The McDonnell Douglas MD-90 has been resurrected…sort of.
A former Delta Air Lines MD-90 (reg. N930TB) took off from the Southern California Logistics Airport (VCV) in Victorville, Calif., last week. Its destination was just 43 miles away, where it arrived at Palmdale Regional Airport in Palmdale, Calif., 14 minutes later.
However, avgeeks hoping to see the iconic “Mad Dog” in the skies again shouldn’t get their hopes up.
N930TB is the first of two former Delta MD-90-30s – now owned by Boeing Capital Corporation – that will become part of NASA’s Sustainable Flight Demonstrator (SFD) program.
What is the Sustainable Flight Demonstrator Program
According to NASA, the purpose of the SFD program is “to engage with industry, academia, and other government organizations to identify, select, and mature key airframe technologies – such as new wing designs – that have a high probability of transitioning to the next generation single-aisle seat class airliner.”
The 153-feet long MD-90 airframes will be shortened to become full-scale demonstrator aircraft – dubbed by the U.S. Air Force as the X-66A – to test the capabilities of the Transonic Truss-Braced Wing (TTBW) design. The design is a collaboration between NASA and Boeing and is considered the most likely candidate for future airframe development. By repurposing these airframes, the X-66A will mark Boeing’s first commercial demonstrator aircraft since 1954, a milestone reminiscent of the origins of the iconic Boeing 707.
The ultimate goal of the SFD program is to help make air travel more sustainable. With the TTBW design and other technological advances in propulsion systems, materials, and systems architecture, NASA aims to reduce emissions by up to 30 percent (compared to the 737 MAX).
NASA says the agency expects the X-66A to begin conducting missions by 2028.
The successful implementation of the TTBW concept may lead to its adoption by original equipment manufacturers (OEMs) for single-aisle aircraft in the 2030s, aligning with the U.S. Aviation Climate Action Plan’s goal of achieving net-zero carbon emissions by 2050.
Breaking Down the Transonic Truss-Braced Wing Concept
The TTBW design will strategically focus on transforming the performance of single-aisle airliners, a segment responsible for nearly half of the world’s aviation emissions.
The concept involves integrating an ultra-slender and lightweight composite wing atop the airframe, stabilized by two diagonal lift-generating struts. The struts will help significantly reduce drag and improve aerodynamic efficiency during transonic flight conditions. This innovative design allows for smoother airflow over the wings, reducing fuel consumption and emissions while enhancing the overall aircraft’s performance and range.
With a wingspan measuring 170 feet, the TTBW design will be shorter than the Airbus A350 and Boeing 787 in terms of length. But it will exceed the wingspan of the Boeing 737 MAX 8, which spans 117 feet.
“The Transonic Truss-Braced Wing is the kind of transformative concept and investment we will need to meet those [achieving net-zero carbon emissions by 2050] challenges,” says Bob Pearce, NASA associate administrator for the Aeronautics Research Mission Directorate. “The technologies demonstrated in this project have a clear and viable path to informing the next generation of single-aisle aircraft, benefiting everyone that uses the air transportation system.”
In its current form, the TTBW design will be able to withstand speeds of up to March 0.80, similar to today’s jetliners.
From Mad Dog to X-Plane
Both future X-66A demonstrators will feature the fuselages of former Delta Air Lines MD-90s.
The first to make the move to Palmdale was N930TB (tango bravo stands for truss-braced). She spent her entire life at Delta Air Lines as N908DA.
The Long Beach-built Mad Dog began service with Delta in September 1995. After nearly 25 years of service, she sadly became a victim of the COVID pandemic. She was stored at Arkansas International Airport (BYH) in Blytheville, Ark., on 19 March 2020. Just under a year later, on 13 January 2021, she would move to Victorville.
In March 2021, she was purchased by Boeing and received her new registration, N930TB. She would remain in Victorville until her short flight to Palmdale on 21 July 2023.
The second MD-90 was originally delivered to China Northern Airlines in February 1999. She would remain with China Northern until October 2011. Shortly after, she became a Delta bird in November 2011 and began service with them in April 2012 with the registration N962DN.
Suffering the same fate as N930TB, she was parked at BYH on 29 April 2020 as a result of the pandemic. She would remain at BYH until 18 December 2020, when she was transferred to VCV.
Purchased by Boeing in 2021, she was re-registered as N931TB. We don’t yet know when she will make the jaunt to Palmdale. For now, she sits at VCV, awaiting her next assignment.
