Story ID: 
Emissions-reducing diesel under study at Eurocopter
By: Thierry Dubois
Caption: Eurocopter’s new high-compression, diesel engine is expected to bring better environmental performance to turbine-powered helicopters as large as the EC 13
Word Count: 461
Eurocopter’s new high-compression, diesel engine is expected to bring better environmental performance to turbine-powered helicopters as large as the EC 135.The goal of the program is to reduce CO2 emissions by 40 percent and NOx emissions by 53 percent. The company announced the program, dubbed “Bluecopter,” at the Paris Air Show in June. 
Olivier Jouis, head of Eurocopter’s environmental affairs, told AIN that Eurocopter has worked with MB Tech, a subsidiary of Mercedes-Benz, to derive the engine from an existing one in Mercedes’ E-class cars. A 30-percent reduction in specific fuel consumption translates into a 40-percent cut in CO2 emissions (measured against distance), according to Eurocopter calculations. These numbers use helicopters of the 2000 generation, such as the EC 120 and the EC 135, as a reference.
To reduce emissions, exhaust gases go through an oxidizing catalytic converter, which targets carbon monoxide and unburned hydrocarbons. Gases also travel through a filter, which retains particulates. Finally, the exhaust gases flow through a selective catalytic converter that eliminates most of the remaining NOx, turning it into nitrogen and water.
“With a piston engine, you can better adapt the power to your needs,” Jouis said. Compared to a turboshaft engine, a turbo-charged, diesel-fueled piston engine better maintains its power with increases in altitude and temperature. (Humidity, relative to altitude and temperature, has a negligible effect on engine performance, whether diesel or turboshaft.) However, weight remains a challenge for piston helicopter engines. “We are working on improving the power-to-weight ratio, which is still 2.5 times better with a turbine,” said Jouis. Lighter materials will come from the Formula 1 racing industry, but the reliability of automobile materials and engines must be brought to aviation levels.
For research purposes, the MB Tech engine will be operated only on the ground. Eurocopter is also working on another diesel engine that it expects to fly on an EC 120 airframe in 2011. AIN understands Turbomeca may be involved in the program. 
Jouis insisted Eurocopter is now putting environmental concerns at the heart of its strategy. “I am in charge of adding ‘green’ criteria to new programs, even military ones,” Jouis claimed. He said that along those lines, he’d rather see more metal and less composite materials in aircraft construction because the latter have poor environmental performance over a lifecycle.
Hybrid helicopters are also being researched. An architecture inspired by hybrid cars might enable the tail rotor to be powered electrically. This could eliminate the heavy and complex tail rotor shaft in the tail boom. Moreover, stored electrical energy could possibly be supplied to the main rotor in the event of a main (fossil-fueled) engine failure, giving a pilot two to five minutes of powered flight before needing to enter autorotation.