Narrative:The Beech 99 departed Helena (HLN) at 14:35 on flight to Butte (BTM) and was carrying only about 10 pounds of freight. The aircraft was cleared for the VOR B approach to Butte at 14:48. A weather front had been approaching the area from the south to the north/northeast. Weather conditions included icing conditions followed by heavy snow fall with poor visibility and variable winds in the mountains.
According to the approach plate, the transition to the approach is via a DME arc at 9,000 feet with no procedure turn. The flight is to track inbound on the 127 degree radial, descending down to, but no lower than, 7,700 feet to the initial approach fix (IAF). After crossing the IAF, the flight is to turn to 097 degrees for 10 nautical miles and descend to 6,900 feet. The remainder of the 1.5 nautical miles to the runway is to be flown under visual conditions.
During the descent the airplane collided with trees and subsequently the mountainous terrain on a heading of approximately 127 degrees and about 6,900 feet mean sea level. The initial impact point was located approximately nine nautical miles on a magnetic bearing of 130 degrees from the IAF. Documentation of the horizontal situation indicator (HSI) on the left side instrument panel indicated that the course arrow was positioned to approximately 127 degrees, the inbound heading to the IAF. The co-pilot (right side) course arrow was positioned to 115 degrees. The location of the wreckage and the 127 degree heading on the HSI indicate that the pilots failed to follow the approach procedure and turn to a heading of 097 degrees after crossing the IAF.
Search crews found the wreckage of the plane on March 20.
Probable Cause:PROBABLE CAUSE: "The second pilot's failure to follow the published instrument approach procedure and the captain/PIC's inadequate supervision. Snow and mountain obscuration were factors."
Controlled Flight Into Terrain (CFIT) - Mountain
» 2 killed in crash of cargo plane (Billings Gazette 20-3-2006)
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not
display the exact flight path.
Distance from Helena Airport, MT to Butte Airport, MT as the crow flies is 82 km (51 miles).