AJW wrote:

[snip]
For what it's worth, at 150 kts and 2500 RPM means the airplane advances
about
6 feet per prop rev. A two bladed prop means each balde is in air 3 feet
ahead
of the prior blade.

That's the same number I came up with, but that assumes there's a
one-to-one ratio between engine RPM and prop RPM. Is that true of all
single engine piston aircraft? I'm obviously not an AC mechanic, but I
thought I could see a reduction gear in the cowl.

I don't know of a SEL airplane in general use that uses reduction gearing
between the shaft and the prop, Dan.