Page:CAB Accident Report, TWA Flight 891.pdf/40

 .40- 11.3.1.1 AnalySis of the breakage points of the lnleldual pieces of wreckage

This study was undertaken in order to ascertain, on the basis of the construction calculations, the results of the breakage tests made on the prototype, and the breaks that occurred in the wrecked plane, whether disintegration of that plane in flig was due to aerodynamic stresses of any kind or to other

causes.

It was concluded that disintegration of the plane was due to exploswe forces originating in tank No. 7.

ll.h.2 Study of the trajectory of fall of some Significant parts of the aircraft which became separate?! in flight from the plane after its disintegration

This study was undertaken in order to ascertain, by comparing the actual distribution on the ground of some of the signifies: parts which became detached in flight with the position obtained by calculation, the height at which the plane disintegrated.

Within the framework of the asawnptions on which the studg,r was based, the results showed, with the same degree of probability1r the follomng three combinations of altitude and speed (With wind):

560 knots I.A.S. at an altitude of 5,000 ft. 290 II II II II II II 10,000 II' 125 II II II II II 1| 15,000 It

Hence, also because of the uncertainty existing in the evalua- tion of certain parameters entering into the calculations, the results of the study must be taken as indicative and not concluswe.

1.1.11.3 Pressure tests on fuel tank caps P.N. 075010843

To the north—east of Nizzolina, preciSelyr at the beginning of the path of fall of the lnd1V1dual pieces of wreckage, was found the upper plate of a fuel tank cap. The plate was clear mthcut damage of any kind, and was identified, by process of elimination, as belonging to tank No. 7, or No. 6 (see par. 12 point 1).

These tests were made in order to ascertain whether pressure, and if so how much, could cause cap P.N. 750438—13 to separat.

into its component parts so that one of those parts, namer the upper plate, could appear in the same condition as the

one that was found.

The tests, made on new caps, brought out that the caps in question: