Narrative:Northwest Flight 115 originated at Chicago and was heading for Seattle Via intermediate stops. At Minneapolis, the first scheduled stop. both the equipment and the flight crew were changed. N93040 departed Minneapolis at 00:30 and proceeded uneventfully to Billings, Great Falls and Helena. At Helena, the aircraft was fueled and was off the ground at 07:53, using runway 29. The flight plan, amended before takeoff, specified an altitude of 10,500 feet MSL under instrument flight rules via Amber Airway No. 2 to the Whitehall (Montana) Range Station and from there to the Butte Airport via Red Airway No. 2. Following takeoff from runway 29, the aircraft was flown in a climbing right turn so that it passed approximately over the Station as it headed south toward the Whitehall Range Station. At 08:01 the flight reported to Helena that it had reached its cruising altitude. This message was acknowledged. The next message from the flight was to Butte at 08:14 stating that it was over Whitehall Range Station at 08:11 and starting descent. Butte acknowledged this message, gave that flight the station altimeter setting of 29.97, advised that the wind was south, calm, and that the Weather Bureau advised what the ceiling was lower to the east and north and better to the south and southwest. Flight 115 replied that it had vertical visibility at 10,500 feet. This was the last radio contact with the flight.
At approximately 08:15 the aircraft had struck the eastern slope of a ridge about 30 feet below its crest, at an altitude of about 8,250 feet MSL. The site of impact was approximately 2-1/2 miles east of the control tower at the Butte Airport, and about 1-1/2 miles to the right of the center of the on-course signal from Whitehall to Butte. The ridge which was struck is paralleled by another somewhat similar ridge approximately three or four miles to the east.
Probable Cause:PROBABLE CAUSE: "The failure of the captain to conduct the flight in accordance with the prescribed procedure."
» CAB File No. 1-0125
» ICAO Aircraft Accident Digest No.2, Circular 24-AN/21 (41-43)
memorial plaque at the crash site of Northwest Flight 115
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).