The Imaginary Future Of UAM


Dating occurrences from memory is always an iffy thing, but I can clearly recall a phone conversation I had with Burt Rutan. I know it was in the summer of 2001 or 2002 because my old home office in Connecticut had a skylight and I was sweating as the afternoon sun streamed through the glass.

That associative memory causes me to recall this number: 20,000. It was his estimate of how many light jets would be manufactured per year by the end of decade. You might recall we even had an acronym for them—VLJs or very light jets. (You forgot, right? Me too.)

It didn’t happen, of course. And not even close. What Rutan saw as disrupting the market was the then-emerging revolution in affordable, computer-aided manufacturing equipment that would vastly reduce the cost of building a light airplane and thus expand the market multiple-fold. The CAD-CAM evolution happened all right and it continues, but even little jets still cost in the several millions. And a new Cirrus SR22 is most of a million.

The VLJ thing failed for two related reasons, at least for Eclipse. The on-demand air taxi model that accounted for much of its sales prospects failed to gel and the entire segment never achieved anything like economic volume. A third related reason was bad timing.  

So recall that prediction as another surfaces about the coming disruption caused by the aspirationally exploding urban air mobility market. Industry analyst Frost & Sullivan predicts that by 2040, the UAM fleet could total 430,000 units. Let’s put that number in perspective. It’s about twice the size of the entire current U.S. fleet of aircraft, including general aviation and air transport airplanes. It definitely qualifies as disruptive. (Just this month, Boeing and Kitty Hawk announced a new eVTOL, the Cora. They come fast and furious.)

Let’s break these numbers down. I’m confident in saying there will be no significant UAM volume in 2020 and casting ahead, my prediction is there won’t be much by 2025, either. I’ll define significant production as 1000 or more units. After 2025, I think it’s going to get interesting. When I visited Pipistrel in Slovenia last summer—they’re a leading developer of electric aircraft—they thought 2028 would be the year we would begin to notice UAM aircraft. But they are not necessarily bullish on big numbers.

Using Frost’s prediction, the industry would have to produce 400,000-plus airframes in, say, 12 years. That’s more than 30,000 a year. For the sake of amusing myself, I’m accepting Frost’s high-end estimate, even though I think it’s a fantasy based on wispy data.

It’s not because there are certification hurdles, technology limitations, infrastructure barriers, noise considerations and safety issues, although all those things exist. I think it’s a mistake to assume that just because battery limitations stunt progress now, that this will always be the case. It won’t.

I just think the basic business model is flawed. I’m skeptical that a profitable market will develop for that much air taxi volume ever, much less in 20 years. And that includes cargo and short-range delivery traffic, the initial early driver. The UAM concept assumes that a network of data-driven autonomous aircraft will draw people in the millions to flying across town rather than using mass transit, a car or a ride hail.

Ever confident of its own data-driven model, Uber is pressing forward with its Elevate UAM concept, despite a decade of money losing performance recently amounting to about a billion dollars of red ink per quarter. Tech companies are forever hopeful of the turnaround, but some drop like flies, same as other businesses. The UAM idea requires something ride hailing doesn’t: huge ground infrastructure and vehicle investment. 

So in a moment of candy land fantasy, let’s just pretend by 2030, the UAM industry really is cranking out even a conservative 10,000 airframes per year and that half are people carriers. If that happens, it would be fundamentally transformative for general aviation. At this juncture, people building electric aircraft aren’t saying they’re cheaper to buy than piston-engine versions. The opposite is true. Pipistrel’s Alpha Electro costs $60,000 more than the gasoline version, when the charging system is included. But these economics are based on cottage-industry volume—dozens a year, not thousands. They remain sharply limited due to battery cost and capacity.

At the higher volumes, the ever-elusive and much-dreamed-about economy of scale kicks in. It has to or the entire business case crumbles. A rule of thumb is that reducing cost of goods/price by 10 percent increases sales volume by 2.5 percent. But Frost’s numbers are so fantastic as to be outside this relatively modest consideration.

The unpredictable wildcard is how much automation will be used to be build these aircraft, even if the volume Frost predicts materializes as just a fraction. Eventually, it’s likely to be a lot of automation, for most of these designs aren’t traditional riveted aluminum but molded composites. Structurally, they are simpler to build than a modern automobile, even an electric one.

And the aircraft themselves are likely to be equally automated. Multi-rotors have to be or they’re not flyable and a multi-motor electric fixed-wing airplane will be flown with robotics, too. Pipistrel showed me how they’re going to do that in their UAM multi-rotor. These are, of course, envisioned as commercial passenger vehicles but there’s no reason they can’t be private aircraft, too.

What would flying such a thing be like? You’d have the option of voicing in a destination and letting the machine do everything or flying it manually by simply pointing the stick where you want to go. I’m sure this will ignite sputtering apoplexy in the dedicated stick-and-rudder crowd, but not from me. I’d love to fly such a machine or fly in one while it whisks me to my destination. I may not be an actual child, but I’m a child of the modern age, ownership of a pre-war Cub notwithstanding.

If this level of disruption comes to pass—and that’s a galactic if bordering on slim chance—the spillover into what we now understand as traditional GA would be profound. That much efficient production would not coexist economically alongside bashing airplanes together by hand with rivet guns, hammers and sanding blocks. It would draw in a lot of talent and new designs that may or may not be electric, but which can’t possibly look like a Skyhawk. At least I hope not.

It’s only 20 years away. Not that far off. For those of us who imagine that if aircraft cost much less than they do now, the market would expand, these economics are enticing and would prove—or disprove—once and for all that more people would fly if it weren’t so expensive. And at the moment, it’s the only thing on the horizon that might do this. No amount of airline pilot demand is going to force volume in GA manufacturing.   

Two decades hence, if creation hasn’t canceled my ticket, I’ll be 90. Someone please preserve the foregoing babble and send it to me. I’d like to see how close I got.

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  1. If you combine the FAA approved ‘Garmin Autoland’ with Skyryse Robinson R-44 autonomy where the helicopter is already certified… it could happen, I’ll take the glass half-full approach.

    The FAA is still the reason these dreamers of eVTOL aren’t happening. The FAA is on strike when it comes to signing anything off.

  2. I, too, fail to see the vast “urban mobility” market that others envision. For carrying people, anyway.

    I DO see a “robust” market for autonomous vehicles that could carry four occupants between 300 and 1,000 miles between traditional airports (mostly non-air-carrier ones, for obvious reasons).

    How robust? Maybe 1,000 airframes per year – IF the idea is well-executed.

    Think in terms of an autonomous, up-engined Cirrus Vision jet, with no flight controls or instrumentation. Any paved runway of 3,000 feet or more would become a node in a point-to-point network that would offer an attractive alternative to today’s “airline travel experience.”

    Pure speculation, of course. Another YARS-ism: “What’s do-able is not always done.”

  3. Paul,

    FINALLY someone applies common sense!

    Of course UAM systems have a place, and it will increase in the future for all the reasons you mention. I like your reference to the “disruptive VLJ” which panicked the FAA into accelerating its NEXTGEN programs back in geologic times – I doubt they will be fooled twice.

    The most truly disruptive transportation revolution I’m aware of was Henry Ford’s application of existing mass production methods to automobile manufacturing. Ford showed it was possible to introduce a society-altering innovation in the absence of preexisting infrastructure. Ford’s business model was to replace an increasingly non-scalable technology (horses) with an alternative that was within the means of a middle class citizen. These criteria weren’t met by VLJs. Will UAM systems fare better?

  4. Paul,
    Your thoughts as usual are very rational and seasoned with good experience. We all wonder what happened to the pervasive flying car that was supposed to happen. I do think that something new is afoot. I am an avid fan of technology and electric vehicles. I confess to disbelief in electric airplanes, but there are two disruptive things that might make this possible (one that you spoke of). The quadcopter (hexacopter, number-copter) has become incredibly feasible at least at the small end. I personally have 4 such aircraft, the latest being a DJI Mavic Mini. This latest (under $500) is incredibly stable and I was struck by surprise by some of my recorded video about how much it looks/feels like the view from a small private plane. But then it can do what a helicopter can do also. And it folds into a three inch by five inch block that fits easily in your hand. Yes, there are problems – not the least being avoiding collisions, but the really big thing is what you spoke of – economy of scale. Not guaranteed to happen, but it is definitely going to be interesting.

  5. Paul –
    I think there is a sort of pollyanna feeling that, “Some day technology will work out the problems with electric airplanes, and then we’ll have them.” Well, it’s not that easy. There have been three obstacles to electric vehicles for a long time: motors, controllers, batteries. Motors is essentially solved – current three-phase brushless motors have efficiencies in the high 90% range. High-power controllers to generate that three-phase current and recover braking energy are now available and relatively cheap. (Regenerative braking is perhaps not as useful for airplanes as it is cars.)

    The real problem is energy density, and physics prescribes absolute limits there. While a battery has to carry all the energy-producing materials with it, and of course weight is an aircraft’s nemesis, an internal-combustion engine only carries 1/15th. How so? Because the stoich ratio for gasoline is about 15:1 – by weight, not volume – which is to say that the engine picks up 15/16 of what it needs from its environment and then dumps it back out – continuously. And gasoline is extremely energy dense already. (Interestingly, a pound of gasoline – still doing weights here – has about 15X the energy as a pound of TNT. Why do you think fuel-air bombs are so devastating?).

    Please excuse my pedantry. As one of my electrical engineering profs used to say, “You can’t spell geek without EE.”

  6. Paul: I’ll take your “babble” any day over what the rest of the aviation world is saying! Excellent comments from you and the thoughtful readers….and I’ll start your countdown to 90 (following you by 5 years!)

  7. Great thoughtful analysis, enlightening comments especially the one comparing the ICE to battery-operated motors. When comparing refueling rates between the two, batteries need to eat for two in a sense.

    The schemers, dreamers, drum beaters would have us all believe WALL-E world is here, now, but were it not for the FAA being on strike to the MAX.

  8. I’m enough of a technology optimist to think that the battery and self-piloting issues can be solved. (The latter at dedicated landing pads, anyway.) But this whole idea of large scale Urban Air Mobility implies a taxicab equivalent – you can jump in a UAM anywhere and go anywhere. People who hawk this idea are smoking something way better than I’ve been able to find.

    You can’t land one of these things on any random street corner! The laws of physics say the noise and propwash will be unacceptable to the current inbahitants. Not to mention the unpredictable obstacles in the street environment. UAM systems will be limited to carefully controlled environments like rooftops, secure landing pads, and airports. IOW, just an extension of existing helicopter service. The lower price will boost traffic volume, but nowhere near the point where sales will justify the setup cost of automated manufacturing.

  9. Regarding VLJ’s, I recall that it was Mac McClellan who was among the first to publicly point out that the emperor was essentially unclothed. Paul, the best aviation journalist currently working, has the same ability to peer through the smoke and see the obvious!

  10. “Eventually, it’s likely to be a lot of automation, for most of these designs aren’t traditional riveted aluminum but molded composites.”

    Same premise was assumed with the Cirrus and Columbia. Original man-hours to complete a factory-built SR-20 started at 5,000+ in 1995 and went down to 2869 man-hours by 2001. At 2869 man-hours, Cirrus was still losing money. After 6 years of continuous production Cirrus had not made a profit. They had hoped 19 years ago to get down to 2500 man hours. Still not happening.

    Cessna, in 2001, was taking 2,000+ man-hours to complete a 172…with the best lean manufacturing techniques they knew about applied. Still the same.

    At its zenith the Columbia was estimated to be in excess of 3,000 man hours to build with a very experienced composite workforce. When Cessna resumed production of the same design, it was higher, as they did not have that same expertise.

    A Quick Build RV-10, with 75% of the riveting factory completed, and firewall forward kits included, the average completion times are about 1500 man hours according to Van’s.

    My conclusion, the build time for a 4 place, aerial conveyance, including the use of composite construction, lean manufacturing, and accounting for all the installation times of the electronic wizardry of the required automation/stabilization devices to make it safely fly will be very similar. This includes the addition of electric power-plants. None of that includes the considerable investment required to design, engineer, and perfect this technology to a minimum requirement of FAA certification as a reasonably safe flying machine.

    There is no economy of scale for manufacturing a 4-5 place autonomous flown urban aerial conveyance. If we cannot perfect within the known certified and Experimental aviation world enough scale of economy to move efficiently, profitably forward, I believe it is unrealistic to think we can in an entirely new frontier.

  11. “The on-demand air taxi model that accounted for much of its sales prospects failed to gel and the entire segment never achieved anything lie economic volume.” “The UAM concept assumes that a network of data-driven autonomous aircraft will draw people in the millions to flying across town rather than using mass transit, a car or a ride hail.”

    In my mind, Paul’s two comments is the heart of aviation’s marketing problem. It is where the rubber meets the road ( pun intended) regarding flying in general and specifically flying as it relates to the public as mass transportation.

    My contention is… flying is not natural to human beings. Proportional to US population, the numbers of people who attain pilot licenses has been about the same since WWII. Today, I thoroughly love flying. But I remember distinctly my first flight. It was scary and uncomfortable experiencing for the first time so many different, conflicting sensations. But the view was captivating. So, like all rated pilots, I had to overcome all these initial sensations/fears by voluntarily getting enough flying experience. To get the flying experience, a rated pilot must also invest a significant amount of time to learn the required aeronautical knowledge in tandem with the physical experience of flying. I became a passionate aviator after an accumulation of all above.

    Learning to comfortably fly is a series of lessons of overcoming the reality of sensations that result because of the physics of flying. Learning to comfortably fly requires a continuous investment of time and dedication building a knowledge base to be a reasonably safe pilot. These attributes result in a personal dedication of over-coming challenges. This over-coming dedication is not something most people seek. The love of flying comes from our peculiar, unusual nature of consistently wanting to meet the challenges of flight and enjoying the satisfaction that results. The pilot numbers in relationship to the population, in my mind, proves this to be true.

    Flying is an acquired taste. Most folks that fly on an airplane, even those with scads of sky-miles, do not like the experience. They average passenger is not looking at flight the same way pilots are. If given a choice between ground-bound high-speed conveyances and airplanes, the ground-based conveyances almost always win. They are intrinsically more comfortable to homo sapiens. Plus, as pilots, we all know there is preflight planning, weather, evaluating the airplane’s mechanical condition, even the chore of getting the airplane out of the hangar that is unavoidable time spent to simply fly at all.
    To think most of the public has acquired a similar taste is not included in the Frost’s projections, nor most market analysis.

    Flying is not for everyone. Certainly not for the masses. Now add to the mix, the idea that people will be drawn to flying in these UAM’s without a pilot relying completely on autonomous control for their safety and comfort. We have the autonomous technology today demonstrated in airports driving the various trams and monorails such as used at ATL, for example. Take that experience and start navigating up and down, around city skyscrapers, power lines, antennas, in turbulence, and with other autonomous and manned flying vehicles already in the same airspace, some visible some not.

    Marketing hype portrays the experience of flight as seen through a well stabilized Go-Pro video as being the same as real flight. The reality of flight characteristics of a 4 place UAM in an urban, turbulent environment will make being in the back seat of a V-tail doing the Bonanza Boogie on a hot bumpy day, a fun and satisfying experience.

    No amount of gyro stabilization will remove the varied sensations of flight. There is a reason for the popularity of drones. You get to see the aerial view without all the uncomfortable experiences previously required. Getting into a big enough version of $100-500 Go-Pro equipped drone to carry 3 other equally scared people and doing this without a pilot is not going to happen for the numbers of people projected by the non-aviation savvy marketing gurus. For that matter, it will not happen even with a pilot. One flight in these futuristic UAM’s will be enough for even the wealthiest of passengers to choose something more comfortable and less frightening.

    • Just in the last couple of days, I heard that another Tesla Model 3 had had a serious accident … in the TWO dimensional world. I do not see 100% autonomous flight — especially in purely electric powered machines — as anything any of us within arms reach of 90 will see. For me — personally — I will NOT get into anything I can’t manually take over if a SHTF scenario unfolds. Even if reliability of 10 to the minus 9th were true. And the idea of putting an electric motor in a Beaver and making it viable … fuhgetaboutit.

    • “My contention is… flying is not natural to human beings.“
      Jim, my contention is driving on a two dimensional road is not natural to most human beings.
      Every time I get in the car with my wife my beliefs are validated. She thinks the yellow lines on the road are supposed to go down the centerline of the car. I keep telling her, “no honey, you’re supposed to drive in between the lines not on top of them.” I’ve given up a long time ago. Suffice to say, driving with my wife keeps my blood running.
      If you lived where I live, you’d quickly learn most people shouldn’t be on skateboards much less anything with a motor in it. UAM for the masses, I don’t think so.

  12. “Flying is not for everyone. Certainly not for the masses.”
    No, BEING A PILOT is not for everyone. One of the chief features of autonomous vehicles is that they do not require ANY occupant to be a pilot. THAT will be “aviation for the masses.” But I agree that this idea of Jetsons-like “urban aerial mobility” for human passengers is a pipe dream. Now, inter-city aerial mobility… that’s another concept – one that I think will fly (couldn’t resist the pun).

    • I MIGHT be cajoled into flying in an autonomous airplane after a decade or more or proof that it’s safe. But climbing into a machine that’ll turn itself into a cement block if the rotors stop … no freaking way !!! And IF the autonomous vehicle is piston powered or single engine .. I ain’t doing that, either.

  13. UAM people movers, electric powered Beaver conversions, X-57 Maxwells with 14 electric motors, 300mph electric air racers, X-59 supersonic transports, electric powered airliners, vehicles to turn well-heeled people into astronauts, flying cars, autonomous flight … what’s next … matter transporters? Methinks aviation draws in people with some pretty strange ideas. Paul Moller has been pushing his M400 Skycar in Popular Mechanics for 50 years … Geesh !!

  14. I just don’t understand why all this matters to me. Therefore, I say it is, once again, just hype or aeronautical market naïveté.

  15. I pretty much agree with the various posters in that this is a challenge to see the future as the study presents it. However, there may be one facet of the public that we might be overlooking. Selling this to rich people in the U.S. may be a stretch for high volume production, but it might be a different story in other parts of the world. The unspoken selling point in many developing nations might be security. In many parts of the world like the Middle East, Far East and South America, well-healed individuals commonly live in guarded communities or in walled compounds. Those families do not relish mixing it up with the ordinary population on public roads – particularly at night – where a fancy car becomes an attractive nuisance. A fully armored Mercedes could be close to the cost of a UAM. They might be interested in a flying conveyance that can transport them in safety and still would not require a pilot’s license like a helicopter would. If the UAM could land in a limited space behind the walls (even on a residential roof), noise issues would be less of a problem. Plus, aeronautical regulations in the “third world” are less stringent on location of landing pads, etc.

    In that case, an argument might be made for a good customer base willing and able to afford such a device. Plus, I suspect any volume production system would be set up in China, Korea or similar far eastern country where FAA certification is not an issue. There, labor hours are not so much of an impediment to profit as they would be in Kansas, USA. Just a thought…