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Unread 01-18-2008, 03:59 PM
dtilman dtilman is offline
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Default 180 HP Conversions C172 - prop pitch

Question sent in from a customer via email

I have ordered a 0-360 A4M overhaul 180 hp conversion for my skyhawk 172M from Penn Yan aero and have also ordered the powerflow exhaust from you.

Here is the question I sent to Sensenich followed by their response.

I have ordered a 0-360 overhaul 180hp conversion from Penn Yan for my 172M and will also be adding a powerflow exhaust. Should I request a different pitch from Penn Yan due to the fact that I will also be adding the powerflow exhaust to this engine? I am operating out of a 1,800 foot grass strip at 1,000 foot MSL. I would prefer climb a little more than cruise as my runway gets a little soft at times and I figure a climb prop would be more helpful in this situation.

Response from Sensenich:

That would be stated in the STC paperwork either with Penn Yan’s STC or Powerflow’s STC. I cannot alter the mandates established by those STC’s.

Response from Penn Yan:

Penn Yan told me their standard pitch is 60 inch and have no other recommendations based on using the Powerflow system on their engines. They suggested contacting you.

Do you folks have any suggestions for a prop pitch based on your past experience with this configuration and the factors listed in the paragragh at the top? If I use the standard 60" pitch do I need to be concerned about running RPM to high?
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Unread 01-18-2008, 04:00 PM
dtilman dtilman is offline
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Default 180 HP conversions - Prop Pitch

For any of our customers, we always recommend first flying with the Power Flow installation on your propeller WITHOUT changing the pitch, in your typical flying conditions. The amount of improvement for each engine does vary and so it isn’t possible to say you should get x number of additional pitch without having seen what it does.

My advice is to install the standard 60 inch pitch propeller from Penn Yan. I understand your concern about possibly running the propeller at too high of an RPM, but in reality, that seldom seems to happen. The Penn Yan conversion will list an acceptable range of Static RPM – usually about 80-120 RPM wide. Most aircraft don’t seem to be at the top end of that range, more near the bottom to the middle. When you add the Power Flow for an average gain of 60-75 RPM, you generally will still be in the range, but at the top. So, from a certification stand point, you are normally ok.

From an operational standpoint, I think you’ll find that you will have plenty of power and acceleration from the combination of the bigger engine and Power Flow Exhaust to address your concerns.

I can’t recall any of our O-360 customers reporting that they have re-pitched. Most tell me they have more than enough climb and are grateful for the increase in RPM to go faster, or for the fuel savings now achieved with the PFS.

If, after installation and flying the plane for a while, you find that you are at the high end of the static RPM limitation and Penn Yan’s STC allows for a pitch change (I don’t recall if it does), then you can consider taking the propeller off to have it re-pitched. Re-pitching is a relatively inexpensive operation. But you have to refer to Penn Yan’s paperwork and approval.
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