Page:CAB Accident Report, Braniff Airways Flight 542.pdf/11

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Only a limited nmnber of front spar pieces Could be identified; however, the separation pOint was identified by fitting together two mating pieces of top cap, the inboard of which has been found at the main wreckage Site and the outboard of wnich.was dug out of the ground at the left wing Site. This pOint was eight inches outboard of Wing station No. 83. Most of the rear Wing Spar Section from station No. 65 to station 137 was recovered excapt for minor fragments. That portion of the rear Spar inboard of Wing station {10. 97 remained With the center Section, while the outboard section from this Wing station fell with the Wing.

The lower planking inboard of wing station No. 137 showed eViuence of upward sending With the bending being slight in the area of the No. l plank and being progressmely more pronounced toward planks Nos. 8 and 9.

The lower planking stiffeners were severely column—buckled at every bay from plank No. l to No. 9. The rear plank was "8" shaped, being horizontal from wing Station No. 65 to approxmately Wlng station No. 75, curling sharpr upward through Wing station “To. 85, and turning down to horizontal at approximately wing station No. 90.

The upper planking pieces in the No. 2 tank area were, in general, Jaggedly rectangular With the long dimenSion spanw‘ise. Only a fewr pieces of planking oridged a rib cap, and those which did usually contained a plank lap Jomt. Upper plank No. 9 from Wing station No. 75 to Wing station No. 101 showad the same "S" shape as did the lower plank but to a less pronounced degree. In contrast with the lower planking the stiffeners of the upper planks had separated along or very close

do the radii.

The fracture faces of lower wing plank No. 3 at Wing station No. 65 left, snowed eVidence of haVing recontacted each other after the fracture occurred. l-hcroscopic examination disclosed at least three cycles of recontact. Two of these were ev1denced by contact scratches; the third by a zinc chromate depOSit.

The wing station No. 83 closing rib of the left leading edge contained metal- tc—metal scratches at nine points. These marks were prr'edmnzlnantlyr vertical, but microscopic examination showed three to four changes of direction at three different pomts.

Substantially the entire section of the left wing that fell separate from the aircraft showed eVidence of varying fire damage. The fire pattern on the upper and lower planking of the No. 2 fuel tank was of a random configuration such that one piece or section would exhibit severe exposure to fire or heat whereas its mating pieCe would not. The 21110 chromate in sections of the flaps aft of and inboard of the We. 2 nacelle and in sections of the fillet area between wing and fuselage had been browned by exposure to heat, however, the patterns once again were random and showed lack of continuity. This same general fire pattern was eVident on pieces of wing leading edge. The left wing flap geek screws were found in the fully retracted peeition.

In the NO- 3 fuel tank area of the right wing the lower planking was shattered into narrow spanWise strips. There was more deformation present than there was in the No. 2 tank area, particularly the stiffeners which were torn awe—r from the __lanking and bent in random directions. rfhere was some evidence of column-buckling of the stiffeners on the No. 1 to No. h planks, but much less severe than in the left wing.