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established standards of purity and octane rating. The carburetor was removed and was flow-tested at the Naval Aircraft Factory, Philadelphia, Pennsylvania. It was found to be in normal operating condition. The possibility of an air or vapor lock was considered, but, due to the design of the fuel system and the type of fuel being used, such an occurrence is extremely improbable.
The possibility that the loss of power in the right engine could have been caused by the action of the pilot in inadvertently shutting off the fuel supply to that engine was also investigated. Two tests were conducted on a Boeing Model 247D airplane by an investigator of the Safety Bureau to determine the length of time which would elapse between the act of placing the engine fuel selector valve[1] in the "on" position for one engine only and (a) the lighting up of the fuel pressure warning light for the other engine, and (b) the loss of power in the other engine. In the first test the engines were operated at 27 inches manifold pressure and 2150 r.p.m. and the engine fuel selector valve was then turned to the one engine "on" position. The fuel pressure warning light for the engine from which the fuel was cut off lighted up approximately 10 seconds after the fuel supply had been cut off. By this time the fuel pressure had fallen off from the normal 5 lbs. per square inch to about 2½ lbs. per square inch. In the second test, which was also begun while the engines were operating at 27 inches manifold pressure and 2150 r.p.m., the engine from which the fuel
- ↑ This valve may be set in either of four positions. Reading clockwise on the dial they are: Both engines off; both engines on; left engine on; and right engine on.
