Flight plan change under scrutiny in Mont. crash

BUTTE, Mont. -- Investigators said Tuesday that a pilot's change of course shortly before his plane nose-dived into a Butte cemetery, killing all 14 aboard, has emerged as a potentially crucial factor in the crash.

Flying at 25,000 feet, pilot Buddy Summerfield requested the diversion from Bozeman to Butte half an hour before the single-engine Pilatus PC-12 crashed at the edge of Butte's airport Sunday. Seven children younger than 10 were among the victims.

National Transportation Safety Board acting chairman Mark Rosenker says why the plane diverted is at the forefront of his agency's investigation.

Summerfield said nothing to controllers to indicate he was having trouble, and did not say why he was changing course from Bozeman to Butte, about 75 miles away.

The probe into the crash will include a review of Summerfield's medical history, based on speculation that a heart attack or other health issue might have been at fault.

Also under scrutiny are weather conditions that could have caused icing on the plane's wings and possible overloading. The plane was configured to seat just 10 people, but the fact that several of the 14 passengers were small children has dampened speculation that excess weight was a factor.

The investigation has been hampered by the lack of a cockpit voice recorder or data recorder, which were not required on the private flight.

Rosenker said his agency may subpoena cell phone records of the victims to see if they could provide further clues.

Federal officials on Tuesday gave a few reporters and photographers their first close look at Sunday's crash site.

Working among rows of charred granite headstones cordoned off by yellow police tape, investigators removed the last of the victims' luggage as they combed through the wreckage. Shredded metal, pieces of propeller and a seat cushion were among the few discernible items left at the scene.

Small pieces of debris were picked up, logged and placed in plastic bags. The larger pieces, including a wing and a section of the plane's tail, were to be removed beginning Tuesday night and taken to a hangar in Bozeman for inspection.

Most of the wreckage was confined to a small area, consistent with witness reports that the plane nose-dived straight into the ground. As many as 20 witnesses to the crash have stepped forward.

While descending toward Butte's Bert Mooney Airport, the plane passed through a layer of air at about 1,500 feet that was conducive to icing because the temperature was below freezing and the air "had 100 percent relative humidity or was saturated," according to AccuWeather, a forecasting service in State College, Pa.

Safety experts said similar icing conditions existed when a Continental Airlines twin-engine turboprop crashed into a home near Buffalo Niagara International Airport last month, killing 50.

A possible stall created by ice -- and the pilot's reaction to it -- has been the focus of the Buffalo investigation, which remains open.

Former NTSB chairman Jim Hall has said there were similarities between the Montana crash and a 2005 crash near Bellefonte, Pa., that killed a pilot and five passengers. The plane in both cases was a Pilatus PC 12/45, and in both there were reports of conditions conducive to icing at lower elevations and witness reports that the plane appeared to dive into the ground.

Rosenker said the Pilatus PC-12 was certified to fly in "known icing conditions."

NTSB spokesman Keith Holloway said it was too early to single out any one factor in the Butte crash.

"We're looking at mechanical issues. We're looking at weather. We're looking at the structure of the aircraft. We're looking at human performance, weight and balance issues," Holloway said.

Bert Mooney airport -- surrounded on three sides by mountains and a high butte -- is known among pilots as a tricky airport for landings.

Jerry McLaughlin, a semiretired Butte pilot with 40 years' experience flying commercial and private planes, said the proximity of the mountains can instill panic in people who aren't accustomed to them.

"You're in a bowl here," he said. "The flatlanders hate flying into here."

But others said a highly trained pilot with experience flying in the mountains should not have had any major problems. Summerfield was a former military pilot who had logged 2,000 hours flying the type of plane that crashed, according to federal officials.

Since 2001, federal authorities have investigated 15 crashes involving PC-12s. Six involved fatalities, with a total of 14 killed before Sunday's crash. Rosenker said his agency has yet to find a common thread that would link those accidents.

About 800 PC-12s are in service in the U.S.

Two weeks ago, the Federal Aviation Administration issued a warning known as an "airworthiness directive" for PC-12s. The agency said cables used to lower and raise the plane's elevators could become stuck. The NTSB's Hogenson said that issue has been ruled out in Sunday's crash.

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Associated Press writer Joan Lowy in Washington contributed to this report.