Here is another interesting chart form Klause's forum.
This is aircraft efficiency plotted with fixed pitch prop efficiency
for a typical high speed home built.
Aircraft efficiency is defined as 100 percent at minimum
drag or the best glide speed. This usually occurs about 
130 MPH for most home builts. For a slower airplane like
a Cessna 172 cruise and glide speed are much closer together
and fixed pitch props are much more satisfactory.

This is why you need a variable pitch prop to get good take 
performance on a high speed airplane. The fixed pitch prop optimized for
cruise is down around 15% efficient  at takeoff speeds.

The yellow line is my attempt to enhance a yellow line that was on
the chart representing the combined efficiency.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

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