The European helicopter industry has until February 23 to answer a call for proposals under the Clean Sky joint technology initiative, a public-private partnership aimed at making aviation greener. The initiative comprises six integrated technology demonstrators, one of them called Green Rotorcraft. Targets include reductions in noise, carbon dioxide (CO2) and pollutant emissions.

The most recently issued call for proposals included development of computational tools that would provide laminar airflow on main rotor blades. This is one way to cut fuel burn. Maximum budget for this is €130,000 ($190,000).

Another project is active rotor blades. Adding flaps on the trailing edge of the blades could help offset slower rotation speeds, which improve fuel consumption. Maximum budget is €225,000 ($324,000).

Rotor hub reduction research is funded for €500,000 ($720,000). But maybe the most spectacular topic is “to design, develop and test a prototype electric tail-drive machine.” It is funded with a €2.5 million ($3.5 million) budget and is expected to last more than five years.

For turbine-powered helicopters, Green Rotorcraft has set an objective of 26 percent less CO2 emissions. Nitrous oxides (NOx) emissions should be cut by 65 percent. Noise should be reduced by 10 EPNdB.

For light helicopters, the goals are even more ambitious. Turboshaft engines could be replaced by diesel engines. Carbon dioxide emissions should be cut by 40 percent and NOx emissions by 53 percent. The noise target is the same as for turbine helicopters, -10 EPNdB.

Diesel Research
France-based engine maker Turbomeca used to be seen as a likely (and probably strong) contender in diesel technology for helicopters. However, senior v-p for product and market strategy Charles Claveau now seems less enthusiastic about diesel engines than he was previously. Cost is proving to be an expensive challenge, he said. Turbomeca does not want to go ahead with diesel-engine development unless there is a strong business case for diesel alternatives. “If you want it to be certified and able to fly at 20,000 feet, the cost is nowhere close to that of a car diesel,” Claveau summarized. Moreover, a diesel in the 300- to 500-shp range is suitable only for light singles. This also affects the business case. Eurocopter, for example,  manufactures only 30 to 35 EC120 singles per year, Claveau estimated.

Technical challenges with diesel engines remain. Although progress has been made on weight, with a power-to-weight ratio now feasible above one shp per kilogram (2.2 pounds), this would still be prohibitive for a twin-engine aircraft. Regardless, weight has to be cut further and this inflates the research and development cost. Therefore, Turbomeca is looking for other applications for a 300- to 500-shp diesel, and this would help spread non-recurring costs over higher production numbers.

Eurocopter has been urging the engine maker to launch a diesel research and development effort. In addition, the European Clean Sky joint technology initiative includes diesel research. Nevertheless, Turbomeca has not set any deadline to decide for or against further explorations of diesel technology.

Clean Sky, a ?1.6 billion ($2.3 billion) program, covers the 2008 to 2013 period.