Jaybird180
Final Approach
I have a question that's been bugging me off/ on and it seems I may have some misunderstanding about the power selection involving constant speed props.
The common advice given for Mooneys is full throttle from takeoff to destination pattern with performance adjusted with RPM selection.
My reading and interpretation of Deakin suggests this typically yields the greatest engine efficiency as the intake tract is designed to flow best air at WOT. In this case the pilot need only adjust mixture for altitude to keep the mixture in a burnable range. It also suggests this may not be best for all airframes due to drag...that total cruise performance typically reaches max efficiency before the engine, in that it (the airframe) reaches peak of efficiency curve somewhere above 75% engine power, but this may not be conducive to engine longevity.
Planes with constant speed props typically have a power chart showing suggestions for 55%, 65%, 75%, etc at altitude ranges and different combinations of throttle MP and RPM to yield the desired power, showing the resultant cruise speed.
What is the need for all the variation? Why not just run the engine WOT from takeoff to pattern and simply go high RPM on takeoff and move the prop back to the bottom of the green arc for cruise? What's wrong with this as SOP for every CS prop airplane?
Did I answer my own question in the underlined portion? I feel like there is one critical piece of data that I am missing, which is causing me to revisit this in my mind.
Someone please show me the way to get off this carousel.
The common advice given for Mooneys is full throttle from takeoff to destination pattern with performance adjusted with RPM selection.
My reading and interpretation of Deakin suggests this typically yields the greatest engine efficiency as the intake tract is designed to flow best air at WOT. In this case the pilot need only adjust mixture for altitude to keep the mixture in a burnable range. It also suggests this may not be best for all airframes due to drag...that total cruise performance typically reaches max efficiency before the engine, in that it (the airframe) reaches peak of efficiency curve somewhere above 75% engine power, but this may not be conducive to engine longevity.
Planes with constant speed props typically have a power chart showing suggestions for 55%, 65%, 75%, etc at altitude ranges and different combinations of throttle MP and RPM to yield the desired power, showing the resultant cruise speed.
What is the need for all the variation? Why not just run the engine WOT from takeoff to pattern and simply go high RPM on takeoff and move the prop back to the bottom of the green arc for cruise? What's wrong with this as SOP for every CS prop airplane?
Did I answer my own question in the underlined portion? I feel like there is one critical piece of data that I am missing, which is causing me to revisit this in my mind.
Someone please show me the way to get off this carousel.
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