Propeller replacement on a Cherokee 180

[flyzone]

I just replaced my 45 year old propeller on my '72 Cherokee 180. I didn't really have a problem with the old prop but years ago they did say they wouldn't overhaul it due to wear limits. I finally decided to replace it as well as get a dynamic balancing which balances the prop-engine combination on the airplane.

It is hard to identify the resulting changes but they are there. In the past my engine would overspeed at full throttle to 2800 RPM (vs. 2700 red line). That is no longer the case with the max. RPM now at the red line of 2700. This is significant. If I understood it right, I read that a 1" change in pitch equals 30 RPM in engine speed. So with over 100 RPM difference that would be about 3" in pitch change.So, perhaps the old prop was whittled down to 57" which is even below climb prop territory. I have a 60" pitch prop so this should give me some more speed. I am guessing to say that I am seeing up to a +4 mph difference at low altitudes but airspeed indicator fluctuations make this an imprecise estimate at best. I'll be interested to see my results at higher altitudes and on longer trips with GPS. I will also be interested to see any difference in fuel consumption as I expect there now to be higher consumption with the same cruise RPM (usually at 2500 RPM).

I would be interested in knowing the experience of other fixed pitch prop owners of changes they have observed.

BTW, this is a $5K cost item (installed and balanced).

 

[flyzone]

There is some refinement needed here. I got the 30rpm figure from an AOPA article (below) and on a re-read it tells me 30-50 rpm change will result from 1" of pitch change. Using the higher figure of 50, for my experience that would mean an equivalent 2" pitch change for the 100 rpm reduction in max. rpm I'm now experiencing.

Since I now have a 60 inch prop (Sensenich 76EM8S5-0-60) that might mean I previously had the equivalent of a 58" prop? However, since it was worn down maybe there were other aspects of it that were goofed and resulted in a wasteful spin rather than a climb prop equivalent.

I'm sure this is all pretty confusing since I really don't know what I'm talking about but still would be interested in the experience others have had with prop changes.

One thing I had considered was a change to a cruise prop while switching it out. I'm sure glad I didn't do that. Not only did the new prop restore some cruise pitch, I had read from one posting that if you do that you will hate every climb you make from that day forward. It looks to me like I now have a good engine-prop match. So, if you are thinking of making a change in your prop based on your current performance, think again.

https://www.aopa.org/news-and-media/all-news/2013/july/16/propeller-care-overhauls

 

[GlennAB1]

However, since it was worn down maybe there were other aspects of it that were goofed and resulted in a wasteful spin rather than a climb prop equivalent.

That's exactly what I was going to hit on.