Enter the radius (distance from the hub/axis), the pitch (lead per revolution), and the pitch angle into the calculator to determine the missing variable (at that radius).
Blade Pitch Angle Formula
The following formula is commonly used to calculate the geometric blade pitch angle (helix angle) at a given radius for a propeller or rotor, based on the pitch (lead per revolution) and the radius.
θ = atan(P / (2πr))
Variables:
- θ is the pitch angle (in radians for the raw
atanresult; convert to degrees if desired) - r is the radius (distance from hub/axis to the blade section), in meters
- P is the pitch (lead per revolution), in meters per revolution
To calculate the pitch angle, take the arctangent of the pitch divided by 2πr. This gives the pitch angle in radians; multiply by 180/π to convert to degrees.
What is a Blade Pitch Angle?
The blade pitch angle (often called the geometric pitch angle) is the angle between the chord line of a blade section and the plane of rotation. For propellers and rotors, this angle varies with radius if the blade is twisted. Changing pitch angle affects the aerodynamic loading (lift/drag distribution) and can be used to optimize performance across different operating conditions.
How to Calculate Blade Pitch Angle?
The following steps outline how to calculate the Blade Pitch Angle at a given radius.
- First, choose the radius r where you want the pitch angle (distance from the hub/axis to that blade section).
- Next, determine the pitch (lead per revolution) P for the propeller/rotor.
- Next, calculate the pitch angle using the formula θ = atan(P / (2πr)).
- Finally, convert the angle to degrees if needed and interpret it as the blade section pitch angle at that radius.
- After inserting the values and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
Radius (r) = 0.50 m
Pitch (P) = 1.20 m per revolution