what is the difference between propeller pitch and chord length?
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Imagine you took a saw and cut off the end of a propeller blade. Now place a ruler on the cut end. Align the ruler so it goes from the leading edge to the trailing edge where you made the cut. The length you measure from the leading to trailing edge is the cord length. The angle of the ruler (from the disk of the propeller rotation) is the pitch angel. I’ll call this the aerodynamicist’s definition of pitch angle (see more below). For airplane and boat propellers, both the cord length and pitch angle of the blade will usually change as you move outward along the blade. For a helicopter’s main rotor, both the pitch angle and cord length are likely to be be the same for most of the length of the blade
Note that the pitch of a propeller (especially a fixed pitch propeller) is usually given as a length, not an angle. For example a 30 inch pitch. This is how far the propeller wound advance if it made one full turn with no slip. For a fixed pitch propeller, all areas of the blade will generally have the same pitch **length**, but the pitch angel will get smaller as you move further from the center of the propeller.
For a variable pitch propeller, the term “pitch angle” can be used to describe the angle to which the propeller as a whole is adjusted. This is related to , but not the same as the definition above. If the pitch of a variable pitch propeller is set at, say, 10 degrees, the aerodynamicists pitch angle will still change along the length of the blade — it won’t be 10 degrees everywhere. This is a case where the same term can mean slightly different things depending on where it is used.
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