Propeller Question

[8233]

My 120 was built at the factory with a C-85 installed. A few years back, someone installed a C-90. I have to look and confirm but I may have a Sensenich 76AK-2 installed and I assume they may have just moved the prop from one engine to the other. I do not have a prop logbook for this plane.

If I confirm I have this model, will it pose an issue? I don't think I see it on the TCDS for the airplane listed for anything other than a C-85 but there are a lot of other planes with C-90s where this propeller is indeed on the list for use on a C-90. Sensenich also lists the C-90 as compatible with this model prop on their own TCDS.

Should I be concerned or is this installation ok? Assuming of course I have the model number right which I would have to confirm.

Appreciate anyone's thoughts.

Thanks

[6643]

From a regulatory perspective, you need an STC or a field approval. An on-the-ball IA would not sign the plane off as airworthy.

[8233]

Thanks John, I will have to dig deeper. To my knowledge, I don't think there is an STC for that. Any idea how difficult a field approval would be? I'll confirm I have the right model information.

Thanks

[6643]

The only Sensenichs approved on the Aircraft Specification are wooden. Doubtful you'd mix them up. (If yours is wooden, and meets the hp and static requirements, then you're good to go.)

If you can find someone else who has had it approved it would probably be an easy road, relatively speaking, given all the other data available. (Approved on the airframe with the C85, and approved on the C90 in other airframes.)

[8233]

The only Sensenichs approved on the Aircraft Specification are wooden. Doubtful you'd mix them up. (If yours is wooden, and meets the hp and static requirements, then you're good to go.)

If you can find someone else who has had it approved it would probably be an easy road, relatively speaking, given all the other data available. (Approved on the airframe with the C85, and approved on the C90 in other airframes.)

This is the only STC I can find.

https://www.cessna120-140.org/member-on ... enDocument

Doesn't work for me unfortunately.

[4004]

Beg to disagree - that STC is exactly what you are looking for. Try to contact the owner direct, failing that, contact the NY ACO and seek related STC ownership/current contact info, STC holders that are on the market have to be FAA available. Randy can comment with correct info. That STC is directly related to your prop and aircraft.

Be careful - I wouldn't contact FSDO until appropriate and required (field approval) or you may find yourself "unairworthy" as John C says. If successful getting STC then just a 337 recording and straight to OKC.

If you have to get a field approval, call NY ACO and seek the cognizant engineer and discuss with him to see if a field approval is feasible and with a possible approval providing you provide the proper documentation . Be prepared for this call with all the tech data as discussed above. My experience with these situations is that FSDO will seek ACO concurrence. FSDOs have to go the bureaucratic route and forward documentaion thru the chain-of-command. However, we as owner/operators, A&Ps, & IA can just call direct to the ACO engineers and discuss informally and I don't hesitate to tell the FSDO contact that the issue has been discussed with ACO engineer - course the inital paperwork has to go thru FSDO. FSDO contact generally appreciate that you have taken "pressure" off him by broaching with ACO, however, we know that some FSDOs are not cooperative.

As to the propeller log, it is common for smaller aircraft to have the propeller log incorporated with the engine log - no requirement to have a separate log. Research your logs carefully.

P.S. If you do go the field approval route, load itup with all the technical tecnical details and with copies of excerpts from available TCDS, etc. Saves time and effort for approver - and don't forget an ICA. Apologize for being lengthy - just passing on experience.
Big Edd

[4006]

A 72CK is not the same as a 76AK-2 . So I doubt that STC will help.

[6643]

If you can contact Bruce, he may be able to help. Last time I tried, though, I was unsuccessful. He used to run US Propeller in Lititz, PA, across the street from Sensenich...

[8233]

I will see if I can contact Bruce. I went diving through the paperwork that came with the plane and I did find this STC paper but not sure if that helps me? Does anyone know what the real differences are between a 72CK and a 76AK-2?

IMG_0393 (4).jpg (157.31 KiB) Viewed 6533 times

[4004]

Thanks Mike G. for correcting me, I'm still "wiping the egg off my face"! Case of "couldn't see the forest for the trees"!
David, be sure to order the OKC disc for your aircraft for $10 if you haven't done so already, may be some info there that will help.

Big Edd