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How to Calculate Propeller Top Speed

Whether they are on boats or airplanes, propellers work using the same principles. A mathematical equation exists to determine propeller top speed; however, it is theoretical, as it does not figure in drag, wind and water resistance. These variables are different in every case and entail boat and plane weights, propeller pitch and the forces of nature acting upon the propeller. The equation that figures propeller speed is: Speed = (Revolutions Per Minute X Propeller Pitch) divided by 1056. This formula gives top propeller speed in perfect operating conditions.

Things You'll Need

Calculator

Instructions

- 1
  Determine the propeller's revolutions per minute, or RPM. Assume the propeller is operating at 10,000 RPMs. Any value may be used for the RPM number.
- 2
  Convert 10,000 RPMs to revolutions per hour, or RPH. Multiply 10,000 RPMs X 60, which equals 600,000 revolutions per hour.
- 3
  Determine the pitch of the propeller. Propeller pitch determines the inches per hour the propeller pushes the vessel. The propeller's pitch is stamped onto the propeller itself, either on the outside or inside; if the latter, you'll need to remove the propeller. For the purpose of the equation, the propeller pitch is 10. Multiply the RPH and propeller pitch: 6000,000 X 10= 6,000,000 inches per hour.
- 4
  Convert inches per hour to miles per hour (MPH). First, multiply 12 x 5280, which determines the inches in a mile (63,360). Divide the inches per hour, 6,000,000, by 63,360. This equals 94.7 miles per hour. The top propeller speed for this propeller, with a pitch value of 10 at 10,000 RPM, is 94.7 MPH.

Aviation