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Spitfire IIa is fastest with the prop pitch set to fully fine.
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Vmax occurs at maximum rpm and manifold pressure in any aircraft. Although it is called "course" and "fine" pitch, as the other posters have explained it is really maximum rpm.
The blade pitch will open as velocity increases and maintain rpm. In a selectable pitch propeller, the pilot must open the blade pitch to maintain maximum rpm as the aircraft speed increases.
This the reason for the VDM clock. It gave the pilot a measure of his blade pitch to set to achieve desired performance.