WASHINGTON — Proponents of the F-35 joint strike fighter highlight the plane's immense data-fusion capabilities, its stealth technologies and its overall connectivity.

But while the high-tech aspects of the plane draw the attention, the jet's simulator has become vital to both the training of pilots and development of tactics. And with Pentagon officials saying the advanced jet has classed itself out of some traditional range training, it will only grow in importance.

As the head of the Air Force Warfare Center at Nellis Air Force Base, Nevada, Maj. Gen. Jay Silveria is in charge of developing tactics for the F-35A. He was also the first general to be checked out on the F-35, giving him a unique perspective on how to train and test with the jet.

The simulator is being used to develop tactics against enemies or situations that can't always be effectively created on a traditional range, Silveria said during a Dec. 5 media roundtable. That data is then fed back into live tests, creating a feedback loop of sorts to give the tacticians at Nellis a wealth of information.

"In addition to doing operational testing in the aircraft as we're flying them on the range and flying them at Edwards and Nellis, we're going to also fly them in the simulators where we're going to add in a lot of the capability that we [will] have as well as a log of the threats that we have," he said.

Silveria offered an example of how the simulator can inform live tests. During a live-flight weapons test for a precision-guided munition, pilots felt that the distance the weapon could be used was not correct. They went into the simulator, ran the same scenario, and used that data to correct the range used during live flights.

"There is a validation of things you see in the air, and then there is a sort of feedback back to the way it's presented in the simulator to test," he said. "We're going to continue to refine the sim, because we want to continue to test it in the sim, and we will continue to refine it in the airplane for obvious reasons."

But while the simulator plays a key part in Silveria's work, the testing remains "overwhelmingly" live, he said.

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For training, however, the simulator offers the ability to do things that the physical jet cannot — including some challenges to live training caused by how advanced the plane has become.

A major tool touted by proponents of the F-35 is its data-fusion package. Where a pilot on a legacy jet needs to take inputs from multiple sensors and make a judgment call on what a potential threat is, the F-35's sensor suite gathers that information together and presents a clear picture to the pilot.

That is helpful in operations, but presents a challenge for training against ground targets at test ranges. Older surface-to-air weapon systems, such as an SA-6, can be spoofed using emitters and receivers to look more like an advanced integrated air defense system that might be seen in advanced operations.

Steven Pennington, director of Bases, Ranges and Airspace for the Air Force, however, notes that the F-35's sensor fusion takes in the information and dismisses the spoof as bad data, identifying the system as the correct older model. In other words, the plane is too advanced to be fooled — even for training purposes.

"What's happened here is we've seen a technological leap in military aviation with the 5th gen [generation] aircraft," Pennington said. "Our ranges in the past have evolved from F-86 s to Century series fighters, into the F-15 and F-16 era, and they've been able to evolve to meet new requirements because they weren't that much different."

"But we've seen a leap of magnitude in the capability of 5th gen, and our ranges have to make the same leap."

What can be done? After all, getting a real enemy system onto the range would not only be cost prohibitive, but logistically challenging.

"So it's very expensive to be able to recreate, whether it is the Soviet Union or folks in the Pacific, it's very expensive to create that environment on the ground," Pennington offered. "It's probably much more reasonable to create that environment [through] virtual and constructive [simulation]."

The use of simulators also frees pilots of concerns about impact to the surrounding area, Pennington said.

He pointed out that training for GPS or cyber-denied operations can be difficult, because those denied environments are not geographically constrained and could have an impact on the real world around the ranges. If a GPS blackout on a range could affect nearby cars, it would limit when and where those tests could be performed; doing it virtually eliminates that issue.

Similarly, local landmarks such as wind turbines can impact testing envelopes. Again, Pennington points out, you can simply eliminate those during virtual tests.

Moving toward more virtual and constructive training is hardly new. The Air Force has pursued the idea for years, although it has taken on special emphasis in the last two years as the service has attempted to find budget savings. But the recent explosion of cheap, high-tech simulation capabilities has created greater fidelity, which allows pilots and tacticians to rely more on the simulator than in years past.

Silveria said he flew 30 hours in the simulator versus eight hours in the real plane before being certified, and called the system an "incredibly capable simulator."

"When I had my first flight — and it's a single-seat airplane so there was nobody sitting in the back for my first landing — the confidence I had in the training, and the confidence I had in the simulator on the first flight, I felt well prepared," he said. "So that was a big eye-opening moment for me."

Challenges remain, including linking up F-35 simulators across service lines. That's not an issue of technology, said Lt. Gen. Christopher Bogdan, the F-35 program head. Instead, it's a matter of security and communication.

"We have to figure out how to connect those together," Bogdan said. "It's not hard to do, but the question is, what are the standards for connecting them together? And that requires coordination among the services and [Office of the Secretary of Defense] to figure that out."

That problem only grows when you bring in the eight international partners and three foreign military sales customers for the F-35 program. The biggest concern there becomes ensuring what Bogdan called "multilevel security" — ensuring that the data being shared with a partner isn't leaking out through another connection that the other country may have with an unsecured server.

"You need to worry about that boundary," Bogdan said. "We don't have a problem with connecting a partner's F-35 enterprise with the bigger F-35 enterprise. It's on the back end of that, what is the partner's enterprise connecting to, and you want to make sure you protect that."