Originally Posted by
currawong
I shall attempt to remain polite.
During engine run up, one exercises the propeller pitch lever.
The funny noise you hear as the lever is moved rearwards?
Is the propeller cavitating.
No.
I believe vihai is correct in asserting that cavitation only occurs in liquids, specifically incompressible liquids, like water, so cavitation is a factor with marine propellers but not aircraft propellers.
As with any propeller there are pressure differences around a propeller in water. AIUI when the local pressure drops significantly the water changes state explosively (implosively?) with a release of energy creating micro cavities in the liquid. When the pressure relaxes the water changes state again back to liquid equally implosively. That energy release causes erosion to the propeller, but the cavitation happens in the liquid. Erosion of the propeller is not the cavitation, it's the result of cavitation.