Cheap aircraft are simply impossible? :(

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

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  1. Mar 31, 2019 #1181

    Pops

    Pops

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    Back in the 1970's I got to spend some time talking to Fred Weick at Osh, nice man.
    I ask him what he thought about the aluminum covered Ercoupe wings. His answer " that makes it not an Ercoupe ".
    One my Ercoupes won first place at the national Ercoupe fly-in in the 1990's.
     
    Last edited: Mar 31, 2019
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  2. Apr 1, 2019 #1182

    lr27

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    Regarding the engines, any engine based on automotive technology will need a redrive or other transmission so as to turn an efficient prop. That adds weight and considerable technological effort if you want it to be reliable. If you're putting in a lot of technological effort, I wonder if a low rpm, direct drive, air cooled motor that's built with the same level of design sophistication as our current cars might be just as efficient. Particularly if tightly cowled with a thermostatically controlled cowl flap.

    When it comes to fly by wire systems, besides concerns about the reliability of the software, there would have to be very careful attention to exactly how the wiring was done. All the fancy electronics in the world won't do any good if a critical wire fatigues and breaks.

    As far as testing by RC, I'm sure one could hook up servos to an existing control system. There might be some regulatory problems or issues finding a place to do this, but it seems to me flying the first 10 or 50 or 100 hours remotely might really enhance safety. Plus you could do testing that would be pretty dangerous with a person on board. You could, for instance, explore the entire flight envelope, check flutter speed, etc. I imagine pulling a few g's under different control inputs would be a great follow up to static testing. Plus there'd be no risk of corrosion from the pilot's or flight engineer's barf. If I get organized enough to build full scale, I'd feel a lot better about it if I could test it like this. I guess it would be too expensive to evade the regulatory problems by renting an aircraft carrier and taking it out into international waters. ;-)
     
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  3. Apr 1, 2019 #1183

    David Lewis

    David Lewis

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    Roy LoPresti predicted in 1979 that by the year 2000 there would be no significant advances in general aviation airframe or powerplant technology.

    It could be there aren't enough airplanes produced over which to spread the research and development costs out, and there is a lack of engineering talent.
     
  4. Apr 1, 2019 #1184

    David Lewis

    David Lewis

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    That would be the cat's meow, but you'd have to sell a lot of engines to keep unit price within reason, even if manufacturing costs were rock bottom. An engineer once told me it took millions of man-lifetimes to develop the automobile engine.

    Remotely piloted airplanes crash more frequently than manned airplanes even if the control system functions perfectly. The manufacturing and rigging tolerances are tighter because the pilot doesn't have as much sensory input.
     
  5. Apr 1, 2019 #1185

    pictsidhe

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    Despite the vast amount of time put into modern fly by wire fighters, they still sometimes crash when an unseen bug pops up and bites. Since there is no standard fly by wire system, each one is generally unique to it's aircraft, and needing a metric ton of debugging until it is safe. Yes, it can be done, but it an awful lot of work. It's took me a long time to have a totally reliable pi, but it does still reboot itself sometimes. Much more often it has to reset other devices. I don't know why it reboots, I just made sure it can reboot when it stops running properly. It doesn't fly a plane, so I don't care about the 30 seconds downtime twice a year. Pulleys and cables don't glitch.
     
  6. Apr 1, 2019 #1186

    lr27

    lr27

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    Well, presumably you wouldn't start from scratch, but the volume would still be a problem.

    RPV's are often used because there's a potential of crashing in the first place. Particularly in the case of test flying as suggested here. Not being on board makes this increased risk somewhat less painful. Also, presumably such testing would be conducted where there weren't so many people on the ground. Maybe, given that there wasn't anyone around, most of the testing could be done at very low altitudes, permitting a landing before things got too far out of hand. At low altitudes and short distances, it's possible to fly remotely even if the telemetry fails, just by watching the aircraft. I'm even pretty good at it already. I admit I've never flown anything with more than a 20 foot wingspan or more than around 1.5 lbs/ft^2 wing loading.
     
  7. Apr 1, 2019 #1187

    Victor Bravo

    Victor Bravo

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    But control cables and pulleys are not broken, they work almost perfectly at a very very low cost. The cost (time, money, development) of replacing control cables and pushrods with electric servos or actuators or muscle wire is very high.

    Be kind to an old guy for a moment, and indulge me on one very obvious example of "progress".

    five or ten thousand years ago, a cave man named "Ugh!" invented the wheel. It worked then and it works now. Plenty of small incremental improvements over thousands of years, but the same basic principle. The wheel, specifically the use of steel wheels and smooth tracks together as a railroad, are still the most efficient form of transportation. Even though we have put people on the moon with rockets, and created a way for people to fly above the earth like the birds, the wheel is still the most efficient transportation now in widespread use. Ugh! would be proud.

    But mag-lev trains are shown to be possible, they have been tested in prototype form, and mag-lev train cars may eventually replace the wheeled train cars. They crete far less friction, and have the prospect of moving people and cargo on less fuel. It would be very easy to just stand up and demand that the world's railroad systems be converted to mag-lev immediately.

    Are all the world's governments and freight companies and passengers un-intelligent luddites because they have not changed over to mag-lev? Or is there a common sense reason that we still accept the ancient wheel and have not abandoned Ugh!'s way of doing things?

    Mag-lev is going to take billions and trillions of dollars to develop and install. The cost of a train ticket would double or triple for along time until all that development is paid off. Millions of commuters and travelers will be inconvenienced and delayed while the teething problems are sorted out. There would be several train crashes during the time when all of this is sorted out, and the legal mess from that will wreak havoc. When it's all said and done, the benefits of mag-lev will take decades to save more time andmoney than the development cost.
     
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  8. Apr 1, 2019 #1188

    blane.c

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    When "Ugh!" brought the wheel to the Eskimo, they laughed at him, and pointed at him, and called him names.
     
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  9. Apr 1, 2019 #1189

    henryk

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    =BIRDS can fly thausends kilometers iff to finde food=

    -the same or better we can too=airships with
    zero drag =allmost zero energy for fly...

    =no runways,no roads !
     
  10. Apr 1, 2019 #1190

    gtae07

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    The talent is there in plentiful supply.

    The problem is cost, as you note. To get adoption in any more than the "early adopter" type segment of the homebuilt market (where "alternative engines" and even things like EFI still are) and get significant market penetration, you need to go certified. And that's a deceptively attractive path that has bankrupted far too many projects. Without a Musk/Bezos type sugar daddy to bankroll such a project it'll probably never happen--the market is too small now, with turbines dominating the high end and electric encroaching from the low end.

    That's the way I'd go. Heck, even build upon the basic Lycoming/Continental platform to save R&D and cert costs; these engines are already pretty efficient from a pure thermodynamic standpoint. I think your major gains here are going to come from making them more tolerant of alternative fuels (mogas), optimizing air, fuel, and spark delivery across the entire operating envelope, and reducing or even eliminating the need to manually babysit the engine. Change the cylinder head shape and tweak the valves, clean up the intake path, and add an automotive-style engine controller.

    All of this technology already exists. Most of it is even available on the experimental market at competitive cost; I'm personally implementing those things on my airplane (better intake, EFI, E10 tolerance).
     
  11. Apr 1, 2019 #1191

    Little Scrapper

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    There's a difference though. This "Ugh" guy actually did it, he did the work, he followed through. He's a doer and a producer.

    Talk is cheap, anyone can do it. I'm not pointing fingers just pointing out the difference. People complain yet they've produced nothing but a opinion. Cheap aircraft are only available to the "doers". The "Ugh's" of the world.
     
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  12. Apr 1, 2019 #1192

    BJC

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    I had been on the job for a few weeks when the VP of Engineering called me into his office and asked me what I recommended on a particular issue.

    I said, “In my opinion, ...” He politely interrupted me and explained, “Opinions are like a**holes, everyone has one, and it is important to the owner, but no one else. I’m paying you to provide sound engineering assessments, not opinions.”

    One of those moments, never forgotten, from 47 years ago.


    BJC
     
  13. Apr 1, 2019 #1193

    Hot Wings

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    RPM is not the only way to make power from a fixed displacement. PSRUs, belts and gears, are easy to understand. They get the first, and too often the last thought.
    << >> Redundancy takes care of the wire breaking problem and a host of other related 'problems'. Add another wire, a wireless link, or both. Even certified aircraft (except LSA)have a backup for the primary mechanical control system.
     
  14. Apr 1, 2019 #1194

    blane.c

    blane.c

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    The wheel was useless to the Eskimo. It got stuck in the mud and snow.
    It is not the answer to everyone.
     
  15. Apr 2, 2019 #1195

    lr27

    lr27

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    Of course you can make more power by using something like a supercharger. However, I suspect a car engine operating at, say, 2,500 rpm and the same hp it used to make at 5,000 rpm is going to have some problems.

    I wasn't saying wire problems couldn't be solved, but that they required close attention. Not just redundancy.
     
  16. Apr 2, 2019 #1196

    Jean Crous

    Jean Crous

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    In my country ,South Africa there is a saying, " The words cheap, safe and aeroplane , cannot be used in the same sentence". I have found this to be true, by experience. A new LSA type should not as a rule "break the bank". Look outside of America for affordable aircraft. The Dollar is strong against many other currencies and this makes for affordable buying.In South Africa there are Kitplane manufacturers that have lots of experience, and available product, but our market is very limited. For example we produce an 80% scale copy of the Piper Cub, leaning more to the Supercub. This little aeroplane performs very well and compares well with imported kits in looks and performance , at a lot less money.Have a look here on Homebuilt Airplanes under the Manufacturers thread, look for Cubby Aircraft Factory in South Africa. And NO....I am not a scammer or charlatan of sorts;):DAlso visit our Facebook page Cubby Aircraft Factory. I am also very active on another aviation forum called Avcom, type in www.avcom.co.za.
    Regards
    Jean
     
  17. Apr 2, 2019 #1197

    Little Scrapper

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    Many of us cringe when people use the word "safe" when it comes to the airplane itself because often times it just doesn't make sense.

    Statistically "safety" or "safe" has more to do with the pilot than the airplane. In fact, it does so by a long shot. Looking over thousands of incident reports clearly shows pilot error as the source of safety issues.
     
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  18. Apr 2, 2019 #1198

    Pops

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    Flying is an activity where your safety is more in your hands than most things you do. Driving an auto, your safety is in a lot of other people's hands ( My son got hit head on by a semi-truck on the interstate when he was 24 years old). I flew 7 hours one day and driving home another car hit me head on my lane. I feel far safer flying where most of my safety is up to me. But people today tend to want someone else to take care of them in every way.
     
    Last edited: Apr 2, 2019
  19. Apr 2, 2019 #1199

    blane.c

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    Like when the last 737 crashed it was clearly a matter of pilot incompetence because of crew duty times they were propping their eyes open with toothpicks at the last safety meeting that mentioned how to deal with the problem that Boeing had built into the plane. Or that recent floatplane crash in Florida when the engine failed shortly after takeoff, clearly pilot error as well, at least that is my bet when the accident report comes out. BS.
     
  20. Apr 2, 2019 #1200

    Little Scrapper

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    Basically yo
    Basically you decided to compare a couple of anomaly type accidents to compare against home built aviation?

    Come on, I think everyone can see what you're trying to do here. A 737 vs a LegaL Eagle? Two accidents? Lol.
     
    Last edited: Apr 2, 2019

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