experimental aircraft/ usefull load

So I read it's up to the builder to determine gross weight/ usefull load of the aircraft he builds and uses the manufacture for a guide line. If I build and list it over 1320 lbs then this would eliminate it for a sport plane? But if I list it lower, say 1310 lbs max take off weight, and I have a bad accident and they can prove I should have known it was over weight, I don't think my insurance would cover any liablity?
So the question is, does the home builder list the gross weight of the airplane? thanks

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Originally Posted by rudder

But if I list it lower, say 1310 lbs max take off weight, and I have a bad accident and they can prove I should have known it was over weight, I don't think my insurance would cover any liablity?

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the manufacturer lists the gross weight. the homebuilder is the manufacturer. so the answer to your written question is, yes. but the homebuilder also attests to who built the aircraft, and why. so if one intends to ignore the rules and fly an aircraft intentionally mis-listed, why bother to insure it? why bother to register it at all? just paint on one's own registration number, scan somebody else's registration and airworthiness, insert made-up names and addresses, and go fly. oh, and for that, one needs no airman certification, either.




(yes, i'm kidding about pirate airplanes and aviators)

In your example you are stressing over a <1% wt. variation. That's trivial. If you want to keep a homebuilt in the LSA category, you can certainly establish a gross wt. to allow that but you have to operate in compliance with with that limitation. I don't think I would knock 20% off an airplane's load carrying capabilty just so I can fly it LSA but if I the designer says 1400# gross and I wanted to operate LSA, I'd limit the gross to 1320# for and certify it as such. Nothing wrong with that.

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Originally Posted by martymayes

I don't think I would knock 20% off an airplane's load carrying capabilty just so I can fly it LSA but if I the designer says 1400# gross and I wanted to operate LSA, I'd limit the gross to 1320# for and certify it as such. Nothing wrong with that.

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concur, Marty. and you'd FLY it with 1320 max takeoff weight, too, of course.

the phrase "But if I list it lower, say 1310 lbs max take off weight, and I have a bad accident and they can prove I should have known it was over weight..." is what gave me pause.

buddyamine built a kitplane with a proven track record that has a decent design gross weight/empty weight spread. he optioned his up and kept it at 1320 as the designer designated for light sport. fine. i do some of the phase I testing and performance verification for him, another guy flies off the rest. no problem. now he wants me to instruct him in it. oops. empty weight plus me 200 plus him 265 leaves six gallons for fuel, and it burns five an hour. ok, we do thirty minute day vmc flights. now he wants it ferried to another state and asks if i'll cfi his kid enroute. quick mental calculation, kid's only 180, we can take 20 gallons, plenty of range, sure, i'll do it. so the morning of the flight the kid has 50 lbs of baggage. plus spare oil (uses car oil) and charts and gps and tiedowns and canopy cover and etc etc etc. i have toothbrush, deodorant, fresh shirt and skivvies. we chop his "can't leave this" stuff down to carry 12 gallons at takeoff and have a wonderful day visiting small airports meeting friendly people. kid learned a lot, had fun. we updated dad along the way. but still dad asked after landing, "why did it take so many stops? it has thirty gallon tanks." uh, the designer says it's 1320 max, and so does YOUR limitations page, and so does the flight testing. "but if i put float fittings on it, you can take it to 1430 max gross." there were hints to his attitude before, but that was the clincher. don't think i'll be flying his plane any more.

so "rudder's" question struck a nerve. your mileage may vary.

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Originally Posted by cdrmuetzel@juno.com

the phrase "But if I list it lower, say 1310 lbs max take off weight, and I have a bad accident and they can prove I should have known it was over weight..." is what gave me pause.

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Yup, may have have gotten the numbers mixed up or may have been asking if compliance with the "paper" number is mandatory. Lots of folks have trouble with paper limitations.

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I have a bad accident and they can prove I should have known it was over weight

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List what the aircraft is designed for and fly at that weight and nothing more. Actually, what I was taught was to give yourself a ten to twenty pound margin of error for calculation errors, etc. Or, as one of my former instructors put it, for "when you're having a fat day" (which is a really funny phrase to hear come out of a cigar-chomping, gruff, all-American redneck pilot such as that instructor).

Given that in a lot of the homebuilt crashes, the FAA inspector who does the scene investigation (the NTSB apparently can't be troubled to send someone out for every occurrence of something as insignificant as a fatal experimental crash so quite often the scene investigation is handled by someone from the local FSDO) can't be bothered to thoroughly document things like restraint use, the exact nature of major structural damage, attitude at impact, ground scars, whether occupants were thrown from the aircraft and other pertinent facts, I somehow doubt that they are going to weigh all of what is left of your plane. They are going to just take the empty weight you list and add the weight of you (and your passenger) from your medical records or autopsy reports and any baggage on board and try to figure out how much fuel you had on board. That's how they calculate the weight so unless you're grossly over the limit the chances of them noticing are pretty slim.

However, the bigger concern with an "overweight" aircraft is the effects on the structure and the way the weight and balance works out. It is also often a "slippery slope" as you "get away with" one thing which can lead to you cutting corners or taking unnecessary risks in others. The botched takeoff attempt at Gaston's a few years back comes to mind when people talk about flying

I just started work on the construction of an LSA I designed and the goal is to sell plans for an inexpensive, safe(r) and easy to build and fly LSA since this market is largely overlooked in the rush for $100,000+ quick-build kits and gee whiz gadgetry. The core of the LSA is going to form the basis for the construction of a more 'normal' homebuilt so much of the structure (the fuselage and empennage mostly; the wings are different in that they feature plywood covered wood structure in the LSA version but an all metal wing in the second version although both are designed to similar loads and are the same size. The main reason for the difference is some concerns over flutter and the easier maintenance of metal) in the LSA was designed around the loads associated with a "regular airplane" which is intended to be much faster and significantly heavier than the LSA. However, this does not mean that the LSA is able to be flown safely at the category standard MTOW without testing. Any time you're outside of the defined test envelope during normal operations, you're a test pilot again. What happens should be fairly predictable but not so much that you should be betting your life or anyone else's on it.

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so "rudder's" question struck a nerve

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It did with me too.

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Given that in a lot of the homebuilt crashes, the FAA inspector who does the scene investigation (the NTSB apparently can't be troubled to send someone out for every occurrence of something as insignificant as a fatal experimental crash so quite often the scene investigation is handled by someone from the local FSDO)

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most ga accident investigations are delegated to the local fsdo as well, homebuilts do not enjoy an exclusive.

Related question for someone with better engineering chops and me:

Let's say I build a hypothetical kit that the seller says has a MGTOW of 1000# and load limits of +/-5g.

Can I safely (not legally; I know it's legal) adjust the MGTOW upward if I adjust the g limits downward? Is it simply a matter of doing the math to stay under the max load in pounds (eg. change the limits to 1100# and +/-4.5g)?

I realize there's a performance penalty paid with increased weight. I'm asking if I can improve the utility of a plane designed for acro by registering it closer to utility category limits.

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Originally Posted by Eric Page

Related question for someone with better engineering chops and me:

Let's say I build a hypothetical kit that the seller says has a MGTOW of 1000# and load limits of +/-5g.

Can I safely (not legally; I know it's legal) adjust the MGTOW upward if I adjust the g limits downward? Is it simply a matter of doing the math to stay under the max load in pounds (eg. change the limits to 1100# and +/-4.5g)?

I realize there's a performance penalty paid with increased weight. I'm asking if I can improve the utility of a plane designed for acro by registering it closer to utility category limits.

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I'd do that - if I had a degree in engineering and experience in aircraft design!

Otherwise, just pick a plane closer to your actual needs and abilities is my advice.

When one starts monkeying around with gross weights lots of unintended consequences can start to pile on, and it could be in very insideous ways. It's not just CG, it's stress on the aircraft. There may be places that just weren't designed to take the extra weight and might fail over time.

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Originally Posted by martymayes

most ga accident investigations are delegated to the local fsdo as well, homebuilts do not enjoy an exclusive.

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Very true. I was simply pointing out homebuilts since we are on a forum that specializes in that.