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PA12-150 with Stoddard Mount and Borer Prop. Kosher?

JDWilliams

JDWilliams

Registered User
Need some clarification if possible. Here’s the current recipe: PA12-150 just back from Ly-Con, 26” Goodyears on 3” extended gear, Stoddard/Univair engine mount, Borer prop. Installation instructions I have for the Stoddard mount specify Sensenich M74DM prop. STC SA02179AK from Dan’s covers install of McCauley 1A175-GM8242 “Borer” prop on PA12-150. The airplane is fully STC’d for all mods (all 23 of them) - want to keep it that way.

Question1: Is it kosher to install the Borer when the engine is hung on a Stoddard mount as long as I’ve got Dan’s Borer STC?

Question2: The Stoddard mount installation instructions also specify a lot of other details including exhaust type and oil cooler. So I have the same question about using a Sutton exhaust and rear baffle mounted oil cooler STC with a Stoddard mount. Legal for certified?

I’ve looked at the Crosswinds STOL mount STC kit. I happen to have an O320-A3B - a version not included in that STC (far as I can tell).

Would like to avoid field approval process but will do it if that’s what it takes to stay “certified.”

Thanks in advance for any help.
 
Sooooooo, it depends. It depends on who is doing the paperwork!!! Most STC's say that the approval for multiple STC's is up to the IA. Read the STC closely!!! Depending on training the IA had and part of the country the plane is it it may or may not be an issue. It would help if you would say what part of the country you are talking about.
DENNY
 
Almost every STC has a limitation that says the installer has to determine that the interaction of this STC won’t have a negative impact on airworthiness. I always make a statement on the 337 to that effect. I guess the big issue is haw do you make that determination.


Sent from my iPhone using Tapatalk
 
As stated above, installing mechanic determines compatibility of STCs. I wouldn't have an issue with it. Look at the engine type certificate data sheet for the difference between your engine and the engines listed on the STCs. You might call Charlie and discuss the Crosswind STOL mod, it is more involved than some.
 
Thanks for the replies! My installing mechanic (here in Arkansas) is an IA but does not have a great deal of experience with overlapping STC’s with this many “moving parts.” But he’ll be good with signing off on it as long as it’s legal for him to do so. And I’m fortunate to know the MSI at the LIT FSDO. So I’ll consult with him ahead of time now that I know I’m not automatically shooting myself in the foot if I do. In my experience, LIT is a great FSDO by the way.

My thinking is that since I’m hanging more weight up front with the bigger prop, I want to change from the long mount to a shorter motor mount to keep the “mostly empty” CG in the right place. The Sutton exhaust was about getting rid of the stock exhaust AD and keeping some of that horsepower Ly-Con and PAP Cylinders hooked me up with. I decided to go with the Stoddard over the the Crosswind STOL mount because of all the extra parts required for the Crosswind. I put that money into the exhaust and I’ll do most of the manual labor/sheet metal more to shorten the cowl as required by the Stoddard install instructions (under the ever watchful/all seeing eye of my mechanic)

…and I’ll see you sometime soon, Steve. Going to wait until we get a little closer to the end of the project to head your way.
 
JDWilliams said:
Thanks for the replies! My installing mechanic (here in Arkansas) is an IA but does not have a great deal of experience with overlapping STC’s with this many “moving parts.” But he’ll be good with signing off on it as long as it’s legal for him to do so. And I’m fortunate to know the MSI at the LIT FSDO. So I’ll consult with him ahead of time now that I know I’m not automatically shooting myself in the foot if I do. In my experience, LIT is a great FSDO by the way.

My thinking is that since I’m hanging more weight up front with the bigger prop, I want to change from the long mount to a shorter motor mount to keep the “mostly empty” CG in the right place. The Sutton exhaust was about getting rid of the stock exhaust AD and keeping some of that horsepower Ly-Con and PAP Cylinders hooked me up with. I decided to go with the Stoddard over the the Crosswind STOL mount because of all the extra parts required for the Crosswind. I put that money into the exhaust and I’ll do most of the manual labor/sheet metal more to shorten the cowl as required by the Stoddard install instructions (under the ever watchful/all seeing eye of my mechanic)

…and I’ll see you sometime soon, Steve. Going to wait until we get a little closer to the end of the project to head your way.
Click to expand...

Let me know how this goes... I'm in the same boat...
 
I've got a -B2B (160hp) mounted on a Stoddard short mount, which was installed with Ron Sullivan's STC (Day & Night). I had bought the Kenmore STC for the 0-320, but didn't use it. I did take the mount to Atlee and had the lower tubes doubled (wrapped) as per the Kenmore STC, but it wasn't required. The -B2B is not on Mr. Sullivan's STC, but it was installed with the associated 337. My point is in agreement with other posts in that the STC can be modified if the installer/IA agrees and she states that the installation doesn't conflict with other STCs on the 337.
 
in my opinion the 12’s especially with bigger engines and borer props tend to be nose heavy especially when light on fuel. After having a 12 for 43 years I would recommend a short mount to move the engine back for a more favorable CG and a larger tai to increase elevator authority.

I can’t fail to recommend that you discard and replace any Pa-12 fuel tank before you fly it again.
 
My buddy started with the long mount on his 12 when he did the engine swap to an 0320. It was the plane I did my initial training and solo in. If you lifted that tail above waist high you better be hanging on or its gonna rip out of your hands and go on its nose. He ended up putting it on it's back on landing. I would go for the short mount or put some lead in the tail or its just a tiger waiting to bite you.
 
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