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A flight test was also conducted on a Boeing Model 247D airplane to determine whether sudden opening of the throttle from the closed position or actuating of the throttle control would adversely affect the automatic mixture control and result in malfunctioning or loss of power in the engine. The engine responded normally throughout this test.
The testimony with respect to the fuel system of the right engine of NC 13359 and the tests subsequently run furnished no evidence that the fuel system was not operating properly at the time the right engine lost power or that the loss of power in the engine resulted from insufficient fuel. Therefore, while the possibility remains, it seems improbable that the loss of power resulted from improper operation of the fuel system or insufficient fuel.
During the tear-down inspection of the right engine two small pieces of cloth were found in the carburetor grid.[1] These two pieces of cloth were found wadded together in such a way that they covered most of two openings of the carburetor grid, or approximately 2% of the total grid area. When they were removed from the grid and unwadded it was found that one of them was about 1½ inches long and 1 inch wide and that the other was about 3 inches long and ¼ inch wide. The National Bureau of Standards concluded in its report:
"The presence of cloth and threads in the induction system and charred cotton on one of the pistons indicates that cloth portions, threads, or fibers had passed through the induction system and at a time which evidently coincides closely with the time of the engine failure.
- ↑ See photograph attached to National Bureau of Standards Report, Appendix B.
