109 prop pitch (rpm) and the supercharger

[JtD]

Related - at lower altitudes, Merlin engines developed at least as much power at 2850 rpm as they did at 3000 rpm (depending on source). Below full throttle altitude, climb was to be done at 2850 rpm, while at high altitude, above full throttle altitude, these rpm were to be increased to 3000 rpm. Just like with any other engine, it increased boost and engine power. However, the handbook said to always fly at these 3000, not change pitch back and forth. No idea if pilots ever tried that.

With the two stage pitch, it would probably be too hard to get the timing right to make it an efficient, practical option, though maybe pilots on occasion had to employ a similar scheme - with high rpm being too high to sustain and low rpm being too low for sufficient power output.