Boeing has begun extensive modification of an airplane that will become the X-66 Sustainable Flight Demonstrator (SFD), removing engines and completing 3D metrology scans to inform the plane’s design and build plan.
The MD-90 jet’s original wings will soon be removed to test the Transonic Truss-Braced Wing (TTBW) design with new ultrathin wings braced by struts with larger spans and higher-aspect ratios. TTBW’s wider wing span and aerodynamic efficiency could significantly accelerate opportunities to reduce fuel use and emissions.
The X-66 is NASA’s first experimental plane project focused on helping the U.S. achieve its goal of net-zero aviation greenhouse gas emissions. Ground and flight testing is expected to begin in 2028. Boeing released a time-lapse video of recent steps in the conversion including:
Removal of the engines and thrust reversers
Jacking and shoring of the jet to simulate the condition of the airplane during full modification
3D laser scanning of the airplane structure
With the scanning data, Boeing will use 3D modeling software to overlay the existing MD-90 structure with the new X-66 components, enabling more accurate spatial integration and the opportunity to identify and mitigate risks early in the modification process. Boeing will continue to provide updates as the project progresses.
Boeing, which was selected by NASA in January 2023, is using two MD-90s for the X-66A project but intends to modify only one as a demonstrator. “ This arrival marks an important step in the Sustainable Flight Demonstrator project, advances Boeing’s commitment to sustainability, and brings us closer to testing and validation of the TTBW project ,” said Todd Citron, Boeing’s Chief Technology Officer.
NASA funding through the SFD Space Act agreement totals $425 million. The SFD program will also leverage up to $725 million in funding from Boeing and its industry partners to shape the pilot program and meet required resource needs. Separately, Boeing’s previous internal investments on recent phases of sustainable aviation research total $110 million.
The X-66A is part of NASA’s Sustainable Flight Demonstrator program, an effort to study technologies that will improve the efficiency of aircraft. With ultra-thin wings supported by struts with wider spans and higher aspect ratios, NASA’s X-66A “TTBW” design and other technological advances could lead to fuel burn and emissions reductions of up to 30%. Boeing and NASA have collaborated for more than a decade on the concept through the Subsonic Ultra Green Aircraft Research (SUGAR) program.
Boeing has been studying Transonic Truss-Braced Wing configurations for decades, and while longer wings generate less drag, they are not without their challenges, particularly the tendency to develop the dangerous condition of rapid vibrations and oscillations called flutter. Once the testing is complete, it is hoped that aircraft manufacturers will incorporate such technologies into their next planes, helping the industry reduce carbon output. Boeing and Airbus are expected to bring new single-aisle jets to market in the 2030s.