The second-deadliest known climbing accident on Mount Hood came on a sunny spring day in prime conditions.

The icy volcanic cone has been a deadly lure to Oregonians for decades, drawing millions of hikers, skiers and tourists annually. Although experts consider it an easy climb for a glacier-covered peak, it has claimed 130 lives in 100 years.

In the latest deadly chapter, nine climbers fell into a crevasse on Thursday and three of them died.

While trying to rescue the stranded climbers, an Air Force helicopter nosed into the 11,240-foot mountain and rolled down the slope.

One of the helicopter crew members was in critical condition, but the three others walked down the snowy slope away from the shattered aircraft.

Only 50 miles, or 90 minutes from Portland by car, Mount Hood dominates the view from the city and is a popular climb for outdoor enthusiasts from around the world. On winter weekend days, it draws thousands of skiers and snowboarders from the city.

"Mount Hood is one of the most-climbed mountains in the world," said Keith Mischke, executive director of the Mazamas, a local climbing group. "This can be a very safe sport, but when things go wrong, the results tend to be quite severe."

"Elevation is a factor, and you are dealing with constantly changing snow conditions," Mischke said. "The snow coming down will be softer than it was going up."

More than 40,000 people fill out self-issued permits to climb Mount Hood each year, said Gerry Mills, spokeswoman for the Mount Hood National Forest. Many thousands more hike amid the volcanic boulders and conifer trees on its lower slopes. About 1.9 million people visit Hood's Timberline Lodge every year.

Some people take needless risks on the mountain. Last week, an Argentinean man who had hiked with companions to the top and was on his way back down abruptly returned to the peak and strapped on his snowboard to make the descent.

He toppled down a 2,800-foot cliff to his death.

On spring days, said Mischke, "you see unbelievable people up there doing unbelievable things."

May is prime time for a visit to the top, with most climbers starting near midnight, crossing Hood's glaciers and snowfields in the dark, when the surface is firm, then descending through the dawn to Timberline Lodge, at 6,000 feet.

From May through July, "there is still fairly good climbing and it's fairly safe," said Mischke. "This happened in the morning, so the snow should have been pretty solid still."

The climbers fell into a crevasse on the south route, which is considered the easiest approach. However, near the summit, climbers must either cross or walk around a deep cleft in the ice.

"The crevasse fills up with snow during the winter, leaving snow bridges in the spring," Mischke said. "Certain years it may be 25-30 feet deep."

"Normally people rope up at that point," he said. "They go across the bridges one at a time. A snow bridge can be between two feet or 15 feet wide. If somebody falls they could pull the others in."

The calamity Thursday rivaled the drama of the worst accident on Mount Hood, which killed 11 people in May 1986.

Nine teen-agers and two teachers from the Oregon Episcopal School in Portland froze to death on Hood after attempting the summit in poor weather.

That equaled the worst known mountaineering disaster in the Cascade Range, in which 11 people died on 14,410-foot Mount Rainier in Washington, in 1981. The victims of that climb were caught in a massive icefall.

The highest death toll of any known event in the Cascades was 57 dead from the eruption of Mount St. Helens in 1980.