Page:CAB Accident Report, TWA Flight 891.pdf/38

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11.2.3.7. Malntenance records of the aircraft and engmes

11.3

11.3.1

11.3'2

11.3.3

The maintenance records were carefully examlned an order to determine whether pre-emstlng condltlcns of abnormallty might have had a dlrect or 1nd1rect relatlon to the causes of the crash. In part1cular, 1t was ascertalned that prev-lonely the aircraft had made five landlngs 1n an overloaded condltion and one landlng Wthh had been cla551f1ed as a "hard" landing; however, inspectlons made after such landings had dlsclossd nothlng abnormal. It was also disclosad that the automatic control of the pressurlzatlon system had, no the past, glven continuous trouble and was still domg so at the tune of the last fllght; however, the system's manual control was an

good working order. The records showed, lastly, a ser1es of minor troubles and dlfflcultles, whlch were taken 1nto

account in the examinatlon of the wreckage. Included 1n these were some leaks 1n the fuel tanks, whlch had been promptly repaired as soon as dlscOVered.

Supplementary mquirlis

Parallel w1th the mquirles descrlbed 1n par. 11.2, a serles of tests on various accessories, materlal and parts were made an the plants of the Alfa Romeo, Secondo Mona, and other industnal f1rms.

li‘he follomng 13 a. summary of the results of those texts.

Ingpectlon of the seat of cap P.N. 700168—13 on the mug top of tank No. 6

The 1nspection was made in order to ascertaln whether a burn mark found in the seat of the cap had been caused by llghtnirlg. It was determined that the mark had been caused by welding, done 1n the course of repalr work.

Tests on samples of metal taken from the mug frame and 1nspectlon of the 'Tfracture areasr

The tests were made in order to ascertaln the characteristlcs of the metal and the type of the fractures.

It was found that the metal conformed to the speciflcatlons and that the fractures showed the characterlstlcs of breakage by tearlng.

Microscoplc examlnatlon of the fuel tank vent outlets

The examnatlon was made 1n order to ascertain whether some traces of blackemng and heatlng, found on one of the vents, could be ascrlbed to electrlc d15charges.

It was concluded that the presance of such traces was due to the heat of the ﬁre and that the two vents bore no eVidenee of llghtning strrkes.