Pitch

• The term "pitch" refers to a propeller's blade angle relative to the aircraft's vertical axis. A higher pitch means more angle, and a lower pitch means less.
  
  

Pitch and Flow

• A prop with more pitch angle will move more air per revolution than one with less pitch, meaning that its theoretical top speed is higher.
  
  

Pitch and RPM

• Blades with a higher pitch will cause engine RPM to drop, since the engine will have to work harder to turn them.
  
  

Pitch and Efficiency

• Since all engines have a "sweet spot" where horsepower is the highest, pitch angle must be matched to the engine to ensure that engine stays within this range.
  
  

Incorrect Pitch

• A pitch angle that is too steep will cause an engine to drop below its sweet spot and cost speed, whereas a blade without enough pitch will not exploit the engine's full power potential.