Call them sky bums.

Each weekend dozens of sky divers converge on a dusty airfield in rural Yolo County, where they camp out in tents, RVs and school buses. They trade hugs and, over beers at sunset, swap tales of the day's adventures.

Some are true sky-diving bums, itinerant athletes who pack parachutes for food money. Others are professionals who work to dive on weekends.

They all describe the experience of leaping from a plane at 13,000 feet as a rush followed by euphoric bliss – a transcendent experience that's hard for them to put into words.

The subculture of good vibes and adrenaline reaches its annual zenith this weekend at the American Boogie 2009, a gathering of hundreds of sky-diving junkies from across the West, hosted by SkyDance SkyDiving at Yolo County Airport.

The Boogie, which kicks off the summer sky-diving circuit nationwide, is an opportunity to "see old friends, meet new people and soak up the vibes," said Kimberly Avadikian, a nurse from San Anselmo.

She and her husband spend every weekend they can at the airport, living out of their RV. They came to rural Yolo County on Thursday for the festival's start, and looked forward to leaping from balloons, helicopters and planes.

As she prepared to jump at 9,000 feet, Avadikian yawned. The coffee she drank earlier hadn't worked, she said.

"This will," said Tim Brennan, who sat next to her on the cramped single-engine aircraft circling over Davis and Lake Berryessa.

The side door rolled open and Avadikian tumbled into the void, the plane giving a sickening lurch as it lost the weight of another occupant.

On the same flight, Holly Yearwood and David Ferazza were ready to make their first jumps strapped to instructors.

Tandem jumps are the way most get started in the sport. Some scream on the way down. Others cry with joy afterward. Rarely does someone refuse to go out the door, instructors said.

Yearwood, a 24-year-old aerospace engineer from Alabama, seemed remarkably calm as she sat strapped to instructor Dan Blakeley. Blakeley asked to see her hand: It didn't shake.

They rocked forward and out the door they went.

After jumping, Ferazza, 26, an arborist from Roseville, said his view of the world changed in the moments he'd been airborne.

"It's all overwhelming," he said with glassy eyes. "You look at things differently – nature and everything."

Ray Ferrell, who started SkyDance with a partner in 1987 said many remember their first jump as transformative.

Ferrell, 57, first jumped in the 1970s in his native North Carolina. There was the rush of air and free-falling, then the peace of a slow descent by parachute.

The sun was setting in the west, the moon rising in the east. "The world couldn't have been any prettier or stiller," he said.

He said the experience of falling at 120 mph immediately clears a person's mind of mundane concerns about work and bills.

Ferrell said sky diving used to be considered a sport of "crazies," who used military surplus parachutes and fell to the ground in what amounted to controlled crashes. Today's modern equipment renders it relatively safe, he said.

Many sky divers at the Yolo airport were quick to defend their sport as safe and controlled. Yet dangers remain.

Almost as soon as a person sets foot in the SkyDance headquarters and asks to get on a plane, workers push a liability waiver across the counter and tell them to sign away their right to sue for death or injury.

In 2002, Daniel Enney, 27, of Antelope, died after a tandem jump with a SkyDance instructor when his reserve chute became entangled.

In 1998 at SkyDance, Stephanie Ann Cotter, 26, and her sky-diving instructor Seth Blake, 28, died while jumping in tandem when Blake opened the chutes incorrectly, a federal investigation found.

Two other sky-diving deaths occurred at SkyDance in 1989 in a tandem jump.

"It's like any other high-adventure sport," Ferrell said. "There will be fatalities."

As quick as they are to defend their sport, sky divers speak fondly of its camaraderie and thrills.

"It's an international community that follows the sun," Ferrell said.

Tom Grayson, 33, of the Suisun City area, uses a wing suit when he jumps, allowing him to glide high above Yolo's checkerboard of farmland.

"It's like when you were a kid and you dreamed about flying," he said.

Nicola and Allisyn Martinez are a young couple who recently married. They are sky divers and base jumpers, who leap from cliffs with only one brief chance for their chutes to open. "It completes my soul," Nicola said.

They had pitched their green tent at the SkyDance campground and were busy packing chutes for $5 and $10 each as sky divers returned from jumps.

They spend their year moving from Yolo to Moab, Utah, and Yosemite, sometimes traveling to Europe.

Coming to the Yolo airport, they said, is an opportunity to spend time with like-minded souls.

"This is our life," Allisyn said. "There's always the energy that people are doing something that they love. It's a good place to be."

Call The Bee's Hudson Sangree, (916) 321-1191.