Howdy - a couple related questions about how modifications should be properly documented:

1. Let's say you're looking at an early '53-'55 180. You assume it should have an A or J model engine in it, but see that it has a K model engine. The K model engine is listed on the TCDS for the 180 and you find a log book entry for when the engine was put in. Is that all that's needed? I assume since the K model engine is included in the TCDS you wouldn't have an STC or 337.

2. Let's say you want to put a new engine monitor in your plane. Cheapskate that you are (I am), you see they can be bought for $500 on eBay or $2500 from the manufacturer. If you decide to buy the eBay version, how does the STC and paperwork get handled - can it transfer from the original owner?

Cheers!

It would take someone more knowledgeable than I am to properly answer your question, but as the owner of a very much modified airplane (56 changes/updates/modifications at last count, 25 of which required either STCs or 337s), I rely on my IA to do the paperwork and to make sure that all of the paperwork is there. That's part of his responsibilities. He's annoyingly punctilious about doing that, refusing to install anything before the FAA has blessed it with its "holy water", never taking the chance that a modification request will be refused. He's right, of course, but that has meant some really annoying delays at times, when the FAA has dragged feet.

Cary

In regards to the engine swap it would need to be approved on the TCDS by S/N for your airplane, approved field approval including a 337 signed by a fed, or installed in accordance with an STC, including a 337 signed by a&p and IA, these are the only legal examples I can think of.

Regarding a used engine analyzer often you can get the manufacturer of the instrument to issue new STC paperwork for a fee, some do not however, best to check with them first.

You're correct in that the K engine is listed as approved for the 53-55 models on the C180 TCDS.
The K engine uses a different later-model engine mount and different later-model (single) exhaust--
I assume that those are also approved, due to their being part of the standard 470K installation.
So if that's what it's got, I'd say that a logbook entry is all that's required.
However......
My own 53 model C180 has a K engine, but it was modified to fit on the original (470 A & J) engine mount.
The original (dual) exhaust was also retained, after being modified to fit the 4-bolt exhaust flanges on the K engine.
These mods were both done to avoid buying more new stuff (mount & exhaust), but now it is no longer a standard 470K installation.
But I have a field approved 337 documenting these changes, which makes it all kosher.

I guess the point of this story is that every airplane is different, and the paperwork needs to be evaluated on a case-by-case basis.

@Halestrom - question: continuing the example, let's say we're looking at a 1955 Cessna 180 that has a K model engine in it but started life with an A model engine. The FAA hosts TCDS info, and the TCDS for the 180 can be found on the FAA's website here:

http://rgl.faa.gov/Regulatory_and_Guida ... Rev_68.pdf

Right at the top it says that the 180 (not 180A/E/G whatever) is approved for A, J, and K model engines, but I don't see anywhere on there that specifically calls out those planes by serial number. Scrolling down, it's obvious that the 180A isn't approved until December of 1956 so we can at least infer that the '55 model is a 180 and would likely have the K model engine allowable. If this plane started life with an A model engine in it but now has a K model engine, is all that would be required for the change a logbook entry? Also, how do we identify these planes by serial number?

hotrod180 wrote:You're correct in that the K engine is listed as approved for the 53-55 models on the C180 TCDS.
The K engine uses a different later-model engine mount and different later-model (single) exhaust--
I assume that those are also approved, due to their being part of the standard 470K installation.
So if that's what it's got, I'd say that a logbook entry is all that's required.
However......
My own 53 model C180 has a K engine, but it was modified to fit on the original (470 A & J) engine mount.
The original (dual) exhaust was also retained, after being modified to fit the 4-bolt exhaust flanges on the K engine.
These mods were both done to avoid buying more new stuff (mount & exhaust), but now it is no longer a standard 470K installation.
But I have a field approved 337 documenting these changes, which makes it all kosher.

I guess the point of this story is that every airplane is different, and the paperwork needs to be evaluated on a case-by-case basis.

Interesting. So in your case, you have a 337 documenting the change. But also in your case, there were some pretty major modifications to the K model engine to make it fit. Is there anything in the 337 that would suggest that the 337/field approval was done because of A) the mods, or B) in general for the engine swap, i.e. it would have been needed for the engine anyway?

There was a field-approved 337 filed for installing "bracket, engine mounting" p/n 534470 (quantity four) (as removed from the old A model engine) on the new K model engine-- replacing the K's p/n 539518 brackets. This allowed use of the original p/n 0751000 engine mount, and saved the cost of a new, later-model engine mount.

The field approval also covered cutting the 2-bolt flanges off the early dual exhaust system, and welding on 4-bolt flanges. This saved the cost of a new later model single exhaust system, as well as having to cut holes in the lower cowl for the tailpipes.

Now, were these two items "major alterations" requiring a 337?
I dunno, that could be argued either way.
But apparently the IA and/or the FAA inspector who signed the 337 thought so.

There was also a second field approved 337 filed, for the installation itself.
This noted the use of the early style mount, and the early style exhaust,
as well as the installation of an (STC'd) McCauley C203 prop.
IMHO this second 337 didn't need to be a field approval, but apparently (again) the IA and/or the FAA guy thought it was.

FWIW in retrospect, I think the exhaust mod was a good idea, as I like the old duals,
but I wish they'd ponied up the dough to replace the engine mount.
IMHO the later style Lord mounts are a superior design and hold up better over time.

Thanks for the responses, guys. Everyone likes to hear how a story ends, right? Well, here's the official answer, may be of interest to someone in the future:

I called the FAA ACO and was put through to an engineer and described the situation. We pulled the 180 TCDS and went through it together. He said that typically the TCDS call out aircraft by serial number but if they don't (as in this case) it would be by time of manufacture and/or model number. That the TCDS doesn't specifically call out aircraft by serial number is okay.

The TCDS lists the A, J, and K model engines for that year of 180. In general, an engine change would be considered a "major" alteration but in this case, because the engine installed is included in the TCDS, it is considered a "minor" alteration and therefore only a logbook entry is required - no 337 or other approval needed. The TCDS lists a number of props that are allowable as well, and the prop that is installed on the plane is listed there, but those props don't specifically say which engine they are approved for. The prop on the plane notes that it is "for aircraft re-worked by Cessna Service Kit XYZ". If you pull up that Service Kit, it specifies aircraft by serial number where that prop is allowed (which includes this plane), but also doesn't specifically note which model engine must be on the plane. Apparently, the document that officially ties the prop to that engine would be the Type Certificate of the prop, which we couldn't find in the time available (would have to click through tons of McCauley type certs - it wasn't a searchable database), but we did find the McCauley Application Guide which ties *that* prop to *that* model aircraft, to *that* engine, and lists the STC under which that prop would be installed. This aircraft does have the STC and 337 filed for the prop, in which case everything appears to be kosher. If we wanted to go the extra mile, we'd track down the text of the STC or the prop Type Certificate, but at this point it's pretty clear that it's an approved combination.

So there you go!

In between the aircraft TCDS, the prop manufacturer's application guide, and the prop TCDS, it ought not to be too hard to figure out if it's OK. I guess you're talking about an O470K engine, what prop is it?
This link might help with TCDS's, STC's, etc

http://rgl.faa.gov/

I'm kinda wondering if maybe you're overthinking this--
is there some reason why you think the prop is NOT approved on this airplane / engine combination?

I wasn't worried about the prop, honestly. The guy at the FAA was, though, and kind of keyed on it because while the prop is listed, it doesn't specifically state which of the three engines it was approved for or if it was for all three (which is what we were able to confirm). I was just giving the detail in case anyone else needed to confirm paperwork like that. The major item for me was: if it's on the TCDS, it's not a "major" alteration and only needs a logbook entry, but... in certain circumstances it might not be that simple - like, the engine might be okay, but what about the prop? What about the exhaust system, etc etc. You could go down any one of those rabbit holes and figure it out in a similar fashion.