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Borer 3rd seat conversion STC SA5-7

White City, Oregon
I am in need of the installation instructions for this STC in order to determine if it was installed correctly in a PA-18-150 that I am currently working on. The 337 refers to drawing number 18-1. Any information would be greatly appreciated.

Thanks.

Brian.
 
I have the paperwork for the 3rd seat STC I purchased for N18SY in the hangar. I'll try to get out to the hangar over the weekend to take a look. If I have it I will scan and post it.
Darrel
 
My STC for the 3rd seat (180lb baggage) is from Ronald E. Sullivan. It is SA554AL. I have a drawing with the STC titled "3rd Seat Installation" Drwg No. 7-0, dated 25 Jan 1975. It is a poor quality blue line but I could copy it in sections and hope for the best if that would do you any good.
Regards, Darrel
 
Darrel

The aircraft I am working on is supposed to already have the Borer 3rd seat conversion. I am not sure if it is installed correctly, therefore need the installation instructions for that particular STC. The aircraft's paperwork does not have it. If the Sullivan STC is the same installation then I suppose it would work in the interim.

If anyone knows how the Borer STC is supposed to be installed, please let me know.

Brian.
 
So Brian do you want me to scan the drawing? It will take about 6 sections so I don't want to spend the time if it won't help. Let me know.
Darrel
 
Darrel

Not at this point, but thanks for the offer.
I will try to get a picture of what I have so that it can be determined if it is right.

Brian.
 
I have drawing 18-1. Let me know what part of the drawing your looking for and I can take a picture and email it to you.
 
My STC for the 3rd seat (180lb baggage) is from Ronald E. Sullivan. It is SA554AL. I have a drawing with the STC titled "3rd Seat Installation" Drwg No. 7-0, dated 25 Jan 1975. It is a poor quality blue line but I could copy it in sections and hope for the best if that would do you any good.
Regards, Darrel

Mark Ericson at Dakota Cub redrew this drawing and is what they sent me the last time I bought the STC.
 
180 lb baggage /3rd seat questions

So I am building a project and was wanting to know what is involved in this mod. Is it just seatbelt tabs and some additional tube? If so what are the tubing sizes and how are they installed. Any help or photo/ drawings would be appreciated.
 
yes, just an "X" of tubes and add belt attaches

Mike thanks for the info-as usual. I however cannot find any photos or drawings. I'm Kinda a new at this and may not be looking in the right places. Is the "X" welded under the floor or to the longerons and what thickness and dia of tube.
 
I've never seen a 3rd seat, although heard about them - just curious - anybody have a picture of a couple of people in the back seats? How do you fit two people back there? I have a hard time getting one person in the back seat ( I have some heavy set friends!)
 
I've never seen a 3rd seat, although heard about them - just curious - anybody have a picture of a couple of people in the back seats? How do you fit two people back there? I have a hard time getting one person in the back seat ( I have some heavy set friends!)
Otta make the 3rd row seat in the back of a Skywagon look plum spacious!
 
It raises the baggage floor.

Hi Steve
Do you have a pic or drawing of this? About every other Cub here has the third seat stuff and I've never seen a difference in the baggage floor. I was under the impression that it was just the 'butt brace' and seat belt tabs. Does it make a difference whether the dog leg has been flipped?

Web
 
Any one have a copy of the stc that they would let me look at and see if this is what I want to attempt. I would be grateful.
 
The dog leg is the three tubes located at the back of the stock baggage compartment with the shortest tube on the bottom left looking aft (stock) or the top right of inverted. It is common to flip this (mod) for extended baggage compartments. Photo failure it looks like a "Y"
 
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Here is the factory dogleg and 180 lb Sullivan STC installed.
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The third seat conversion has the third person sitting aft of the person in the passenger's seat...in other words, in the original baggage compartment. Hence the increase of the baggage area weight limit to 180 lbs, and the addition of seat belt tabs in the aft corners of the baggage compartment.

It helps if someone is actually going to sit back there (a uniquely bad idea in any but an emergency) to have a narrow passenger seat back in your rear seat, so that the aft passenger can rest their feet on either side of the "middle" passenger.

This modification originally came about as a result of the polar bear guides hunting off the coast of NW and western AK. They typically operated with two Super Cubs, one with the guide and client, the other with an assistant guide and lots of five gallon gas cans.....till some of these guys figured out how to increase fuel capacity.

Once they found a bear, the guide would land, and if that went well, he and the client would stalk the bear or vice versa, as the case may be. The assistant guide would land and if they killed the bear, they'd skin it and load the hide and skull in the assistant guide's plane, and launch both planes for AK.

On the other hand, if the guide broke his plane landing, the assistant guide would find a safer place to land, they'd put gas in that airplane from the cans, all three would board that plane, and they'd fly back to AK.

At some point, the FAA objected to the notion of three guys flying home in one two passenger aircraft.....hence the development of the third seat conversion.

In matter of fact, now that polar bear hunting with aircraft is illegal, the third seat conversion is most frequently used to stiffen the airframe in this area and to increase the legal load capacity of the main baggage compartment.

MTV
 
The third seat conversion has the third person sitting aft of the person in the passenger's seat...in other words, in the original baggage compartment. Hence the increase of the baggage area weight limit to 180 lbs, and the addition of seat belt tabs in the aft corners of the baggage compartment.

It helps if someone is actually going to sit back there (a uniquely bad idea in any but an emergency) to have a narrow passenger seat back in your rear seat, so that the aft passenger can rest their feet on either side of the "middle" passenger.


MTV

I always wondered why my rear seat back was narrower than other super cubs. It has the 3 rd seat mod - makes perfect sense now.
 
The small diagonal tube is. The horizontal tube is the bottom of the back seat, front tube. Springs are removed and we might have replaced the perforated tube with a solid tube I can't remember.
 
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