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Old 02-05-2011, 05:58 PM
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Kevin Horton Kevin Horton is offline
Join Date: Jan 2005
Location: Ottawa, Canada
Posts: 2,352

Were you at full throttle for the 2800 rpm/182 kt TAS points? If you add more pitch so you hit 2700 rpm at full throttle, the engine power will be less due to the lower rpm. If the torque is contstant, the power will vary linearly with rpm. At the same conditions, the TAS will vary with the cube of the power, so your TAS at 2700 rpm and full throttle would be about 180 kt.

You can only optimize a fixed pitch prop for one point. Are you more interested in low altitude full throttle speed, or are you more interested in higher altitude cruise at some lower power? If you optimize the pitch for low altitude, high rpm speed, you may find that you lose speed at higher altitude as you hit full throttle at a lower rpm.
Kevin Horton
Moses Lake, WA, USA
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