On 4/28/2025 2:36 PM, Randall Smith via KRnet wrote:
It’s definitely gonna be a different propeller. If they stay with the
standard numbers for propellers. 54 is how long it is and 49 is how
many inches it will pull through the air in one revolution. If your
Edd sturba did well, then this one here is probably gonna over rev.
But you can still fly.
Sent from my iPhone
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Here are some ballpark numbers, assuming that both props are equally
efficient, that prop pitch in inches are of near equal accuracy, and
blade shape is also equally efficient. Lots of assumptions here.
The old prop would make 158 mph at 3100 rpm. (with 100% efficiency)(90 %
is good)
The new prop would make 143 mph at 3100 rpm. (with 100% efficiency)
If the new prop will allow the engine to pull more rpm in cruise and the
pilot is inclined to do so, some of the speed can be gained back. Also,
and again, with all else being equal, the engine can pull higher rpm on
takeoff with less pitch so more horsepower and shorter takeoff and
climb. Best outcome would be if the new prop has a more efficient
profile and less drag and gives you better overall performance. If you
get close to equal performance you are a winner.
Another issue to consider that's not mentioned here is tip speed. If
you get close to 90 % speed of sound you start to suffer loss of
performance. (C in inches X rpm X 60 / 12 / 5280 = mph ) In this case
, with above numbers, near 500 mph should not be a problem.
Because there are too many variables to be accurately measured on two
different props, flight testing is the only way to know. I suspect,
with all else being equal, a slight loss in speed. I hope it turns out
that you are even happier with the new prop and the gear failure turns
out to be a positive event.
Larry Flesner
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