A panel discussion at AERO focused on the opportunities and challenges of the proposed alternative propulsion systems of the future. The views were as enlightening as they were divergent.
Mike Kraft of Lycoming engines emphasized that traditional spark-ignition engines remain the most efficient at transforming avgas into power. Lycoming has been conducting tests with biomass fuels, but so far Lycoming has concluded that it will be difficult to anticipate the exact nature of future general aviation fuels.
“We’re anticipating the software and strategies that we may have to use,” Kraft said, adding, “If we go to a fuel that doesn’t have the current energy properties of avgas, traditional engines won’t behave the same. So airframe manufacturers, engine manufacturers, and fuel suppliers must all cooperate in developing a future fuel.”
Professor Rudolf Volt-Nitschmann of Stuttgart University somewhat disparagingly addressed solar power. “It makes no economic sense in general aviation. A solar engine for the typical general aviation airplane would cost about 200,000 euros [about $270,000]…more efficient diesel-electric hybrid designs are coming, and these would make more sense,” he said. “In the end, I think it will be a mix of strategies and engines in the future.”
AOPA Executive Vice President of Government Affairs Andy Cebula said, “AOPA is trying to defend the use of existing fuels as we watch and assist companies like Swift Enterprises, which is making a biomass-based fuel. An AOPA survey reported that 65-percent of our members feel that threats to 100LL avgas are their biggest concerns right now.” Cebula stressed that while avgas is a leaded fuel, “it is important to remember that general aviation uses a mere 250 million gallons per year. Automobiles, on the other hand, use 355 million gallons per day!”
Cebula said that room must be made for innovation and that organizations such as AOPA, the Experimental Aircraft Association (EAA), and the General Aviation Manufacturers Association (GAMA) must take the leadership on behalf of the users of any future fuels.
Norbert Lohl, director of certification for the European Aviation and Safety Agency (EASA), said that certification authorities are not always involved early enough in the development of new designs. In order to come up with safety and performance standards, certification agencies need to be educated by staying in contact with any research being performed by manufacturers.
“We take a conservative approach,” Lohl said. “And we cannot reduce the level of safety. So I invite industry and the research community to involve us early in the idea stream. It could take six to seven years for next-generation engines and fuels to be certified.”
Swift Enterprises’ Jon Ziulkowski said that his company’s biomass-based fuel offers realistic hope of an early alternative to traditional, leaded-hydrocarbon fuel. Swift has been working on biomass fuels for four years, Ziulkowski said.
“We can make a fuel that’s compatible with current engines, and can produce an increase in range of 10 to 13 percent,” he said. “Biomass fuels have one-half the manufacturing costs of avgas, and the acreage needed to meet the U.S. demand for general aviation avgas would take only one-eleventh the area of the state of Rhode Island.” Biomass-origin fuels weigh more than avgas, Ziulkowski said, adding that in a Piper Warrior or Arrow, for example, there would be a weight penalty in useful load of some 25 to 30 pounds.
Finally, Michael Feinig of Diamond Aircraft Industries offered that Diamond has tested a hydrogen-powered design under a partnership with Boeing, as well as an electrically powered motorglider. The motorglider design, if committed to production, may take two to three years to bring to market. Such an airplane would be able to cruise at 60 knots for up to two hours using battery power alone. Feinig said that kerosene-based jet fuels have the most promise today, and that its popularity will increase. He said that from Turkey to Japan, avgas is simply not available. “In the future, Diamond feels that a mix of jet fuel—and electrically powered aircraft stand the best chance of market acceptance,” Feinig said.