Jay and David Groen spent the past 12 years planning to change the way people think about flying.

When the Groen Brothers Aviation Hawk III gyroplane entered production Tuesday, they moved within arm's reach of their goal.The Salt Lake City-based company should finish its first production gyroplane - which looks like a cross between a helicopter and an airplane - within about 2 1/2 years, David Groen said Wednesday.

And once the Hawk III receives all of the necessary Federal Aviation Administration approvals and the production line is complete, he said, hundreds of gyroplanes may take to the skies to help with everything from enforcing laws to scanning pipelines.

David Groen said the gyroplane was invented in 1919, before the development of helicopters. But the Great Depression of the 1930s wiped out private development of the aircraft, he said, and the government favored the new helicopters for military use.

A few gyroplanes were built in the late 1950s and early 1960s, David Groen said, but they did not perform or sell well.

"We've brought the gyroplane into the modern age, with modern materials and manufacturing techniques," he said.

He said the gyroplane has a rotor like a helicopter and a propeller like an airplane. It can take off and land vertically, like a helicopter, but it cannot hover.

David Groen said he and his brother have built and flown three prototypes of their gyroplane, and they started the formal FAA certification effort for the three-passenger Hawk III on March 3. The four gyroplanes they are building now will be the first certified aircraft produced by their company.

"We probably won't sell these four, because they'll be important to us for historic reasons," David Groen said.

After the first four, he said, Groen Brothers should be able to produce about 200 per year in its current facility, which employs 46 people. And if orders take off as expected, the company will move to a larger plant where it could build up to 1,500 aircraft per year.

The gyroplanes will be priced like similar-size helicopters, David Groen said, but they cost about half as much to operate.

"Its biggest advantage is cost," he said. "The market that really will use this aircraft is anyone that needs eyes in the sky and the ability to fly low and slow. . . . Probably our biggest single buyer next to the military will be law enforcement."

David Groen said the company already has received letters from more than 550 U.S. law enforcement agencies asking for more information about the gyroplane. And Groen Brothers' first commercial show of the aircraft will be at an October convention of police chiefs in Salt Lake City.

But even though the future looks bright for the company, David Groen said he and his brother know their work is far from over.

"If you're trying to change the world, which we're trying to do in aviation, it's hard," he said.