Accident Boeing 377 Stratocruiser 10-30 N74608,

ASN Wikibase Occurrence # 334706

Date:	Monday 2 April 1956
Time:	08:10
Type:	Boeing 377 Stratocruiser 10-30
Owner/operator:	Northwest Orient Airlines
Registration:	N74608
MSN:	15954/50
Year of manufacture:	1949
Total airframe hrs:	18489 hours
Engine model:	Pratt & Whitney R-4360-B6
Fatalities:	Fatalities: 5 / Occupants: 38
Aircraft damage:	Destroyed, written off
Category:	Accident
Location:	8,7 km SW off Seattle/Tacoma International Airport, WA (SEA) - United States of America
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Seattle/Tacoma International Airport, WA (SEA/KSEA)
Destination airport:	Portland International Airport, OR (PDX/KPDX)
Investigating agency:	CAB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
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: "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."

Accident investigation: