Hi guys,
I have a cessna 172 k with a 180hp cs. prop conversion. It still has a 12v generator. My engine is from a mooney m20c,and I have the alternator and attach brackets and want to use them on my plane.I need help with the log book entry or 337 form. how do I sign this off? I am an a/p-I.A. thanks ,f4.

From my limited experience the easiest way is to find another plane that has done this same thing and copy the 337 word for word with the new numbers and names and submit with a copy of the donor form. Failing this just reference everything to the standards book and get your local fisdo to help walk it through. Good luck

Do you know anyone who has done this mod or a source to check previously approved 337's
thanks f4.

What kind of alternator do you have? If it is a Plane Power, Interav, etc there is quite likely an STC available from the mfr. If it is a alternator that is commonly installed on the Lyc O-360, and on the TCDS for the engine, I think maybe you don't even need a 337 let alone an stc -- just a logbook entry as it is already approved equipment.
No offense, but I would think that as an IA you would have some experience already with doing 337's, both for stc's & field approvals. You should talk to your local PMI with regards to field approval 337's and what he needs to sign off on one.

Eric

See if your engine STC specifies using an alternator with the conversion. If so, it would be a minor within the STC limitations. Otherwise you would need to file a 337 field approval specifying the engine conversion STC utilizing the alternator system from the already approved installation on the Mooney.

I had a similar problem a few years ago that required a field approval. Did a 0-470 conversion on a Cessna 175 and installed a Inter-Av alternator STC. The alternator STC did not have the 175 listed on their STC AML list. So I had to do a field approval based on the engine conversion being the same base engine installation as on a 182, which is listed on the alternator AML list.

Good luck

Brian.