Page:CAB Aircraft Accident Report, Northwest Airlines Flight 705.pdf/5

 nine seconds of the readout the altitude trace continued to decrease, the airspeed trace increased until the stylus hit the mechanical stop, the acceleration trace increased in a negative direction, and the heading remained fairly constant at 330 degrees. The final maneuver from the onset of the climb at 1347:25 lasted approximately 45 seconds.

The main wreckage 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 hammocks 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-$1/undefined$ miles wide and 15 miles long, indicating in-flight breakup of the aircraft structure. Approximately 90 percent of the wreckage, including all large segments, was found in the most westerly two miles. The remaining portions of wreckage found to the east of this concentration consisted mainly of light material which was drifted east-northeast by the prevailing winds aloft. The most westerly piece of wreckage was the upper part of the rudder, which was used by surveyors as a zero datum point. Approximately 500 feet east of this point were engines Nos. 1, 2, 4, 3, in that order, oriented along a south to north line one-half mile long. Five hundred feet northeast of the No. 3 engine was the cockpit area. Next, approximately 1,500 feet east of the rudder fragment were the outboard portions of both wings. Two thousand and seven hundred feet east of the datum point were the main fuselage and wing center sections which landed inverted on a heading of 060 degrees. The tail section was 1,00 feet farther east. Approximately 97 percent of the aircraft was recovered.

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. An attempt was made to partially reconstruct the aircraft at the site, but as the work progressed it became apparent that a more sophisticated study of the wreckage was required, and arrangements were made to remove the wreckage to a U. S. Coast Guard hangar at Opa Locka Airport in Miami. The transfer was accomplished by a U. S. Army H-37 helicopter which airlifted all parts either to waiting trucks or directly to the hangar.

A mockup (see attachment C) of the aircraft was completed on April 1, 1963, and the detailed study, was resumed. The main failures in both wings and horizontal stabilizers were in a downward direction, and virtually symmetrical. The forward fuselage broke upward and the vertical stabilizer failed to the left. All four engines generally separated upward and outboard; however, certain peculiarities in the No. 3 engine separation generated considerable interest during the investigation. The reverser on this engine landed approximately 1,300 feet from the main engine section. The No. 3 engine also varied in that its final position was 150 on an azimuth of 015 degrees relative to its initial impact point. The other engines bounced approximately 40-45 feet on azimuths of 055, 080, and 060 degrees from their respective craters. Approximately four feet of the right wing, from the leading edge aft to the front spar, and inboard of the No. 3 nacelle, was broken away. Collision of the reverser with this leading edge section was indicated in the pattern of scratches found within the creases which resulted at ground impact. The main engine mount fractures were examined for fatigue, which might have resulted from damage sustained at the Fort Lauderdale accident, but none was found.