With the leader of the free world yelling, "Bail out! Bail out!" as she sped down an icy slope on a saucer sled, Barbara Bush crash-landed into a tree yesterday at Camp David, breaking a bone in her left leg.

The accident ended an after-church sledding party that included President Bush, four of the Bushes' grandchildren and the chairman of the President's Council on Physical Fitness, actor Arnold Schwarzenegger.

The 65-year-old First Lady was taken by ambulance to a hospital in nearby Hagerstown, Md., where X-rays revealed what the White House described as "a non-displaced fracture of the fibula bone in the left leg." The fibula is the outer and smaller of the two bones between the knee and the ankle.

Mrs. Bush, who was ordered onto crutches and off her leg for three days, also sustained several minor lacerations and bruises, "a couple on her face," according to her press secretary, Anna Perez. She described the First Lady as "in very good spirits" and "laughing about it" later when she returned to Camp David. Doctors told her that though the fracture was minor, it could take five to six weeks to heal completely. Her leg was not placed in a cast.

Perez said Mrs. Bush told her that when the president saw her going down the hill he started yelling, "Bail out! Bail out!"

"She doesn't know why she didn't bail out. She just held on and the next thing she knew, there was the tree," said Perez.

Described as very icy and steep, the slope proved more of a challenge for Mrs. Bush than she apparently counted on. She told Perez that when the sled veered off course, she was unable to control it.

An experienced sledder from her childhood in Rye, N.Y., the First Lady went sledding Saturday with a friend, Betsy Heminway of Greenwich, Conn., an outing that passed "without mishap," said Perez. Yesterday they were joined by the president, the Bushes' daughter, Dorothy LeBlond, and her children, Sam, 6, and Ellie, 4, and their son Marvin's wife, Margaret, and their children, Marshall, 4, and Charles Walker, 1.

In addition, the group included Schwarzenegger's wife, NBC correspondent Maria Shriver, and their infant daughter.

Perez said that after examining Mrs. Bush and noticing some swelling, Lawrence Mohr, a White House physician, sent her to Washington County Regional Hospital in Hagerstown for X-rays. Heminway and a medical corpsman accompanied her. The president and Mohr stayed behind at the Catoctin Mountain retreat.

Later, when returning to the White House, Mrs. Bush was carried off Marine One to a waiting wheelchair. Then, with Millie and Ranger, the Bush dogs, darting in and out of her procession, the First Lady shook her head and mugged as if in disbelief as she was wheeled into the mansion.