# Cheap aircraft are simply impossible? :(

Discussion in 'Hangar Flying' started by Inverted Vantage, Nov 15, 2009.

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1. Nov 15, 2009

### Inverted Vantage

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"If it was easy, someone else would've done it..."

Another one of these threads. I just ran through the gamut with an aeronautics grad student friend of mine - we spent a good 8 hours discussing and researching a myriad of ideas - and everything we did turned up short.

We tried all plastic structures; but no luck, nothing had a good enough strength to weight ratio.

We tried all plastic structures with aluminum spars; no luck, same problem, and it was just too heavy overall.

We tried thermoformed plastic with carbon fibre or fiberglass insets as strengtheners; the labor costs required in piecing it all together and trimming/fitting those composite strips would make the other labor savings negligible.

We tried a hershey bar wing that was literally just an extruded aluminum shape; this was OK, but we found a lot of difficulties attaching the wing to anything else. This was probably our best option though - but still expensive.

Fiberglass has it's obvious limitations, as does welded/rivited aluminum.

I'm really beginning to think that a manufactured airplane below $50,000 really is just a pipe dream for people who don't really know the nitty gritty of aircraft design. The more I learn, the more I realize just why this hasn't been done before. How about you guys? Any ideas? Last edited: Nov 15, 2009 2. Nov 15, 2009 ### PTAirco ### PTAirco #### Well-Known Member Joined: Sep 21, 2003 Messages: 3,477 Likes Received: 1,000 Location: Corona CA It's funny how most airplanes will weigh about the same regardless of what material they are made of and it similarly it seems they will cost pretty much the same. (Until you get into really exotic materials and processes.) I firmly believe it is possible to produce a decent two seater and sell it with a reasonable profit margin for under$50,000. The fact that LSAs are selling for two and even three times that much is simply due to that's what the market will bear, not because of the inherent cost of material or manufacture.

3. Nov 15, 2009

### Inverted Vantage

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The labor costs are just astronomical though; with such small runs, it's not feasible to cut out the labor costs to the point where you can sell a sub $50,000 plane. At least it seems so. I'd be welcome to see another approach - I figured we were going pretty out there with the plastics and extrusion methods; we were also using other things like servo-actuated control surfaces to save weight and cost of putting in control linkages. But a lot of it came down to manual labor in the end. 4. Nov 15, 2009 ### Autodidact ### Autodidact #### Well-Known Member Joined: Oct 21, 2009 Messages: 4,513 Likes Received: 799 Location: Oklahoma Re: Cheap aircraft impossible? You'ld have to greatly simplify all of the fiddly stuff, I think. If GM only built 500 Cobalts a year, they'ld probably cost more than$150,000 each. Maybe if you simplified the control system? Like make it an enclosed cockpit weight shift flying wing? The wing could be cantilevered with no internal systems and could be an internally braced wing; might even have a tail on the end of a boom attached to the wing and not the "pod". But then your getting into the realm of what I call "flying machines" instead of airplanes, but if the control was accomplished with a joy stick instead of the "a-frame" of the usual weight shift aircraft, it would still be fairly satisfying from a design standpoint (flying is always fun regardless of the vehical type IMHO). No reason it can't be a "tractor" configuration, then you could have a rudder in addition to the two-axis pivoting wing for conventional (inputwise anyway) control. Needs an inexpensive engine as well; I prefer four stroke, personally, but thats just my personal prejudice. Going into the airplane buisiness?

5. Nov 15, 2009

### Inverted Vantage

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At that point you're, like you said, leaving the realm of airplanes; at which point sure, you can build something for under $50,000. However you're not going to get a very wide market, and you'll be lucky if the end product isn't more than a fat ultralight that's registered as an LSA. I just posted (you probably started writing yours before I put mine up ) that we attempted to simplify the controls; using direct input electric actuators (so not fly by wire where the controls are adaptive, it's simply 100% joystick = 100% deflection) so that all you had to do was slap in two servos and it's done. We even came up with a system where the wing could have the amount of aileron area vs amount of flap area changed at the factory, so you could have "sport", "trainer", "cargo", etc models. Still too expensive though. I'd like to get into the airplane business after college, but at the moment it seems like something that really can't happen. Honestly, the only way I can think of it happening is if several small manufacturers banded together to agree on a singular "standard" body, then wrapped their own shells and feature around it. That's the only way the amount of production would justify the costs of tooling. And this is just production costs. Add to it the$30,000 engine overhaul every 100 hours, and it becomes laughable that you can get something to be very cost effective?

6. Nov 15, 2009

### Topaz

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I know, UT. I've said before, my belief is that real cost reduction will come from carefully accounting for manufacturing methods and processes from the moment the aircraft's design begins, so that you design the structure and components of the airframe to methods and processes that promote low-cost. Perhaps they won't be the absolutely best strength-to-weight ratio compared to what might be possible in conventional design, but so long as the aircraft meets the mission requirements and cost targets, it doesn't have to be the 'ultimate expression of light weight construction.'

Take your plastic shells with a metal sub-structure. Sure, they're a bit heavy. But if you can still meet the mission requirements with this structural model and it saves you a ton of money in manufacturing, so what? The aerospace industry has built up a culture of 'performance orientation', and that colors everything that's done. I honestly read an article critical of a particular spacecraft design (much earlier than the Constellation project) because that project "wasn't requiring any new technologies in its development." HUH??? It met the mission requirements and cost a lot less than some full-on R&D effort, and it actually flew. Not everything we do has to "Push Forward The Boundaries Of Science."

What I see - from my admittedly limited perspective - is that airplane companies and engineers tend to design the airplane first, and then try and figure out how to make it inexpensive. That doesn't work very well. You lock in most of the man-hours (and cost) to build an airplane from the moment you decide on the mission parameters, the major configuration, and structural materials/construction methods. Without careful consideration of costs right from the beginning, you get what we have today - "cheap" airplanes that really aren't. The other thing I see is the inventor with the "eureka" idea that saves costs in one part of the airplane and simply pushes them into some other part of the airframe or manufacturing process.

The other half of the equation is the simple overhead of running a company. Cost needs to be carefully considered there, too. Insurance costs, inspection requirements, documentation, marketing, sales, accounting, HR, ... All play their part in cranking up the cost of the airplane. If you can't keep those under control, don't bother trying to engineer costs out of the airplane itself. And the design of the aircraft can have an effect here, too. If the manufacturing method you choose is cheap to build and easy on material costs, but requires huge investments in equipment and man-hours for quality control on the factory floor, you've just eaten up all your cost savings.

This nut isn't going to be cracked by a single clever configuration, material choice, manufacturing method, or any 'eureka' idea in the design of the airplane. It'll be cracked by a thousand little carefully-considered decisions made from the moment pencil is first put to paper defining the draft mission requirements. Not terribly exciting, but it is what it is.

My quite uninformed and not-so-SWAG gut feeling is that a two-seat LSA-type airplane could be built and profitably sold for somewhere in the $35,000-$50,000 range if the entire design process and business plan are tailored for design-to-cost. It probably wouldn't look like a jet fighter or anything exotic - just a simple, light, utilitarian airplane with some attention paid to aesthetics and a lot of attention paid to selling it inexpensively.

Last edited: Nov 15, 2009
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7. Nov 15, 2009

### Autodidact

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How about a new Cub? NOT a high wing tube/fabric thing, but a very simplistic (from a structural standpoint) square edged hershey bar tandem seat with a minimum of intrumentation and one panel in front, low wing, no flaps, optional nose wheel, with the (blown) canopy and (molded) engine cowling plus a leaned back leading edge on the vertical fin giving some refinement to the lines? Other than that, what Topaz said. (Uh, gee that kinda IS what Topaz said! Doh!)

Last edited: Nov 15, 2009
8. Nov 15, 2009

### Autodidact

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Oh, I read a book not long ago about Edgar Schmued called "Mustang Designer" I think. Toward the end of WWII He did a study about building an aircraft out of spot welded sheet STEEL (car body stuff). It was a bit heavy, but perfectly feasible. The market for mass produced "everyplanes" ( like the Grumman G-63 Kitten, neat little plane) never appeared, of course.:depressed

9. Nov 15, 2009

### Richard Schubert

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Check out this plane and construction method

Rohr 2-175

They were going to produce wings like waffles :gig:

10. Nov 15, 2009

### Inverted Vantage

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Topaz; the plastic was simply too heavy to actually get off the ground; with the weight limitations of the LSA class, there was no way to get any adequate structural strength from the plastic in an easy manner. We went through several plastics, up to and including carbon fibre reinforced plastic; and even then it was still only about as strong as mid-grade aluminum, and at that point it'd be a pain to work with. Also, any reinforced plastic would have a void problem, where the strength of the structure could only be calculated as a general idea - there would be parts where it was much weaker than design loading. And we'd have to test the parts, which requires losing some of them and, you guessed it, man hours. The weight allowances are simply too tight; you might be able to get away with it by making a single seat and making it weigh as much as a two seater would, but then you're going to have anemic performance relative to other single seaters, and no one's going to buy it because they want to fly with their honey as well.

Anything with welding is also out, as you'd have to check each weld for every aircraft you produce, and randomly test a sample from the production to make sure the welds were being done properly. And to weld a complex shape like a box fuselage, you're going to need man hours.

The fact is that you CAN design an aircraft that's quick to build, and if you had a factory you, you could pump out a dozen a day. The problem is the cost of that factory, tooling, etc, far outweighs whatever profits you can get (aat least in the short to mid term).

11. Nov 15, 2009

### wsimpso1

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We build carbon and/or glass and/or aramid reinforced plastic parts all of the time. Most of us are talking laminated parts with oriented fibers and 50-65% fiber volume content in epoxy or vinylester resins and we can assure you that they are light and fly just fine...

Perhaps you are talking about short fibers at 10-20% volume randomly oriented in thermoplastics or polyester resin. Weak stuff by comparison...

Yeah, the biggest part of any flying machine is going to continue to be MONEY for a long time yet, and that is no surprise to any of us.

Billski

12. Nov 15, 2009

### Inverted Vantage

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wsimpo1, what parts are you building? And yea, we were talking about basically chopped strand suspended in a plastic matrix.

With your method, are you laying up the fibres on the structure and then putting plastic on it, or is it a sheet of thermoform plastic material with the fibres inside it, and you simply lay it up on top of a mold? That would be the ideal, as it would require no finishing work.

13. Nov 15, 2009

### BBerson

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I think spot welded steel is a solution. Instead of hard to weld tube structures, structures designed for fast welding, maybe even with robot welding machines.
BB

14. Nov 15, 2009

### Dan Thomas

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Steel is heavy, but a really thin sheet of high-alloy stuff would be plenty strong yet light enough to fly. The 1930s Fleetwing Seabird amphibian was made of stainless steel sheet.

Problem with spot welding is the embrittlement around the spot. the heat changes the characteristics of the steel, and work-hardening around the spot as the structure flexes causes cracking.

Aluminum sheet is being stir-friction welded now on some airliners. No rivets. The sheets are butted together and a small carbide tool with a tiny ridge on it is spun at high speed and pressed onto the joint and travels along it, with the resulting heat fusing the pieces together. The alloys properties are unchanged, they say, though I dont know how they can get away with that. The beauty of it is the lack of concentrated forces around rivets or spot welds.
Friction stir welding - Wikipedia, the free encyclopedia

Dan

15. Nov 15, 2009

### orion

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We've looked at this issue numerous times over the years and in each exercise, regardless of the approach, we still came out with substantial costs once we examined the whole picture. One of the most promising ideas came relatively recently after taking a tour of Eddyline Kayaks - their process utilizes a vacuum formed Acrylic shell that is laminated on the inside with a reinforcing fabric. The laminate (glass or graphite) uses Vinylester resin, which adheres to the Acrylic quite well. It also is a solid laminate without core so even a hand layup goes rather quickly. The benefit is not only lower cost tooling and processes, but also a pre-finished exterior surface.

At first glance the approach seemed a bit heavy but when considering the amount of primer and paint most aircraft (especially composite structures) have on them, the penalty was actually not as bad as we first thought.

The concept can use several internal structure configurations including a composite based egg-crate type of thing (fuselage), or simply a tubular weldment. We took this idea pretty far actually in that we came up with a design (actually, sort of a family of shapes) and figured out how to attach varying outer shells.

But while the idea had much merit, there still were a few bugs that we really didn't address in enough detail. These included things like skin shape stability (especially for the wings), handling concentrated loads, determining the long term suitability of acrylic bonding, and so on. All in all, I think the idea has merit but the level of savings is still questionable since you still have issues of tooling, jigging, labor, and so on.

Below is the airplane we tried this on - the design is based on the P-40Q.

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16. Nov 15, 2009

### BBerson

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A full skin of steel is indeed heavy. I meant an open structure of steel. A sub-structure of steel covered with a light skin, as mentioned by Topaz.

The MIG welder does nice spot welds with 4130 steel sheet.

As for for friction stir welding... I asked the Eclipse Jet salesman at oshkosh about the friction stir welding, he said: " the machine cost more than a million, we only have one machine."
BB

17. Nov 15, 2009

### Topaz

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Yeah. Eclipse. At first I was really pushing for them, but as I learned more it became clear that this should be the poster child for designing the airplane first and then trying to make it cheap to build. They hung the whole ball of wax on friction-stir welding, and then had the nerve to look shocked when the FAA said, "Friction-stir what? Qualify that process for us..." Even a day's research and a quick letter to Oklahoma would've saved them millions of dollars in development and process qualification costs. They had their "eureka" idea, didn't follow through all the ramifications, and it bit them.

Eclipse is a prime example of how not to do it, IMHO.

18. Nov 15, 2009

### PTAirco

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I have often doodled with number to figure out how to reduce the number of hours it takes to build an airplane, for some reason the subject the of production engineering fascinates me. Production engineering as opposed to design engineering. Somewhere in another thread floating around somebody mentioned a Hawker Hurricane and it is a perfect example of great design engineering with total disregard for ease of production. (OK, total disregard is exaggerating, but then again labor was relatively inexpensive then.)

If anyone would like to know about the trials and tribulations of starting a an aircraft manufacturing business, read "Slide Rule" by Nevil Shute and the "Airspeed" company. (Nevil Shute is an acquired taste, but how many aircraft designers are out there who are also novelists?)

The only variables you have to play with in airplane manufacturing are:
cost of materials,
man-hours required,
parts you need to buy from the outside over which you have no control.
(Plus completely unrelated costs such an insuring yourself against idiots and ambulance chasers, but let's ignore that for now.)

As far as material costs go, it is still hard to beat aluminium sheet, but the overall cost variations between materials are not a huge factor. Pound for pound, the final effect on price is fairly small.

Man-hours - this is the biggie: The time to cut a huge amount of hours is in the design stage, not on the production floor. CNC machinery will have a huge impact on this in the future (it already is for companies like Vans) Most of the parts for my little single seater (UL3) can be produced on a CNC router or water/plasma/laser cutter, saving huge amounts of hours. Feed the machine and collect the parts when it's done, minimal human attention needed. A manual machine shop around here will charge about $60 an hour. A CNC machine will cost up 150$ an hour, but it spews out parts at ten times the rate of the human machinist, so do the math.

Parts count is another major area to save. I see an awful lot of "bitty" airplane designs out there. Places where it would have been easy to make one part do the job of two. A single spar wing will take half the time spent on making spars as a two spar wing for example. Making two lift struts instead of four will take half the time. A tapered rod landing gear will take a fraction of the time to make compared to the many parts need for a sprung, bungee or oleo-type of gear. The opportunities for saving time are endless. Yes some will have to be balanced against cost, but if your labor costs are high, the simpler solution will usually win.

Overheads can be cut by working in less than desirable areas - Southern California is not a place to set up shop, whereas someplace like Alabama can halve your shop rental costs.

Parts you have to buy in - a huge source of of uncontrollable cost, the biggest of which is the engine. Airspeed actually bought engines form DeHavilland, at first, a direct competitor. They soon realized the folly of that and set up their own engine division. This, I think is crucial - half the cost of an airplane is in the engine. Produce a cheap engine and you have taken a huge chunk out of the cost of an airplane. Buying Rotax 912s and making money for another manufacturer and not yourself is not an ideal solution. Remember our design goal here is a simple and cheap airplane here, we don't need to power it with anything other than a simple 0-200 clone or something like that.

Glass cockpits now account for about a third of the cost of some of the high end LSAs like the Remos - people looking to buy and fly an affordable airplane don't need or want \$30,000 worth of of gadgets to fly with. Use the electronic stuff where it is cost effective when compared against traditional instrumentation, like an engine monitor and find a cheap basic GPS and you're set. This kind of thing is much harder to produce in house, but if you could find a clever electronics graduate with a passion for aviation....? This stuff takes brains to design, but not to manufacture.

The costs of insurance might make all the above efforts moot, unless you can find another way of legally protecting yourself from disasters - that is question for lawyers, not engineers. But I believe Maule has always been building without product liability insurance.

I still think it can be done, and if nothing else it provides an entertaining challenge for the grey matter.

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19. Nov 15, 2009

### Topaz

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Well said, PT.

The idea of farming out batch parts to CNC job shops could be a huge money-saver. HUGE. Especially for a start-up so they don't have to sink a lot of capital into equipment and skilled people to run it.

I just don't know if the FAA would certify that production process, even for an LSA, since so much of it is outside your company's control. The inspection requirements to make sure everything conforms might eat up a lot of the savings. Be interesting to look into, however.

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20. Nov 15, 2009

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