Propeller Pitch gauge calibration

[Nat Penton]

Peter,
Prop pitch is measured at the 70% station.Pitch distribution along the span ( deviation from true pitch ) is proprietary and is, in the case of APC, what accounts for their excellent performance and low noise.

A way to calibrate your gauge is to make a template , a triangle with the x axis equal to the circumference  at a given blade station and a slope of ,say, 10 inches and check this against the guage reading at that station.

i.e. at each station a prop will "twist" forward the same amount in one revolution if it has true pitch ( no slippage ).

You do not need to express inches of pitch as degrees.
When are you going to give me a report on the Alliance trim !!
  ----- Original Message ----- 
  From: Peter Pennisi 
  To: discussion at nsrca.org 
  Sent: Friday, October 15, 2004 5:18 PM
  Subject: Propeller Pitch gauge calibration


   

   

   

  Hi Guys,

   

  I have modified a propeller pitch gauge to accommodate larger propellers. The gauge I have is a very old prop shop model.

   

  I have decided to check my APC props because I was getting mixed performance results between all my prop sizes.

   

  Anyway I thought I would check my gauge with a new prop to see how accurate it was and the numbers I got were different to what was on the prop. I tried another new prop of exactly the same size I got a different result again. Anyway I am shocked to find that what is displayed on the prop is different to my measurements.

   

  What part of the prop should I be measuring my pitch as this varies slightly over the length of the blade?

   

  Secondly, how would I go about calibrating my unit because I can't do it with new props because there all different.

   

  How do I express for example 13 inches of pitch as degrees?

   

   

  Thanks

   

   

  Peter 
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