THE basic idea of accomplishing both a power limitation and a control of the mixture with one unit was evolved by the late Thorp Hiscock. He proposed, by throttling the air entering the carburetor, to maintain the density of air entering the venturis equivalent to that at an altitude of 7000 ft. Thus the carburetor would virtually be held at 7000 ft. and would deliver, even though the airplane might be at sea level, a mixture of the same fuel-air ratio that it would normally deliver at 7000 ft.
Details of the development of the automatic power and mixture-control unit are given, together with descriptions of tests made and statements of results obtained.
In conclusion, it is stated that, from the reports available on general fuel consumptions, it is apparent that some method of control is desirable. Further, that it is also highly desirable from a standpoint of engine reliability and durability that a means of controlling the horsepower output of supercharged engines as well as the fuel consumption be provided. The device described provides both these features, with certain limitations.