I just got off the phone with Aerotech engines and they said that they would look into the possibility of getting the c203 added to the STC. They said to not expect anything on the short term.
C180_guy what options are you referring to that are available now that weren’t a few years ago. Are there other props that are approved for this STC or are you referring to installing a converted IO-470 under a different STC. Also I will only ask one more time because it seems like you are avoiding the question. What is the basis for approval of the C203 prop on your 180 with the Norland engine conversion?

No, not approved for this STC (that is up to the STC holder to get added to their paperwork). I am referring to props approved for the IO470. Mac came out with the C230 several years ago (documented on the C185 TCDS, for example). Doesn't MT have a prop approved for the IO470? Hartzell? So, that covers the engine application and you need an approval for the airframe combination.

Thanks C180_guy. MT might be the easiest possibility. I am currently running an almost brand new 2A34C203 McCauley on an O-470R. I was hoping to use this prop on the Norland conversion as I already have it and like the performance. I noticed that you mentioned you are running this prop on an Norland converted IO-470F in a C180. I made the assumption that you had some type of approval.

C180_guy wrote:....The Norland STC (unless something has changed) allows for different suffix IO470s. ....
If you look at the TCDS for the O470 and the IO470 (http://www.faa.gov), you will see the different suffix engines documented and a description of the differences. For example, the crankshaft damper configurations are covered. .....

There are two different TCDS's for the IO-470:
E-273 (same as O-470) includes the IO-470-A & -C.

https://rgl.faa.gov/Regulatory_and_Guid ... _Rev38.pdf

3E1 covers all the other IO-470's.

https://rgl.faa.gov/Regulatory_and_Guid ... E1_R28.pdf

From E-273:
"NOTE 4. Crankshaft damper configuration: O-470-A, S/N 41000 and up, and -E, -J, -R, -S, and -T engines are
equipped with one 5th and one 6th order damper.
O-470-B, -H, and -N have two 6-½ order dampers.
O-470-K, -L, -M, -P and IO-470-A and -C have four 6th order dampers.
O-470-G has one 6-½ and one 9th order damper.
O-470-A, S/N 40001 through 40655, and -P, have two 6th order dampers.
O-470-U has two 6th, one 5th, and one 4½ order dampers."

From 3E1:
"NOTE 5. Models IO-470-D, -E, -F, -G, -H, -M, -N, -R, and -S incorporate crankshaft with four sixth order dampers.
Models IO-470-J and -K incorporate a crankshaft with one fifth and one sixth order damper.
Models IO-470-L and -LO incorporate crankshaft with two fifth and two sixth order dampers.
Models IO-470-P, -T and LIO-470-A incorporate crankshaft with two sixth and one-half order dampers.
Models IO-470-U, -V, and -VO incorporate crankshaft with two sixth, and one fifth one fourth and a half
order dampers."

To substitute a prop that isn't listed on the STC, I would look for a prop approved on an engine with the same damper configuration as what you're using For example, the C203 generally required an engine with one 5th & one 6th order damper (see McCauley TCDS P3EA, note 9)

https://rgl.faa.gov/Regulatory_and_Guid ... E/P3EA.pdf

But even that's not necessarily written in stone--
for example, I have the North Sound Aviation STC which approves a C201 or C203 on a K engine, which has four 6th order dampers.

The O-470-L is approved with the C203, so perhaps that is the correlation. For reference, I have an IO-470-F that I was going to use the Norland STC on, and the prop was one of the holdups. I have a C204, which is approved for the U, but not the others. Lots of people seem to use the C204 on other things with field approvals.

Has anyone here made any headway on getting a modern prop onto a Norland conversion motor?