7E7: New airplane, new technologies

Engineering designers are focusing on composites, systems and aerodynamics to make the all-new Dreamliner a success

BY LORI GUNTER

Don't let anyone else tell you otherwise: The 7E7 really is an all-new airplane.

Advancements in three key Boeing technology areas combine with new engines to make the Boeing 7E7 Dreamliner an efficient, effective tool for airlines. Materials, systems and aerodynamics improvements over the past 10 years present engineers with new opportunities to refine and optimize airplane designs. The end result is an airplane whose design integrates these advances to achieve its standard-setting advantages.

"Boeing is always ready with the new technologies that shape our industry," said Walt Gillette, vice president of Engineering, Manufacturing and Partner Alignment for the 7E7. "With the B-47 we introduced high-aspect-ratio swept wings, engines in pods and flight control surfaces at the back of the airplane. These innovations continue to be featured on every successful commercial jet airplane. With the 747 we found the way to bring big jets to reality. And now with the 7E7, we are bringing forward the innovations that will shape our products and our industry for decades."

COMPOSITES CREATE OPPORTUNITIES

When Boeing announced its decision to make the 7E7 of primarily composite materials, it took a leap from the mature material system of aluminums into the burgeoning category of composites. Still, the composite system being used on the 7E7 is not radically new.

"We're using the same basic composites that have been in service on the 777 from the beginning," said Frank Statkus, vice president of Advanced Technology for the 7E7 program. "We understand this material system."

That said, the team still faces development challenges.

"To create the entire fuselage and most of the wing out of this material, we need to really define the design allowables and do a lot of testing to ensure we're really getting the full advantage," Statkus said.

He explained that introducing a new material system for these types of structures means that the designers have more to consider in creating their designs. As one example, Statkus recounted how a test structure that was being tested to the point of failure actually failed well later than anticipated. While this might seem to be a good thing, the goal was to adhere to the stipulated failure limit, which is conservative and ensures the highest levels of safety. Going beyond this limit means introducing inefficiency and unnecessary weight.

Landing exactly on such targets is exactly the intention behind materials testing. Tests are done at this phase of the program to create a database that tells designers the properties of the materials so that they don't overachieve and never underachieve.

Another challenge that composites are bringing to designers is the need to rethink the entire design of the airplane. Composite parts can be bigger, better tailored to achieve the needed performance and yet simpler, but they need to be designed to "get the full advantage of the material system," Statkus said. "If we just substitute composites for aluminums and don't create new designs, we're not going to see the improvements we need."

Statkus said the 7E7 team is pursuing these challenges vigorously. In fact, the team is creating test fuselage section tooling to check the current design efforts and the new tapelaying machines being developed for the 7E7.

"Our team is facing these challenges with a great energy and enthusiasm," he said. "They're really focused on doing this right."

Interestingly, Statkus said that challenges are important early in a program. If everything is easy, he said, Boeing hasn't set stringent enough targets. "We don't lose sleep over these challenges," Statkus concluded. "We don't have all the answers, but we see the path forward and are confident in our ability to find the answers."

GAINS FROM ADVANCED SYSTEMS

There's a plethora of advances being introduced in the systems arena with the 7E7 as well. Most significantly, the highpressure bleed air system, a standard for the last 60 years on jet airplanes, has been replaced by new electronics.

"Today's bleed air systems rob the engines of efficiency," said Mike Sinnett, chief project engineer for 7E7 Systems. "In the past, we had to accept this because it was the only way."

Now, electronics have advanced to be light enough and robust enough to provide a better solution.

"We've talked about this concept in systems for years," Sinnett said. "But this is the first time we've been able to really achieve it."

Each 7E7 engine will have two 225 kilowatt generators. The auxiliary power unit will also have two similar generators. They will be used to provide electric anti-icing, power the environmental control systems and hydraulic pumps, and drive the motors on the brakes-all functions formerly powered by pneumatics or hydraulics.

Sinnett said the program is looking for other opportunities to expand the use of electronics. One potential under review is using electrical actuation for some of the secondary control systems.

The primary system would still operate like the 777, with electronic fly-by-wire signals that cause hydraulic power to move the control surfaces. But the backup system may use the electronic signals to move electronic motors that would move other control surfaces. It would be a redundant source of power that would remain in the unlikely event of a total loss of hydraulics.

In addition to eliminating bleed air, the 7E7 will introduce an open systems architecture managed through a common core system.

"In an open architecture, you plan for change even if you don't know what it will be," Sinnett said. "Part of the advantage of being computer-driven is that we can achieve upgrades and introductions through new software."

In today's airplanes, new technologies are often not introduced because they would require extensive modifications to the airplane.

One technology Sinnett sees on the horizon is a fuel cell auxiliary power unit.

"Fuel cell technology won't quite be ready for 2008, when the 7E7 enters service," Sinnett said. "But because the auxiliary power unit is only required to provide electrical power now and not bleed air, the 7E7 will easily be adaptable to the fuel cell technology when it is ready."

With its common core system, the 7E7 is reducing the number of computers on board and centralizing data processing to allow more efficient use of resources. Sinnett said the 7E7 could be down to about 30 unique computers, compared with about 80 on a 777.

For systems, the 7E7 is all about providing better functionality with fewer parts and greater flexibility.

"We're designing a systems architecture that will start providing service in 2008 and continue well past 2050," Sinnett said. "There's no way we can know what the future will bring, but we can sure be ready to bring it on board."

BETTER TOOLS FOR DESIGN

The 7E7 also reflects a greater understanding of the laws of aerodynamics. Obviously, these laws haven't changed. But, said 7E7 Chief Project Engineer Tom Cogan, "our understanding of the laws has continued to evolve and so have our aerodynamic tools."

Chief among those tools is computational fluid dynamics, complex codes that run on supercomputers to develop designs that are optimized for minimal drag.

"As computers have become faster and more powerful in recent years, we have been able to do a better job in modeling the entire airplane and predicting the three-dimensional effects of the airflow around it," Cogan said. "The codes we have developed allow us to look at more potential design options faster than ever before."

Indeed, Cogan said the process for developing airplanes today begins with the computer model. The coding is so accurate that designers can evaluate miniscule changes in a design to determine impacts on aerodynamic efficiency, he added.

In fact, the accuracy of the coding has also focused the application of another aerodynamics tool: wind tunnel testing.

In the '80s, the Boeing 767 team took more than 50 wing designs into the wind tunnel to verify their designs, Cogan said. In the '90s, the Boeing 777 team took 18 designs into the tunnel. "We were really not verifying the designs as much as we were verifying that our computation tools were accurate and looking at performance at the extreme operating conditions, which the coding couldn't do," Cogan said.

"With the 7E7, we will take fewer than 12 wings into the tunnel," Cogan said. "We are still proving our coding and testing the extremes. The tunnel is a great tool but it's not very cost-effective. So, being able to really focus on a few designs to get the data we need is helping us be more cost-effective."

Cogan said the program is in its second round of wind tunnel testing, and the tests are going extremely well. "We continue to find that our computational fluid dynamics programs are extremely accurate in predicting the performance of our design," he said.

Boeing and its partners will conduct about 15,000 hours of wind tunnel testing on the 7E7 at sites around the world, including the Boeing transonic wind tunnel in Seattle and the QinetiQ low-speed wind tunnel in Farnborough, U.K.

In addition to using the wind tunnel data to select the best designs, Boeing uses it to create the simulation data that will help pilots prepare to fly the airplane.

"By the time we get the first 7E7 in the air, there will be no surprises," Cogan said. "And that's how it should be. The pilots will know how it handles and reacts because of the work we are doing in computational fluid dynamics and the wind tunnels."

INTEGRATING NEW TECHNOLOGIES

These three Boeing-led technology areas combine with new engines to provide a 20 percent improvement in fuel usage on the 7E7. In fact, the combination is the key to realizing the full improvement.

"It is the integrated effect that allows our improvement to be so dramatic," Gillette said. "You can only take full advantage of these technologies with a brand-new airplane."

As an example, Gillette noted the cycling effect of composite materials and new engines. If the engine is more efficient, you don't need as much fuel-meaning your wing can be smaller. If the wing is smaller, the airplane is lighter and your engine can get smaller. "This allows another cycle of downsizing everything: the wing, the engines and so on," Gillette said.

In this way, with a new airplane, Boeing can optimize the design to ensure all of the benefits of each improvement are fully realized.

"We've had people ask about taking the 7E7 engines and using them on older airplanes," he said. "But you wouldn't get the full advantage, because to put them on an older airplane you'd have to introduce bleed air again, and that would make the engine less efficient. Plus this engine is bigger than the engines found on today's airplanes in this class so you'd have higher drag and more inefficiency. It just wouldn't be the same."

Likewise, just making today's designs out of composite materials doesn't create the full set of benefits unless you completely redesign the part to take advantage of the material.

"That's how we know it's time to do a new airplane and not modify our existing airplanes," Gillette said. "When the technologies add up to something truly unique, it's the right time to go forward with a new design. And now is the right time with the 7E7."