- 4 -
The rudder separated from the fin at the hinge points and was broken into four sections, one of which was not recovered.
The empennage surfaces were unmarked by fire although fuselage structure located immediately ahead was heavily sooted by fire.
The right wing separated in flight. It broke downward along a chordwise line near the wing root. This wing panel fall in flames, was damaged by ground impact, and partially consumed by fire.
The left wing outer panel separated in flight along a chordwise line in the area of the No. 1 engine nacelle. This panel separated from forces that failed the wing spar forward. Between the Nos. 1 and 2 nacelles the wing panel was broken into several sections, the spar was bowed downward, and the upper wing skin was failed by tension loads. Near the inboard fracture line the wing spar failed rearward. The stub end of the left wing and wing center section remained attached to the center fuselage. Evidence showed that the left wing separation and breakup, which tore open fuel cells, was accompanied by an intense flash fire. The left outer wing panel fell in flames and continued to burn on the ground until it was nearly consumed.
The landing gear was retracted and locked; flaps were up.
The fuselage broke up in flight into three principal sections. These, in general, were the cockpit and forward passenger cabin, the cabin rearward to the last row of seats, and the aft fuselage from the last row of seats to the area below the vertical stabilizer. Much of the fuselage shell and overhead structure tore away in small pieces. These were found scattered over the full 2-1/2-mile long wreckage path.
Examination of all passenger seats, except one not recovered, showed they had been subjected to positive loads. Because these were opposite to the loads imposed on the seats during breakup, they obviously occurred earlier.
Nearly the entire left side of the fuselage was sooted by fire and in areas of the heaviest deposits paint was blistered. Study showed this occurred after many pieces tore away because some pieces normally located next to those that were sooted were clean. Comparatively, the right side of the fuselage showed little exposure to fire.
In other areas of inflight fire damage there was much evidence of a flash fire during the breakup; there was no evidence that a fire or explosion preceded the disintegration. The wreckage was also examined for evidence of a lightning strike. It was not possible to conclude that lightning did not strike the aircraft; however, it was conclusively established that there was no significant damage to the aircraft as a result of a lightning strike.
All four powerplants separated from the aircraft about the same time and fell reasonably close to each other in the main wreckage area. Examination showed that the nacelles failed at their attach point to the wing as the result of uploads, although downloads had occurred prior to separation. The latter caused damage to the propeller reduction gearing assemblies and to the "W" struts.
