Dallas,--During a redesign of the nacelle, or the engine housing, on the C-17 Globemaster III, Boeing and Northrop Grumman took the opportunity to make a dramatic change in the way the two companies interacted. They invested in a virtual product development process. "We basically came up with a new way of doing business," says Bob Eastin, chief design engineer for the Nacelle/Engine Affordability Team (N/EAT) at Boeing (Long Beach, CA).
The two companies standardized on the Unigraphics CAD/CAM software platform, with Unigraphics Solutions' IMAN (Information Manager) software installed to manage all the data involved in the project. The key to the virtual product development process is the ability to make changes easily and quickly, says Chris Wilt, program manager for N/EAT at Northrop Grumman. "That's the advantage of concurrent engineering around a common digital 3D model--it's less expensive to spend engineering time up front making changes than it is to find those problems when you're actually into metal," says Wilt.
The 174-ft-long C-17 transports equipment like tanks, trucks, helicopters, and artillery into short airfields. Its maximum payload is 84 tons. Four Pratt & Whitney F117-PW-100 engines power the aircraft. The engines are encapsulated in the nacelles which attach to the wings by cantilevered pylons. Originally, the nacelle was designed using composite materials. In the final design stage, a decision was made to redesign it with a less expensive material that would weigh the same amount. Ultimately, engineers settled on a combination of metals including aluminum and titanium.
"The nacelle redesign program is primarily driven by the need to affect cost reduction," says Wilt. "We wanted to make the equipment more affordable."
Boeing performs all the product design work in Long Beach. The design information is transmitted to Northrop Grumman in Dallas for tool design, numerical controls (NC) programming, and subsequent manufacture, fabrication, and assembly. IMAN helps the Boeing/-Northrop Grumman virtual team keep track of all revisions made during the concurrent product development process. A wide variety of departments, including product design, tool design, release control, illustrations, manufacturing engineering, planning, tool handling, and NC programming, have access to the information.
"We transmit the 3D solid model design information to Northrop Grumman as soon as we generate it, without waiting to finish and officially release the designs or create the 2D drawings," Eastin says. "This progressive disclosure of engineering information to manufacturing means we can get to work on the designs as soon as possible, before they're completed and released."
This is the first time that Boeing's Military Transport Aircraft Division and Northrop Grumman's Commercial Aircraft Division have worked concurrently around the digital master model approach. "We are definitely getting shorter lead times," says Wilt. "We also expect that, since we're building a virtual model of the nacelle in the computer and designing and manufacturing the tools to that 3D package, the parts will go together better the first time, with less interference and reduced engineering changes, rework, and repair after the fact."