Northwest Orient Airlines Flight 2

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Northwest Orient Airlines Flight 2
Summary
Date April 2, 1956
Type Crew error
Site Puget Sound, Washington, US
Passengers 32
Crew 6
Injuries 2
Fatalities 5
Survivors 33
Aircraft type Boeing Stratocruiser
Operator Northwest Orient Airlines
Tail number N74608
For the 1938 accident in Bozeman, Montana, please see Northwest Airlines Flight 2.

Northwest Orient Airlines Flight 2 was a Boeing Stratocruiser aircraft that was ditched into the Puget Sound just off the Seattle waterfront shortly after takeoff from the Seattle-Tacoma International Airport (Sea-Tac) on April 2, 1956. All of those aboard survived the ditching and escaped the aircraft before it sank, but four passengers and one flight attendant subsequently died.

Flight 2 departed Sea-Tac at just after 8:00 AM. Its intended itinerary would have taken the aircraft to Portland, Oregon, Chicago, and New York City. The takeoff was uneventful until the first officer retracted the flaps; the aircraft suddenly began to buffet violently and also began a roll to the left. The captain believed that an asymmetric flap condition had developed and made numerous attempts to control the aircraft, but to no avail. Believing the aircraft unairworthy, he considered returning to Sea-Tac and diverting to McChord Air Force Base, but the buffeting worsened and the Stratocruiser began to lose altitude. They decided their best chance was to ditch in the relatively shallow and (on that day) calm waters of Puget Sound. The first officer's Mayday transmission relaying the intention to ditch was heard by the captain of a Coast Guard vessel and the pilot of an Air Force amphibious Grumman Albatross aircraft, both of whom readied their vessels to assist the stricken aircraft.

The captain brought the aircraft down smoothly. Although it took on water quickly, the passenger cabin remained in one piece, and all of those on board were able to depart safely, most using their seat cushions as makeshift flotation devices[1]. The Air Force Grumman landed in the water near the ditching site ten minutes after the ditching and launched a number of inflatable liferafts, but not all passengers and crew were able to reach them; many remained in the freezing waters of Puget Sound hanging onto their seat cushions until they were rescued less than thirty minutes later by the Coast Guard vessel. Four passengers, including a six-year-old boy and his mother, and one male flight attendant were not recovered and were thought to have succumbed to hypothermia. The Stratocruiser sank 15 minutes after the ditching in approximately 430 feet of water.

Investigators with the Civil Aeronautics Board determined that the underlying cause of the accident was a single error made by the flight engineer. Stratocruiser engines were cooled by opening panels called "cowl gills" or "engine cooling gills" which circled the rear part of the engine and allowed heat to dissipate when open. The open gills could also disrupt the flow of air over the wings and it was therefore necessary to close them during critical phases of flight such as takeoff when maximum lift was needed. When the captain during his pre-takeoff checklist called, "Cowl flaps set for takeoff", the flight engineer replied "Set for takeoff", but had not actually closed them. When the aircraft took off and the flaps were retracted, the loss of lift caused by the open gills caused the aircraft wings to partially stall. Tests performed by CAB investigators showed that a Stratocruiser that took off with all cowl gills open would respond very similarly to a Stratocruiser with one engine shut down and could be turned and flown for some time before becoming too unstable to remain in the air. However, the captain was convinced that the problem had been caused by asymmetric flaps, a situation that would make all but the slightest turn dangerous, and decided to ditch based on that analysis.

The CAB found that the captain had incorrectly identified the cause of the aircraft's control and stability problems, but that it would have been extremely difficult if not virtually impossible for him to have correctly identified the problem given the information he had, the nature of the emergency he was faced with, and the time in which he had to make the decision as to whether to ditch or to attempt a landing at McChord AFB or back at Sea-Tac.

The accident flight is known in some references (and in the CAB report) as Northwest Airlines Flight 2, but it actually flew under the Northwest Orient Airlines name.

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[edit] Footnotes

  1. ^ Aircraft whose flight plans took them over land were not at the time required to be supplied with liferafts, lifejackets, or other flotation devices.

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