Page:CAB Accident Report Amendments, TWA Flight 891.pdf/2

 AMENDMENTS TO THE REPORT OF THE BOARD or INQUIRY ON THE CRASH OF THE S. C. PLANE NO. 7313/0

Chapter XI

(1) Par. 11 4.18 These tests made in a specialized laboratory, disclosed that:

[1] On an L—1649 plane static discharges should occur at the vent outlets if the aircraft is struck anywhere by lightning and, if, it is not struck, they may occur when the aircraft flies through clouds that are charged with electricity.

[2] Static discharges, comparable in strength to those that can occur in flight, generated in still air in a container filled with flammable fuel vapors, cause those vapors to ignite.

[3] The tests mentioned in the preceding paragraph cannot, however, on the basis of the knowledge available at the present time, be taken as conclusive evidence that static discharges generated at the vent outlets of an aircraft in flight, from which (outlets) flammable fuel vapors are escaping, will necessarily cause those vapors to ignite, but they do indicate that such a danger is within the realm of possibility.

[4] The evidence and considerations referred to in the two preceding paragraphs indicate very definitely that adequate precautionary measures should be developed and adepted, the most important of which would be to insert anti—flame wire gauze onto the vent outlets and to have the said out—lets shaped and constructed in such a way as to render them less subject to the development of static discharges.

[5] Static discharges can, and generally should, develop without leaving on typical aircraft metals, and therefore on the vent outlets, any normally visible evidence.

Chapter XIV

(2) Par. 14.4.2.6 (b') (b') The possibility that static and nonstatic electrical discharges, under the testing conditions described in pars. 11.4.4 and 11.4.18, might ignite flammable gasoline vapors has already been tested in the United States, with positive results.