Combined with new powerplants developed under Clean Sky's Sustainable and Green Engines project, these technologies have been shown in simulations to enable advanced regional aircraft configurations to meet the Clean Sky target of reducing carbon-dioxide emissions by 10-20% and noise by 10 db relative to 2000 technologies, says Andrzej Podsadowski, GRA project officer.
“There are three main full-scale ground demonstrators: the composite fuselage barrel demo, the composite cockpit demo and the composite wingbox demo,” he says. “All of these apply to a 90-passenger turboprop.” Tradeoffs between advanced metallic and composite materials and manufacturing concepts have been conducted, leading to the selection of composite technologies for final demonstration.
“They are based on considerable weight reduction due to more innovative multi-functional layer and multi-layer architectures that ensure electrical conductivity and lightning resistance without additional weight,” says Podsadowski. “In addition, we will see better acoustic insulation, increased hail impact resistance and the possibility to embed sensors in the composite to monitor the health status of the structure and report any degradation of its mechanical properties.”
Other technologies have been down-selected across the airframe, from cockpit and cabin to wing. “For the wing, we are focused on high-performance devices for noise reduction,” he says. According to Podsadowski, the biggest challenges are a natural laminar-flow wing for reduced drag and fuel burn; load control and alleviation to save structural weight; and reducing external noise from high-lift devices and landing gear through aerodynamic optimization to reduce the turbulence they generate.
Construction and testing of the demonstrators planned under GRA runs from late 2012 to the end of 2015. Flight demos will focus on reducing or eliminating hydraulics and pneumatics and replacing them with electrical systems for ice protection, cabin pressurization and air conditioning, flight controls, landing gear operation and braking activation. This bleedless architecture will enable the engines to be more efficient at producing thrust. “This will be the first step toward the so-called all-electric aircraft, where all onboard utilities will use only the electrical power from generators driven by the engines.”
Technologies selected for flights testing on a modified ATR 72 include electrical environmental control and energy management systems, the latter providing 270-volt DC power distribution and control logic with electro-mechanical actuators for the rudder and landing gear providing electrical loads.
Wing load control and alleviation will be tested in the wind tunnel. Tunnel tests of low-nose nose and main landing-gear designs are scheduled for mid-2015. Also planned for 2015 are wind-tunnel tests of advanced regional-aircraft configurations: a 90-seat turboprop and two 130-seat aircraft, one powered by geared turbofans and one by open rotors. “Tradeoff studies are being performed on 130-seat configurations with under-wing and rear-fuselage geared engines,” says Podsadowski.