What is a dual pitch Propeller ... ?

B y, Joe Zingali 

Pres. of J &Z Products Inc.

It may be a little confusing, but I am going to try to explain the functions of our dual pitch propellers. First, of all, we will take a specific size propeller so that I can explain the pitch by the numbers.  The size propeller I am  going to start  with is 18-6-10 propeller.  The 18 is the diameter and the 6-10 is the progressive  pitch that you have been  hearing about. The 6 pitch is the lowest pitch, and it is closest to the hub of the propeller. The 10 is the highest pitch and  that Is at the FARTHEST POINT FROM THE HUB (at the tip of the Propeller). Now that we know where high and the low pitches are I will try to explain the reason for the  duel pitch and the benefit you can get out of them. First of all the pitch closest to the hub (6 pitch) progressively increases higher as it moves toward the tip of the propeller,(10 pitch ) therefore making the center of the propeller approximately 8 pitch ( 4.500 in. from the tip). When this propeller (18-6-10) is operating at level flight the propeller is operating normal or has its, least load in respect to taking off, climbing, turning, and making attitude changes and etc.  Because of this, the propeller is flying at its greatest EFFICIENCY, because it is not Carrying the load like it would if it was climbing etc.  And the propeller is at its greatest angle of attack (highest pitch-10) therefore moving forward 10 in. per REVOLUTION (allow 15% for Slippage).  At the instance there is an altitude change in a climbing configuration the propeller is giving in to the extra load causing it to flatten out at the highest pitch of the propeller (the tip). With this happening the propeller is literally twisting to the next pitch that will support the load that is developing with the plane climbing, in this case would be the next favorable pitch (like shifting down to a lower gear in your car when you start to climb a hill. Remember the weight of your plane and the size of your motor (horse power) have a lot to do with how much the Propeller will change pitch. In figuring the size propeller to use, just take the size you are using and match it to the center pitch of the duel pitch propeller.  EXAMPLE lf you are using an 18-8 you would use a 18-6-10. I hope I have cleared up some of the questions about ZINGERS DUAL PITCH  PROPELLERS.