The small plane that crashed in the Alaska Range near Mount McKinley last summer, killing a well-known pilot and three National Park Service rangers, disintegrated in flight, according to a report on the accident by the National Transportation Safety Board. The wings separated from the fuselage before they and other pieces of the aircraft crashed into a brush-covered hillside above the Yentna Glacier, 52 miles northwest of Talkeetna, the report indicates. But the report, made available recently by the NTSB, draws no conclusions about what caused the crash. It is a summary of facts only, NTSB investigator Clint Johnson said Thursday in Anchorage.

A probable cause of the accident is to be determined by the five board members in Washington, D.C., probably within the next three weeks, Johnson said.

Weather, including turbulence, low clouds and fog, played a role in the crash, the report suggests. Don Bowers, a seasoned 52-year-old pilot working for Hudson Air Service, had left Talkeetna in late afternoon on June 19 in a ski-equipped Cessna 185. He was headed 50 miles northwest to the glacier airstrip and mountaineering base camp on the southeast fork of the Kahiltna Glacier, 10 miles south of McKinley.

The Park Service had chartered the flight; Bowers' three passengers were to begin a routine ranger patrol up the mountain's West Buttress route. The plane never got there. Bowers flew through one mountain pass and reached the main trunk of the Kahiltna but was met there by deteriorating weather, the report states.

One of his passengers, 25-year-old ranger Cale Schaffer, radioed the Talkeetna ranger station and said they were turning around and coming back. Another pilot, who was in radio contact with Bowers after she took off from the Kahiltna base camp, told NTSB investigators that Bowers reported low clouds over the Kahiltna and said he was returning to Talkeetna, the report states.

The second pilot, not identified in the report, also observed "low weather conditions" and returned to the base camp, according to the report. Before the other pilot landed, Bowers radioed her again to say that weather had closed in over other parts of the Kahiltna near him and therefore he was turning west toward the Lacuna Glacier, where he could see some light, the report says. That was the last contact anyone had with those in Bowers' plane, it says.

The plane was reported overdue an hour later, at 8 p.m. After an extensive search, the wreckage was located and confirmed the next afternoon. The report notes that weather in the vicinity of the crash was said to include low clouds, scattered snow showers and fog. At a lodge 31 miles south of the accident site, people reported "a large wall of cumulus clouds" approaching from the south preceded by strong winds about the time of the crash.

The storm brought "the heaviest rain the (lodge) owner had ever observed," according to the report. When investigators later examined the plane wreckage, they found "that both wings separated from the fuselage in a downward direction." An unidentified official with Hudson Air Service said Bowers had phoned ahead to the base camp manager that day, asking about flying conditions on the Kahiltna, the report says.

Glacier pilots headed for the 7,200-foot base camp often check with the camp manager about the local weather. The camp manager, however, said Bowers "did not telephone the base camp, and if he had called, the manager said she would have advised him to not fly to the base camp, since one airplane was already remaining on the ground due to low clouds," according to the report.

Schaffer, the ranger, called the base camp about noon that day, the report says, and the manager told him "not to bother" coming. Jay Hudson, manager of Hudson Air Service, could not be reached for comment Thursday.

The NTSB reported that Bowers, Hudson's chief pilot, had more than 9,000 hours of flight time, including about 2,000 in the Cessna. Autopsy tests showed no drugs or alcohol in his body, the report states. He was regarded as a careful pilot. The Cessna had been regularly maintained, the report says, though it had flown about 12 hours beyond its required
inspection time.

Besides being an experienced pilot who had flown on numerous McKinley search-and-rescue operations, Bowers was an author, teacher and Iditarod musher. The others killed in the crash were both volunteer rangers, Brian Paul Reagan, 27, of Anchorage, and Adam Kolff, 27, of Boulder, Colo.