The advantages of the engine were increased propeller efficiency through the reduction gearing effect of having the engine effectively running at 1, 800 rpm for only 900 rpm of the airscrew, and excellent high-altitude performance due to the high compression ratio achieved.
12.
Even before the start of World War II, engineers were beginning to realize that engines driving propellers were self-limiting in terms of the maximum performance which could be attained; the limit was due to issues related to propeller efficiency, which declined as blade tips approached the speed of sound.
13.
If the reduction in pressure is too much in relation to the ambient pressure of the fluid, " cavitation " occurs, bubbles form in the low pressure area and are moved towards the blade's trailing edge where they collapse as the pressure increases, this reduces propeller efficiency and increases noise.
14.
The Bureau of Aeronautics analyzed the possibilities of the plane becoming a competitive race plane, and decided that the extra weight of the supercharger could be better put to use by installing an epicyclic reduction gear, for improved propeller efficiency, thereby providing greater improvement in performance than what the supercharged engine with a direct drive propeller could provide for the same weight.
