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Accident
Last updated: 15 December 2017
Statuts:Enquête Officielle
Date:lundi 2 avril 1956
Heure:08:10
Type/Sous-type:Boeing 377 Stratocruiser 10-30
Compagnie:Northwest Orient Airlines
Immatriculation: N74608
Numéro de série: 15954/50
Année de Fabrication: 1949-10-10 (6 years 6 months)
Heures de vol:18489
Moteurs: 4 Pratt & Whitney R-4360-B6
Equipage:victimes: 1 / à bord: 6
Passagers:victimes: 4 / à bord: 32
Total:victimes: 5 / à bord: 38
Dégats de l'appareil: Perte Totale
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:8,7 km (5.4 milles) SW de Seattle/Tacoma International Airport, WA (SEA) (   Etats-Unis d'Amérique)
Phase de vol: En vol (ENR)
Nature:Transport de Passagers Nat.
Aéroport de départ:Seattle/Tacoma International Airport, WA (SEA/KSEA), Etats-Unis d'Amérique
Aéroport de destination:Portland International Airport, OR (PDX/KPDX), Etats-Unis d'Amérique
Numéro de vol: 2
Détails:
Northwest Flight 2 (Seattle-Portland-Chicago-New York) took off from Seattle at 08:06. As the aircraft reached 2000 feet, at 145 knots airspeed, the flaps were retracted. Severe buffeting started and the aircraft tended to roll to the left. Thinking it was an asymmetric flap condition, the captain reduced power to stop the buffeting, but of no avail. Full power was applied again and plans were made to divert to McChord AFB. The plane continued to lose altitude and was not able to reach McChord. A ditching was carried out in Puget Sound. The aircraft sank 15 minutes after the ditching. It appeared that the aircraft had taken off with the engine cowl flaps fully open. Though not emphasized as a contributory factor, it must be noted that the cowl flap control on the Boeing 377 and Lockheed L-1049 move in opposite directions for the closing of the cowls. Most of the flight engineers flying time had been on L-1049 and DC-6 aircraft.

Probable Cause:

PROBABLE CAUSE: "The incorrect analysis of control difficulty which occurred on retraction of the wing flaps as a result of the flight engineer's failure to close the engine cowl flaps - the analysis having been made under conditions of great urgency and within an extremely short period of time available for decision."

Sources:
» ICAO Accident Digest No.8, Circular 54-AN/49 (72-75)


Photos

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Plan
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 Seattle/Tacoma International Airport, WA et Portland International Airport, OR est de 207 km (129 miles).
Accident location: Approximate; accuracy within a few kilometers.

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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