How to find the real gross weight a plane can carry?

Talk about airplanes! At last count, there are 39 (and growing) FAA certificated S-LSA (special light sport aircraft). These are factory-built ready to fly airplanes. If you can't afford a factory-built LSA, consider buying an E-LSA kit (experimental LSA - up to 99% complete).

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WDD
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Re: How to find the real gross weight a plane can carry?

Postby WDD » Mon Feb 19, 2018 5:59 pm

FastEddieB wrote:
WDD wrote:On the other hand, if it can only truly handle 1320 pounds or so, its not going to have a lot of reserve performance - if any.


You and most others here probably are aware of this, but the word "performance" here can be misleading.

I've heard time and time again that a plane limited to 3,200 lbs, let's say, has "performed" just fine up to 3,500 lbs, with excellent rate of climb even at the higher weight. I honestly think that many think that engine output and rate of climb are what establish maximum weight. It may be a factor, but weight limits are more often the result of loads on the structure at higher weights, regardless of horsepower reserves. I guess "performance" can include the ability of the structure to handle loads, but again, I don't think thats the way its normally uses.


Yeah, that could be what's throwing off the discussion. When I stated "performance", I was thinking the structure could handle more loads, landing gear more robust, etc. I was also thinking that if a plane could handle itself well at 1600 pounds (handling well, agility, be able to get out of a stall and spin), it would be even better - more reserve performance - that a plane that was maxed out at 1320 by design.

The discussion seems to keep bouncing back to "don't overload / go beyond 1320 lbs. Which isn't the premise of the question. Perhaps think of it this way. "Do certain LSA airplanes provide a benefit over others because we WON'T load it beyond 1320lbs ?"

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Re: How to find the real gross weight a plane can carry?

Postby FastEddieB » Mon Feb 19, 2018 6:22 pm

WDD wrote:"Do certain LSA airplanes provide a benefit over others because we WON'T load it beyond 1320lbs ?"


I'd say in the real world, "Not really".

I suppose if someone told me my plane's airframe had been tested to 2,000 lbs, let's say, I'd think that was an interesting factoid and store it away in the back of my mind.

But I would not see it as a benefit. If Sky Arrows are not routinely falling out of the sky due to structural failures - and I don't know of any that have - it becomes difficult for me to see any reasonable scenario where that added robustness would provide a practical benefit to me. A theoretical benefit? Maybe in some bizarre edge case. But planes, including Light Sports, are already built with large safety margins in place. Making them even larger is unlikely to ever provide a real life benefit.

Though I see your point. In theory.
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Re: How to find the real gross weight a plane can carry?

Postby 3Dreaming » Mon Feb 19, 2018 6:45 pm

drseti wrote:
3Dreaming wrote: On a airplane like a LSA an increase of 200 pounds will reduce your safety factor by about 15%.


Actually (and you know this, Tom; this response is for the benefit of others), that's only part of the story. Yes, a 15% increase in weight will reduce safety factor, but by far more than 15%. Here's why:


When I made that post I was speaking only to the structure of the aircraft in flight, and not energy in a crash.

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Re: How to find the real gross weight a plane can carry?

Postby 3Dreaming » Mon Feb 19, 2018 6:48 pm

FastEddieB wrote:
Half Fast wrote:

(OTOH - don't know how this works. Your plane is experimental and you can now fly as a PP under Basic Med; could you certify your Arrow to a higher weight and take it out of the LSA category?)


Nope. No modifications allowed that would take it out of Light Sport limitations.


Actually it could be moved to experimental exhibition category at a higher gross weight. However the operating limitations would make the airplane less useable.

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Re: How to find the real gross weight a plane can carry?

Postby TimTaylor » Mon Feb 19, 2018 7:39 pm

FastEddieB wrote:
And why even waste time on pointless hypotheticals?
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Re: How to find the real gross weight a plane can carry?

Postby drseti » Mon Feb 19, 2018 8:01 pm

3Dreaming wrote:When I made that post I was speaking only to the structure of the aircraft in flight, and not energy in a crash.


Yes, Tom, I understood that. I'm engaging in mild thread drift chiefly because I am less concerned about structural failure of the airframe than I am of its occupants.
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Re: How to find the real gross weight a plane can carry?

Postby TimTaylor » Mon Feb 19, 2018 8:09 pm

If we're going to consider overloading an LSA, we might as well consider flying at night and IFR. Why the hell not? If you're inclined to ignore the rules, why adhere to any of them? What about flying above 10,000 feet? Who can that possibly harm?

What if I tow a banner at night in IFR above 10,000 feet for hire over 1320 pounds with 2 passengers? Would that be a problem? Maybe I could fly a twin but only use one engine? (I've done that plenty of times.)
Last edited by TimTaylor on Mon Feb 19, 2018 8:22 pm, edited 4 times in total.
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Re: How to find the real gross weight a plane can carry?

Postby HAPPYDAN » Mon Feb 19, 2018 8:14 pm

But is it possible to find out what it can really safely carry? That is, how much margin do you have?(Quote from OP)
Sure. Just use the tried and true Heineman/Savage Mythbusters method of practical application :D .
Load and fly one, incrementally increasing the weight, until the wings fall off. Then you'll know, all the way to the ground :shock: . Oh, and, wear a parachute. It helps. OK Moderator, you can ban me now. :wink:

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Re: How to find the real gross weight a plane can carry?

Postby drseti » Mon Feb 19, 2018 8:19 pm

HAPPYDAN wrote:OK Moderator, you can ban me now. :wink:


There will be no banning - chiefly because everybody here was thinking the same thing. :)
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Re: How to find the real gross weight a plane can carry?

Postby Nomore767 » Mon Feb 19, 2018 8:54 pm

WDD wrote:An LSA needs to be no more than 1320 lbs to be legal for a Sport Pilot to fly.

Hence, Vans RV 12, Sling 2, etc are rated at 1320.

But is it possible to find out what it can really safely carry? That is, how much margin do you have?

A Sling 2 looks nice because while we would load it only to 1320 lbs, it looks like if you registered it as a non LSA it can carry 240 lbs more. A nice safety margin. Same probably for the Jabiru. Have no idea what the RV 12 could really carry.

Thoughts?


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Re: How to find the real gross weight a plane can carry?

Postby drseti » Mon Feb 19, 2018 9:19 pm

WDD wrote:it looks like if you registered it as a non LSA it can carry 240 lbs more.


Registration issues notwithstanding, I wonder how one determines that additional 240 lb figure from from "it looks like". Structural analysis by visual inspection?
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Re: How to find the real gross weight a plane can carry?

Postby 3Dreaming » Mon Feb 19, 2018 10:11 pm

TimTaylor wrote:If we're going to consider overloading an LSA, we might as well consider flying at night and IFR. Why the hell not? If you're inclined to ignore the rules, why adhere to any of them? What about flying above 10,000 feet? Who can that possibly harm?

What if I tow a banner at night in IFR above 10,000 feet for hire over 1320 pounds with 2 passengers? Would that be a problem? Maybe I could fly a twin but only use one engine? (I've done that plenty of times.)


Why do you keep making the assumtion that someone is considering overloading a LSA? You are on a rant for no reason at all, and apparently you don't even know the rules.

Any LSA can be legally flown above 10,000 feet. Any LSA can be flown at night if properly equipped. Some LSA can be flown IFR if they have the propper equipment, transponder, and pitot static system checks. I have flown my CTLS at night, and could fly it above 10,000 feet if I chose to do so.The sister ship to my airplane can be be legally flown IFR at night above 10,000 feet.

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Re: How to find the real gross weight a plane can carry?

Postby TimTaylor » Mon Feb 19, 2018 11:02 pm

I thought this was Sport Pilot Talk.
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Re: How to find the real gross weight a plane can carry?

Postby WDD » Mon Feb 19, 2018 11:47 pm

drseti wrote:
WDD wrote:it looks like if you registered it as a non LSA it can carry 240 lbs more.


Registration issues notwithstanding, I wonder how one determines that additional 240 lb figure from from "it looks like". Structural analysis by visual inspection?


That's what they list it as if you don't register it as an LSA.

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Re: How to find the real gross weight a plane can carry?

Postby WDD » Mon Feb 19, 2018 11:53 pm

TimTaylor wrote:If we're going to consider overloading an LSA, we might as well consider flying at night and IFR. Why the hell not? If you're inclined to ignore the rules, why adhere to any of them? What about flying above 10,000 feet? Who can that possibly harm?

What if I tow a banner at night in IFR above 10,000 feet for hire over 1320 pounds with 2 passengers? Would that be a problem? Maybe I could fly a twin but only use one engine? (I've done that plenty of times.)


Who are you trying to argue with? No offense, but you're pretending things were said just so you can argue against them.


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