X-48B Marks 50th Flight
<X-48B in flightThe Blended Wing Body aircraft made its 50th flight April 2 and is set to undergo an aggressive research flight series. (NASA Photo / Carla Thomas) The X-48B Blended Wing Body aircraft team April 2 notched a milestone when the experimental aircraft made its 50th flight.

Dryden and The Boeing Co. are conducting flight tests with the 500-pound, remotely piloted test vehicle that so far has examined parameter identification, a technique for developing models that can predict how the aircraft will fly, and maneuvers to research the limits of the aircraft in flight conditions that could cause it to stall.

Following the milestone flight, the aircraft began to have its software upgraded and its aerodynamic and propulsion system models updated to increase aircraft stability for a far more aggressive series of 25 flights. To this point, the flights have centered on gently probing the capabilities of the aircraft, said Tim Risch, X-48B project manager.

X-48B flight-testing is taking place at Dryden with center staff providing critical support to a Boeing-led project team that also includes the U.S. Air Force Research Laboratory in Dayton, Ohio, and Cranfield Aerospace Ltd., of Bedford, England.

"Accomplishing this many flights in a safe and successful manner with this class of X-plane is unprecedented in my career thus far; it says a lot about the experienced and dedicated NASA, Boeing and Cranfield Aerospace team that has worked on this project from the beginning. Flight test success does not happen by itself without excellent teamwork and knowledgeable personnel," said Gary Cosentino, X-48B flight operations engineer.

X-48B crew in front of hangarThe X-48B Blended Wing Body aircraft team has worked hard to keep the project flying high. So far, project team members say the aircraft is performing as well or better than expected. (NASA Photo / Carla Thomas) Now comes the nail-biting part - increasing the risk and aggressiveness of the flight research to examine and push the boundaries, or flight envelope, and how the aircraft performs at a number of maneuvers in the air, or angle of attack, Risch said.

"The fact that we are intentionally exploring the envelope limits and stall boundaries as part of the flight test is risky. So far the aircraft has been very well behaved and our pilots have always had positive control to recover from maneuvers; it flies extremely well with a robust flight control system," Cosentino said.

Following these flights, the BWB team will place limiters on the software for the aircraft to allow it to maintain control at the outer limits of its flight envelope. In a series of flights called Phase 1.5, researchers will engage in a 10-flight series to determine the effectiveness of all 20 flight control surfaces and how they best work together, Risch said.

"The plane has been very successful so far. The technology will eventually lead to the development of a larger flight version. We see no showstoppers. Technical integration is still a needed piece of the puzzle," Risch said.

In other words, the goals for the BWB in the Fixed Wing Subsonic program called for the integration of NASA-developed technologies to be used in a combination that ultimately results in a quieter aircraft that burns less fuel and is more environmentally friendly by drastically reducing emissions.

While the flight vehicle might still be off in the future, Risch said it is a logical next step for developing the next generation of aircraft.

NASA's participation in the blended wing body research effort is focused on fundamental, advanced flight dynamics and structural design concepts within the Subsonic Fixed Wing project, part of the Fundamental Aeronautics program managed through NASA's Aeronautics Research Mission Directorate.

To date, the X-48B has proven that the aircraft can be landed, that it has excellent handling qualities and that pilots think it is a great aircraft, Risch said.

"There have been no uncontrollable deviations from flight and it has proven to be a controllable and responsive aircraft. It flies like a dream. The plane has performed as well or better than we envisioned when we started the program," he said.

Cosentino said the aircraft's design has performed well.

"Everything we've seen so far indicates this hybrid wing-body configuration is aerodynamically well-behaved and very controllable," Cosentino said.

The X-48B first flew on July 20, 2007, and flight data has been consistent with wind-tunnel findings attained with the first of the two blended wing body research vehicles. The second vehicle is currently being flown for project work, although the first remains available if needed.

Potential benefits of the aircraft include increased volume for carrying capacity, efficient aerodynamics for reduced fuel burn and possibly significant reductions in noise due to propulsion integration options.

By Jay Levine
X-Press Editor