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Accident
Last updated: 23 October 2017
Status:Schlussbericht
Datum:Montag 4 September 1950
Zeit:14:02
Flugzeugtyp:Martin 2-0-2
Fluggesellschaft:Northwest Orient Airlines
Kennzeichen: N93051
Werknummer: 9136
Baujahr: 1948
Besatzung:Todesopfer: 0 / Insassen: 3
Fluggäste:Todesopfer: 0 / Insassen: 15
Gesamt:Todesopfer: 0 / Insassen: 18
Sachschaden: schwer beschädigt
Konsequenzen: Repaired
Unfallort:Billings Municipal Airport, MT (BIL) (   USA)
Flugphase: Start (TOF)
Betriebsart:Inländischer planmäßiger Passagierflug
Flug von:Billings Municipal Airport, MT (BIL/KBIL), USA
Flug nach:Bozeman, MT (BZN/KBZN), USA
Unfallbericht:
Flight 163 departed on schedule at 06:15 from Minneapolis for Seattle. During a planned intermediate stop at Billings a routine change of crew was made. The plane taxied out or takeoff at 13:56. Throttles were advanced, but before the aircraft had rolled far, blue smoke was noticed between the rudder pedals on the left side of the cockpit. When the aircraft had progressed about 1/3 of the way down the runway, and when it had accelerated to an airspeed of approximately 80 miles per hour, a large puff of this blue smoke suddenly filled the cockpit. Accompanying it was a sharp smell of burning. Throttles were retarded and brakes applied to discontinue takeoff. Brakes were effective only momentarily. There was only slight deceleration, and the aircraft continued with speed unchecked toward the end of runway 04. Runway 4 at Billings has a downhill gradient which increases from 1.9 percent at the approach and to 3.1 percent at the northeast end. It seemed to the crew that because of this down grade the aircraft actually increased in speed after they discontinued takeoff. As soon as it became apparent that brakes were useless, the captain applied full reverse thrust and instructed the Copilot to steer the aircraft by the nose wheel control. However, the nose wheel steering control, as were the brakes, was totally ineffective. Both pilot's then observed that the hydraulic pressure in the main and emergency systems had dropped to zero. As the aircraft progressed over the runway, it turned slightly to the left and went off the paved area 1,074 feet from the northeast end. Since the ground was hard and dry, no appreciable loss of speed resulted from leaving the paved runway and rolling onto the drift surface. By application of reverse thrust the aircraft was slowed to about 15 miles per hour. After that, even reverse thrust seemed to be ineffective. At reduced speed the aircraft continued to roll to and the northeast boundary of the field where the ground level dropped sharply in a bluff. In anticipation of rolling over this bluff, the crew turned off all electrical switches and fuel valves. Before the aircraft reached the bluff, however, it struck a cement culvert and light standard. As a result, the right main landing gear failed to the rear which permitted the right wing to touch ground. This turned the aircraft slightly to the right and brought it to a full stop.

Probable Cause:

PROBABLE CAUSE: "The Board determines that the probable cause of this accident was the failure of an "Ermeto" hydraulic fitting due to improper installation."

Informationsquelle:
» CAB File No: 1-0094


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Map
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 Billings Municipal Airport, MT to Bozeman, MT as the crow flies is 201 km (126 miles).

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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