Calculate propeller advance ratio from aircraft velocity, rotational speed and diameter, plus thrust/power coefficients and efficiency.

Use axial speed relative to the fluid and propeller shaft speed. Positive rotation and diameter are required; signed speed, advance ratio and thrust are supported.

Related Calculators

Propeller Advance Ratio Formula

The following formula is used to calculate the propeller advance ratio for a given set of parameters.

J = V / (n ร— D)

Variables:

  • J is the propeller advance ratio (dimensionless)
  • V is the axial velocity relative to the surrounding fluid
  • n is the propeller rotational speed (in revolutions per second, rev/s)
  • D is the propeller diameter

Note: Use consistent units so that n is in revolutions per unit time. For example, if n is given in RPM, convert to rev/s by dividing by 60 before using the formula.

To calculate the propeller advance ratio, divide the velocity of the aircraft by the product of the propeller rotational speed (in rev/s) and the propeller diameter. The result is a dimensionless number.

What is a Propeller Advance Ratio?

The propeller advance ratio is a dimensionless number that describes the relationship between the forward speed of an aircraft and the rotational speed of its propeller. It is an important parameter in the design and analysis of propellers, as it helps to determine the efficiency and performance of the propeller at different operating conditions. A higher advance ratio indicates farther axial advance per revolution relative to its diameter. Advance ratio alone does not determine thrust or efficiency; those also depend on propeller geometry and operating conditions.

How to Calculate Propeller Advance Ratio?

The following steps outline how to calculate the Propeller Advance Ratio.

  1. First, determine the velocity of the aircraft (V).
  2. Next, determine the propeller rotational speed (n) in revolutions per second (rev/s). If it is given in RPM, divide by 60 to convert to rev/s.
  3. Next, determine the propeller diameter (D).
  4. Finally, calculate the Propeller Advance Ratio using the formula J = V / (n * D).
  5. 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.

Velocity of the aircraft (V) = 200 m/s

Propeller rotational speed (n) = 1500 RPM

Propeller diameter (D) = 2.5 m

Convert rotational speed: 1500 RPM รท 60 = 25 rev/s

Then J = 200 / (25 ร— 2.5) = 3.2