Dassault embraces green technology

By: Thierry Dubois

July 1, 2009
Aircraft

With an eye toward ever-increasing environmental awareness, Dassault Aviation is aiming for 2020 entry into service for new technologies that will reduce the fuel burn of future Falcon business jets by 40 percent from that of current in-production Falcons.

Ten percent of that improvement would come from the engines’ specific fuel consumption, Dassault head of research Bruno Stoufflet said during a press briefing late in May at the company’s Bordeaux final assembly line. The rest would come from design of the airframe and its systems. Carbon dioxide emissions, which are proportional to the aircraft’s fuel consumption, would thus also be cut by 40 percent.

One area being explored by Dassault is an all-electric system architecture–eliminating pneumatic and hydraulic systems–that uses smaller power generators. For example, the installed power for systems on a Falcon 2000 is electric (33 kW), hydraulic (33 kW) and pneumatic (550 kW). While each power generator has to be sized for the maximum demands of its related systems, the three generators are never used at their peak power simultaneously. Moreover, the total power requirement for a Falcon 2000 averages 85 kW. “The installed power represents 14 percent of the propulsive power, while the average power used represents 3 percent,” Stoufflet said.

Unifying power by moving to electricity therefore reduces the maximum power needed. For a Falcon 2000, this would be just 195 kW. Another reason for the decrease is that some electrical systems need less power than their pneumatic counterpart. The bottom line is that smaller power generators save weight.

Moving to an all-electric aircraft also suggests control surfaces will be moved electrically. Today, flight controls are electric but power for the control surfaces is still hydraulic. Discussing control surfaces, Stoufflet hinted at the future addition of a forward lifting surface (à la Avanti), possibly one incorporating movable parts. This could offset the effect of the empennage, which creates negative lift, therefore allowing a smaller wing, with the attendant benefits in weight and drag reduction. “However, the benefit is not obvious if you consider all the necessary [contingency] modes,” Stoufflet asserted.

Meanwhile, Dassault believes the aircraft’s noise footprint could be halved, possibly by relocating the engines above the horizontal tailplane, although such a change could prove complex to design. For example, Stoufflet noted, jet outflow interaction with control surfaces is highly variable and needs to be thoroughly researched.

New software tools allow engineers to address environmental effects earlier in the design process. For example, design engineers can precisely calculate how a lower cruise speed translates into reduced CO2 emissions, and the same goes for noise predictions.

Dassault is also working to make its aircraft production processes more efficient.

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