All Wing, No Noise: Steve Cross

How would you design an aircraft if your main aim were to keep its roar from waking up the entire neighborhood during takeoffs and landings? A group of 40 engineers from the Massachusetts Institute of Technology and England´s University of Cambridge took on that challenge and, three years later, has unveiled designs for the SAX-40. Thanks to a host of noise-silencing innovations, the 215-seat airplane should be virtually inaudible outside the airport. Designers estimate that the aircraft will emit just 63 decibels at takeoff, about as loud as an average conversation. (Today´s airliners hit up to150 decibels.)

To achieve such relative silence, researchers needed to rethink nearly every aspect of the typical airliner. â€There´s no one thing you can do,†says Will Graham, who headed up the Cambridge airframe-design team. â€You have to treat all the noise sources.â€

Chief among them is the airframe. The faster a plane flies, the louder it roars. So Graham and his group designed the SAX-40 with a blended-wing body, a concept that jettisons the tube-and-wing approach for a tailless, triangular structure. That shape provides extra lift, enabling the plane to fly more slowly during takeoff and landings. It also saves a significant amount of fuel, getting some 35 percent more passenger-miles per gallon than a Boeing 777.

A number of other researchers, including at Boeing, are working on similar concepts. But challenges remain. An aircraft without a stabilizing tail would be far more difficult to fly. And then there´s the question of how to make its flattened fuselage as structurally strong as a cylinder. But perhaps the biggest hurdle is the airline industry´s financial investment in conservative design. Betting on such a radical plane, Graham says, â€would be a huge step for manufacturers.â€

WHAT MAKES THE SAX-40 SO QUIET?