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3 Answers

The difference of Geometric pitch and Effective pitch , Slippage meaning?

Asked by: 3881 views , ,
Aerodynamics, Commercial Pilot, Flight Instructor, General Aviation, Private Pilot

hello sir !

Can I have a question? I don't understand meaning of slippage.

"The pitch is the distance in inches, which the propeller would screw through the air in one revolution if there were no slippage."

Ref) PHAK 5-29

What does slippage mean?

In the dictionary, slippage means failure to meet a standard or deadline; the extent of this.

this is right?...

Could you explain about the difference between geometric pitch and effective pitch?

 

 

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3 Answers



  1. Craig on Jun 05, 2020

    Think of “pitch” as the horizontal distance. Slippage is the difference between the horizontal distance (over land or through water) that propeller blade (or plane/boat) would have traveled in 1 revolution (complete circle) of the propeller blade in a theoretical no drag situation (geometric pitch) vs. the actual horizontal distance (effective pitch) that propeller blade (or plane/boat) traveled in 1 revolution in real life, which has drag and holds the blade/plane/boat back from traveling the theoretical horizontal distance.

    As an example, think of running forward on land vs. running forward in 4 ft of water for one 60 second revolution of the second hand on your watch. There will be a difference in the distance you travel on land through air (geometric pitch) vs. through the water (effective pitch). The increased drag from water should decrease the forward distance you travel (effective pitch) in water. That difference in distance that you travel on land vs. water would be the slip/slippage.

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  2. Mark Kolber on Jun 06, 2020

    The visual I always think of for slippage is trying to screw a screw into shipped cream and have it grab.

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  3. KDS on Jun 08, 2020

    Look at AC 65-12A, Airframe and Powerplant Mechanics Powerplant Handbook. Just Google “AC 65-12A” to find it online. Start reading at Chapter 7, Propellers. You won’t have to read far.

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