Sling S-LSA vs. EAB vs. ???

[cogito]

Stupid idea I'm sure, but have any of you left your airplane unpainted? Might save 8 or 10 lbs and with all the polishing you'd make sure to never gain too much weight yourself.

This is the larger, 4 seat version of the Sling on a 'round the world trip:

[drseti]

Hey, the Sling shot 'round the world!

[Jack Tyler]

"Gill Harrelson built 51+% of this Lancair?"
Bill certainly had help with some aspects of it. E.g. good friend Wes Whitley, formerly a NASA engineer, helped him with the advanced avionics and HF radio system required by transoceanic flight...but Bill remained directly involved and is certainly allowed under the 51% rule as I understand it. FYI another Lancair owner, Doug Johnson, took 5 years to build his comparable Lancair and has routinely used it for flying out to the West Coast from Florida. Doug's a radiation oncologist and formerly a Flight Surgeon with the USAF. I guess the point is that busy but capable people still somehow manage to tackle very complex challenges and succeed. Sure puts watching TV in perspective for the rest of us...

[FastEddieB]

My point with the cessna 150s was that when you see one flying with two people it is over gross weight unless they weight 100 lbs each and have half fuel.

Not true.

I sent a lot of students for checkrides in C-150's. Each and every one had to show the examiner they were in weight limits before the flight.

Same as a modern day LSA. Nothing new. There are thousand of them out there flying and they arent falling out out of the sky. Dont worry about it.

I strongly disagree with the above sentiment.

It seems to say that a pilot should be free to pick and choose which Limitations he or she chooses to honor.

In 1996 I had a renter pilot destroy a rental Citabria of mine and kill himself and a teenage passenger. He was over gross. The plane had been fueled for a cross-country that got canceled, leaving more than the 1/2 fuel I normally left in the plane. That was probably not the proximate cause of the structural failure, but it was listed as a contributing factor in the accident report, which I can link to on request if anyone's interested.

Anyway, maybe that accident pilot thought like you and just didn't worry about being over gross.

Over on the Cirrus Owner's site, one can find discussions of SR20's that the pilots overloaded and then crashed. In some of those cases the overloading WAS the proximate cause of the accidents.

It's a slippery slope. We can stipulate that a Light Sport will probably not suffer structural failure and/or be able to climb if its flown at 1,321 lbs. Or 1,322 lbs. Or possibly even 1,400 lbs. Or more. But that's a potentially deadly game to play, each pilot deciding that he or she is qualified to set limits higher than the engineers who designed the plane saw fit to establish.

We're grownups here (for the most part), and should seriously consider the effects of the advice we give here - most pilots who flaunt weight limits and crash probably filed away similar advice and acted upon it successfully...until they didn't.

[jnmeade]

It's a slippery slope. We can stipulate that a Light Sport will probably not suffer structural failure and/or be able to climb if its flown at 1,321 lbs. Or 1,322 lbs. Or possibly even 1,400 lbs. Or more. But that's a potentially deadly game to play, each pilot deciding that he or she is qualified to set limits higher than the engineers who designed the plane saw fit to establish.

There are several factors at play here.
One is that 1320 lbs seems arbitrary to many of us. What is the basis for that weight? We see evidence that some LSA are certificated for higher weights in certain places so we assume our identical model will be safe to the higher weight.
We want to fly over legal gross because we can't meet our mission unless we're over legal gross. If it is in fact safe to fly over legal gross we are risking our certificate but not our life.
You could make the point that an airplane can suffer catastrophic structural damage at 1319 or 1318 and on down. That is what Va is about. How slowly should we fly to be certain that when very light we won't over stress the airframe? We pay scant attention to Va below max gross.
We read of airplanes that are cleared by the FAA for ferry or other flights where they are significantly over gross. If the FAA is OK with that, why shouldn't we be?
LSA to the 1320 weight limit is a developing design concept. New LSA may be designed to optimize that weight but at this stage there are many varying designs that are LSA legally but are designed differently. How do we lay owners know and who are we to say what their design limits are? We see people allege they are "pared down to meet weight" but this is patently not always the case.

We're grownups here (for the most part), and should seriously consider the effects of the advice we give here - most pilots who flaunt weight limits and crash probably filed away similar advice and acted upon it successfully...until they didn't.

You're certainly right that C150 had to meet w&b on the checkride, but the other point that they may seldom have met it otherwise is well taken based on my observations (I did not say personal involvement) in C150 training, some of which involved cross country and night when fuel requirements were higher.
Any discussion of w&B ought to start and end with the regs, most of us may agree. In the middle, it's hard to know for sure what is physically safe and what is not. A lot of the conversation is anecdotal and seems aimed at answering questions that should be readily apparent but aren't. Have we seen the flight envelope chart on our specific airplane or even model?



No one can be faulted who prefers to leave the conversation at the regulatory position. Maybe that will save someone from feeling they can exceed the limit with impunity but that person may not know he can kill himself pulling the wings off at 1250 lbs. Maybe people will exceed the weight limit not knowing how badly they are stressing the airplane - if you can get it in the airplane it will carry it.

I'd rather we started with the regs but each of us knew enough physics to understand the stress in various flight regimes. We don't do a good job of teaching that, likely because most of us don't understand it ourselves. Thus the anecdotes.

[FastEddieB]

I don't disagree with most of what you said, but when one says something "seems" so-andso, or that we can "assume" so-and-so, it makes me nervous.

I just worry that the wrong message is being sent, and that new pilots will read the message as implied permission to roll their own limitations, so to speak.

Just remember that virtually every pilot who crashed due to being over gross almost certainly had done it before to no ill effect, and possibly boasted about it, until that fateful day.

Part of being a professional pilot is adherence to procedures, FAR's and Limitations. Whether getting paid or not, I would like to think that professionalism is a worthy goal for every pilot.

[CharlieTango]

...Just remember that virtually every pilot who crashed due to being over gross almost certainly had done it before to no ill effect, and possibly boasted about it, until that fateful day....

Eddie,

I'm on your side of this discussion but it is worth pointing out that an over gross condition increases stall speeds which increases your margin at Va but can force you to land with a higher stall speed than what you have experience with.

Another consideration is that even my SLSA at 7,100' gets airborne in 5 seconds leaving almost 1 1/2 miles of runway in front of me. My point is that if I'm too heavy to fly in a light sport I know it in a few seconds and have ample opportunity to abort.

[FastEddieB]

Good points but...

...far too many pilots assume that max gross has to do with performance.

Hear it all the time on the Cirrus site - "I've had my SR22 more than 200 lbs over gross and it still climbed just fine..." - that sort of thing.

Climb performance may be one consideration, but more often its structural limitations.

My advice - go by the book. Once you're outside of it you're a test pilot, and an unpaid one at that!

[jnmeade]

This is like sex education.

One sides advocates abstinence, the other side accepts the premise of abstinence but promotes education. I'm with the latter. The reason is that those who were given only the abstinence lecture may someday find themselves out of or in danger of being out of compliance but with no idea of the consequences, which cold be minimal or could be fundamental. The educated practitioner can assign risk and act accordingly.

[drseti]

The educated practitioner can assign risk and act accordingly.

As an educator, how could I possibly disagree? But, that education has to include the true risks. Those have little to do with structural failure, and everything to do with stall speed.

I read a lot of NTSB accident reports, and have noticed that a disproportionate number of stall/spin accidents mention aircraft over gross. So, consider this scenario: Pilot has a tailwind on base, overshoots the turn to final, steepens the bank in the turn, adds power (i.e., torque), and then gives rudder to further yaw the nose without having to bank still further. Let's say this is in an LSA with 45 knot stall speed. 20% overgross (not hard to do in an LSA) raises stall speed to 50 knots. A 60 degree bank, if you haul back on the stick and pull 2 Gs, can further increase stall speed to 70 knots. And, if you were approaching at normal speeds, you just entered the classic stall/spin domain.

Was the cause of the accident being overgross? I doubt that would be the NTSB's judgment. Proximate cause was that tight turn to final. But, had the plane not been overgross, might the accident have been prevented? That is at least arguable.

So, will the plane "handle it" at higher weights? Of course it will - unless the pilot screws up. Why paint yourself into that corner in the first place?

[Mark Gregor]

Ed,

You bring alot of experience to the forum and I appreciate your valid comments.

I also have to agree with Jim that its not always that black and white.

Most of the LSAs we are talking about here are flying at higher weights in other countries with no airframe changes. I dont believe that is true for many part 23 aircraft not held to an artificial weight limit. That puts LSAs in a unique position.

Ed,
How would you handle this situation? When I got my P2008 and were going back to Minnesota I did the preflight W/B before departing and determined with the instructor I had been given we could only put in 12 gallons to be legal. We were heading across the mountains and me having little experience with mountainous terrain I was uncomfortable. The instructor insisted he would not allow more fuel and we would be fine. Which is more dangerous?

How many accidents do we know that have been caused by running out of fuel?
How many accidents do we know have been caused by overloading?

I am not advocating flying overweight. I want to be clear about that.
I am just saying it is not as black and white as we would like.
I have suggested several times that the LSA weight limit is not practicle.
My suggestion would be to give weight exemptions for safety features such as the parachute.

And we havent even started the discussion on the pros/cons of building a stronger more substantial aircraft that is potentially safer VS a lighter built aircraft that is more prone to landing gear failures as we have regularly seen in LSAs.

Mark

[cogito]

The educated practitioner can assign risk and act accordingly.

As an educator, how could I possibly disagree? But, that education has to include the true risks. Those have little to do with structural failure, and everything to do with stall speed.

I read a lot of NTSB accident reports, and have noticed that a disproportionate number of stall/spin accidents mention aircraft over gross. So, consider this scenario: Pilot has a tailwind on base, overshoots the turn to final, steepens the bank in the turn, adds power (i.e., torque), and then gives rudder to further yaw the nose without having to bank still further. Let's say this is in an LSA with 45 knot stall speed. 20% overgross (not hard to do in an LSA) raises stall speed to 50 knots. A 60 degree bank, if you haul back on the stick and pull 2 Gs, can further increase stall speed to 70 knots. And, if you were approaching at normal speeds, you just entered the classic stall/spin domain.

Was the cause of the accident being overgross? I doubt that would be the NTSB's judgment. Proximate cause was that tight turn to final. But, had the plane not been overgross, might the accident have been prevented? That is at least arguable.

So, will the plane "handle it" at higher weights? Of course it will - unless the pilot screws up. Why paint yourself into that corner in the first place?

Question Paul: In your scenario, a 20% overload corresponds with a 5kt stall speed increase. An EAB Sling built to 700kg (rather than an LSA at 600kg) is 16% heavier but the factory specs page lists only a 1kt increase in stall speed either clean or full flaps. Do you believe the data sheet is incorrect or misleading? http://www.airplanefactory.co.za/sling2.asp

[drseti]

Do you believe the data sheet is incorrect or misleading?

Well, let's do the math. Stall speed varies with the square root of load factor. (700 kg / 600 kg) equals a load factor of 1.167. The square root of that is 1.080, or an 8% increase in stall speed. That means a 45 knot stall speed now increases 8%, to 48.6 knots ( a 3.8 knot increase).

To have an 8% increase in stall speed add only 1 knot, the original stall speed would have had to be 12.5 knots. I find that hard to believe. So, yes, I would question the published specs.

[rsteele]

Stupid idea I'm sure, but have any of you left your airplane unpainted? Might save 8 or 10 lbs and with all the polishing you'd make sure to never gain too much weight yourself.

Unpainted planes, like the one pictured are usually polished to get the shine and smooth the surface to reduce corrosion.

Polishing works, or not depending on the alloy used to build the plane. I'm building a Zenth which uses 6061-T6 aluminum. This aluminum is very corrosion resistant and there are quite a few polished Zeniths around. Polishing is said to save about 20lb on the Zenth 601, and I'll be polishing mine. On the other hand Vans are build of all-clad 2024 aluminum. I've never seen a polished Vans as the metal is prone to corrosion, or at least surface blemishes. You would have to put clear coat over polish. I was out at my hangar last weekend and cleaned off bird poop that had been there on the unpolished/unpainted surface for some time. It came right off with no indication it was ever there. Compare that to a friend's RV-7. Before it was painted, a drop of sweat would leave a mark.

Ron

[cogito]

Stupid idea I'm sure, but have any of you left your airplane unpainted? Might save 8 or 10 lbs and with all the polishing you'd make sure to never gain too much weight yourself.

Unpainted planes, like the one pictured are usually polished to get the shine and smooth the surface to reduce corrosion.

Polishing works, or not depending on the alloy used to build the plane. I'm building a Zenth which uses 6061-T6 aluminum. This aluminum is very corrosion resistant and there are quite a few polished Zeniths around. Polishing is said to save about 20lb on the Zenth 601, and I'll be polishing mine. On the other hand Vans are build of all-clad 2024 aluminum. I've never seen a polished Vans as the metal is prone to corrosion, or at least surface blemishes. You would have to put clear coat over polish. I was out at my hangar last weekend and cleaned off bird poop that had been there on the unpolished/unpainted surface for some time. It came right off with no indication it was ever there. Compare that to a friend's RV-7. Before it was painted, a drop of sweat would leave a mark.

Ron

Ron,
20 lbs.? that could be very helpful, could make the difference between going LSA or EAB. Do you have any data on the 20 lbs? Anyone weigh an LSA-sized plane before and after paint? Online I've seen everything from 5-30 lbs. (and that a 747 carries 400-500 lbs. of paint.~) Sling uses 6061-T6, though I was planning on having it alodined to prevent corrosion. I wonder if they can do that on the interior parts only.

There are a number of polished RV's online. Not all look as good as this one: