Page:CAB Accident Report Amendments, TWA Flight 891.pdf/3

-2- Amendments to the Report

[1] The tests mentioned in par. 11.4.18, made in a specialized laboratory, disclose that:

(a) On the strength of available knowledge, it cannot be stated positively that static electricity discharges generated at the vent outlets of an aircraft in flight, from which (outlets) flammable gasoline vapors are escaping, will necessarily cause those vapors to ignite, but the indication is that such a danger is within the realm of possibility.

(b) The atmospheric conditions existing at the time of the crash were extremely favorable for the development, at the vent outlets of Super Constellation aircraft No. 7313/C, of static—electricity discharges entirely capable of igniting flammable gasoline vapors under the test conditions described in par. 11.4.18.

[2] The tests referred to in par. 11.4.4, which were made in the tunnel:

(a) On one only of the original manifolds, located on the trailing edge of a wing contour, from whose four outlet pipes (compare par. 14.0) there was an escape of vapors containing a mixture compressed within the limits of flammability (tanks Nos. 6 and 7) and not included in said limits (tanks Nos. 3 and 4);

(b) At a pressure corresponding to the altitude of 1,700 feet;

(c) At an air flow speed of 170 knots I.A.S.;

(d) On the velocity of the vapors escaping from the individual pipes, corresponding to climbing speeds of 900, 600, and zero feet a minute, revealed that said vapors, as the result of suitable electric discharges of a nonstatic nature, become ignited only under conditions that would occur when the plane was climbing, and that the flame did not spread to the interior of the tanks.

In conclusion, although the evidence referred to in the aforesaid pars. 11.4.4 and 11.4.18 does not warrant the assertion that static electricity discharges generated at the vent outlets of the Super Constellation aircraft in flight can.ignite the flammable gasoline vapors issuing from those outlets, it nevertheless indicates that such a danger is within the realm of possibility and that the ignition of said vapors would actually take place if the electrical discharges were of sufficient intensity and of a non static nature.