Paul Lamar wrote:
Vance why would your fixed pitch and constant speed props have about the
same eff. at 30, 60 and 90  MPH? I think you are off here.
I think you are way off.  I think you forgot to increase the eff.
for the constant speed prop. Put a HP column in there for the constant
speed prop.

Let us define our terms here.

Theory thrust is = HP * 550/FPS.

Prop eff is = actual thrust/ theory thrust

tcarrico wrote:

I would think the Constant speed, or variable pitch prop would have the
benefit of acting like several diferent fixed pitch props.  You could
have a fixed pitch prop that performs well for climb, but not for cruise
a Constant speed works better in both cases.  If you took a constant speed
prop and set it up for best performance cruise, I would think that the
fixed pitch prop optimized for cruise would give basically the same
numbers... at cruise.

In the table Vance provided I would expect the fixed pitch prop to be close
or better in one part of the envelope, but the variable pitch prop to be
better overall.  Am I missing something?
tc

tc

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