Roadable aircraft

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Topaz, Jun 30, 2006.

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  1. Jun 30, 2006 #1

    Topaz

    Topaz

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    Thought I'd take this thread out of Orion's Raspberry thread.

    I remember a really great article some years ago - unfortunately I can't remember who wrote it, although possibly it was Molt Taylor - that discussed the realities of roadable aircraft design.

    The gist of the article was that a practical roadable airplane/flyable car was an engineering possibility, as Molt himself demonstrated with the Aerocar series back in the '50s. Certainly any such vehicle would be a bit of a compromise, somewhat lacking in performance both on the road and in the air, but that a really good engineer (or more likely team of engineers) could probably reduce the compromises to an acceptable level, given the advantages of the entire system.

    The major holdup, then, is not engineering, but regulatory. Not only do you have to meet FAA certification standards, but also all the standards for automobiles: front and rear bumper impact and height requirements; side impact standards, airbags, automobile seatbelt standards, luminosity standards for road and brake/marker lighting, roll over, general collision testing... ad nauseum.

    Then pile on top of that smog system requirements, CAFE fuel-economy standards for you as a manufacturer, and the like, most of which will probably force you to burn auto gas in the motor, and where are you going to get that at most airports? Do you have to land with enough reserve so you can drive to a gas station? Do you carry around an entirely separate 'flight' motor and fuel system to get around that problem and what about the weight penalty of that?

    In short, trying to meet the regulatory standards of two industries is the major problem in roadable aircraft design. It's also one of the reason you've seen a rash of roadable designs with less than four wheels on the 'car' component: anything less than four wheels and the Feds think it's a motorcycle, which has far less stringent 'certification' requirements than a car. But then, if you went that way, all your customers would have to get motorcycle licenses to drive your vehicle...

    It doesn't seem to end. :wail:
     
  2. Jun 30, 2006 #2

    superflea

    superflea

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    well then what about classifying the road portion as a kit car. would that allow for some relaxation in DoT regs. I don't know much about kit cars, so I don't know if there is an equivelant to the 51% rule there. but perhaps the flying car could be sold as the chassis and wheels etc needing to be bolted on, far short of home built A/C requirements but maybe if the major car components need to be bolted on the DoL might consider it a kit, and therefore not be subjected to the same testing criteria. While at the same time meeting the criteria for a certified A/C just a thought. sometimes the answers are not found in engineering but in a legal clarification of the regs themselves.
     
    Last edited: Jun 30, 2006
  3. Jul 1, 2006 #3

    Topaz

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    I could certainly be wrong, but I don't think the kit car guys get much of a break these days from the basic regs. AFAIK, there isn't a road-car equivalent to the 51% rule, "you built it, you risk your own butt" Experimental category.

    Again, I could be wrong, but I think that if you're in any kind of mass production, the DOT pretty much says you're an auto manufacturer, and subject to the overall rules. I think that's why most of the kit cars you see today are either 'dress ups' of a complete chassis, or a fairly exact replica of an existing, already engineered, auto. I think the guys duplicating old cars get to grandfather on that old car's 'certification date', in terms of crash standards, etc.

    Kinda makes it tough to come up with a new design without massive investment in crash certification, etc.

    Anyone in here know about this stuff? I'm getting well into the limits of my knowledge here.
     
  4. Jul 1, 2006 #4

    orion

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    It's been years since I was into restorations and customization and part of the SAE (Society of Automotive Engineers) so this may be out of date but as far as I know, kit cars really need only the basics for driving - brakes, emergency brake, signals, driving lights and restraints. That's about it. Interestingly enough, most of the safety stuff we keep hearing about is really at the behest of the car manufacturer's marketing group more so than any regulations. For instance, I thought that things like anti-lock brakes are required - they're not, but manufacturers are so afraid of liability that most models today incorporate the system. Never mind that accident and fatality rates of the new cars actually climbed after they were introduced, and continued to climb for several years thereafter - it's the feeling of safety they were selling, not actual safety.

    But it is an interesting question - how much of the car and flight system would fall under the 51% rule? Would be sort of cool to get a Cobra kit and incorporate a flight structure to it.
     
  5. Jul 1, 2006 #5

    superflea

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    mmm a cobra kind of thing.
    like an O-2 with a single pusher running off of a PTO type of system getting its power from the shelby cobra 'pod' that could be disconnected and driven away cool. sign me up
     
  6. Jul 3, 2006 #6

    Nilsen

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    It costs about $200 and a weekend to get a motorcycle license in NYC. So, I think a flying motorcycle (3 wheeler) could be a great compromise. The draw backs of the hybrid design might keep you off the interstate but if you want to get somewhere fast ... thats why you are also a plane.

    I don't know if there is a limit of number of passengers on motorcycle registrations even with a sidecar; so that might be an issue if you want a 4 seater.

    The Dymaxion Car is a rear drive 3-wheeler that looks like a good candidate for a set of wings:
     

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  7. Jul 5, 2006 #7

    Nilsen

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  8. Jul 5, 2006 #8

    orion

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    I know this one and so far I think he'll have a few problems with control. He's modifying the motorcycle structure and steering and coming up with a new way of controlling the airplane - based on his description and diagrams, I don't think I'd feel comfortable trying to fly it and neither would most pilots.

    He'll also have a few issues with ground handling, especially in connection with cross-wind landings.
     
  9. Jul 6, 2006 #9

    Peter V

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  10. Jul 6, 2006 #10

    cheetah1

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    Looks a little like the carver...
     
  11. Jul 12, 2006 #11

    pylon500

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    Saw this (a model) at Epcot Centre, Orlando back in '92.
    Had the real driveable part there with a small opposed twin motor driving a CVT with a take-off for the prop.
    Power unit had two wheels with the 'Bike' section mounted out front on a tilting beam to lean over with pilot seated on same.
    Don't know any more?
    Arthur.
     

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  12. Jul 12, 2006 #12

    Topaz

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    That's a neat looking concept. I amuses me that it's often possible to tell whether the design is by a 'car guy' who's adding flying surfaces, or an 'airplane guy' who's adding roadability.

    Or an art student with no training in either discipline. :gig:
     
  13. Jul 12, 2006 #13

    orion

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    That's actually one of the prettiest interpretations of the concept I've seen. It also seems to represent a more realistic configuration that could evolve into something bigger.

    The forward swept wing will have somewhat of a structural weight penalty due to the associated stresses and deflections but with proper use of composite materials, this could be maintained at a reasonable level. The high placement of the wing then keeps it out of the ground during cross wind landings or ham-fisted handling.

    Yaw and pitch stability I'd say is for now questionable but a better empennage design could take care of that relatively readily. I like that the designer did not feel cornered into using a canard layout. This allows for a wider CG envelope once the tail is sized properly, and it also allows for flaps for shorter field perfomrance.

    But the layout still does not seem to address the functionality of the idea. Simply said, what do you do with the flight hardware when you get to where your're going? Do you leave it at the airport or is there a way to take it along? For most folks who are interested in the roadable car, the idea is to fly to your destination and back. However, if one encounters unfriendly weather along the way, the vehicle should be able to land, convert to a land vehicle form, and nearly seamlessly continue the trip (along with the flight hardware) on the road.

    It'd be interesting to see what the designer had in mind here.
     
  14. Jul 12, 2006 #14

    superflea

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    About the only way I can think to move that thing with the wings on the ground would be to remove them and trailer them with the wing surfaces horizontally. The structure is clearly very light, so if the wings are vertical then any gust of wind, like say a truck passing by, would make the thing very unstable on the road.
     
  15. Jul 15, 2006 #15

    awolff

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    Hi!

    The AeroCycle is my concept. I'd like to clarify some of the points that Orion made.

    I am not modifying the motorcycle structure. It is a bolt-on handlebar clamp that allows for multi-axis movement.

    Yes, new way of control of an aircraft. Current pilots will need to relearn some habits. (no rudder pedals)

    No known issues with ground handling or crosswind (if out-rigger wheels equipped as shown in diagrams).

    -Adam (of Wolff AeroCycle)
    http://www.wolffaerocycle.com
     
  16. Jul 15, 2006 #16

    Nilsen

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    Hi Adam,

    Welcome.

    It's nice that you joined the group to reply to Orion's post.

    I have a question for you. The out-rigger wheels seem a little odd to me. Motorcycles with side-cars, 3 wheelers and ATVs allow for no banking and in actuality are far less stable than a 2 wheeler. So, I wonder why you chose the out-rigger wheel configuration? Why don't you just have the craft take off and land on the 2 very able and stable wheels it has? Gliders do it all the time.
     
    Last edited: Jul 15, 2006
  17. Jul 15, 2006 #17

    awolff

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    Thank you for the kind welcome. My general experience with newsgroups has been checkered at best.

    Yes, that was the original thought as I had also thought of gliders with ground operations using aileron balance. On my craft, if the operator could articulate the ailerons and the steering simultaneously then the ground operation could be balanced on the two in-line motorcycle wheels. (more detail on the web & patent ap)

    As the craft is fanciful enough with the whole "roadable" concept, I wanted to make the rest of it as conventional as possible. As Orion had hinted at, the balance operation adds some complexity to the training and would make ground operations unique. I wouldn't say harder because it could actually be a great advantage if lean is used properly. It is just easier for most people to understand if you don't have to explain how the two-wheel operation will work.

    Also another reason I'd chosen to market the outriggers in the initial model is because they answer the challenge of how to support the flight portion of the craft when detaching the motorcycle.

    Thanks,

    -Adam
     
  18. Jul 16, 2006 #18

    Nilsen

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    I think you'll find these boards some of the nicest and most knowledgeable around. Of course I'm still new here ...:D

    Looking forward to seeing how the aerocycle progresses.
     
  19. Jul 17, 2006 #19

    Nilsen

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  20. Jul 17, 2006 #20

    Peter V

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    Hi Adam,

    I'm guessing you would have considered at some point using the motorcycles powerplant to drive the airframe's props. Can you tell me what made you decide on using aditional engines instead?
    Having 90 odd hp dormant between your knees seems a real shame. :(
     

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