O235-C2C Propellers and power

I've been deliberating for a while on whether to have my original O235-C overhauled, or to go for an O320 STC mod. The decision was kind of made for me when I found and bought a zero timed O235-C2C The advantage of course being that this is basically a plug and play upgrade and will be going in as an LAA (Experimental category in the USA) modification. The question now is which propeller to use, the C2C has the Type 1 hub which allows either an SAE type 1 or 2 propeller to be used. I already have a Sensenich M76A-M2 propeller (currently called 76A-M6-2) which is a type 2 hub/flange.

Looking at the Sensenich guide both the 100hp -C and the 108hp -C1 use the same propeller, with different pitch settings and my propeller from the -C would therefore be a climb prop on a C1.

Has anyone fitted a C2C to a PA-12 and which propeller did you use if yes?

On a second question thread, the C2C produces a theoretical 115hp at 2800, the same as the C1 and 100hp at 2400, again the same as the C1 and as the C2C is described as "Similar to a C1 but with Slick Magnetos" "I'm therefore deducing from the C1 specific power curve in the Lycoming Operator's Manual, it will be producing 108hp at 2600, the same as the C1, can anyone confirm this please?

I tried to send a PM, is this Julian?

nbills77 said:

I tried to send a PM, is this Julian?

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Please resend, just cleared the inbox a bit and no, I’m not Julian!!


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still too full

nbills77 said:

still too full

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My membership had expired! Just rejoined and I'm guessing the mailbox should work again now, please try sending the PM again

Philly5G said:

I've been deliberating for a while on whether to have my original O235-C overhauled, or to go for an O320 STC mod. The decision was kind of made for me when I found and bought a zero timed O235-C2C The advantage of course being that this is basically a plug and play upgrade and will be going in as an LAA (Experimental category in the USA) modification. The question now is which propeller to use, the C2C has the Type 1 hub which allows either an SAE type 1 or 2 propeller to be used. I already have a Sensenich M76A-M2 propeller (currently called 76A-M6-2) which is a type 2 hub/flange.

Looking at the Sensenich guide both the 100hp -C and the 108hp -C1 use the same propeller, with different pitch settings and my propeller from the -C would therefore be a climb prop on a C1.

Has anyone fitted a C2C to a PA-12 and which propeller did you use if yes?

On a second question thread, the C2C produces a theoretical 115hp at 2800, the same as the C1 and 100hp at 2400, again the same as the C1 and as the C2C is described as "Similar to a C1 but with Slick Magnetos" "I'm therefore deducing from the C1 specific power curve in the Lycoming Operator's Manual, it will be producing 108hp at 2600, the same as the C1, can anyone confirm this please?

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Happy holidays everybody!! From the less than usual numbers of replies to this question, I'm guessing that unusually I've asked a new and unknown, or maybe just a very boring question I've done a lot of research on my questions and can now post the answers which will hopefully help someone else

I've been in contact with the EXTREMELY helpful tech support team at Lycoming who have been BRILLIANT!! and the flange in my C2C does indeed support type 1 and type 2 propeller mounting bolt configurations and I CAN therefore use my existing O235-C Sensenich propeller as a Type 2 climb prop on the C2C. I'll be using this propeller for initial testing and using the collected data to choose the correct cruise prop.

I also now know that my C2C actually left Lycoming in 1947 (the same year my 12 was built!!) as a C1, which of course is the other engine on the PA-12 type certificate and as the C2C is described as "similar to a C1 but with a type 1 flange and Slick magnetos" the modification request process suddenly seems even more straightforward and the power of 108hp at 2600 is confirmed

The other point I'd add is that when I stripped the engine down, there weren't any thrust buttons at the end of the valve rocker shafts. Lycoming have confirmed that there should be (as the parts manual shows) and I now have 8 of them to go with the 4 new rocker shafts

Final point, my supercub.org calendar arrived yesterday and what a FANTASTIC piece of work!! Thank you to all involved!!!!!

The differences between type 1 and type 2 flanges is the bolt hole diameter. Type 1 is 5.5” and type 2 is 6”. I think Lycoming made crankshafts that we’re drilled for either, and where you put the bushings determined what style prop you used. Not sure with the O-235, but on some Lycoming engines you can’t change the bushings with the engine assembled.

The Sensenich has a 2600 rpm limit, so in theory can only be used up to 108 hp.


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dgapilot said:

The differences between type 1 and type 2 flanges is the bolt hole diameter. Type 1 is 5.5” and type 2 is 6”. I think Lycoming made crankshafts that we’re drilled for either, and where you put the bushings determined what style prop you used. Not sure with the O-235, but on some Lycoming engines you can’t change the bushings with the engine assembled.

The Sensenich has a 2600 rpm limit, so in theory can only be used up to 108 hp.


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Correction, flange diameter is 5.5 or 6.0, not bolt hole diameter.


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dgapilot said:

The differences between type 1 and type 2 flanges is the bolt hole diameter. Type 1 is 5.5” and type 2 is 6”. I think Lycoming made crankshafts that we’re drilled for either, and where you put the bushings determined what style prop you used. Not sure with the O-235, but on some Lycoming engines you can’t change the bushings with the engine assembled.

The Sensenich has a 2600 rpm limit, so in theory can only be used up to 108 hp.


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Thanks for this and this confirms the research so far!! The SAE type 2 flange diameter spec is 6.00” and the actual measured flange diameter is 5.897” which is close enough to make it a type 2.

The 2600 Sensenich rpm limit is new info and really helps! I’ve always assumed that to get to the 2800 it would either need a variable pitch propeller, or be in a different aircraft type with a higher rpm setup in general.




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Ps The propeller bushings CAN be swopped around with the crankshaft and flange attached to the engine


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Philly5G said:

Thanks for this and this confirms the research so far!! The SAE type 2 flange diameter spec is 6.00” and the actual measured flange diameter is 5.897” which is close enough to make it a type 2.

The 2600 Sensenich rpm limit is new info and really helps! I’ve always assumed that to get to the 2800 it would either need a variable pitch propeller, or be in a different aircraft type with a higher rpm setup in general.




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Keep in mind that with each different prop installation, there are diameter limitations and with the McCauley 1C90CM or LM, the diameter limitation changes your max RPM limitation. Likewise, with fixed pitch props you have static rpm limitations that are lower than the max rpm limitation. Suggest you look up the type certificate data sheet for each prop you are considering for your installation. You can also look up the TCDS for different airplanes that use O-235-C series engines (low compression versions). For Piper, you can look at PA-12 which I’m guessing you already did, PA-14, PA-16, PA-18-105 Special, PA-20-115, and PA-22-108. Go on the Sensenich web site and look at their applicability listing, it will give you an idea of what pitch gives you climb, cruise, or average performance. There is a similar document for McCauley as well.

I picked up a used Sensenich from a PA-22-108 that I’m going to use on my PA-16. Based on the Sensenich applicability, it will be a climb prop on my Clipper.


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dgapilot said:

Keep in mind that with each different prop installation, there are diameter limitations and with the McCauley 1C90CM or LM, the diameter limitation changes your max RPM limitation. Likewise, with fixed pitch props you have static rpm limitations that are lower than the max rpm limitation. Suggest you look up the type certificate data sheet for each prop you are considering for your installation. You can also look up the TCDS for different airplanes that use O-235-C series engines (low compression versions). For Piper, you can look at PA-12 which I’m guessing you already did, PA-14, PA-16, PA-18-105 Special, PA-20-115, and PA-22-108. Go on the Sensenich web site and look at their applicability listing, it will give you an idea of what pitch gives you climb, cruise, or average performance. There is a similar document for McCauley as well.

I picked up a used Sensenich from a PA-22-108 that I’m going to use on my PA-16. Based on the Sensenich applicability, it will be a climb prop on my Clipper.


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Thanks for this and yes, I've looked at the PA-12 Type Certificate https://www.cubclub.org/tc/Piper/A780.PA-12.pdf and the Sensenich Aluminium Propeller application guide http://www.sensenich.com/wp-content...luminum_Propeller_Applications_1349891787.pdf and the propeller and pitch I currently have is a cruise prop on the current O235-C and will be a climb prop on the C2C.

It's interesting that the maximum static RPM limits aren't always listed against the different props on the Type Certificate, I wonder if this means that the manufacturer approved and stated O235-C/C1 limits of 1900-2300 rpm apply in these cases?

Philly5G said:

Thanks for this and yes, I've looked at the PA-12 Type Certificate https://www.cubclub.org/tc/Piper/A780.PA-12.pdf and the Sensenich Aluminium Propeller application guide http://www.sensenich.com/wp-content...luminum_Propeller_Applications_1349891787.pdf and the propeller and pitch I currently have is a cruise prop on the current O235-C and will be a climb prop on the C2C.

It's interesting that the maximum static RPM limits aren't always listed against the different props on the Type Certificate, I wonder if this means that the manufacturer approved and stated O235-C/C1 limits of 1900-2300 rpm apply in these cases?

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The C was only a 100 hp engine at 2600 rpm, the C1 and later are 108hp at the same rpm. That’s why you go from a normal prop to a climb prop with the same pitch. If you want a cruise prop, you can have the prop repitched at a prop shop. Most Sensenich props can have 7” of pitch change total.

The TCDS doesn’t specify pitch, but it does specify the max and min static rpm limits. Figure a climb prop will be closer to the max Static rpm, and a cruise prop will be closer to the min static rpm. With a cruise prop, you sacrifice hp on take off since hp is a function of rpm.


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Philly5G said:

Thanks for this and yes, I've looked at the PA-12 Type Certificate https://www.cubclub.org/tc/Piper/A780.PA-12.pdf and the Sensenich Aluminium Propeller application guide http://www.sensenich.com/wp-content...luminum_Propeller_Applications_1349891787.pdf and the propeller and pitch I currently have is a cruise prop on the current O235-C and will be a climb prop on the C2C.

It's interesting that the maximum static RPM limits aren't always listed against the different props on the Type Certificate, I wonder if this means that the manufacturer approved and stated O235-C/C1 limits of 1900-2300 rpm apply in these cases?

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Those static rpms are for the wood 74FE prop. Do you have a wood prop, or a metal 76AM-2 prop? If you have the metal Sensenich prop, your static limits are 2425 to 2150 on wheels.


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dgapilot said:

The C was only a 100 hp engine at 2600 rpm, the C1 and later are 108hp at the same rpm. That’s why you go from a normal prop to a climb prop with the same pitch. If you want a cruise prop, you can have the prop repitched at a prop shop. Most Sensenich props can have 7” of pitch change total.

The TCDS doesn’t specify pitch, but it does specify the max and min static rpm limits. Figure a climb prop will be closer to the max Static rpm, and a cruise prop will be closer to the min static rpm. With a cruise prop, you sacrifice hp on take off since hp is a function of rpm.


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Thanks that all makes sense!

On the props that have been approved by other people and don’t have static RPM limits set, can it be assumed that the static limits are the same as Prop 1, which is the one the manufacturer approved?


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Philly5G said:

Thanks that all makes sense!

On the props that have been approved by other people and don’t have static RPM limits set, can it be assumed that the static limits are the same as Prop 1, which is the one the manufacturer approved?


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Part of any fixed pitch prop approval should also include static rpm limits.most all the STC prop installations I’ve seen do have static rpm limits. Most will also have a flight manual supplement as it will impact engine limitations and performance sections. Note even with the props listed on the TCDS, you are supposed to make notations in your fight manual.


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dgapilot said:

Those static rpms are for the wood 74FE prop. Do you have a wood prop, or a metal 76AM-2 prop? If you have the metal Sensenich prop, your static limits are 2425 to 2150 on wheels.


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BRILLIANT!! Thanks! Yes, I currently have the 76AM-2 prop (76A-M6-2) so the static RPM range IS 2425-2150

I'm looking forward to finding out what the extra power feels like!!