Page:CAB Accident Report, Braniff Airways Flight 542.pdf/14

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Smoke and soot dePOSits eXisted in a nunber of places on the left fuselage surfaces. The white painted area above the windows from fuselage station No. 875 to fuselage station No 1030 was heavily sooted with streaks running up and back at a 20 degree angle. The soot depOSits were heav1er in areas between the rings and stringers than they were directly over the ring and stringer stiffeners. A scallop pattern of soot depos1t was ev1dent for about 1.5 inches aft of each ring between stringers. This scallOp pattern became progreSSively more eVident toward the rear fuselage section. A streak of black Oily substance was depoSited from fuselage station No. 570 to the tail cone. This streak, unlike some of the other deposits on the aircraft, could not eaSily be wiped off and gave the appearance of haying been partially baked to the metal. In addition to the 12 inch wide band which started about 42 inches behind the galley deor and extended all the way rear- ward, numerous fine streaks existed both above and below the window line. while most of the streaks were parallel.to the flight path, there were minute streaks upward and aft at an approximate angle of 30 degrees.

The tail section conSisted of vertical fin and rudder, stabilizer stubs, tail cone (fuselage station No. 1117 and aft), and the lounge floor. The direction of collapse of the right underSide of the cone indicated that this section struck the ground while mOVlng rearward, cauSing damage to the elevator power package, the base of the rudder, and the elevator root sections. The vertical fin was undamaged except for a series of Slight linear dents in the leading edge. It was found that the wing planking stiffeners exactly fit these marks.

One other matter should be mentioned. On the ground at Houston and shortly before departure, First Officer Hollowell remarked to a representative of the engine manufacturer (Allison—General Motors), “This aircraft trims up funny.“ There was no further discusSion on the matter nor was it made an item of record in the air- craft's logbook.

As a result of this and another accident Six months later to the same model aircraft, the manufacturer instituted a searching reassessment of the aircraft’s deSign. The work was largely analytical but also included wind tunnel testing and. flight testing. The program of deSign reevaluation was extremely extensive.

Two questionable items in the deSign of the airplane came to light. One of these was that Significant loads imposed on the wing intermediate ribs between the fuselage and outboard.nacelles by shell distortion had not been included in the design loads. The other was that the dynamic response of the outboard nacalles in turbulence was different than that used in the original deSign, with the result that the torSional loading of the wing inbOard thereof was increased. In addition, the reevaluation program disclOSed that, with the stiffness of a powerplant nacells installation reduced below normal, propeller "whirl mode" could perSist undampened and couple with the wing thus exciting it to failure.

Aircraft Hist cg

N 9705C was a new aircraft. Its final assembly was started in April 1959, and the first of its three production test flights was on September 4, 1959, 25 days prior to the accident.