How do Rans, Just, Zenith, BackCountry SuperCubs, KitFox, Cubcrafters,and others do it?

I was on the phone the other night with an old bush flying stick I really respect. Anyway, he mentioend that certain aircraft from certain companies just fly super smoothly. With these smooth as butter planes if one for example increases power, the aircraft does not give you any bad misbehaviors such as excessive pitch or yaw.

I asked whether if all wasn’t just a matter of proper rigging, and he felt it was much more than that. It involved an inherent quality of good clean earonautical design and that the basic Cub for example was a superbly clean creation. He mentioned two other contemporary companies who he felt had MUCH less well executed and designed aircraft and that they flew far less gracefully, well rigged or not.

So, that begs the question. I am sure Boeing and AirBus have massive computer modeling programs and wind tunnel testing. I am curious what the “small guys” like Rans, Zenith, VANS, Backcountry Super Cubs, CubCrafters, and others do when it comes to design and testing? Do they just use some basic airfoil programs, build a few prototypes, and then go fly them ? Do they have access to windtunnels or can newer computer sim programs now do it all? Can those simulations calculate parasitic drag and accomplish all the needed testing to an acceptable degree?

Maybe it is just say JimBob in the back garage wth a case of Scotch and a little luck busy whipping out cool designs that more or less work. Does anyone know just how they whip up their desgns ? Is it Jack Daniels engineering or far more? I get the feeling it is a cottage industry, with sometimes modest resources. So how do they develop these new designs?

Your friend is right about normal airplanes flying right. I have had limited, scary, and almost deadly experiences with newer, less regulated, aircraft. We all hate regs, but it is nice to fly an airplane that does what they used to be designed to do. I helped my cousin with his kit built Zenith 601. He didn't get me involved until it was completely built with the nose gear and tapered wing. He weighed 240 pounds. I asked him why he didn't get the square Hershey bar wing. He said the gross weight limit was the same. I said it couldn't be, it had a smaller area. We called Sebastian at Mexico, Missouri. They had kept the gross figure for the bigger wing the same because they were going to manufacture it. I loaded my cousin up on a very cool day and it flew like an out of rig, overloaded Pawnee with a spreader. I had to put the forty hours on it alone. We were asked by the Suburu engine guys to cut down two different props they sent us trying to get full rpm. They finally sent a different belt drive reduction for the prop. I finally got my cousin to put the radiator flat up against the fuselage. It was a mess and never did feel right. I was always pulling too much air, like a bi-plane or spray plane with spreader. You can't just hang things on an airplane and expect it to fly right. Back when they carried and extra wooden prop between the mains, they expected to be pulling too much air.

Denali wrote:How do Rans, Just, Zenith, BackCountry SuperCubs, KitFox, Cubcrafters,and others do it?

I don't have inside information from those companies, but I am a computer scientist. I can tell you for certain that they *could* be running affordable high quality simulations for the kinds of variables you mentioned. Given how old some of the designs are, I don't know if they are doing that or not though.

Related: http://etd.auburn.edu/etd/bitstream/han ... sequence=1

A lot of the companies you mentioned just simply lie to them selfs and others.

Buyers be ware!

8GCBC wrote:A lot of the companies you mentioned just simply lie to them selfs and others.

Buyers be ware!

I'd be interested in knowing more about this.

gbflyer wrote:

8GCBC wrote:A lot of the companies you mentioned just simply lie to them selfs and others.

Buyers be ware!

I'd be interested in knowing more about this.

I flew around the country taking to many commercial builders both kit and certified. It scared the crap out of me how misinformed these people can be. Doing my homework paid.

I think a lot of it depends on the flight test program conducted on the prototype and the designers willingness to follow through on these findings to eliminate the quirks that are found during flight testing. There is a tendency to conduct a first flight and give it the OK and freeze the design because so much work went in to getting to that point, and often budgets and schedules are exceeded getting there. Do you think that the first prototype J-3 flew flawlessly? I doubt it. A mid fifties supercub had years of development behind it.

8GCBC wrote:

gbflyer wrote:

8GCBC wrote:A lot of the companies you mentioned just simply lie to them selfs and others.

Buyers be ware!

I'd be interested in knowing more about this.

I flew around the country taking to many commercial builders both kit and certified. It scared the crap out of me how misinformed these people can be. Doing my homework paid.

I got ya. What did you settle on?

gbflyer wrote:
I got ya. What did you settle on?

I like the 8GCBC. 70gals, 2600# (restricted), amphibs, hydraulic skis, MT prop., ACA never stops, they have the first IO-390 certified flying aircraft, based on the Scout.

I am very glad to have purchased a Scout! Wish they had a kit!

I find the comments very interesting. I hope everyone appreciates that this discussion is not to disparage any particular manufacturer. Instead I am asking whether the current crop of small single engine LSA and EAB aircraft is well designed and tested, or are they sort of glorified garage specials. Most are probably more than safe given the performance and altitudes, but they might not be the cleanest flying design by a long shot. How much of a hit, for example, do you take on a metal wing covered with exposed pop vs solid sunken rivets? Is the bonging of oil canning metal fuselage surfaces something that could be easily remedies by better design?

In recent years at least one US manufacturer of small home-bult was the focus of an FAA special review team which was tasked to investigate the causes of in-flight structural break-ups. It is one thing to be saddled with a noisy, drafty aircraft with poor aileron balance, funky stick force gradients that just won’t fly right no matter how you rig it. On the other hand a midair break up due to rudder flutter (or dither), marginal wing strength, or insufficient fuse structure represents a far more serious problem. In each case, better engineering, design, and testing could help to minimize such issues

Is the average small cottage industry aircraft/kit manufacturer up to the task ? I would NOT expect a small manufacturer to have a NASA like wind tunnel. However, in 2014, the computer power and software capability makes dynamic computer modeling very doable. Surely these days a manufacturer ought to be able to know if they are offering consumers a clean or dirty plane based on computer aerodynamic modeling.

Finally, good design and engineering cost money. At some point the price of a kit may become unacceptable. I find it all very confusing. All I know is that I would like to buy a kit that at least has had some design effort put into it, has been sufficiently tested, and flies in a relatively effortless, smooth fashion, and with out issues.

In effect beta testing a newly introduced aircraft design is not my thing. YMMV.

Denali wrote:I find the comments very interesting. I hope everyone appreciates that this discussion is not to disparage any particular manufacturer. Instead I am asking whether the current crop of small single engine LSA and EAB aircraft is well designed and tested, or are they sort of glorified garage specials. Most are probably more than safe given the performance and altitudes, but they might not be the cleanest flying design by a long shot. How much of a hit, for example, do you take on a metal wing covered with exposed pop vs solid sunken rivets? Is the bonging of oil canning metal fuselage surfaces something that could be easily remedies by better design?

In recent years at least one US manufacturer of small home-bult was the focus of an FAA special review team which was tasked to investigate the causes of in-flight structural break-ups. It is one thing to be saddled with a noisy, drafty aircraft with poor aileron balance, funky stick force gradients that just won’t fly right no matter how you rig it. On the other hand a midair break up due to rudder flutter (or dither), marginal wing strength, or insufficient fuse structure represents a far more serious problem. In each case, better engineering, design, and testing could help to minimize such issues

Is the average small cottage industry aircraft/kit manufacturer up to the task ? I would NOT expect a small manufacturer to have a NASA like wind tunnel. However, in 2014, the computer power and software capability makes dynamic computer modeling very doable. Surely these days a manufacturer ought to be able to know if they are offering consumers a clean or dirty plane based on computer aerodynamic modeling.

Finally, good design and engineering cost money. At some point the price of a kit may become unacceptable. I find it all very confusing. All I know is that I would like to buy a kit that at least has had some design effort put into it, has been sufficiently tested, and flies in a relatively effortless, smooth fashion, and with out issues.

In effect beta testing a newly introduced aircraft design is not my thing. YMMV.

I agree, I do not want to bash anyone in this type of forum regarding manufacturing aircraft.

"Sport pilot" has turned many people into chronic law breakers. The rules are plain stupid. All that crap just so you do not need a third class medical? It should be about 3500LBS or smaller to preclude a medical. Opinion. I have no background in medicine, but pilots have the ability to self police better now.

I would doubt the small guys have any sophisticated aeronautical design software (modeling software, sure)... look at the Skycatcher. They lost two aircraft before the final version with a redesiged tail. If it were easier/cheaper to do it on a computer, every production aircraft would be OK from the first prototype. I think it is mostly a matter of copy what has been proven to work, make minor modifications, then test.

Denali, there are universities, and even private aeronautics companies that will analyze an aircraft design and even do some types of testing. I don't remember names off the top of my head, but I've seen them mentioned in various articles in Kit Planes and EAA publications before.

I can't speak for other designers or manufacturers, but in one of the articles about the Patrol Bob mentioned the university that he had analyze the design before he built the prototype, and the group he worked with to select the airfoil. And I know that during the prototype testing period he redesigned the ailerons to eliminate a vibration problem at full deflection, and changed the control arm length on the rudder a couple times to get everything balanced properly. And probably a lot of other minor tweaks as well. I imagine other small companies do the same, at least the ones who's designs are still around.

The designs that worry me are actually the ones that have been around for a long time, and have slowly been added to until they're a far cry from the original, but have never been fully re-evaluated. This seems to happen mainly with designs that started as Ultralights and are now pushing the limits of the light sport definition.

The proven method to designing aircraft is to plagiarize what works without anyone having the authority to stop you!

Then purchase or license the rest!

Boeing comes to mind.

8GCBC wrote:"Sport pilot" has turned many people into chronic law breakers. The rules are plain stupid. All that crap just so you do not need a third class medical? It should be about 3500LBS or smaller to preclude a medical. Opinion. I have no background in medicine, but pilots have the ability to self police better now.

Not to get too far off topic, but I think the problem you're referring to is more do to the fact that most current pilots look at Light Sport as just a way to get out of needing a medical. When it was intended to bring some much needed regulation to 2 seat ultralights, and provide a lower cost way to get into flying, and keep flying. Which it is beginning to do. Even though I don't have any medical issues, I really hope the proposed medical exemption for private pilots goes through, if only to protect the LSA rules from being destroyed by the law breakers you mention.

Denali wrote:However, in 2014, the computer power and software capability makes dynamic computer modeling very doable. Surely these days a manufacturer ought to be able to know if they are offering consumers a clean or dirty plane based on computer aerodynamic modeling.

Finally, good design and engineering cost money. At some point the price of a kit may become unacceptable.

This is the truth of the matter here ^

It's VERY hard to do good engineering on the cheap. Software has come a long way and really made-good the saying "enough knowledge to be dangerous". Garbage in = garbage out; the error handling fools you into thinking you got the right answer. Basic 2D modelling of an aerofoil and computer modelling the characteristics of a 3D flying aircraft (prop, controls, and all) are day and night.

Speaking to a couple of kitset manufacturers, there's apparently so little money in the business - like many things in aviation - I expect even small follies could leave them bankrupt.
So personally, I expect the adage "if it looks right it flies right" is applied more often than exhaustive engineering analysis. Copy something already proven to work and it'll fly. That would be my guess

Bear_Builder wrote:

8GCBC wrote:"Sport pilot" has turned many people into chronic law breakers. The rules are plain stupid. All that crap just so you do not need a third class medical? It should be about 3500LBS or smaller to preclude a medical. Opinion. I have no background in medicine, but pilots have the ability to self police better now.

Not to get too far off topic, but I think the problem you're referring to is more do to the fact that most current pilots look at Light Sport as just a way to get out of needing a medical. When it was intended to bring some much needed regulation to 2 seat ultralights, and provide a lower cost way to get into flying, and keep flying. Which it is beginning to do. Even though I don't have any medical issues, I really hope the proposed medical exemption for private pilots goes through, if only to protect the LSA rules from being destroyed by the law breakers you mention.

I may have a skewed view of the regulations (I apologize, I live on an island in the middle of the ocean). But, the end result did not change the sport from the social tier I am on. I am big and so is my wife. We could never fly under the new regs very far. I have a Class 2, CFII, ATP and certified. I am trapped by the present regs. Oh well still have fun under the old law!

8GCBC wrote:

Bear_Builder wrote:

8GCBC wrote:"Sport pilot" has turned many people into chronic law breakers. The rules are plain stupid. All that crap just so you do not need a third class medical? It should be about 3500LBS or smaller to preclude a medical. Opinion. I have no background in medicine, but pilots have the ability to self police better now.

Not to get too far off topic, but I think the problem you're referring to is more do to the fact that most current pilots look at Light Sport as just a way to get out of needing a medical. When it was intended to bring some much needed regulation to 2 seat ultralights, and provide a lower cost way to get into flying, and keep flying. Which it is beginning to do. Even though I don't have any medical issues, I really hope the proposed medical exemption for private pilots goes through, if only to protect the LSA rules from being destroyed by the law breakers you mention.

I may have a skewed view of the regulations (I apologize, I live on an island in the middle of the ocean). But, the end result did not change the sport from the social tier I am on. I am big and so is my wife. We could never fly under the new regs very far. I have a Class 2, CFII, ATP and certified. I am trapped by the present regs. Oh well still have fun under the old law!

Exactly. Light sport wasn't written for you. Let's just hope that it's set some precedents that will help ease the regulations for the rest of us.

Writing more regulation is not easing regulations. EAA is a fricking trip man.

Is it the engineering software or the engineer that is more important?

CC has an engineering staff of five or so full time aeronautical engineers. Their chief has been in the business for decades. Can't beat good talent I would think? That being said...they also use fairly high quality 3D design software to do their jobs.

But I would imagine that a very good engineer with pencil and paper could still do a great job if he had been appropriately taught/trained in the art of old school aircraft design, whether OTJ or from an old-timer.