Converting 2-seater to 4-seater?

Capt. Geoffrey Thorpe said:
If you start with a kit and build it under the Experimental Amateur Built rules (meet the so called 51% rule), not a problem. If you start with a factory built aircraft you are basicly out of luck.

Warning: This is my video and I will get a fraction of a penny if you watch it. So it's best that that you don't click on it. Plus, it's boring.

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Thanks for the reply! Can a kit-plane like Sling 2 kit be modified and applied for Experimental Certificate?

One important fact I missed in my calculation is the fuel load. The useful load of 696 lbs also includes fuel. The full-tank fuel load on a Sling 2 would be about 245 lbs and it totally messes up my calculation! I might still be able to carry four of us, but I won't be left with any allowance for the parachute.
 
tsts4 said:
Room is only part of it. Does the airframe structure support adding seats and restraints? Way simpler to go with a 4-place design from the get-go instead of trying to make 2 seater into a 4 seater. Also you didn't include fuel load in your useful load equation.
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Thanks! Yep, the structural strength of the airframe would definitely be an important factor to consider while installing the seats. And yes, I did realize that I did not include the fuel load.

A 4-seater kit (Sling or Van's) are almost twice as expensive as their 2-seater kits and that places 4-seaters in an unreachable territory. 2-seater kits in 2023 are about $110K, which is the price of a luxury car. Some down and some loan makes 2-seaters somewhat affordable (though tight, still somewhat affordable) for normal people like me.
 
Jitendra Pandey said:
Thanks for the reply! Can a kit-plane like Sling 2 kit be modified and applied for Experimental Certificate?

One important fact I missed in my calculation is the fuel load. The useful load of 696 lbs also includes fuel. The full-tank fuel load on a Sling 2 would be about 245 lbs and it totally messes up my calculation! I might still be able to carry four of us, but I won't be left with any allowance for the parachute.
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It's a kit airplane. It has to be certified as either an E-LSA or E-AB which are both experimental types of Air Worthiness Certification. Based upon what you're asking to do E-LSA is out for a number of reasons. So that leaves E-AB under which you could mod the design to your heart's desire. But the issue is most kit aircraft don't come with engineering drawings, but rather assembly instructions. This could make it more difficult to safely make a major alteration to the basic design. I strongly recommend not going down this path if you aren't an engineer and/or have no experience building.
 
Thanks for your input! Even though I hold an engineering degree and understand basic to advanced concepts of physics, I am inclining towards getting a 2-seater kit and not modify it at all.

I am glad I could get some replies from a 5 year old thread. Thanks all!
 
Jitendra Pandey said:
2-seater kits in 2023 are about $110K, which is the price of a luxury car. Some down and some loan makes 2-seaters somewhat affordable (though tight, still somewhat affordable) for normal people like me.
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You can get something already flying for significantly less as long as you don't need a designer label airplane like a Vans.

Wittman Tailwind, T-18, etc., etc., etc.
 
Capt. Geoffrey Thorpe said:
You can get something already flying for significantly less as long as you don't need a designer label airplane like a Vans.

Wittman Tailwind, T-18, etc., etc., etc.
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And unless you're wedded to E-AB (either building or buying already flying), a used standard certificated aircraft (eg 172, Cherokee/Archer, etc) certainly meets your requirements. You really need to take a hard look at your mission and what's available to meet it. Building is an endeavor not to be taken lightly, even with today's modern kits -- you need to approach it as a journey you're interested in taking and not as some inexpensive path to aircraft ownership.
 
The only LSA I know of where this might be physically (but probably not legally) possible is the Jabiru J230. https://en.m.wikipedia.org/wiki/Jabiru_J230 The 230 uses the same wings and fuselage as the 430, which is a 4-seater.

Essentially, Jabiru removes the rear seats and placards the plane to LSA limits. But I don’t know how you could convert a 230 into a 430 and comply with regs.
 
Converting 2-seater to 4-seater?
Simple, follow the airlines lead on this; remove the 2 seats and replace them with 4 seats half as big as the 2 you removed.
 
Don’t forget people frequently get heavier as they age

Your 80 lb children will be 120 by the time you finish building your plane
 
Half Fast said:
The only LSA I know of where this might be physically (but probably not legally) possible is the Jabiru J230. https://en.m.wikipedia.org/wiki/Jabiru_J230 The 230 uses the same wings and fuselage as the 430, which is a 4-seater.

Essentially, Jabiru removes the rear seats and placards the plane to LSA limits. But I don’t know how you could convert a 230 into a 430 and comply with regs.
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Thanks! Yes, Jabiru 430 kit could be a good options for my use case. I am going to try and find out if Jabiru 430 can be fitted with a Rotax 914 UL. Jabiru 3300 6-cylinder does not have the most reliable track record, outputs 120hp and weighs dry at about 185 lbs, where as Rotax 914 UL produces 115 hp but weighs only 142 lbs. Jabiru 430 kit already comes with a wooden-composite so no weight savings there.
 
FORANE said:
Converting 2-seater to 4-seater?
Simple, follow the airlines lead on this; remove the 2 seats and replace them with 4 seats half as big as the 2 you removed.
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This is not a bad idea at all, every ounce counts when you are trying to lift yourself in the air!
 
Randomskylane said:
Don’t forget people frequently get heavier as they age

Your 80 lb children will be 120 by the time you finish building your plane
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Agree! This fact should also be in consideration while dealing with months long assembly time. However, my second 80 lbs is only a year old and not 80 lbs at all at this time! But again, this conversion seems out of question at this point after doing some further research and going thru the opinions provided here on this thread. Nothing is impossible but it boils down to how much time is worth spending going thru all those difficult steps, especially getting any-category air worthiness certificate to get it in the air legally.
 
Half Fast said:
The only LSA I know of where this might be physically (but probably not legally) possible is the Jabiru J230. https://en.m.wikipedia.org/wiki/Jabiru_J230 The 230 uses the same wings and fuselage as the 430, which is a 4-seater.

Essentially, Jabiru removes the rear seats and placards the plane to LSA limits. But I don’t know how you could convert a 230 into a 430 and comply with regs.
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Good answer ;)


Salty said:
I think Jabiru used to market an LSA in the US as a 2 seater that is a 4 seater in other countries. You couldn't fly it here legally though.
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Jitendra Pandey said:
Agree! This fact should also be in consideration while dealing with months long assembly time.
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Months long, with little kids. I almost spit my drink out over my keyboard at that one. Good luck with that. I would caution against being overly optimistic on the time required to build. Typically, it's usually longer, in some cases much longer, than the builder anticipates and that's if you stick to a stock build with no significant mods added in. Life, especially with kids, has a habit of getting in the way. Also don't rely on kit manufacturer projections -- they are often generic. Find a builders' forum for the make/model you want to build and get data from actual builders.
 
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The CH640 is a 4 seat version of the certified Alarus. Although the fuselage is not stretched, it has longer wings, larger stabilator, larger ruddder, and an O-360 instead of an O-235. It is probably also beefed up in some areas to account for the increased loads as well. Just putting in 2 extra seats is probably not going to safely make a conversion from 2 seats to 4 seats.
 
Stevea621j said:
The CH640 is a 4 seat version of the certified Alarus
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The CH640 was a set of plans that allowed a person to convert a certified Alarus into a CH640. Unfortunately, Zenith Aircraft stopped selling the plans in 2020.
 
odie451 said:
The CH640 was a set of plans that allowed a person to convert a certified Alarus into a CH640. Unfortunately, Zenith Aircraft stopped selling the plans in 2020.
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Not exactly. It was a kit (or set of plans) for a 4 seat aircraft based upon the Alarus. I don't know of anyone who converted an Alarus to a CH640. The plans do not really address converting an already built Alarus to a CH640. Since there is nothing that shows what is different between the two aircraft, you would somehow have to obtain a copy of the drawings for the Alarus, then compare them to the drawings for the CH640, and see where they differ.
 
Fellow_Pilot said:
convert a two seater lsa to a four seater, ... shouldn't pay an extra $30000 to get two extra seats.
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Allen Millyard has converted 2x 4 cylinder Yamahas into a 6 cylinder Honda.

That seems a very similar proposition, but likely saved more than $30,000.

 
From
http://all-aero.com/index.php/57-planes-x-y-z/12101-zenair-ch640


"Heintz used the Zenith CH 2000 as the basic platform for his new design since the aircraft already boasted a huge cabin area, and the type-certificated design could easily be stretched into a four seater. Starting with a basic CH 2000 fuselage assembly, the CH 640 started to take shape by stretching the cabin area and adding the rear seat. New wings and horizontal tail sections were also developed, and the firewall-forward side was borrowed from the Heintz’ STOL CH 801 design which utilizes the same engine."
 
odie451 said:
From
http://all-aero.com/index.php/57-planes-x-y-z/12101-zenair-ch640


"Heintz used the Zenith CH 2000 as the basic platform for his new design since the aircraft already boasted a huge cabin area, and the type-certificated design could easily be stretched into a four seater. Starting with a basic CH 2000 fuselage assembly, the CH 640 started to take shape by stretching the cabin area and adding the rear seat. New wings and horizontal tail sections were also developed, and the firewall-forward side was borrowed from the Heintz’ STOL CH 801 design which utilizes the same engine."
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Exactly. It is a new design based off the Alarus, But even in the fuselage, which looks the same externally and has the same overall dimensions, because of the higher loads, increased speeds etc it has thicker skins in some places, different rivet spacing or larger rivets in areas, additional bracing etc. Its not a conversion kit to turn an Alarus into a CH640.
 
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