The Short, Happy Life of the Prop-fan

Meet the engine that became embroiled in round one of Boeing v. Airbus, a fight fueled by the cost of oil

Boeing’s 150-seat 7J7 concept (left) would meld prop-fan technology and lightweight composite structure to deliver big gains in fuel efficiency. (The Boeing Company)
Air & Space Magazine

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McDonnell Douglas tried to carry on with prop-fan development. It had the rear-engine MD-80, but it was losing ground to the A320 and 737. MDC fitted a UDF engine to an MD-80 in late 1987 and wanted to launch the UDF-powered MD-91 and -92 by July 1988. The company even saw a 300-aircraft market for a Navy patrol version of the MD-91. But GE wanted to see 100 to 150 airline orders before committing to the program. Recalls Conboy, “If people aren’t going to buy it, there’s not much you can do.”

GE and MDC flew the MD-80 to the Farnborough airshow in September 1988, but the effort was already out of steam now that McDonnell Douglas was building the MD-90 with a conventional engine. “We all shook hands and said that it was a valiant effort,” says Conboy. MDC did fly the Allison-P&W engine on the MD-80 in 1989. “The operation was successful,” says Al Novick, who was part of the Allison-P&W team, “but the patient died.”

The UDF demonstrator is in the engine collection of the Smithsonian’s National Air and Space Museum, and the Allison-P&W prototype is in a company training center in Indianapolis. But nobody involved in the prop-fan or UDF writes the experience off.

GE put the UDF’s blade technology directly into the GE90, its most powerful commercial engine. “We trained a lot of good guys,” Rowe says. One was Mike Benzakein, then the company’s leading technologist. GE is still looking at counter-rotating turbines and fans, and came close to proposing such an engine for Boeing’s new 7E7.

Colman Shattuck, the program’s leader at Hamilton Standard (now Hamilton Sundstrand), says that the project was “one of the best times of my career” and that it spurred today’s all-composite propeller technology. The firm’s French subsidiary, Ratier-Figeac, makes the multi-blade propeller for the Airbus A400M military transport.

For Allison, the benefit had little to do with technology. “We got involved publicly with Boeing and Douglas,” says Novick, “and it helped us tremendously in getting back into the commercial business.” Embraer picked an Allison turbofan, the AE 3007, for its EMB-145 regional jet, and Rolls-Royce, which acquired Allison in 1995, cranks turbofans out by the boatload.

Mulally and Condit became the leaders of the next major Boeing project, the 777. It had little resemblance to the 7J7, but the underlying technologies and disciplines—computer-aided design and manufacture, and integrated electronics—were similar. Mulally quotes Boeing chairman Thornton “T.” Wilson as saying that the 7J7 “was the best investment in aircraft development that Boeing ever made” and adds that “we could not have done the 777 without the 7J7.” Condit went on to head Boeing until he resigned in late 2003, accepting responsibility for ethical and performance problems.

At the 2001 Paris Air Show, Mulally whipped the covers off another radical, rear-engine airplane, the tail-first Sonic Cruiser. In an echo of 1985, Boeing promised vast improvements over anything the competition could do. Like the 7J7, the Sonic Cruiser failed to ignite customer interest, and Boeing is pushing the 7E7, now redesignated the 787. Both aircraft offer more comfort with a lower fuel burn, Mulally says. “The cool story about the 7J7,” Mulally says today, “is that it’s exactly the same [idea] as the 7E7, but at a smaller size.”

The Airbus A320 went on to become one of the most successful airliners in current production, second only to the 737 in total unit sales. Airbus’ Adam Brown also compares the 787 to the 7J7. “The issue is whether the advanced-technology combination can give you a big enough gain in efficiency to supersede what’s already on the market,” he says.

And once again, the key to the fortunes of both companies could be the price of a barrel of


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