Ed Cesnalis Posted May 13, 2013 Report Share Posted May 13, 2013 I have been hearing this lately and its a myth: "Propellers are made in varying pitch angles, and the angle can be optimized for a specific mission. Generally, a coarse pitch (high angle) lets the propeller take a larger bite out of the air with each revolution, which tends to slow the RPM but increase cruise speed. A fine pitch (low angle) permits higher RPM, generally improving takeoff and climb performance, at the expense of cruise speed." The myth stated simply is that a coarse pitch will increase cruise speed. The fact is a coarse pitch will reduce cruise speed but will gain economy. A fine pitch will not increase climb performance at the expense of cruise speed. That's another way to state the myth. A fine pitch will increase performance in both climb and cruise at the expense of economy, limited by the redline. Fast Eddie says: "It all depends on the engine's torque/HP peaks and the ability to turn that into thrust. As always, a fixed pitch prop is like a car with one gear, and as such, a compromise." He's right that there is a compromise but confused about what the trade off is. The trade off is economy at the expense of speed, not climb performance at the expense of speed. Look at the max engine output line, it tells the story. When you flatten the pitch and lighten the load on the engine more RPM and power is realized. When you coarsen the pitch and increase the load on the engine less RPM and power is realized. "A fine pitch (low angle) permits higher RPM, generally improving takeoff and climb performance, at the expense of cruise speed." Finer pitch always means more power, it can't slow you down, it just costs more gas. Link to comment Share on other sites More sharing options...
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