NASA Continues Developmemt on the Truss Wing.

 I have blogged before about "The Truss Wing" Concept that NASA is developing, another step forward when a former

Delta Airline MD-90 left Victorville to be a donor aircraft for this project.  I do wish that Boeing would work on the "797 NMA" also.  it is like they are putting all their eggs in the MAX basket and surrendering a huge share of the market to Airbus.  The "Boeing 757" is a unique airplane and there is nothing else in the world that can do what she does, you can load it down with passengers and cargo and "weight optimized" issues that force a plane to fly with empty seats don't happen with a 757 like what happens with the "A321" series of airplanes although the NEO version has stronger engines and it is the closest to falling in the catagories that the B757 have.  The 757 is getting long in the tooth and eventually they will retired as is the nature of airplanes. I wish that Boeing hadn't quit making the plane but they did to focus in the 787 and "Boeing MAX" development.

MD-90 ferry flight

Credit: NASA/Carla Thomas

A former Delta Air Lines MD-90 is being prepared for conversion into Boeing’s X-66A transonic truss-braced wing (TTBW) experimental aircraft after arriving at Palmdale, California, on Aug. 15 following a short ferry flight from nearby Victorville. 

The aircraft, which has been in storage since its retirement from the Delta fleet in 2020, will be modified for NASA’s Sustainable Flight Demonstrator (SFD) project with a new strengthened center fuselage crown section to support the 145-ft. span, high aspect ratio transonic wing. To be mounted above the fuselage, the new wing will have an increased span of 46 ft. compared to the aircraft’s original low-mounted wing and will be structurally braced by trusses that also generate lift.

The low drag wing design alone is expected to reduce fuel burn by up to 10% compared with the conventional cantilevered wings on today’s single aisles. NASA, which launched the SFD project in January, says that when combined with advanced propulsion, composite structures, and other technologies, the TTBW is expected to reduce fuel consumption and emissions by at least 30% for an aircraft entering service in the 2030s.

The goal of the SFD program is to validate the benefits of the TTBW concept at the aircraft level and, if successful, is expected to form the basis for a next generation airliner family to succeed the 737 in the 2030s. Boeing has outlined a possible future family of single-aisle TTBW aircraft, the VS-1 and VS-2 (for Vision System). The smaller VS-1 seats 130-160 passengers while the 180-210-seat VS-2 has a bigger wing and engines.

Based on a configuration developed by Boeing and NASA over more than a decade of collaborative studies under the Subsonic Ultra Green Aircraft Research (SUGAR) program, the X-66A conversion will begin with removal of the MD-90’s existing tail-mounted International Aero Engines V2500s. The forward fuselage will then be shortened by around 14 frames to balance the airframe around the new center of gravity. Additional airframe and system spares will be available from a second MD-90, which was ferried to Palmdale in July.

The X-66A will be powered initially by a pair of Pratt & Whitney PW1100G geared turbofans and, for later tests, is expected to be re-engined with the CFM Open Fan—now in development under the GE Aerospace-Safran RISE program.

The conversion program will take several years with flight tests scheduled to take place at NASA Armstrong Flight Research Center at Edwards Air Force Base in 2028. Although the basic modification could likely be achieved over a shorter timescale, Boeing plans to use the X-66A program for in-depth preparation for a follow-on new development program. The design will therefore go beyond a traditional experimental X-plane to include certifiable features such as a production-like fuel system and fail-safe engine pylon, wing truss, and fuselage structures. 

Although Boeing does expect some fuel to be stored in the center of the X-66A wing, the overall thin cross section means the fuel system will likely be augmented with auxiliary belly tanks, a feature previously developed for the MD-90