Graphs of power coefficient ($C_P$), thrust coefficient ($C_T$), and efficiency ($\eta=JC_T/C_P$) of the 5868-R6 propeller as functions of advance ratio ($J=V/(nD)$) and propeller pitch (blade angle at 0.75R?) are found in many textbooks (such as McCormic):
From these curves it seems that for a given propeller pitch $C_P$, $C_T$, and $\eta$ go to zero at the same value of $J$. At also seems that the slopes of the $C_T$ vs $J$ curves for higher value of $J$ (where $C_T$ approaches zero) are the same.
I have two questions:
- Do $C_P$, $C_T$, and $\eta$ always go to zero simultaneously at the same value of $J$ for all propellers? Why?
- Are the slopes of the $C_T$ vs $J$ curves where $C_T\rightarrow 0$ the same for all values of propeller pitch?