John Boyd's Aerial Attack Study

Clearing up the paperwork on a Piper J-3

On the Yahoo mailing list, Piper Cub Builders, an owner named Rich described his J-3 Cub with a data plate showing it with a Continental C-85 engine instead of the original Lycoming 65 hp. Rich bought the plane without an engine and intended to install a Continental A-65, and of course he also wanted to clear up the paperwork. He got a small blizzard of advice, which caused him to ask this question: "Please excuse my ignorance, but you referred to TCs and A-691.... What are these? Where would I get copies of the two certificates?"

Here's the answer from Jim Ash, which I thought should be preserved for future reference:

Grab a cup of coffee (or maybe scotch) and have a seat.

TC is short for Type Certificate. When a (US) manufacturer puts out a new airplane model in standard type, they generate one of these. It's got all kinds of information about the aircraft down to the serial numbers, which for our purposes, includes all the factory-approved options. Any A&P should have access to this data, and know how to use it.

There are three TC's for J3 Cubs, A-691, A-692, and A-698. The kicker for me (and possibly you), is that they did it by the engine they were using in that model, Continental, Franklin, and Lycoming respectively. The TC (A-691) for the Continentals shows all the Continental engines factory-approved for the Continental Cubs (pay close attention here). But the TC (A-698) you and I care about is for the Lycoming Cubs. It only shows Lycoming engines as approved for our airplanes, and no Continentals. This is TC piss-off number 1. If they only wrote up one TC for J3 Cubs, we (and a pile of other people) wouldn't have these problems. I just found a web site where you can see and print both these TC's. I suggest you do it:

Note that although this is an Australian web site, it links back into the FAA database. I believe revision 32 is current for A-691, and rev 13 for A-698, but I wouldn't swear to it. If you need an official current one, go suck up to an A&P.

Now go look at which model Cub you have. Notice from the TC's, a J3C-85 isn't listed. Such an airplane technically never existed, and anyone who registered it as such either screwed up or was just too lazy to straighten out the paperwork and got away with it. The model of the plane should not have changed, no matter which engine was in it, unless an official model change was done (and I don't know how to do it). If that were the case, you'd see some log entries somewhere to that effect. One quick way to play is to take your N number to (assuming your plane is US-registered):

If you look at mine (N30358), you'll see it's a J3L-65. This is one of the officially listed models in the type certificates. Yours says J3C-85. Based on this, I don't have a clue what TC your plane is covered under, but I'll bet it punts back to your airworthiness certificate. What's that say? Chances are, it's a J3L-65. No Continental engines are approved per the TC for this model [but see below]. Take special notice of your serial number and see if there are any specific statements in the TC regarding the number range yours falls into while you're in there.

I see that model J3 was covered under TC 660, which was superseded (I'm not sure exactly what that means. Did those planes get new model assignments or just disappear, or ?). This applied to planes manufactured before 10/15/1939. It's possible, but I doubt that's what you've got.

This doesn't mean you can't do it. Putting an A-65 in a Cub is the most popular engine swap for the plane. What it means is that if the engine were approved for your plane, you could just mount it up and make a log book entry. If you want to use a non-factory-approved engine, it's considered a major alteration. Enter stage right: Form 337, and more importantly, an A&P willing to write you one.

This sounds easy, and if you're connected, maybe it is. If you walk in cold from the street, a lot of A&Ps won't touch ragwings, and rightly so. The only fabric work they've done is the minimum requirement for the certifications, which ain't much. Besides, they don't know you from Adam, and a lot of them have been burned by lawyers and insurance companies before, so don't expect anyone to stick their neck out for you until you've got a rapport with them. You need to find either an old-timer or someone who works with ragwings on a regular basis. Drive past all the asphalt airports and find a grass one, then ask around.

You also need to find one who isn't gun shy about writing 337s. Cubs have been around forever, and any number of modifications have been done to them. When you buy the 337 from the Cub Club, you're getting a copy of a 337 for somebody else's airplane. Armed with this, you take it to your A&P, and a 'normal' one will issue you a 337 based on someone else's previous 337. I guess it helps them spread the liability around. If you wanted to bolt your new new gorilla cage mod to your wing, good luck getting somebody to sign off on it. You certainly ain't the first, so it will help to ease the liability concern for your A&P if you do something stupid.

While you're at this, there are three more things you should do.

First, get a list of the current ADs (Airworthiness Directives) from your A&P. He's going to have to run the current list to verify your compliance anyhow, so just have him do it for you first. You'll find a number of them, including the strut AD, but you should also find one for the exhaust system. The gist of it is to have a wire bale inserted in there, so large rust flakes from the interior of the exhaust system can't all lay down together and cover up your exhaust outlet. I mention this so you can comply with it now while you've got things apart. Univair has the sealed struts which permanently satisfy the strut AD. If you're going this far, take the bite and do it. Screwing around with regular inspections on the old ones will never go away, and keep costing you each time.

Second, look at your gross weight limit. A lot of Cub people assume they all gross at 1220. Not true. The Lycoming Cubs start at 1100, and can be increased to 1170 if you do some strut and gear mods (see A-698 rev 13, note 4, page 7). Unless you're lucky enough to own one of those 7800+ serial number airplanes listed in the note, the Cub Club didn't have drawings C-16 and C-22 when I checked in '99. This is TC piss-off number 2. If this were a Continental Cub, you could get your plane up to 1220 with a different set of 5 drawings, which are available (I've got them). My plane is stuck at 1100, unless somebody here knows where I can get those drawings. I can't take my wife for a ride without being over gross. I want that extra 120 pounds. So if you've got an old weight & balance, make sure it complies with the TC. Somebody may have just pulled those numbers out of their ***.

If you can find somebody to fill out the 'type crossover' paperwork for you, two of the Continental gross-up drawings are for the lift struts, front and rear. I honestly don't know if the Univair struts comply with the gross-up drawings or not, but I'll bet they do; I know the forks are a lot beefier in their new ones than the old, and maybe that's why. I don't think anybody would buy them if they didn't. Following the A-691 rules, and assuming they are, you would only need to comply with Drawing 21642 to get the first 70 pounds of gross increase, which are some changes to the lift strut/suspension mount bracket on each side. The additional 50 pounds are from the last two drawings, related to changes in the wheel axles and the shock struts.

Third: Get the FAA records on your plane. If this is what you've got, then good. If not, go to.... [The page is no longer active. Instead, go to the FAA site linked here]. You'll get a set of registration records, and a set of airworthiness records. I got the CD and keep it in my Cub pile. This might help you clear up some questions.

You can wake up now -- Jim Ash

To which the following was added by Stan Blanton: The type certificate for Cubs with Continental engines is TC A-691. This same TC also covers PA-11s. I believe Lycoming engined Cubs are covered under a seperate type certificate.... All of the Cubs with a a 65 hp Continental were certificated as a J3C-65 where C stands for Continental. This could be confusing since the Continental designation for this engine is an A-65. Cubs with a Lycoming had a "L" in the designation and so forth. Many Cubs, including mine, have since had a C-85 or C-90 installed in place of the original A-65 Continental. This is allowed since these engines are listed on the type data sheet even though none were originally installed in J3s. Some of these installations have been done with field approvals and others with merely a log book entry. Whether a field approval is required has been the subject of much discussion between various Cub owners and their respective IAs and FSDOs.

Question? Comment? Newsletter? Send me an email. Blue skies! -- Dan Ford

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