Have any of these features ever been incorperated into a homebuilt?

Discussion in 'General Experimental Aviation Questions' started by AnxiousInfusion, Mar 3, 2010.

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  1. Mar 4, 2010 #21

    lr27

    lr27

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    Seemed like they had a great big streamlined nacelle, then they ignored it and added two more. Looks draggy to me. Of course you could say that about most twins.
     
  2. Mar 5, 2010 #22

    mcjon77

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    Of course we can't forget the Rutan Defiant. Twin engine, centerline thrust, canard, composite, 4 seats, gross weight of 3,000lbs+, cruise of 170-180knots, and a range of +1000nm (IIRC).


    [​IMG]
     
  3. Mar 5, 2010 #23

    Dan Thomas

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    Fly-by-wire is used on large high-performance aircraft, sometimes to stay in control of a machine that would be uncontrollable without sophisticated computers to take the pilot's ideas and convert them to complex, exacting control movements, and sometimes to eliminate long, heavy, friction-plagued mechanical controls that need boosting anyway. In small airplanes this is not a factor in any way, and fly-by-wire would be heavier (and way more expensive) than simple cables or push-pull rods or whatever. And electronic controls introduce many more failure points, something we've seen in the FADEC controls on the Thielert diesels in the Diamond twin. Several have had the engines go to idle when the power failed. Ugly. A forced landing and maybe a crash, with perfectly willing engines that are waiting for you to tell them to go faster.

    There are many ideas we can be tempted to use, but almost all of them are really expensive, ro they add a lot of weight, or both. In any case, the builder has a good chance of never finishing and flying his project. Aircraft homebuilding is already a time-consuming and expensive hobby without adding so much complexity.

    There are at least two Lancair IVPs not far from here. Both, I think, cost their builders more than $500,000 to build. Sticking a turbine in one can jack the cost up another 50% or more. And we still have a four-place single engined airplane.

    Dan
     
  4. Mar 5, 2010 #24

    Inverted Vantage

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    Actually Dan, I'm pretty sure that with FBW the weight exchange would be negligible; the actuators are quite small - the only weight you'd end up gaining would be from an extra battery or two in case of power failure. And as for the multiple failure points; not really. In fact done right it would be safer than rods - there's only three failure points - the actuator itself, it's connector to the main controller, and the main controller - which can be programmed to be completely failsafe. Compare that to rods or pulleys, where you might get slack in the line, pulleys might get broken, one of the multiple guide tubes might get kinked, etc - it's a much simpler system.

    As for cost; the big reason I want to go with fly by wire is because I want multiple aircraft to be manufactured. Laying down wire and bolting it to the airframe is a lot easier and cheaper than putting in cables and machining/ordering all the pulleys and tubing. It saves on both production costs and, more importantly, man hour costs.
     
  5. Mar 5, 2010 #25

    AnxiousInfusion

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    That is one beautiful aircraft! Now substituting some reasonable inclusions such as piston engines/no FBW, would something distantly along the lines of a Mitsubishi MU-2/Twin Otter be possible?
     
  6. Mar 5, 2010 #26

    Dan Thomas

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    Perhaps. But have you ever weighed an extra battery or two? Or worked on airplanes every day, as I do, and see that control cable systems and their pulleys and bellcranks fly for thousands of hours without a hint of trouble? And then, when you start tracking it, you find that most of the problems encountered with airplanes are electrical in nature? Failure points in your example have to be expanded to actuator internal electrical failure, actuator seizure, connection failure, controller failure, EMP- (lightning) induced failures, power system failure, control position sensor failure, and so on. And that only addresses the control inputs and delivery; it doesn't address any of the feedback systems which have control suface position sensors, a processor, artificial-feel actuators on the stick and pedals, and inputs from altitude and airspeed sensors. It gets insanely complicated for a lightplane; it's bad enough for an airliner.

    When I was in high school 40 years ago my Power Mechanics instructor told us that 90% of all automobile problems would be electrical yet most folks will start blaming the fuel system when the thing starts to run haywire. In those 40 years I have found this to be abundantly true, and with modern electronic systems it's no less true. I have a 1951 International pickup with dirt-simple electrical systems and ignition, and that truck gives me far less trouble than our cars with their computers and processors and electrical everything and that stupid check-engine light that's always trying to get me to spend money. Give me simple mechanical controls any day in a light airplane. FBW belongs in big airplanes that can afford the multiple-redundancy systems and all the extra weight.

    The big Toyota recalls are a case in point. The sticking-throttle problem has been blamed on two mechanical causes: interference from floor mats, and a sticking pedal lever. But the sudden, unexpected acceleration can be blamed only on the electronic throttle control, the same setup my Hyundai has in it. I haven't taken it apart, but I presume they're using a potentiometer as a voltage divider, just like so many other position sensors on EFI engines, and such a setup can cause untold grief from a simple loss of ground reference. If the grounded end of the pot loses its ground for any one of several reasons, the output immediately rises alarmingly and the computer reads it as a full-throttle command and away we go. I have no idea why these engineers haven't incorporated variable-inductance controls instead of the pots (which wear out, get dirty and intermittent, and as mentioned, can lose their ground reference) or optical systems (which also get dirty). We have a brand new, really expensive full-motion simulator that uses potentiometers for flight control inputs, and I expect they'll give the same trouble eventually as the other sims we've had.

    Dan
     
  7. Mar 5, 2010 #27

    Waiter

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    Constant speed prop
    Full Retractable Gear
    Glass cockpit (no steam guages)

    I FLY EZ

    Waiter
     
  8. Mar 5, 2010 #28

    lr27

    lr27

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    That's kind of asking if something along the lines of a Pietenpol/Falco is possible.

    If you're looking for something that reminds you of a Twin Otter, how about this:
    Wickham B Homebuilt EAA Airventure 2008 on Flickr - Photo Sharing!
    There was an article about the Wickham B last year in sport aviation. I don't think I'd want a rid in one with just the fixed pitch props, unless there's some reason to think that it has less of a problem with this than other twins.
    -----------
    NOT like the Twin Otter or the MU2:
    Photos: Ghnome Aircraft Pictures | Airliners.net
    How about a twin like this:
    http://farm1.static.flickr.com/186/416128316_3fbdec7397.jpg

     
  9. Mar 5, 2010 #29

    bmcj

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    Here's another example of a homebuilt twin:

    [​IMG]


    And, at the other end, let's not forget the Lazair:

    [​IMG]
     
  10. Mar 6, 2010 #30

    MadRocketScientist

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    Both of those are on my wish list. The lazair seems far more likely as it would use the same engines as the CriCri. I am not sure if the other one even has plans.

    Shannon.
     
  11. Mar 6, 2010 #31

    autoreply

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    Is that a home-made flying boat? Do you maybe have a name for it?
     
  12. Mar 6, 2010 #32

    litespeed

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    Love that big homebuilt amphib.
     
  13. Mar 6, 2010 #33

    MadRocketScientist

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  14. Mar 6, 2010 #34

    Flying Monkey

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    Dean Wilson , who designed the Avid flyer, ( Avid Heavy Hauler is good in the bush ) made a kit like that- Avid Explorer-I think. Wilson Global Explorer - Wikipedia, the free encyclopedia ....The Frenchman De Chevigny was going to try for the North pole in it using only the sun as navigation, I think . He wanted to navigate using only the same instruments as Amundsen, and the early explorers-land on the ice or water, take sun shots, take off again) Don`t know if he tried it, or made it. ......Wasn`t there another fellow who made a large `camper type`of aircraft like that, who passed away in an aviation incident, I think, a year or so ago. Seems to my rusty memory he might have been a french Canadian-made a big recreational vehicle`` type plane ( 2 or 3 sizes maybe ) went down in an aircraft accident.......was a thread on here about it === Ahhhh-beat me by two minutes :) Interesting airplane...lots of room in there on long flights....
     
  15. Mar 6, 2010 #35

    MadRocketScientist

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    You have to be fast around here;):)
     
  16. Mar 6, 2010 #36

    mcjon77

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    That was the Ecoflyer LSA. Here is a link to the story about the crash:Ecoflyer LSA Crashes, Company Owner Killed.
     
  17. Mar 6, 2010 #37

    AnxiousInfusion

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    lol So it CAN be done! This is a great inspiration. I had a twin high wing in mind (but not as big as that!).
     
  18. Mar 6, 2010 #38

    wally

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    build big, take all your friends!
    Wally
     
  19. Mar 6, 2010 #39

    Flying Monkey

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    That's it-thanks.
    ==========================
    Another twin engine ( although I really don't see a valid efficiency in such a small twin) experimental is that Blue Yonder aviation thing
    page7BYA

    ( Breezy clone, I guess )

    His Merlin has more appeal
    index.html
     
  20. Mar 8, 2010 #40

    lr27

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