HELENA, Mont. — Just before a plane carrying 14 people crashed short of a southwestern Montana runway last year, killing everybody on board, the pilot told air traffic controllers that he had “one more cloud to get around” before he could reach the Butte airport.
A minute later, pilot Buddy Summerfield reported that the airport was in sight. That was his last transmission before witnesses saw the single engine turboprop enter a steep left bank turn, then suddenly nosedive into a cemetery near the airport.
New details emerged today in the investigation of the March 22, 2009, crash of the privately owned Pilatus PC-12/45, raising questions about fuel pressure, icing in the area and whether the plane was over its weight limit.
The National Transportation Safety Board has not concluded what caused the crash. The agency says a determination of probable cause will be made when the final report is completed, and no date has been set for that report.
The plane designed to carry 10 people had been carrying 13 family members and the pilot from California to a ski vacation in Bozeman. A half-hour before the crash, Summerfield requested a diversion to Butte for reasons unexplained.
The NTSB docket into the crash released today contains interviews, air traffic control transcripts, investigator reports and other documents that the agency has collected so far in its probe. But the agency provided no analysis for the information laid out in the documents and said it would not give interviews to discuss them.
However, the reams of accumulated paperwork offer new insights into what happened that day and the final minutes leading to the crash:
— The plane appeared to have experienced fuel pressure problems for at least part of the flight, with its fuel boost pumps working to stabilize fuel levels between the right tank and the left tank.
— A low-fuel warning for one of the plane’s tanks lit up six minutes before the crash.
— The flight plan called for nine people aboard the 10-seater plane, but 14 people were actually on the flight. That created a total weight that was 572 pounds over the limit when the plane took off from Oroville, Calif.
— Icing and turbulence had been reported by another plane flying the same route that day. Before taking off, Summerfield did not request a fuel additive that would prevent icing in the fuel system, which is required in ambient temperatures below freezing. The ground temperature in Butte that day was 7 degrees Celsius above freezing.
The NTSB reports also say Summerfield asked air traffic controllers twice to clear him to fly at lower altitudes. The plane had been flying at 26,000 feet, and Summerfield was cleared to descend to 14,000 feet and then 12,200 feet.
That may be significant because of a checklist the Pilatus PC-12 pilot’s operating handbook in case of low fuel pressure that instructs the pilot to descend to warmer air.
“A possible cause is the fuel filter is blocked with ice crystals,” the handbook reads, according to the NTSB.
No authorities have concluded that the plane’s fuel filter was blocked.
After the descent, air traffic control in Salt Lake City asked Summerfield if he would be able to get to the airport. Summerfield responded that he had “one more cloud to get around,” then a minute later told the controller that the field was in sight and canceled his Instrument Flight Rules clearance to fly visually.
The controller acknowledged the transmission and said there was no plane traffic between him and the airport, and the pilot did not respond. There were no further communications between air traffic control and the pilot.
One of the plane’s co-owners organized the March 2009 flight. The co-owner, who was not named by the NTSB, told investigators that the trip was within weight and balance limits but there weren’t enough seat belts.
The NTSB has used the crash as an example in making a case to aviation regulators to require all passengers to have their own seats and seat belts. Children under the age of 2 are now allowed to sit on an adult’s lap during takeoff, landing and turbulence
The reports detail Summerfield’s 44 years of flying experience since his time as a U.S. Air Force pilot. Interviews with employers and people who flew with him all described the 65-year-old pilot as very professional. He had logged 8,840 flight hours in his career.
Summerfield had never had an accident or a violation. He had flown the plane owned by Eagle Cap Leasing of Wallowa, Ore., since 2002, and he had made one previous flight from Oroville to Bozeman the year before.