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Thursday, May 18, 2006 - Page updated at 02:27 PM

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The information in this article, originally published May 5, 2006, was corrected May 8, 2006. A previous version of this article contained an incorrect statement about the cruising speed for the airplane code-named Fozzie.

Clean engines, wings that fold: Boeing dreams of futuristic jets

Seattle Times aerospace reporter

When Boeing names an airplane design after a Muppet, it must be pretty different.

Two small teams at the company are re-imagining the airplane in futuristic configurations that sprout wings, tails and engines in unexpected shapes and places.

The research, illustrated in internal documents obtained by The Seattle Times, aims in two directions: low-cost airplanes, and environmental-friendly planes that will be quieter, use much less fuel and leave fewer pollutants in the upper atmosphere.

In the latter category is the "Kermit Kruiser," a low-noise concept airplane with main wings radically swept forward rather than back, and miniature wings on the front.

Then there's the "Fozzie." It has a "Pi-tail" — two vertical tails joined by a piece across the top, and sips fuel because it flies slower using open-rotor jet engines that resemble old-style propellers.

The concepts are "intended to help us focus technology on a future out beyond the horizon," said Dan Mooney, Boeing vice president of product development, who directs both research teams.

The documents show Boeing has looked at other concepts as well: a supersonic business jet; a megasize freighter; airplanes that use biofuels or hydrogen; and even a "reduced crew" airliner — one with no windows in the cockpit, judging by a sketch in the Boeing documents.

But of all the potential concepts, Boeing has prioritized the "low-cost" and the "green" planes for further research this year. Both teams have begun work with engine companies on the various propulsion alternatives.

Mooney gave a glimpse of some of these designs late last month at an American Institute of Aeronautics and Astronautics conference in Washington, D.C. But attendees didn't get copies, and these images have not been published before.

The Boeing documents include assessments of very similar research projects that its rival Airbus has sketchily mentioned at scientific conferences.

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In an interview, Mooney declined to discuss proprietary details of the designs but offered insight into what his research teams are up to.

He said the latest airplanes being sold today, such as the 787, are designed to meet airlines' projected requirements for about the next two decades. Designers strike a balance among cost, fuel efficiency, capacity, range and other factors based on those projections.

His concept teams, however, think "out beyond 15 or 20 years," where fuel costs, noise or other factors may become more important and reshape what airlines want.

"We need to be developing technology today to allow us to be ready for those uncertainties in the future."

The Muppets

The low-cost team, documents show, is studying the benefits of options such as long, thin wings and new engine types. That team has not yet envisioned new structural designs, however.

In contrast, the Green Team, with a broad mandate to address diverse issues of fuel burn, noise and emissions, has considered some widely differing airplane structures — each with its own whimsical code name. (The Muppet theme may be a reference to the song Kermit sang on "Sesame Street": "It's not easy bein' green.")

• "Kermit Kruiser": Low noise. The engines sit atop a twin-fin tail, so that the noise is reflected upward. The wings are placed so far back they join the fuselage right at the horizontal stabilizer. And most radically, the wings sweep forward, not back, lowering aerodynamic drag and increasing maneuverability at the price of some stability. Keeping this tail-heavy aircraft stable in flight requires a canard — those mini-wings up front. The plane would be a wide-body seating nine abreast.

• "Fozzie": Ultra-low fuel burn. The airplane is designed to cruise at a much reduced speed — 450 mph compared to the 550 mph average cruise speed of current jets. That would add about an hour to the typical transcontinental flight.

Attached to a tail with twin vertical fins and a crossbar (called a Pi-tail because it resembles the Greek letter pi) are engines with an "open rotor" or "unducted fan" design.

The plane has a fanjet gas-turbine engine of the sort used on airliners today, but without the usual duct encasing the fan, Mooney confirmed. At slower speeds, this offers great fuel efficiency.

One internal drawing shows the rotors on the back of the engine, as depicted in The Seattle Times illustration; another shows them on the front, the more usual position.

"That speed is not acceptable in the current marketplace," Mooney said. "But in the future, if fuel burn becomes an even bigger driver, airlines and passengers may be willing to trade speed for lower fuel costs."

Back in the 1980s, Boeing flew an experimental prop-fan engine on a 727. That research ended after oil prices fell and removed the incentive to save fuel.

• "Beaker": Low emissions. This airplane has the low fuel burn and same low cruise speed of Fozzie. It has low-emission engines and long, very narrow wings perpendicular to the fuselage. The wingspan is such that the wings must fold to fit an airport gate.

• "Honeydew": Low fuel burn. Another wide-body, this aircraft seems to be a meld of the traditional "tube-and-wing" shaped airliner and the often-touted "Flying Wing" design that produced the B-2 bomber.

The resulting delta-shaped wing blends in a graceful curve into the fuselage. Yet there is still a distinct fuselage at the front.

The Flying Wing design is more aerodynamically efficient. One disadvantage is that most passengers are far from a window. Honeydew appears to be an intriguing compromise.

Since April, Boeing's Phantom Works research unit, in collaboration with NASA and the U.S. Air Force, has been doing wind-tunnel tests on a small-scale, 21-foot-wingspan prototype of a Flying Wing or Blended Wing Body aircraft concept. Flight testing of the prototype is planned for later this year.

The Air Force is interested in the design's potential as a long-range, high-capacity military aircraft.

Time for a change

So how realistic are these cool-looking airplanes?

"When you look at where energy costs are going in the next decade, it could be time for a change in the rules," said Jerry Ennis, a retired vice president at Boeing's Phantom Works who worked on prototypes.

Like the Detroit carmakers who wheel out fanciful concept cars that never reach the showroom, Boeing may never build an airplane that looks like any of these images.

Still, Mooney said, "Most likely there'll be parts of the technology or parts of the configuration that will find their way onto products of the future."

This fall, the internal documents indicate, the advanced-concepts teams will recommend features from their designs that might be used on the replacement for the 737 single-aisle jet, which is expected to enter service as soon as 2012.

"Our concept-airplane folks stay closely in touch with those working on near-term programs," Mooney said.

Hans Weber, a San Diego-based engineer and aviation consultant, said he's not surprised at most of the Green Team designs — shown to him by The Seattle Times — because many of the elements, from unducted fan engines to the use of canards, have been studied for a long time.

Only the Honeydew model struck him as odd, because he wonders why Boeing wouldn't go for a full Flying Wing design rather than a half-measure.

But he warned that it would take a great deal of work to get such concepts as the Kermit forward-swept wing certified as airworthy by the Federal Aviation Administration.

For Mooney, it's far too early to worry about certifying any specific design. He's directing money into these projects only to find out which of the potential technologies may make sense.

"There's always business pressure on us to invest in the short term, where we know we are going to get a benefit," he said. "But we think it's important to have an ongoing investment in the longer term."

The idea, Mooney said, is that Boeing "be ready — depending on where the future goes."

Dominic Gates: 206-464-2963 or dgates@seattletimes.com

Copyright © 2006 The Seattle Times Company

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