Did You Know: McDonnell Douglas Considered Powering The MD

The collaboration with General Electric almost made it to production.

Although McDonnell Douglas produced multiple versions of the MD-90, including the standard -30, -30ER, and -30IGW, the company proposed many more. According to the Los Angeles Times, they considered shorter variants, like the -10, which would hold around 114 passengers, and the -40, an extended option with up to 180 seats. However, there was one very peculiar design that the aircraft manufacturer poured research into: the MD-94X, featuring propfan engines.

Hoping to bring innovation, compete with Boeing's potential 7J7 propfan aircraft, and lower fuel costs, McDonnell Douglas worked with General Electric to fit their in-development GE36 unducted fan (UDF) engine on a derivative of the MD-80. GE's GE36 was based on work initiated by NASA and was the engine of choice for use on the 7J7 mentioned above, which would replace the 727. It's worth noting that the Pratt & Whitney/Allison 578-DX propfan engine was considered for the proposed MD-90 aircraft, though due to various complications, GE won out.

A critical factor in developing a GE36 demonstration model was newly developed composite materials with intense strength, facilitating the production of thin yet robust curved engine blades. A prototype engine was previously fit onto a Boeing 727 and flown dozens of times. However, moving forward with formal and very hopeful plans, McDonnell Douglas and GE sunk nearly $1.2 billion into the project between the engine and aircraft.

The aircraft would seat 160 to 180 passengers depending on cabin configuration and feature advanced technologies for the time, including canard nose planes, side-stick flight control, and more. On April 5, 1987, the first testbed MD-80 involved with the project was fitted with a proof of concept GE36 on its left side, while the right still featured a conventional jet engine. This way, the two companies could collect data and compare differences in cabin noise, vibration, and, most importantly, fuel efficiency, the hallmark promise of this engine type.

With its mismatching engines, the experimental aircraft took to the skies for its first research flight on May 18, 1987. They started with two eight-blade unducted fans on the GE36, then tested with ten blades on the front fan and eight on the aft. The latter configuration became problematic, so McDonnell Douglas and GE swapped back to the original design before pushing forward with more flights. Despite the mechanical issues, they were confident that the aircraft could obtain certification by 1992.

By March 25, 1988, testing was complete, and the experimental MD-80 obtained 165 hours over 93 flights, traveling at speeds up to Mach 0.865 and as high as 37,000 feet. With their results, demonstration aircraft, and confidence, the two companies flew the MD-80 across North America to the UK, where it would debut publicly at the 1988 Farnborough International Airshow. Part of their plan was to begin marketing to airlines while providing demonstration flights, but this is about where the story ends.

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According to AP, the promises of fuel consumption reductions of nearly 40% weren't enough to convince a single customer to purchase the airliner. This lack of sales may be because the problem had solved itself. Adjusting for inflation, the cost per barrel of oil in May 1980 was about $140, and five years after, it was still high, at around $83. However, the price dropped significantly, to $30, in the coming months and stayed low for years. The necessity to invest in brand new engine tech with potential unforeseen mechanical and safety issues in the years ahead was no more, and as John Wolf, MD's then-Vice President said,

"Our customers indicated they were not interested in buying it."

Sources: LA Times, New York Times, AP

With a background in Chinese language and marketing, Justin merged his passions for air travel and communication to become a writer for the Simple Flying team. He closely monitors industry changes on a global scale, with particular interest in the East Asian and North American markets.