NASA - National Aeronautics and Space Administration

A low-speed, 8.5-percent-scale flight research prototype of Boeing Phantom Works' Blended Wing Body concept aircraft, also known as the X-48B, arrived at Dryden in June.

Image above: Ian Brooks, a Cranfield Aerospace employee, works on the Boeing Phantom Works X-48B Blended Wing Body aircraft. The aircraft and a second X-48B used in Langley Research Center, Hampton, Va., wind tunnel tests, arrived at Dryden in June. The low-speed, 8.5-percent-scale flight research prototype is expected to begin a series of research flights later this year or in early 2007.
NASA Photo by Tony Landis

The X-48B is a subscale testbed for exploring and validating the structural, aerodynamic and operational advantages of a futuristic aircraft design called the blended wing body, or BWB. It is similar to a flying wing, an airplane shaped entirely like an airfoil without a conventional fuselage or empennage. Flying wing concepts of the 1940s looked like propeller-driven or jet-powered boomerangs. The BWB design suggests a flying wing on steroids, with several distinguishing features.

The front section of a full-scale BWB airplane, containing the cockpit, extends forward of the wing's leading edge while the central portion encompasses the passenger or cargo compartment to maximize payload capacity. The tips of the airfoils end in winglets to reduce drag and thereby increase fuel efficiency. A big difference between the BWB and the traditional tube and wing aircraft is that instead of a conventional tail the BWB relies solely on multiple control surfaces on the wing for stability and control.

Image above: Boeing Phantom Works employee Rod Wyatt readies the X-48B blended wing body aircraft for a set of research flights to be flown later this year or in 2007. Research with the X-48B could result in development of aircraft capable of carrying larger payloads with greater fuel efficiency.
NASA Photo by Tony Landis

Boeing officials see the BWB as a flexible, long-range, high-capacity military aircraft that could be used as a tanker, transport, command and control platform or weapons carrier.

Designed to fly at altitudes around 7,500 feet, the X-48B's average research flight is expected to last about an hour and will be focused on low-speed flight characteristics, said Gary Cosentino, Dryden's Blended Wing Body project manager and chief engineer. The first in a series of about five developmental research flights are scheduled to take place later this year or in early 2007.

The aircraft, featuring a 21-foot wingspan, recently underwent a paint job at Cranfield Aerospace Ltd. of Cranfield, England, a subcontractor on the project, and arrived at Dryden with some assembly required. The wings and landing gear were detached for transport and additional work is needed to prepare the aircraft for research flights. The X-48B will fly with a gross takeoff weight of about 400 pounds. A second BWB aircraft recently underwent a series of tests in NASA wind tunnels at Langley Research Center, Hampton, Va.

A successful set of five check-out flights with the X-48B, Cosentino said, could herald the start of a 20- to 25-flight follow-on project that could last an additional six to nine months and further define the flight characteristics of the aircraft as the flight envelope is expanded.

"It's not so much maturing new technologies as it is working to understand the characteristics of the shape," he explained. Dryden is one of several partners in Boeing Phantom Works' Blended Wing Body concept research efforts, which also include work by Cranfield, the Air Force Research Laboratory, Langley and the NASA Subsonic Fixed Wing Program, the latter a key component of the agency's Aeronautics Research mission directorate.

Blended Wing Body aircraft concepts have been studied since the early 1990s and testing of the shape's aerodynamics has been conducted in Langley wind tunnels. Flight research is a welcome next step, said Fay Collier, NASA's Langley-based Fixed Wing Project principle investigator.

"We have computational and ground-based testing," Collier said. "This flight test is going to fill in the flight part of the data for the low-speed flight regime. It will give us a really good set of data, from ground to flight, and in this particular case we're looking at low-speed flight data to go along with computation and wind tunnel test data we've acquired. It's the final straw in acquiring test data for that configuration."

Image above: Andy Walster of Cranfield Aerospace takes the stick of the X-48B blended wing body aircraft simulator.
NASA Photo by Tony Landis

In addition to looking at simulation models, stability and control limits of the aircraft and control laws for the unique tailless vehicle, Collier said NASA also is interested in potential benefits in the areas of noise reduction, lower emissions and aircraft performance.

"This particular configuration is useful in a number of ways. There are combinations of engines and airframes, like this one, that may lead to significant noise reduction. This configuration is expected to be - for a very similar payload - much more fuel efficient than a conventional configuration," Collier said.

Boeing Phantom Works engineers in Huntington Beach, Calif., specified the X-48B's outer mold line - the external shape of the airplane - using their aerodynamic design methods. That information was sent to Cranfield in a computer-aided design file. Cranfield built the blended wing body airplane to Phantom Works engineers' specifications, which are critical to testing a unique aerodynamic design. Phantom Works is Boeing's advanced research and technology organization.

Boeing officials envision the aircraft as a multi-role platform for military purposes capable of a wide range of applications, said Norm H. Princen, Boeing Phantom Works X-48B chief engineer. "We're really trying, with this vehicle, to prove out the technologies that would enable a Blended Wing Body to be built," he said.

Depending on customer need, a next step could be a production aircraft, Princen said, though a more complicated set of requirements could lead to a larger demonstrator.

Dave Dyer, Cranfield Aerospace General Manager of UAV Systems and Cranfield's BWB general manager and chief engineer said the company's role on the project encompasses more than structures work.

"We've designed and built all the avionics and installed them in the aircraft and the ground station," Dyer said on a recent visit to Dryden. "We're supplying a system, not just an airframe. We see it as we're providing a facility to enable (Boeing) to upload their flight control laws into the vehicle for experimentation. The job is not compartmentalized as it might seem; it's an interactive job." The decision to conduct X-48B flight research at Dryden was an easy choice, Princen said.

"Dryden is a fantastic place to do flight testing. The facilities here are really tailored to doing the flight test job and there is really no other facility like it in the country. The large open space where we can get airspace set aside for our use, right over the lakebed, makes a great emergency landing opportunity if you have to do that. Because we're dealing with an experimental aircraft, you never know quite what's going to happen.

"The staff here at Dryden have done many other X-plane projects in the past and we gain from that experience," he continued. "They're telling us a lot of things that are going to help us avoid problems."

The technical expertise of Dryden's staff has been tapped for specific tasks, Cosentino said. Dryden team members include Chris Regan, flight controls; Richard Main, aerodynamics in parameter identification; and operations engineer Kimberly Vaughn. Also working on the project are Jessica Lux-Baumann from the Western Aeronautical Test Range and Tony Kawano, Range Safety Systems Office. Frank Batteas and Marty Trout are providing support with piloted simulations.

Dryden's experience with former X-planes is long. "The past is applicable," said Cosentino, who was project manager for the unmanned X-36 and X-45 vehicles. "Every time we fly a subscale vehicle, we learn something. All the lessons learned from those two vehicles will be taken into account in general."

The X-36, for example, was similar to the Blended Wing Body in that it was piloted from a ground station. Better interface with the pilot is one lesson resulting from that research that will be applied to work with the X-48B.

Dryden's experience with Altair also contributes to a foundation of work with UAVs that will help shorten the learning curve on the X-48B, Cosentino concluded.

Jay Levine
X-Press Editor