‘Blended wing’ craft passes wind-tunnel tests

• 11:10 14 November 2005
• NewScientist.com news service
• Kelly Young

A futuristic "blended wing" plane developed by NASA has passed crucial wind-tunnel tests. These reveal that engineers may have overcome some of the controllability challenges associated with the revolutionary aircraft design.

Designs for blended wing planes are a dramatic leap from that of today's passenger jets – instead having a tube-like fuselage. They look more like paper aeroplanes with engines mounted on top and at the rear.

The unusual shape is much more aerodynamic than a normal plane, which means it could use 20% less fuel. And it should also be much quieter for people on the ground because the engines sit on top of its wings instead of hanging below.

But the extremely sleek design means doing away with a tail – a crucial control element – so engineers have had to come up with other ways to make the aircraft pitch, yaw and roll. For a blended wing plane, this means relying on curved flaps along the edge of each wing and rudders on each wingtip.

Lift drop

NASA engineers have struggled to find the perfect configuration for the design but the latest tests suggest they are getting closer. They took a 5% scale model of their latest blended wing design to a wind tunnel at Langley Research Center in Hampton, Virginia, US, for a free-flying test.

"We were kind of concerned early on that it was going to be difficult to fly,” says Dan Vicroy, head of the project at NASA. "The bottom line from the test: this particular configuration flew great."

The engineers were particularly keen to see what would happen when the aircraft approached maximum lift and then lift suddenly dropped, as can happen when an aircraft hits turbulence. Unlike previous designs, the aircraft did not start to roll or pitch backwards.

During wind tunnel tests, a model is normally mounted while wind flows around it, allowing engineers to measure forces on the static design. This time, however, three "pilots" remotely controlled the scale model's movement during the test. It was the first time anyone has tried such a test of a blended wing design.

Renewed interest

The other design challenge presented by a blended wing body is structural. A tube-shaped fuselage is easy to keep pressurized because pressure is distributed evenly inside. When you squash the tube down into such an irregular shape, it places more stress on the structure. NASA researchers hope to combat this by using composite structures and by adding pillars inside to add strength.

NASA has been researching the flying wing design since the early 1990s and has tested concepts with McDonnell-Douglas, which was taken over by Boeing in 1998. Next summer, Boeing and Cranfield University in the UK will test another blended wing design, the X-48B, at Dryden Flight Research Center in California, US.

Aircraft companies, such as Boeing, have discussed using such an aircraft for both commercial and military purposes. If a company were to start building a blended wing body aircraft today, it could hit the market in about seven years.

"With today’s gas prices, it’s getting renewed interest," Vicroy told New Scientist.