Almost real: digital designs and virtual tests continue to be subject of debate.

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To speed up deliveries and cut costs, the U.S. military's newest jet fighter will undergo much of its testing in digital simulations.

The Defense Department for years has relied on "virtual prototypes" to test advanced weapons systems. Boeing pioneered the technology in the late 1980s with the paperless design of its 777 jetliner.

Simulation and modeling technology is now so much more sophisticated that, in theory, it could save the Defense Department billions of dollars in testing and training costs, say industry officials.

The technology is "orders of magnitude better than it was five years ago ... I don't see it as risky," says John Lenyo, president of CAE USA, a supplier of military simulators.

One of the most complex military vehicles ever built, the Space Shuttle, was designed and tested in simulators, Lenyo says in an interview. "They didn't do too many 'tests' before they launched the real thing for the first time," Lenyo adds. "The industry knows how to do this stuff in simulations pretty well. Everything that's procured these days is done that way ... The Defense Department requires that."

Even so, he says, "You'll never completely eliminate live testing."

Among the military programs that are significantly stepping up the use of digital models for testing and training is the F-35 Joint Strike Fighter, which will continue to undergo tests in simulations even after it begins low-rate production in 2010. This attempt to test and build simultaneously could pose risks, some experts contend, given the complexity and cost of the JSF program.

Engineers are using powerful simulators to virtually fly the new jet while it's still under development. Advanced computing power and complex 3-D imaging are making simulated flights in fighter aircraft more realistic than ever.

The JSF has been fully designed on computers, using no paper, says Ralph Heath, vice president of Lockheed Martin Corp. "The digital thread works," Heath tells an industry conference. This approach to aircraft development has become the standard for military programs, Heath says. "Things will never be the same again."

But the notion that engineers should rely on simulators for testing while the JSF is concurrently being designed and constructed remains controversial, even though the technology is widely used in the aerospace industry.

"The issue is that the simulators don't realistically capture everything that goes in a real aircraft," says Philip Coyle, senior advisor at the Center for Defense Information and former head of the Defense Department's weapons testing office.

Lockheed Martin, manufacturer of the JSF, has designed sophisticated models that are used to test the performance of the aircraft. Other simulations focus on pilot training and mission rehearsals.

The company is "building a system where all the design flaws have not been seen," says Loren Thompson, chief operating officer at the Lexington Institute, a Washington D.C. based think tank.

In the JSF, significant design changes are still being made, which means the simulators are not yet representative of the real aircraft, Coyle asserts. A case in point is the JSF engine. The services continue to fight off congressional efforts to add a second engine, the General Electric's F136, as a back-up to Pratt and Whitney's F135. If they haven't decided which one will be used in the actual aircraft, then "what engine will the simulator use?" Coyle asked.

Lockheed Martin officials say the simulators are as realistic as they can be. "We're able to mimic a lot of hardware in the loop for all aspects of the combat environment," says Dan Crowley, F-35 general manager.

Lockheed Martin signaled its confidence in simulations when it asked the Defense Department this year for approval to cut two test aircraft from the acquisition plan. More evaluations would be done using computer modeling, which would reduce costs.

"Deleting two jets will save money that can be used for higher risk programs," says Crowley. Under the latest acquisition plan for the F-35, he says, the program was restructured to eliminate redundancies in certain areas, such as labs, the flying test bed and test aircraft.

"Now it's becoming easier to simulate every mission because of lower costs," says Crowley.

Advances in the technology in recent years have made simulation a more viable alternative to traditional methods of both testing and training, he adds.

"Simulation technology over the last several years has grown by leaps and bounds," says Warren Wright, manager of Lockheed media relations. "You almost lose the sense that you're in a simulator."

Lockheed's pilot training device has a 360-degree field of view, a helmet-mounted display and an advanced image generator to create a realistic environment, said Matt Robinson, deputy director of Joint Strike Fighter training.

The system also reuses 2.5 million lines of aircraft software code to increase the realism of the simulation, he said.

Simulators offer better training than a real aircraft, Robinson asserts, because the user can control the environment, which allows him to test out different scenarios.

One major benefit of virtual training is that a pilot can "throw all failures into simulations," said JoAnn Puglisi, F-35 training system director.

Detailed analysis goes into deciding which missions can be done in the simulator and which will be tried out on actual aircraft.

"We haven't trained a group of JSF pilots yet," Puglisi said.

So far, only the most highly skilled pilots are trying out the new technology. Lockheed engineers are searching for design flaws and integrating hardware as it becomes available.

A modified Boeing 737 aircraft is also being used as a flying test bed.

To convert the Boeing airplane, Lockheed added an F-35 nose with radar, a targeting pod and short F-35-like wings. It was outfitted with power systems and a cockpit simulator, Crowley says.

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Eighteen F-35s will be built for ground and flight tests. Delivery of those aircraft will begin this month.

If the program stays on schedule, the first low-rate production aircraft will have already been manufactured in 2010, while the flight test program is still in progress. The flight test program is scheduled to be completed by 2012.

Between 2008 and 2010, the pilot training program will get underway, says Puglisi. During that same time period, courseware for pilots and maintenance crews will be completed and devices built, she said. In late 2009, all products will be delivered to Eglin Air Force Base, Fla., where a new F-35 training center is being set up.

The F-35's numerous international partners are participating in the development of the pilot and maintenance courseware using a web-based program, say Lockheed officials.

In the years leading up to the first production aircraft rolling off the line, Lockheed will have to assess whether the F-35 models and simulations can be successfully executed on actual aircraft. But if the company encounters trouble down the road, it will wish it had put more money into the evaluation of the live prototypes, Coyle says.

Companies always cut testing, training, and logistics first when there are concerns about cost, he says, "but they always regret cutting testing." The technology may give pilots the opportunity to "fly" on the ground in the early phases, but that doesn't mean it can eliminate risk, argues Coyle. "It is very difficult to anticipate all the things that can go wrong in a program."

Even though Lockheed says it carefully evaluates which technologies should be tested in an aircraft and which can be done on a computer, it's not easy to determine which is best, Thompson says. "It's hard to know when real live fire is needed. F-35 missions have never arisen in the past."

--Additional reporting by Sandra I. Erwin

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