Stupid Question:

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Boscovius

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I really hate to have to ask this, but this is obviously the forum to have the question answered.

In all of my online queries about FAA regulations on the subject of an individual designing, building, and flying his own LSA, all I can find is information on kit building and certification.

Can someone point me in the right direction? I need to know if the construction methods I'm planning on using, which may be somewhat unconventional in some respects, are permissible so that I dont' find myself in a pickle somewhere down the road with a contraption I've invested a lot of time and money in that I'll never be allowed to fly.

And if there is a clearly defined path for this approach, what is it? Is it clearly defined and documented? Where can I find it?

Any help is much appreciated.
 

Rhino

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Might want to give some info on those construction methods you mention. That might give someone a better idea of how to answer.
 

Boscovius

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I have mentioned in prior posts my interest in using lightweight composite board made of closed cell polyurethane foam blended with fiberglass, some of the boards are a foam/glas sandwich between fiberglass woven mat. Thicker boards for use as bulkheads and the thin stuff for use as a skin applied in panels inset in channels routered into the bulkheads and longerons, all eventually covered with laminations of carbon fiber and resin. This is mostly only for the areas of the amphib hull and deck that require the most durability. Wings and empanage would be fairly conventional.

But all that aside. I'm not asking for a critique on my design plans. Yet. Just need to know is there a clear path for the self-designer? I joined EAA last week, but my membership is still pending.
 

Rhino

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I don't know that there is a defined path, but there are others here far more qualified than me to answer that question. I'm sure they'll chime in.
 

12notes

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If you want to register a plane as an E-LSA, then there are specific rules about the construction of a kit (and it must be a kit) and no variations in configuration are allowed.
If you want to build a plane that meets the LSA limitations and can be flown with a Sport Pilot certificate, but is registered as an E-AB, then you can build from plans or kits, design the plane yourself, or build it nearly however you want as long as it is safe.

E-LSA and S-LSA are specific types of registration for some LSAs, but any plane that meets the LSA limitations can be flown as one regardless of registration type.
 

Kiwi303

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USA is a different set of rules, but the effect is the same here... for something novel that isn't cookie cutter, just showing the engineering calculations by a suitably certificated engineer who is qualified in those substances and their applications is then followed by building a test article, test to destruction and if it holds up to the stresses subjected to it, it's build the plane and fly it for it's required hours.

I don't see it being too different over there.
 

Dana

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The overlap in the regulations does cause a lot of confusion. LSA can mean two different things:

A factory built airplane certificated under the new ASTM standards is a "Special Light-Sport Aircraft" (SLSA). You're not allowed to modify it in any way, and you have to have an A&P or Light-Sport Repairman certificate to work on it.

If the factory chooses, it may offer a kit version of the plane. As built, it will be exactly the same as the factory built plane, and it'll be registered as "Experimental Light-Sport Aircraft" (ELSA). Once it's built and certificated, the builder is free work on it himself and to modify it as he chooses, just like any other experimental aircraft.

Two other paths to ELSA are a paperwork conversion of an existing SLSA (which many owners do to allow owner maintenance), and the now expired timeframe when existing unretistered "fat ultralights" could be registered as ELSA.

None of the above provide a path for a builder designed, scratch built LSA.

However, any aircraft that meets the LSA definition (1320# gross weight, speed limits, 2 seats, etc.) can be flown as if it were LSA (i.e. by a Sport Pilot), regardless of its actual certification basis. These aircraft include older lightplanes (Piper Cub, Taylorcraft, etc.) that meet the LSA limits, and also Experiental-Amateur Built (EAB) aircraft. So you can have an aircraft that's registered E-AB, but operated as LSA.

If you design and build your own aircraft, it will be registered as E-AB, even though it may meet the LSA criteria and thus can be flown by a Sport Pilot.

Now, as far as engineering and construction materials: There are no requirements. You can design and build an airplane out of toilet paper and play-doh and get an airworthiness certificate. The final inspection (by an FAA employee or DAR) only looks at the paperwork and workmanship (are the bolts safety wired?); they make no judgement about the safety of the design (although some DARs may refuse to sign off something obviously unsafe). That's why you have to fly it solo for 40 hours over uncongested areas. The idea is that you're free to kill yourself, just don't take anybody with you.

USA is a different set of rules, but the effect is the same here... for something novel that isn't cookie cutter, just showing the engineering calculations by a suitably certificated engineer who is qualified in those substances and their applications is then followed by building a test article, test to destruction and if it holds up to the stresses subjected to it, it's build the plane and fly it for it's required hours.

I don't see it being too different over there.
Nope, it IS different over here, you don't have to show any calculations, don't need a certificated engineer, don't need to show any test results... you just have to fly the required hours (if you and the aircraft survive).
 

Boscovius

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Thank you to everyone for the replies. Dana, that is exactly what I was hoping to hear. Build a SLA registered as E-AB, and fly it with a Sport License. I expect I'll be working with some EAA guys from my local chapter so I can get help with maff. Now, if you don't mind, I'm going to research that E-AB definition a bit.
 

Rhino

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...you don't have to show any calculations, don't need a certificated engineer, don't need to show any test results... you just have to fly the required hours (if you and the aircraft survive).
Completely true. However, if you do end up getting a picky DAR, having those things could go a long way toward swaying his decision. So, although not required, it wouldn't hurt to hedge your bets if you can make those things available.
 

Boscovius

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Rhino, I agree with that, and I would rely on my EAA friends to help guide me on that one. I think that would be very good to have when discussing wing rib placement.
 

wsimpso1

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To legally fly an Experimental Amateur Built airplane, you do have to demonstrate that you built at minimum 51% of the airframe, which is not hard to do if you design and build it, keep a log and take photos as you go. After showing that you built it, the DAR or FAA rep examining your bird does have to sign off on the airplane. Design calculations, analysis of the airplane's aerodynamics and structures or at least following something that looks like convention is not strictly required, but it sure makes getting the signature easier.

As to your intended methods of construction:
Do you have a source for these glass reinforced PU foam? Most of us have not a chance of making our own core materials. There are many core materials out there ready for use. Pick the material, and there are varying densities and thicknesses. The market really does have the design space pretty well covered here;
  • Fiber-resin laminates over light cores have been widely used and are accepted. There are some conventions within the genre too, and we write about them;
  • One thing seen frequently is that we rarely go lighter than some minimum gage for skins, and that min thickness varies with the fiber and underlying core, but mostly it must keep the nominal slings and arrows of life around an airplane from wrecking the laminates on the outside and where you touch it in the cabin and baggage bay;
  • Your allocation of thinner cores to the skin and thicker cores internally is opposite of what is normally needed in boat hulls and aero structures. When you make the skin cores thicker, you need far less internal structure, and almost invariably makes for less ribs, longerons, etc, at any level of load carrying;
  • Skins on hulls and aero surfaces have stationary air inside, moving fluids outside, run through Bernoulli's equation on that sometime and see just how big the loads are trying to inflate the skins...
As someone who has made a career in engineering, received Patents, and sat on Patent Committees, I can tell you that within the realm of things that work, there is little new under the sun. I suspect that after you get into the design a bit, you may find that your design ends up having similarities to existing craft... But who knows? Maybe you do have a line on something unique and new and useful.

The best reason to build your own design is you want something that is not currently out there. The second best reason is that you want to do the design and build thing. If you are still so inclined have at it. You might even live long enough to fly it. And I am saying that from my perspective of building my design...

Billski
 

Boscovius

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Billski, Thanks for the input. Truly, I am not trying to reinvent the wheel where it comes to the construction. I've just been working things out in my head. Various ways of doing things in a manner that will serve the required function. what I am trying to do that is new is to have an amphibious aircraft, that is not so much amphibious as it is a true fusion of boat and airplane. I see a lot of amphibious aircraft designs, but none of them that truly serve a dual purpose as a boat. That's my inspiration and my design challenge. I want to be able to dive off the prow of my boat, swim around the backside and climb back up. Sit with my legs straddling the prow, and fish for perch dinner. Oh, gosh. It's late. Can't fly at night. No problem. Don't have to. Fold the wings back and speed back to the boat ramp over the waves. You get the idea.
 

Riggerrob

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Boscovius,

The only stupid question is the one that you do not know the answer to when you are on short final.
Hah!
Hah!

Folding the wings then still being able to power back to the marina is a challenge. I have sketched a few configurations, but folding wings seem to only mate gracefully with forward-mounted, tractor propellers, which can be easy to build, etc. but are a high risk to dock-hands.
What does your wing/prop configuration look like?
 

Rhino

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Rhino, I agree with that, and I would rely on my EAA friends to help guide me on that one. I think that would be very good to have when discussing wing rib placement.
Sounds good. But don't forget that many of us here are your EAA friends now. We may not hold an official position in the organization other than 'member', but EAA is made up of mostly homebuilders, and you won't find a better group of those than you will right here.
 

Dana

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Completely true. However, if you do end up getting a picky DAR, having those things could go a long way toward swaying his decision. So, although not required, it wouldn't hurt to hedge your bets if you can make those things available.
Not to mention that a non suicidal person will want to do those calculations and/or tests before he puts his butt in the seat for the first test flight.

I see a lot of amphibious aircraft designs, but none of them that truly serve a dual purpose as a boat. That's my inspiration and my design challenge. I want to be able to dive off the prow of my boat, swim around the backside and climb back up. Sit with my legs straddling the prow, and fish for perch dinner. Oh, gosh. It's late. Can't fly at night. No problem. Don't have to. Fold the wings back and speed back to the boat ramp over the waves. You get the idea.
That's pretty much the vision that Icon is promoting (or Searey, at a fraction of the price). Well, they can't speed around on the water with the wings folded. But just like the flying cars that we'll have Real Soon Now, it's not that easy: good boat design is not good aircraft design and vice versa, so you end up with something that's not a good airplane and not a good boat (though the examples I have are more airplane than boat).
 

Kiwi303

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Sounds like something for that disributed electric power option being talked over in a different thread... central IC power unit close to CoG, with generator, light electric trolling motors that fold up and down like gear legs, Light (lighter than ICE and PSRU anyway) electric prop drive motor mounted wherever conveniently packaged.

FLy in and land, switch from airscrew to waterscrew operation and flick a switch to engage electric wing fold... motor to the dock with the electric trolling motors.
 

Pops

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Even with a dead simple airplane, you will have more time and work in designing than building. Remember there is no such thing as a dead simple airplane.

I ask the FSDO inspector if he wanted to see the thick notebook on all the design and stress analysis for the JMR. Said no. Just ask if I did the fuel flow test. Said, "Yes and the results are here, you want to see them, answer was "No ". There was 2 inspectors, bet the one took 400 pictures. Didn't miss anything inside or outside. Did find a few things he didn't like.
Post 213
 

Boscovius

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Boscovius,

The only stupid question is the one that you do not know the answer to when you are on short final.
Hah!
Hah!

Folding the wings then still being able to power back to the marina is a challenge. I have sketched a few configurations, but folding wings seem to only mate gracefully with forward-mounted, tractor propellers, which can be easy to build, etc. but are a high risk to dock-hands.
What does your wing/prop configuration look like?
Pondhopper desktop.JPG

I made this model 25 years ago or so. Thinking ducted propeller behind the cockpit. Model does not show folding wings, but wings would rotate back from the "shoulder" area by use of a slew bearing or some such mechanism that can take the load. Model showed excellent glide ratio in a water test. COG is at the shoulders. Will make a flying 1/4 scale of the intended full scale project before attempting a real build. Real build would be 8' 6" wide to allow for trailering. Remember. I have no intentions of operating out of an airport with this. Also missing from model is the downward pointing rudder on the empennage. And of course cockpit details.
 

Boscovius

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Pondhopper desktop.JPG

The cardboard is just for temporary support until I get the powerplant and duct installed.
 
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