BUTTE – Investigators probing the plane crash that killed 14 people are looking at ice formation and why the pilot changed his flight plan without explanation, but have not rejected mechanical failure, human error or other factors.
The work is significantly complicated because the plane did not have a cockpit voice recorder or flight data recorder, the pilot apparently made no mayday call, and there is no key radar data on the last stages of the flight.
Investigators say it could take months to pinpoint the cause.
Fourteen people died Sunday when the single-engine Pilatus PC-12 nose-dived into a cemetery near the Butte airport and burst into flames. An experienced pilot was at the controls.
Seven adults and seven children from three California families were killed. Relatives said the victims were headed to an exclusive resort on a ski vacation, and gave the children’s ages as 1, 3, 5, 7 and 9, plus two 4-year-olds.
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 condition 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.
“It’s Buffalo all over again, or it could be,” said John Goglia, a former member of the National Transportation Safety Board. “Icing, given those conditions, is certainly going to be high on the list of things to look at for the investigators.”
But an NTSB spokesman said it was too early to single out any one factor.
“To say that icing is becoming the lead focus is not true at this point,” said spokesman Keith Holloway. “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.”
There is no radar data of the plane’s final moments for investigators to examine because, like thousands of small airports, the Butte airport doesn’t have radar. The radar at the FAA’s en route center in Salt Lake City, which handled the flight’s last leg, doesn’t extend as far as the Butte airport.
The last radio communication from the turboprop’s pilot was with the Salt Lake City center when the plane was about 12 miles from Butte, said Doug Church, a spokesman for the National Air Traffic Controllers Association. Minutes before the crash, the pilot told controllers he intended to land at Butte using visual landing procedures rather than relying on instruments, which is not unusual, Church said.
Mark Rosenker, acting chairman of the National Transportation Safety Board, confirmed that the pilot said nothing to controllers to indicate he was having trouble, including during radio conversations earlier in the flight when the pilot notified controllers he intended to divert from the flight’s original destination of Bozeman, Mont., to Butte, about 75 miles away.
“We don’t know the reason for the requested change to the flight plan,” Church said. “We don’t know whether weather was a factor in Bozeman. There was no apparent reason given for the change in flight plan from Bozeman to Butte.”
The pilot was identified as Buddy Summerfield, 65, of Redlands, Calif. Summerfield was a former military pilot who had logged 2,000 hours flying the type of plane that crashed, according to federal officials.
Former NTSB chairman Jim Hall 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.
The NTSB’s Holloway said the Buffalo investigation remains open.
Rosenker said overloading and equipment failure also were being examined. He said the plane had just 10 seats, including the two in the cockpit.
“It will take us a while to understand,” he said. “We have to get the weights of all the passengers, we have to get the weight of the fuel, all of the luggage.”