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Transportation Technology

Terrafugia CEO Responds To "Flying Car" Criticism 233

waderoush writes "The majority of the comments on last week's Slashdot post It's Not a Flying Car — It's A Drivable Airplane were critical, even dismissive, of Terrafugia's work to build a two-passenger airplane with folding wings that's also certified for highway driving. We boiled down these criticisms to the dozen most commonly expressed points, and today we've published responses from Terrafugia CEO Carl Dietrich. While hybrid airplane-automobiles are an old (some would say laughable) idea, Dietrich argues that current materials and avionics technologies finally make the concept feasible."
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Terrafugia CEO Responds To "Flying Car" Criticism

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  • Welcome. (Score:5, Funny)

    by ahoehn ( 301327 ) <andrew@[ ].hn ['hoe' in gap]> on Tuesday May 13, 2008 @04:50PM (#23396450) Homepage
    From the Article:

    Judging from the comments last week, many commenters hadn't fully absorbed the factual points in the article (to put it politely).

    Welcome to Slashdot.
  • Well... (Score:3, Insightful)

    by LuisAnaya ( 865769 ) on Tuesday May 13, 2008 @04:51PM (#23396470)
    I was thinking about this a couple of nights ago, and the only thing that came up to me was the following:

    1. A "drivable airplane" makes sense. In the way that you do not have to pay for hangar space and keep it safe and cozy at home. You just store it at home. You just "drive" the vehicle to the airport, put it together, do your pre-check inspection, fly, do your post-check inspection, fold, drive to destination. It's not the "Jetson's" concept, you have to be a licensed pilot, but it's, in a sense, practical enough for use.

    2. Terrfugia's CEO state that the materials are not available to make it practical. I certainly hope so. Folding, flying, driving it's going to put a lot of stress to a lot of parts on the vehicle. Flying or driving is bad enough to cause problems to components, combining both in one vehicle it's going to make matters worst. I sincerely wish them luck.

    • by bugnuts ( 94678 )
      You could park 4 to 6 of these in the same hangar space as one small airplane. You don't even need to be driving it much.

      Flying commuters generally already have their vehicles set up at both ends. This could save them a bundle in hangar space, though.
    • 1. A "drivable airplane" makes sense.

      How so? The 'airplane' has to haul around all the crap that makes a car. Bumpers, door guards, drivetrain, suspension, etc, etc. Yes, an aircraft landing gear has to handle quite large impacts. But the ride quality to the end of runway is NOT acceptable for actual driving. Put a car level suspension in a light aircraft and you'll have to remove at least 2 passengers.
      The 'car' has to haul around those bigass wings.
      • Re: (Score:2, Insightful)

        by IdeaMan ( 216340 )

        The 'car' has to haul around those bigass wings.
        Cars like vw beetles haul around surfboards all the time. Airplane wings are designed to be very light. Putting them on the sides where they create a blind spot rather then telescoping or mounting them on top is the part that doesn't make sense to me...
      • You don't need a luxury-car-level suspension; you're not going to be using this thing daily for trips to the grocery store or for six hours of driving on the Interstate for a business trip. You just need a vaguely-tolerable trip between your garage and the airport; the rest of your travels can be smooth and comfortable (weather permitting) and you save on hangar space costs.
        • You don't need a luxury-car-level suspension; you're not going to be using this thing daily for trips to the grocery store or for six hours of driving on the Interstate for a business trip.

          I don't mean luxury car level. Just mid 90's Geo Metro level. FAR heavier/smoother than a typical light aircraft landing gear, because it's built for a different environment.
          Seriously. Ride down to the end of runway in any light plane. Now do the same in any car. Feel the difference.
          Built for different things. Why is t
    • Re:Well... (Score:5, Insightful)

      by element-o.p. ( 939033 ) on Tuesday May 13, 2008 @07:32PM (#23397916) Homepage

      A "drivable airplane" makes sense.

      I'm not entirely sure I agree (and yes, I am a pilot). In town, the drag of a car isn't a real big issue; at speeds of less than 30MPH, wind resistance is pretty minimal. At highway speeds of ~60MPH you've quadrupled the drag, and at typical general aviation aircraft speeds of 120MPH, you have 16 times more drag for a given shape and area than at commuter speeds. Consequently, a six foot wide car in town doesn't matter; at flight speeds, the drag of a six foot wide vehicle is pretty significant. That's why the Cessna 152 (a small trainer) is only something like 39 inches wide -- the narrower the fuselage, the less drag. A Cessna 172, a step up from the 152, is only about three inches wider than a 152, and most light single engine airplanes don't get *much* wider than that (I don't recall off-hand how wide a Cessna 206 or 207 -- the biggest single-engine piston airplanes Cessna makes -- are).

      What does this have to do with how much sense a drivable airplane makes? Well, the drawings of Terrafugia's design show a vehicle with a cross-section much like a car. It's rather wide, presumably for road stability and passenger comfort. Unfortunately, this makes a poor aircraft design because of the much greater speeds at which even a light sport airplane flies. Terrafugia is claiming some pretty impressive fuel economy numbers for their car, but I'm skeptical. I own a two-place tandem airplane ( []); it's about as skinny as an airplane can get, meaning its flat-plate area is pretty minimal, and therefore it's drag should be pretty minimal as well. I burn about 4.5 gallons per hour at 60 MPH. That works out to 13 miles per gallon -- better than my Nissan Frontier, but not by much. I sincerely doubt Terrafugia will get 26-27 mpg, as they claim, in a wider vehicle, at twice the speed of my airplane.
      • Re:Well... (Score:5, Insightful)

        by cecil_turtle ( 820519 ) on Tuesday May 13, 2008 @08:54PM (#23398394)
        I'm a pilot as well, if that somehow qualifies one to speak in this discussion. Anyway, you seem hung up specifically on mileage / air resistance. So let me point out a few things:

        1) A Cessna 152 (a 30+ year old plane) burns ~6 GPH at 111 knots (Vno), which is about double the fuel mileage of your plane and is quite in line with Terrafugia's numbers. It would seem that your plane just gets poor mileage.

        2) Yes, air resistance is exponential, it's relative to the square of the speed - your math is correct. But drag at 30 mph is VERY low, so just saying "16 times that" doesn't mean much. Secondly, to get actual drag you also need to consider drag coefficient and frontal surface area. Frontal surface area is two dimensions - you seem only focused on narrowness. The plane in the article is wide - but it's also a lower profile than "normal" planes. We'd have to have more specific dimensions to know if the overall frontal surface area is more or less than an equivalent plane. Third, as I mentioned above the drag coefficient comes into play. Aerodynamics have come a long way since Cessna's were designed and since your Falcon was designed (20+ years). If you can sufficiently reduce the coefficient, you can increase surface area and end up with the same amount of drag or even less.
        • Re:Well... (Score:5, Informative)

          by mcrbids ( 148650 ) on Wednesday May 14, 2008 @01:07AM (#23399604) Journal
          I'd reinforce your point #1 with the Rutan Long EZ which does 160 Knots (184 MPH) at about 5.1 GPH, for an astonishing 36 MPG at just shy of 200 miles per hour - even my []trusty, highly reliable, and economical Saturn SL2 [] only gets about 30 MPG on the freeway! (at 80 MPH) And, unlike the 152, which is based on technology first developed in the mid 1950s, the Long EZ owes its legacy back to the early 1970s.

          (Yes, you read that right - the C152 airframe was only minimally changed in 1977 as a tweak of the previous, highly successful 150)

          It strikes me as quite appropriate that 21st Century technology would provide a significant improvement in capability/price/performance, when developed by current, high-quality engineers.

          BTW, Burt Rutan is a legend in the field. You might know his company Scaled Composites [] which won the Ansari X-Prize []. He's a legend in the field. Not only did he build an experimental aircraft design that outperformed other designs by a factor of 2 or more in speed, while halving fuel burn, he did so with a design that's relatively cheap and easy to build.

          Some people like Rutan and Al Mooney [] just seem to "get it right" when it comes to aircraft design, and they do it over, and over, and over again. The Mooney Mark 20 is a line of high performance, high reliability, cheap, complex aircraft that provide solid performance, excellent safety and great economy. The Mooney Mark-20 line (there have been lots culminating in the current "Ovation") is one of the few GA single-engine airplanes with a proper "crash cage" resulting in excellent safety numbers - you are half as likely to die (per mile of flight) while flying a Mooney in IFR conditions than the industry average.

          A good indicator of airplane efficiency is its glide ratio - how far it moves forward for every foot dropped without power. The first number is the distance you move forward, the second number is is how far you drop. It's a ratio, and the higher the first number relative to the second, the better. A Mooney has a glide ratio of about 13:1, while a Cessna does about 7:1. A long EZ or a VariEZE can do anywhere from 15:1 to 20:1, a Boeing 767 did about 12:1 in the famous Gimli Glider incident []. Many ultralights do as badly as 3:1.

          Can they do it? I'm quite sure they can. As soon as I can afford one, I'll probably buy. (It'll take me a few years, which is fine, since they won't be ready and tested by the "early adopters" for a few years, anyway)

          I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want I want !!!!!!
        • Re: (Score:3, Informative)

          by DamonHD ( 794830 )
          Polynomial, not "exponential". "Exponential" doesn't just mean "lots and lots"!


      • Re: (Score:2, Informative)

        Don't forget about drag coefficients, and performance at high altitudes. Velocity Aircraft ( can comfortably outrun a Bugatti Veyron while using less than 1/3 of the power, and carrying 4 people comfortably. It's a matter of getting enough altitude. (This plane is at 25000 feet and getting mileage of an SUV)
      • Re: (Score:2, Informative)

        by tweak13 ( 1171627 )
        I'm an aeronautical engineer and I've done a fair amount of work on light sport aircraft designs. Because of the 120 kt speed limit, light sport aircraft never get going fast enough for parasitic drag to take strong effect. You're also neglecting the most important source of drag at low speeds, induced drag. Because of the ratios of induced drag to parasitic drag, the overall drag of the aircraft would most likely decrease the faster you go. It's a strange concept to work your head around, but the end r
  • by EllynGeek ( 824747 ) on Tuesday May 13, 2008 @04:52PM (#23396482)
    It's unthinkable that a story posted on /. should ever receive anything but careful, reasoned analysis. This story implies that most /. commenters are knee-jerk hypercritical dorks who don't read anything or like anything. Some people.
    • It's unthinkable that a story posted on /. should ever receive anything but careful, reasoned analysis. This story implies that most /. commenters are knee-jerk hypercritical dorks who don't read anything or like anything. Some people.
      Pftft. Make several hundred "flying chair" jokes and suddenly everybody's a comedian.
    • by Animaether ( 411575 ) on Tuesday May 13, 2008 @05:53PM (#23397162) Journal
      Really, we used to - this has been some time ago - have new front page posts about a particularly popular topic and have some of the most insightful comments, often from differing views, rehashed as a starting point for a far more interesting comments thread than the original story's (with dozens of trolls, flamebaits, ill-informed comments, etc. often based on just the title or summary).

      In fact, the section is still there. So is the link. Welcome to BackSlash: []

      But where the heck did it go? Did the 'editors' realize that "whew boy, this sure is hard work!"? I never found any information on why it seems to have suddenly just stopped dead.
      Maybe I missed a comment from an 'editor' somewhere in an unrelated thread, perhaps it's under some catch-all in the FAQ (it's not listed as a section in the "What are the sections for?" item).
      What I do know is: I miss it.

      Now to see if I'll get a +5 Off-topic..
    • Re: (Score:3, Funny)

      by antic ( 29198 )

      It's unthinkable that a story posted on /. should ever receive anything but careful, reasoned analysis. This story implies that most /. commenters are knee-jerk hypercritical dorks who don't read anything or like anything. Some people.

      I read the start of your comment and was nodding my head - yes, this should be that sort of place, full of educational and interesting comments, where obvious (especially meta) jokes from people who don't read the article are nowhere to be seen. Then I read the end of your

  • by edn4 ( 1214790 ) on Tuesday May 13, 2008 @05:08PM (#23396682)
    while I didn't read the original article, the slashdot concerns made for an interesting and relevant interview... I say good job slashdot
    • Re: (Score:3, Interesting)

      while I didn't read the original article, the slashdot concerns made for an interesting and relevant interview... I say good job slashdot
      A good point you make, actually. Strong adversity to an idea exerts a selective pressure. Much as the harsh and competitive environment of Africa did spawn the most successful mammals, so too might slashdot spawn successful technologies.

      I wonder (or wander offtopic slightly), has Africa any invasive species?
  • But will it work? (Score:5, Insightful)

    by joggle ( 594025 ) on Tuesday May 13, 2008 @05:33PM (#23396942) Homepage Journal
    That's really all that matters. It doesn't take any money and hardly any skill to make a nice animation of an airplane with folding wings, but to actually build one and fly it, that's entirely different.

    I'm looking forward to the performance of the flying prototype. I wish them good luck on making it and flying it to Oshkosh this year. If they make it to Oshkosh even without meeting all of their planned specs I expect them to make money for years since this really does fit a niche that no other vehicle does. While they'll have plenty of revenue, hopefully they'll be profitable too.
  • by wreave ( 1282730 ) on Tuesday May 13, 2008 @05:35PM (#23396962)
    Great response from Xconomy. The need for an aircraft that can be used for limited driving is real. Some GA (general aviation) airports have very limited and/or very expensive hangar space. In fact, some airports have no available hangar space, in part because companies lease hangar space and use it for business operations rather than aircraft storage. In CA a few years ago, small aircraft were forced out of a hangar so it could be leased to a company that used it for business operations. That's still not right, but at least with the ability to park their airplanes at home and drive to the airport, small aircraft pilots still have options. At the other end, if you're traveling point-to-point, the ability to skip car rental and use your airplane might be an option as well. Obviously, a driveable airplane would be designed for short-distance driving. It's not a car replacement by any stretch of the imagination. (Yes, I am a certificated pilot.)
    • by Zak3056 ( 69287 )
      I really shudder at the thought of something like this. It's scary enough what GA aircraft can be subject to at airports, but can you imagine trusting your $150,000 light aircraft to the mercies of rush hour traffic? You're a braver man than I am...

  • is why they decided to make the thing so unspeakably, shit-hammeringly ugly.

    According to the old aviator adage, "If it looks good, it flies good," this thing will fly about as well as a charred Strawberry Pop-Tart.
  • by fermion ( 181285 ) on Tuesday May 13, 2008 @06:06PM (#23397290) Homepage Journal
    When it is a living room.

    No one thought there was a problem building a living room car that every one can afford. Many people still do not. To many people, the living room car is a reasonable and necessary item. Many even invest in tricking out their living room car with full entertainment centers. The benefits are clear. So much time is spent in a car, wouldn't it be great to have all the comforts of a living room. A beer, a tv, a phone. Room to spread out, get conformable, even made engage in intimate relations. And there is little to show that this is a bad thing. The drive is more conformable. Oil prices are up, which is good thing unless one is stupid enough to live in an oil poor region. General safety is up, unless one is stupid enough to drive a car that is not a living room.

    Reading through the summary and responses there seems to be this same air of uncertainty that existed when the auto manufacturers were using a loophole in a law so that farmers could continue to farm to provide cheap inefficient cars to the masses. There is nothing particularly wrong with it. There is no reason why a person who can afford it should not have a aircar, or a land yacht, or anything else they think they need to be happy. However, such things do have long term effect on the human condition. Speaking personally, there are already severe safety issues on my street dealing with land yachts that they streets are too narrow to accommodate, especially at the speeds that these drivers like to travel. I can imagine somebody buying one of these, and trying to land. At the very least, i would expect a lawsuit demanding that we cut down the trees and pave the front yards to accommodate such planes. And don't laugh. Similar lawsuits have been filed as people wish to reclaim overgrown land for their big houses and big cars.

  • landing places (Score:2, Insightful)

    by alrudd1287 ( 1288914 )
    as a pilot, i love the idea of being able to fly into a tiny strip by the beach and then drive the few miles to the nearby town. what i want to know is what stops someone from landing on a country road somewhere and then folding up their plane and saying 'oh no officer, i drove here'? there are plenty of roads that are landable around.
    • fly into a tiny strip by the beach and then drive

      The article did make me wonder, seams like 80% of the functionality here would be covered by a Vespa stuck inside a normal small plane. driving home to park/repair, and the bad weather recovery (always put the vespa in a rental, and come back another day for the plane, the non ultra wealthy, this is doable quite often for the price.)

      saying 'oh no officer, i drove here'

      same thing that stops a sport bike rider from driving 200MPH then slowing to 50, and saying

  • by AeroIllini ( 726211 ) <aeroillini AT gmail DOT com> on Tuesday May 13, 2008 @06:20PM (#23397424)
    I'd like to take the opportunity to thank Carl for his well thought-out response. It's not every day that busy entrepreneurial CEOs take time out of their schedules to address the unwashed internet masses.

    I think this project has a lot of potential. I'm always surprised at the attitude people have that "well, I wouldn't buy it, therefore it's not a good product." News flash, folks: there are market segments you are not a part of. Just because not everyone would buy something doesn't mean no one will. Judging from the number of preorders this has gotten (and knowing many general aviation pilots who would leap at an opportunity to own something like this), I would say it has been very well received.

    And he's right about the timing. While carbon fiber technology has existed for a long time now, it is just now gaining traction in general-purpose manufacturing, and the economies of scale are bringing the price down to the point where products can be built with it for roughly the same cost as some other materials. The convergence of affordable composite manufacturing and a new type of sport-plane license have finally made this type of vehicle possible.

    The licensing programs for general aviation are much more strict than they are for automobiles. If this vehicle inspires regular car drivers to get their VFR licenses, I suspect the training will also make them better drivers.

    However, I don't envy the cost of Terrafugia's product certification program. This vehicle needs to be certified to both FAA and NHTSA standards, which aircraft and automobile companies spend many millions on separately, just for the paperwork alone. Godspeed to the certification team!
  • by QuantumG ( 50515 ) * <> on Tuesday May 13, 2008 @07:46PM (#23398000) Homepage Journal
    The article mentions walk around inspections. He talks these up and I've heard other pilots do this too. I'm sure it is a good thing to do, if you fly infrequently. If you're flying much more often and that really is the point of this vehicle, to get pilots flying more, then a visual inspection is just "eyeballing" .. you're going to get complacent and miss things. With today's technology is there really any need? Even light planes can have a sensor array network with computer analysis of the sensor data giving a green light to fly or not. Aircraft is so behind the times in this way. Even the big commercial operators get by with people visually inspecting the plane.

    • by yabos ( 719499 ) on Tuesday May 13, 2008 @08:22PM (#23398216)
      The main checks are to see if your pitot tube(tells you air speed) is working and not full of junk, check your tires for wear, check brakes for leaks, check wings for dents or other damage, check your fuel to make sure it's actually full and your gauge is correct, check that your control surfaces move freely, check propellor for damage, etc. I'm not a pilot yet but these are most of the things you visually inspect. Tell me any computer that could do all that for you. You are right that if you just landed an hour ago that not much has changed most likely and you *can* skip the checks if you want. It's your life, just don't take up any one else if you crash or don't aim for people on the ground when you run out of fuel.
      • by QuantumG ( 50515 ) *
        Sure, all of that could be automated.. a lot of what you've said have already been automated for cars.
        • Sure, all of that could be automated.. a lot of what you've said have already been automated for cars.

          It's already automated for a lot of aircraft. And pilots still do an eyeball handson walkaround because you can't just stop when something breaks, even after the computer told you it was OK.
    • One of the inspections that may have some trouble with automation is checking the frame. I know helicopters, and I would assume airplanes as well, have paint that flakes to a different color if there is a problem with a weld, so one can tell right away that a joint is dangerously close to failing. I don't see your average mom and pop commuter doing such an inspection each and every time they fly...

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