TXFlyGuy
Well-Known Member
What is the most efficient diameter for a prop?
Here is some data: Best prop tip speed at full power (take-off) is .88 Mach. Best cruise tip speed is slightly under 475 mph.
In this case, the take-off engine rpm is 5,000, with the prop rpm at 2,200.
84" - .71 Mach
88" - .75 Mach
90" - .77 Mach
92" - .78 Mach
The following is inflight cruise with the engine at 3,800 rpm and the prop at 1680 rpm.
84" - 420 mph
88" - 440 mph
90" - 450 mph
92" - 460 mph
This data clearly indicates the 92" diameter is a far better performer, and would be considered optimum. Is it this simple? Yes, weight is an issue, but what else do you have to consider?
Here is some data: Best prop tip speed at full power (take-off) is .88 Mach. Best cruise tip speed is slightly under 475 mph.
In this case, the take-off engine rpm is 5,000, with the prop rpm at 2,200.
84" - .71 Mach
88" - .75 Mach
90" - .77 Mach
92" - .78 Mach
The following is inflight cruise with the engine at 3,800 rpm and the prop at 1680 rpm.
84" - 420 mph
88" - 440 mph
90" - 450 mph
92" - 460 mph
This data clearly indicates the 92" diameter is a far better performer, and would be considered optimum. Is it this simple? Yes, weight is an issue, but what else do you have to consider?
