Washburn's rescue hovercraft is floating under ice somewhere along the Missouri River after flipping over Wednesday afternoon near Fort Yates.

Washburn firefighters, who own the Air Commander AC6 Hovercraft, were in Fort Yates with an engineering firm using the craft to grid the river and find a deep enough area to lay a pipeline. Hovercrafts work best in those situations because they float on cushions of air above the surface, avoiding obstructions such as sandbars and ice, Washburn's assistant fire chief Clayton Berke said.

The group ran into problems when the hovercraft entered an area of open water and water sprayed the front engine, shutting it down.

"That's no big deal," said Dennis Hammling, Washburn fire chief. "It's happened before."

When the front engine goes out, the craft is used as a boat, powered by a rear thrust engine. But when the crew hit the water, the front nose dipped into the water, filling the craft with water. The four members aboard - two fire officials and two engineers - were wearing cold immersion suits.

At that point a nearby tugboat came over to help, as the hovercraft was becoming increasingly unstable.

"That's when we figured we were in trouble," said Berke, who was onboard the craft. "It's been swamped full of water many times but it's always been stable."

But when the four left the craft to get on the tugboat, the hovercraft flipped over. The tugboat followed it half a mile on the river, trying to attach a rope to it, but lost it when it slipped under ice.

"It's still floating, but it's somewhere under the ice," Berke said.

Berke said the fire department has no way of retrieving the hovercraft, and it will be a total loss.

"When the ice goes out in the spring I would like to go looking for it," Berke said. "With all the ice that's flowing and the currents, it'll be pretty beat up. And being under the ice for that long, the two motors will be junk."

A representative from Air Commander said this is the first time that model of the company's hovercrafts flipped over. Berke and Hammling said they are wondering what happened.

"We've had four to six guys hanging off the side to see its capabilities," Hammling said. "It's never been unstable for us in any condition."

The fire department raised money three years ago to buy the rescue hovercraft as a safety measure for an anticipated increase in river traffic with the upcoming Lewis and Clark bicentennial, Berke said. The total price tag was about $33,000 for the craft, plus another $3,700 for rescue features.

"The fire department had purchased it by not using tax dollars in the hope to go out of our district to help surrounding districts if they needed a craft like that," Hammling said.

Hammling said, as far as he knew, it was the only rescue hovercraft in the state. Since its purchase, the craft has aided in the search for a man that drowned near Underwood and helped people stranded on sandbars.

"It was a very valuable tool for us," Hammling said.

Air Commander hopes to answer the question of why the craft tipped over, after they complete an investigation. Officials from the Washburn Fire Department are waiting for those answers and information from the department's insurance company, to figure out where to go next.