost of solar panels and the need for steady sunshine still make them impractical as everyday aircraft. The next step we are starting to see is the development of battery-powered electric aircraft. It started with self-launching motor gliders, such as the AliSport Targa 2, and the Antares 20E. Putting an electric motor in a sailplane is a good place to start, since sailplanes are the most aerodynamically efficient flying vehicles. Getting to an altitude to begin soaring doesn't require a large engine or much fuel, so it was the logical place to add an electric power system for self-launching.  The next step in electric aircraft development is to go beyond providing enough power (usually only about 10 minutes)  for self-launching, to providing enough energy for sustained horizontal flight of at least one hour or more. This would make a piloted electric aircraft more practical for local fun flying or short cross country flights. Several such planes now under development include Sonex Aircraft's E-flight Initiative, the ElectraFlyer-C and the Pipistrel Taurus ELECTRO, the latter two which have already flown. In fact interest in electric-powered aircraft is increasing so rapidly that a recent technical symposium was held in San Francisco to discuss the latest technical achievements in electric flight.  These promising developments have also lead to the Experimental Aircraft Association (EAA) to petition the FAA to authorize electric motors in ultralights and light sport aircraft.

We are still a long way from having electrically-powered commercial (i.e. carrying passengers for hire) aircraft. However, these recent encouraging developments indicate that it may not be too long before pilots will be able to safely fly a less costly, environmentally friendly, electric aircraft for sport and recreation purposes.