Europe's Clean Sky joint technology initiative is the biggest aeronautical research program out there - Euro 1.6 billion over seven years, funded 50:50 by government and industry. And being European, it's also complicated - involving six integrated technology demonstrations (ITD) aimed at rotorcraft, corporate and regional aircraft, and narrowbody and widebody airliners, each with its own targets for noise and emissions reductions by 2020.
But specific areas of interest are becoming clearer as Clean Sky releases regular calls for research proposals. The latest set, Call 2 (which you can access here), has some interesting ideas.
Under the Green Rotorcraft ITD, Clean Sky is looking at a number of ideas to reduce drag and noise, including laminar-flow rotor blades and an active blade with retractable gurney flap that allows the rotor to be slowed down, making it quieter.
There also plans to demonstrate an electrically driven tail rotor, and to convert the waste heat from the engine, gearbox and avionics into electricity for the aircraft's 270V power bus, using thermo-electric generation.
Also, under the Sustainable And Green Engines (SAGE) ITD, the Turbomeca-led project to build a turbpshaft demonstrator is looking at lightweight titanium-aluminide low-pressure turbine blades and the use of weight-saving organic composites in oil tanks and inlet guide-vane casings.
Under the Green Regional Aircraft ITD, Clean Sky is looking for research proposals on composite structures with embedded fatigue sensors; flow control to reduce the noise generated air flowing round the edges of deployed flaps; and gapless leading-edge high lift devices using smart-material actuators.
Addiionally, under the Systems for Green Operations ITD, they plan to demonstrate a dispatch towing vehicle that would reduce airport noise and emissions by towing all classes of aircraft from the gate to the end of the runway.