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Transportable CAD Speeds Complex Airframe Design

Cuts time from design concept to tooling by more than 80%

—by Larry Olson

Adam Aircraft Industries is a general aviation designer and manufacturer with development and manufacturing facilities in Englewood and Pueblo, CO. Founded in 1998, Adam Aircraft has made significant progress towards production of carbon composite, twin-engine aircraft that employs innovative technology in providing high reliability, comfort, and safety.

The company’s A500 is a 250-knot, pressurized, six-place, centerline-thrust aircraft, designed for certification to 25,000-ft altitudes and a range of 1,150 nautical miles. Production is currently under way, and FAA certification of the A500 piston twin is expected later in 2003. George F. “Rick” Adam, founder and CEO of Adam Aircraft, set the top three priorities of the flight test program as “safety, safety, and safety.” The A500 is his and co-founder John Knudsen’s inspiration. 

The A500 differs from other twin-engine planes in many important ways. Rather than having engines mounted on the wings, its two Continental engines are mounted in-line on the fuselage –– one in the front and one in the rear –– providing the safety of centerline thrust. If one of the engines fails, the aircraft maintains a straight course rather than experiencing the yaw that occurs when a wing-mounted engine fails.

Adam Aircraft’s crew chief John Oakley explains some other features of this unique aircraft. “The A500 has side-stick controls, FADEC (full authority digital engine control) and some other innovations that make the A500 very attractive to pilots.” FADEC, a computerized engine control system, maximizes engine efficiency and reduces pilot workload, resulting in fuel savings of approximately 15 percent.

Another key difference is the A500’s airframe. Instead of having relatively standard aluminum structure with lots of rivets, the aircraft’s structure consists of a carbon composite exterior for superior aerodynamics and a smoother external appearance. According to Dennis Olcott, Adam Aircraft’s vice president of engineering, “This composite structure is unique. The main visible shell of the aircraft is made up of 13 pieces, which reduces the number of airframe sections drastically over the same structure in riveted aluminum. Construction of the airframe involves laying up a shell composed of carbon fiber and epoxy pieces over a master form.”

Still undergoing pre-production flight-testing is the A700, which replaces the centerline-thrust prop engines with two Williams International FJ33 fanjet engines. Subsequent to the A500, the business jet will be about 30 in. longer than its sibling, with a ceiling of 41,000 ft and a top speed of 340 knots. Fuel capacity of 330 gallons will provide a range of approximately 1,500 nautical miles.

 

More functionality, but paying much less

To prove out the design and production process of the aircraft, certification requires a rigorous series of extreme physical testing, ensuring that all of the plane’s components and systems perform to exacting standards. For example, even the A500’s seats must withstand a force exceeding 26 Gs to meet FAA requirements. Achieving this certification usually costs millions of dollars; and, for a company such as Adam Aircraft with its first aircraft, it is important to attain certification as quickly as possible, start producing airplanes, and bring in much-needed revenue. “Time is a consideration in everything we do,” says Pat Fairchild, an engineer at the company.

“At the same time,” Fairchild continues, “we’re always looking for ways to work more efficiently, while maintaining the high level of quality that is an essential part of Adam Aircraft’s reputation.” As a start-up company, the company does not have an unlimited budget for design software. Yet they had big-budget needs, at least where the plane’s outer shell was concerned. “We needed high-end surfacing software to model the sculpted shape of the carbon fiber skin,” explains Fairchild. “But we didn’t have a budget that would let us buy 15 to 20 seats of high-end CAD. We were really looking to hold down costs.”

Olcott recalls, “We began exploring several options that would deliver an improved solution to designing the aircraft using CAD that is less expensive and more capable than Autocad’s ‘Inventor’ and CADKey. What we needed was the capability of generating complex external airframe shapes, while maintaining strict control of surface curvatures and tangencies. Accuracy was the biggest factor. We had to have geometry options that were just not available in other programs. And, we needed all that in a package that was easy to use and transportable –– really essential in the way that the CAD was going to be used.”

Adam Aircraft came up with a solution that suited its budget, while doing everything that Olcott demanded. The company installed 15 seats of EDS’s Solid Edge for part modeling and detail drawings and 3 seats of EDS’s Unigraphics NX for designing the plane’s exterior surfaces. “For the roughly $5,000 per seat price of Solid Edge,” Fairchild reports, “we could purchase enough licenses to spread the software throughout the design team. That, combined with a few seats of premium, high-end Unigraphics NX, gave us all the functionality we needed at a price we could afford.”

“No other programs would have been able to come close to what SE and Unigraphics are producing,” says Olcott produce. A major factor in choosing the EDS products was the high level of support that came with the CAD packages. Because the same geometric modeling kernel –– Parasolid –– is used for Unigraphics NX and the Solid Edge programs, the types of surfaces and their high complexity required some close technical support by EDS in response to the particular nature of the Adam application and the airframe designs. “With some CAD vendors, it’s like pulling teeth to get support. Solid Edge is different — very open and responsive. We use the powerful surfacing capabilities in Unigraphics NX for aerodynamic design and then leverage that data across a wider group of engineers working on Solid Edge.”

The other aspect of this solution that works so well for Adam Aircraft is the interoperability between Solid Edge and Unigraphics NX. Since both are EDS products and built on the same kernel, no file translation is needed to pass files between the two programs. This compatibility is important for Adam Aircraft because data translation would take valuable time away from designing and building parts while working toward FAA certification.

Coordination between the programs works like this: After the outer surface geometry has been created in Unigraphics NX, the file is imported into Solid Edge. The surfaces are given the appropriate thickness to account for the number of carbon plies that will be used in production. Having surface geometry allows designers working in Solid Edge to use the exterior surfaces as references while the internal structures are created. After importing (and giving volume to) the top and bottom wing surfaces, for example, designers can create the wing’s supporting structures — the front and aft spars and internal ribs — in Solid Edge using the exterior surfaces as a guide.

Adam Aircraft also uses Solid Edge to create all mold male and female shapes, and then uses Unigraphics NX to create the necessary tool paths. The company’s shop operates at regular shift hours that occur around the clock, throughout the week, based on 3-day, 12-hour shifts. This timeframe enables design changes to be made during the day and implemented in new parts on the following day, resulting in especially rapid turnaround in bringing the A500 to market.

 

“Five times faster, with fewer people”

Providing the CAD tools to enable engineers to work this way has drastically reduced the overall assembly time and cost. Solid Edge is used to design tooling and tool masters, and to produce shape representations and drawings for documentation. The airframe’s outer skin (which is designed in Unigraphics NX) is supported by a honeycomb core and structure that has been defined in Solid Edge, which has been used to design all internal sections and components of the aircraft, as well.

According to Olcott, Boeing’s 777 design used Catia, requiring a much longer design time and the involvement of hundreds of engineers. By contrast, Adam Aircraft was able to complete a similar project in the design of the A500 using Unigraphics NX and Solid Edge with fewer than 50 employees. Today, the company’s total employment is about 180 people, including 25 engineers and 10 drafting assistants.

Olcott also explains, “With the CAD system, the company was able to accumulate a parts library of common parts that was more efficient for subsequent application to other models, such as the A700.” This process of design and production using EDS’s CAD system also promises to make certification much easier and faster as well. Ultimately, the FAA will have a much cleaner design and overall package to review and approve. Olcott sums up, saying, “The overall timeframe for airframe design, from concept through prototyping and finished tooling, is about five times faster than with other programs — while requiring far fewer people to accomplish the job.”

This integrated combination in a CAD package offered Adam Aircraft more than just affordability. Solid Edge and Unigraphics NX gave the engineers and designers the software tools they needed for doing their jobs quickly and accurately. “Modeling is so intuitive with Solid Edge that it lets the people doing part modeling work fast, and the drafting component of Solid Edge is unmatched in ease of use, ”says Fairchild. “The aerodynamic designers and NC programmers, on the other hand, get from Unigraphics NX the ability to create gracefully curved, yet highly complex surfaces.”

Olcott agrees: “Initial training of CAD operators and engineers, and continuing training, has been made much easier with Solid Edge’s built-in tutorial. The company has built up a core of highly trained operators, and everyone has some capability in using Solid Edge.” The training cycle is about 2 to 3 days for someone starting from scratch, with the operator becoming fully capable soon after. This short learning curve has a big benefit when hiring local people.

“Because Solid Edge’s package is simpler to learn and use — and to apply in all the stages of design and production — everyone is able to use the CAD programs,” he concludes. “Not just a bunch of specialists as required by some other programs.” This versatility also facilitates changes to the design when moving through development and prototyping into production.

Solid Edge’s technology also provides a downloadable viewer for use in reviewing the CAD files in read-only mode. No paper drawings are used on the production floor: all drawings are released electronically and available throughout the plant — further facilitating the drawing change process. All design files are archived when released as final, when paper drawings can also be provided and archived as needed. In addition to a much more rapid and efficient process, there is much less possibility of mistakes occurring by using the wrong drawing or file.

John Hamilton, marketing and western region sales vice president, sums up: “We set ambitious goals from the beginning: we started building tools and tooling masters in August of 2001; by January of 2002 we had the first parts in prototype; and by July of 2002 we conducted the first flight of the first assembled prototype. The company had decided in June of 2002 to demo the first prototype at the air show in Oshkosh, WI. We were able to assemble the first prototype in less than one month, including all systems and engines; and this first aircraft flew in just 5 weeks and 3 days after deciding to go to the show.”

The key element in ensuring success for Adam Aircraft and the A500 was the use of efficient, interoperable CAD packages that drastically cut the time to prototype and market this remarkable aircraft. Solid Edge and Unigraphics NX functionality and transportability provided part modeling and drafting capability that was intuitive, easy to use, and accurate in handling complex design tasks. Everyone on the A500 team agrees that Solid Edge and Unigraphics NX are a couple of high flyers in the world of CAD.


For more information:
Adam Aircraft,
www.rsleads.com/310df-247

EDS,
www.rsleads.com/310df-248

 

 
   

 

 
   
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