1963 — Feb 12, Severe turbulence, Northwest 705 breakup, Everglades, near Miami, FL–43

— 43 AirDisaster.Com. Accident Database. Accident Synopsis 02121963.
— 43 CAB. AAR. Northwest Airlines… Near Miami, Florida, February 12, 1963.
— 43 Kimura. World Commercial Aircraft Accidents 3rd Ed., 1946-1993, V.1. 4-11-1994, p. 2-6.

Narrative Information

CAB: “Synopsis Northwest Airlines, Inc., Boeing 720B, N724US, operating as Flight 705, crashed in an unpopulated area of the Everglades National Park, 37 miles west-southwest of Miami International Airport at approximately 1350 e.s.t, on February 12, 1963. All 35 passengers and the crew of eight were fatally injured

“Flight 705 departed Miami at 1335 e.s.t. Circuitous routing was utilized during the climbout in an effort to avoid areas of anticipated turbulence associated with thunderstorm activity. At 1347 e.s.t, in response to a request for their position and altitude, the flight advised, “We’re just out of seventeen five (17,500 feet)… This was the last known transmission from the flight. Shortly thereafter the aircraft entered a steep dive, during which the design limits were exceeded and the aircraft disintegrated in flight….

“Investigation Northwest Airlines, Inc. Boeing 720B, N724US, operating as Flight 705, crashed in an unpopulated area of the Everglades National Park, 37 rules west-southwest of Miami International Airport at approximately 1350 1 on February 12, 1963….

Flight 705 is regularly scheduled from Miami. to Portland, Oregon, with intermediate stops at Chicago, Illinois and Spokane and Seattle, Washington….

“At 1345 radar service was terminated and control of Flight 705 was transferred to Miami ARTCC. When the flight did not establish radio communication with ARTCC on the initial frequency, Departure Control provided a secondary frequency, and instructed the flight to turn to a heading of 360 degrees which was acknowledged. When Miami ARTCC requested position and altitude, the flight replied, “We’re just out of seventeen five (17,500 feet) and standby on the DME one.” This transmission ended at 1348, and was the last known communication with Flight 705.

“Witnesses in the area reported that a loud explosion had occurred in the air, and several felt a subsequent ground tremor. They also reported that heavy rain had been failing in the area. One witness, in company with five other persons, was seven miles south of the main wreckage site She heard the sound of an explosion which had no echo. When she looked in that direction she saw an orange ball of flame in the edge of a cloud. As she directed the attention of her companions toward this flame, it dropped straight down, becoming a streak, and disappeared behind trees. Shortly after the disappearance a second sound was heard….

The main wreckage area was located in a section of the Everglades which was fairly open and flat, with outcroppings of coral rock, marshy water areas, and groves or hummocks of cypress trees irregularly spaced at one-half to one mile intervals. Access to the area from the nearest road, 15 miles away, required over three hours by surface transportation or 15 minutes by helicopter. The wreckage distribution was aligned 080-260 degrees, approximately 1-1/3 miles wide and 15 miles long, indicating in-flight breakup of the aircraft structure…. The main fuselage section was gutted by severe ground fire, the wings and all tail surfaces were separated and fragmented, and there were indications of severe in-flight breakup of the forward fuselage….

“Analysis ….The final and perhaps most important factor bearing on the departure route was the airborne radar. Regardless of other weather information available to the crew, if the airborne radar was operable and being utilized properly, it is difficult to reconcile the flight’s progress to the southwest within the confines of the squall line. Apparently, the captain believed that he was southeast of the line and intended to resist the inevitable turn to the north as long as possible, in order to gain more altitude. It is significant to note that the acceleration trace of the flight recorder reflects the worst turbulence while the flight was on a heading selected by the crew….

“It is evident from the flight recorder traces that the accident maneuver started some 12 minutes after lift-off at Miami and ended about 45 seconds later when disintegration of the airframe occurred in flight. In this brief time interval the aircraft climbed steeply, reaching a climb rate about Three and one half times its normal rate, pitched nosedown, and dove toward the ground at big airspeed….

“Clearly, many factors, which individually would not be considered as extreme hazards, were involved in producing this accident. In many ways this accident is a classic illustration of the man-machine-environment causal triangle concept. Weather was a factor in this accident but the evidence is clear in indicating, that it was not greatly different from weather which might be encountered during routine airline operation. It is indeed unfortunate that the airborne radar did not guide the crew through “softer areas” during their climbout….

“From all the evidence available to the Board, it is abundantly clear that flight on instruments in heavy turbulence can present a difficult problem to any pilot who departs too far from the recommended practice of using the attitude indicator as the main reference instrument for maintaining control. If the pilot places undue emphasis on any other flight instrument during his normal scan routine….

“The Board determines that the probable cause of this accident was the unfavorable interaction of severe vertical air drafts and large longitudinal control displacements resulting in a longitudinal upset from which a successful recovery was not made.” (CAB. AAR. Northwest Airlines… Near Miami, Florida, February 12, 1963.)

Sources

AirDisaster.Com. Accident Database. “Accident Synopsis 02121963._ Accessed at: http://www.airdisaster.com/cgi-bin/view_details.cgi?date=02121963&reg=N724US&airline=Northwest+Orient

Civil Aeronautics Board. Accident Investigation Report. Northwest Airlines, Inc., Boeing 720B, N724US, Near Miami, Florida, February 12, 1963. Wash., DC: CAB, June 4, 1965, 30 pp. At: http://dotlibrary1.specialcollection.net/scripts/ws.dll?file&fn=8&name=*P%3A%5CDOT%5Cairplane%20accidents%5Cwebsearch%5C021263.pdf

Kimura, Chris Y. World Commercial Aircraft Accidents 3rd Edition, 1946-1993, Volume 1: Jet and Turboprop Aircrafts. Livermore, CA: Lawrence Livermore National Laboratory, Risk Assessment and Nuclear Engineering Group. 4-11-1994.