Studies by the National Bureau of Standards, Department of Commerce, have developed information which has made possible the design of fuel systems for aircraft that largely eliminates the danger of vapor lock caused by the boiling of gasoline.
Vapor lock tends to develop in engines when climbing rapidly to high altitudes, particularly during hot weather. Test by the services and the industry indicated that the pump in the fuel system was most likely to cause boiling of gasoline. By placing a second pump in such a position that the fuel could be moved with the least suction, they found this hazard measurably reduced.
Larger and better-placed fuel lines also were suggested as a result of the Bureau of Standards tests, which covered the reducing valves, operating valves, and all kinds of fittings as well as the piping system itself. Each valve and fitting was found to have an individual resistance to the flow of gasoline and vapor. By analyzing all of them the experts found they could come close to determining the flow rate of the system as a whole and devise improvements.
While the vapor lock problem has not wholly been solved, real progress has been made and the recommended changes in the design of fuel systems have resulted in more dependable performance.
This article was originally published in the "Aviation Engineering" column in the September, 1941, issue of Aviation magazine, vol 40, no 9, p 127.