Hi Del,
Well, I mostly agree with your description, but the act of the aircraft slowing down is comparatively slow while the pitch change is quite rapid, so I don't think that the cycle you describe would appropriately be described as "hunting", and with the engine running at full speed the entire time, there wouldn't be any boost pressure fluctations either.
Considering that there's often some kind of hysteresis effect to compressiblity phenomenons, maybe that could induce actual hunting? The propeller speeds up, increases pitch, the critical Mach number drops, drag increases in a leap, the propeller slows down, drag decreases but stays high, propeller decreases pitch and slows down further, suddenly angle of attack decreases critical Mach number below the lower hysteresis threshold, drag decreases in a leap, propeller speeds up, cycle repeats.
Problem with that is that's not going to be the entire propeller that undergoes the sudden drag rise, as local angle of attack and Mach number are different everywhere along the radius. And if the process is more gradual, the leap is averaged out, so I'm skeptical it could happen like that in practice. (And no boost pressure fluctuations with my explanation, either.)
What do you think?
Regards,
Henning (HoHun)
