Top Prop Install W&B Data

[0TreeLemur]

Somebody ought to know this.   According to the Type Cert, for a M20C, the original  HC-C2YR-1 7666-2 propeller had weight of 53.75lbs and a moment arm of -30.16".    Looking at the post install update to the W&B, my A&P listed the weight and moment arm of the HC-C2YR-1BFP/F7497 "Top Prop" as 58.1 lb and -35.5".   Ok, I get that it is heavier.   Why does it have almost 5" more moment arm?    Looking at the Hartzell manual, I don't see this data.   Must be in the Mooney STC.  I can't seem to find that paperwork right now.    Anybody have reference to this?  Just checking my A&P's work.   He's a genius mechanic, but I check his math.

Thx.

[RLCarter]

Checking math is always good, and/or question him as to how he came up with his figures 

[DXB]

13 hours ago, 0TreeLemur said:

Somebody ought to know this.   According to the Type Cert, for a M20C, the original  HC-C2YR-1 7666-2 propeller had weight of 53.75lbs and a moment arm of -30.16".    Looking at the post install update to the W&B, my A&P listed the weight and moment arm of the HC-C2YR-1BFP/F7497 "Top Prop" as 58.1 lb and -35.5".   Ok, I get that it is heavier.   Why does it have almost 5" more moment arm?    Looking at the Hartzell manual, I don't see this data.   Must be in the Mooney STC.  I can't seem to find that paperwork right now.    Anybody have reference to this?  Just checking my A&P's work.   He's a genius mechanic, but I check his math.

Thx.

I think it is a mistake.  I don't see how the station could change by >5" on a different prop.   I have the identical Top Prop on my C - here is the logged W&B data for it:

				Weight	Arm	Moment
Propeller- Hartzell #HC-CZYR-1BFP/F497	4/2/2011			58.1	-30.16	-1752.3
Propeller Spinner assembly #835-58P	4/2/2011			3.1	-29.18	-90.458

[A64Pilot]

A inch maybe, but think how strange it would look being 5” more forward of the cowling.

Doubt it’s right.

[0TreeLemur]

Digging a bit more, I found this from the M20 STC.  He seems to have taken the example moment arm literally.  Instructions say to use the same moment arm as the prop replaced, which makes a lot more sense.

 

 

[OR75]

The prop CG is not 5 in for the CG of the previous prop , you could tell if it was