I would really like some evidence for this. Some discard the problem as nonsense, while others point out that erosion is quite natural when repeatedly hitting solid water (i.e. drops) at Mach 0,6 to 0,7. Our motorglider has a composite prop, and our SOP is to avoid rain in the first place, for several reasons, but if flying in rain, then limit RPM (preferably use the coarse cruise pitch...