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Last updated: 24 September 2018
Statuts:Enquête Officielle
Date:lundi 4 septembre 1950
Type/Sous-type:Martin 2-0-2
Compagnie:Northwest Orient Airlines
Immatriculation: N93051
Numéro de série: 9136
Année de Fabrication: 1948
Equipage:victimes: 0 / à bord: 3
Passagers:victimes: 0 / à bord: 15
Total:victimes: 0 / à bord: 18
Dégats de l'appareil: Substantiels
Conséquences: Repaired
Lieu de l'accident:Billings Municipal Airport, MT (BIL) (   Etats-Unis d'Amérique)
Phase de vol: Au décollage (TOF)
Nature:Transport de Passagers Nat.
Aéroport de départ:Billings Municipal Airport, MT (BIL/KBIL), Etats-Unis d'Amérique
Aéroport de destination:Bozeman, MT (BZN/KBZN), Etats-Unis d'Amérique
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."

» CAB File No: 1-0094


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Ce plan montre l'aéroport de départ ainsi que la supposée destination du vol. La ligne fixe reliant les deux aéroports n'est pas le plan de vol exact.
La distance entre Billings Municipal Airport, MT et Bozeman, MT est de 201 km (126 miles).

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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