_ 13 -
for the most part was reduced to crushed rubble. A thorough examination of the recovered and identifiable parts from this area showed no evidence of heat, fire, or soot.
The rear fuselage, the center section, including the right wing-to-wing station No. 329, and the rear portion of No. 3 engine struck the ground with great force. The rear half of the lower center section planking remained intact. The rest of the center section box area was reduced to hand—Sized fragments. The planking and front spar of the right wing stub were shattered with only the lower planking material remaining in large sections. The fuselage Side and top panels were dis— tributed over a wide area but the individual panels were relatively free of severe impact marks and crushing effect. There was no evidence of fire or soot on the right Side of the fuselage, in the center section, right wing stub, or the interior of the fuselage.
The exterior surfaces of the left fuselage panels revealed considerable evidence of inflight fire effects. The biaxially stretched plex1glass cabin windows on the left Side aft of fuselage station No. 659 had been surface distorted in the form of intersccting trenches and variable size rectangular raised areas or islands.
The severity of the window distortion increased progressively toward the aft end of the fuselage. This type of surfacc distortion is a common characteristic of this plastic when it is exposed to above normal heating effects either by direct flame impingement or by radiated heat. The exposure time, type of heat and applied temperature are all variables which will cause distortion pattern changes, 1.3., depth of trenching, Size of islands, and degree of edge roughness.
Lockheed Aircraft Corporation conducted tests to attempt to determine the nature of controlled variables which would cause Similar type of distortion of plexiglass mmnples as ev1denced by the fuselage windows. Reasonable correlation between laboratory tests and observed heat effects on the airplane was achieved in several instances; however, it is noted that the controlled test condition did not neces— sarily represent the existing airborne conditions at the time of occurrence. The following is a quoted summary of Lockheed's Report No. 14,281, dated 2/15/60:
“1. The surface heat effects observed on the cabin windows were Caused by flame impingement rather than by radiated heat.
"2. Tune duration of the heat exposure on window No. 18 was between 6 and 10 seconds.
"3. The flame temperature in the region of window No. 13 was approximately 2, 0000F_ u
The blue trim paint which runs longitudinally along the left Side of the fuselage was blistered in two areas: the lower half of the trim stripe on the galley door and the central part of the stripe aft of fuselage station No. 1117. The paint blistering occurred in narrow bands running parallel to the normal air stream and was most severe in the area under the stabilizer. Paint had flaked off in patches throughout the affected areas. It was noted that no paint blistering occurred in the immediate v1c1nity of any of the windows, even those showing the most severe heat effects.
