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A tiltrotor by definition takes a helicopter style rotor and tilts it 90° to generate thrust for forward flight in airplane mode. Helicopter rotors are not just big propellers. The blades bend and twist flexibly, and they must be changed in pitch every rotation to achieve flight at all. This is achieved through the marvelously complex mechanisms called rotorheads.

In practice, two main rotors are used on tiltrotor aircraft. The V-22 is basically two big helicopters that have been yoked together with super complex cross shafting and clutches, then forced to fly tipped over sideways. After decades of development, it works, but at a high cost for acquisition and even higher for maintenance. The AW609, its civil descendent, shares those disadvantages.

In contrast, tiltwings use variable pitch propellers, like those on turboprop airplanes. They are an order of magnitude less complex than rotors. This saves a great deal of cost throughout the lifecycle, from certification through manufacturing to operations.

The last face-off between the two aircraft architectures was in the 1960s. We had the Canadair CL-84 and LTV XC-142 tiltwings vs the NASA/Bell XV-15 tiltrotor. Though all flew successfully, the U.S. chose to militarize the XV-15 into the V-22, leaving no lead customer for the tiltwings. 

50 years later, we have chosen the tiltwing design after careful study of all past VTOL programs.

Our design benefits from three key technology advances in that time: much higher power to weight turbine engines, fly-by-wire flight control, and whole-airframe aircraft parachutes. The resulting Vy 400 design has a fraction of the complexity of the AW609, as can be seen from the latter’s $24M price tag vs the Vy’s $3.5M price.

The Vy is much higher performance as well, with a 4,500 fpm rate of climb at max weight in helicopter mode, and a cruise speed of 353 kts. Computer control of each individual control surface has let us manage the flight dynamics in the transition between helicopter and airplane modes with unprecedented smoothness and precision.

The airframe parachute enables improved safety versus helicopters, and has let us employ a single engine for simplicity and efficiency.

PDF Paper

A380 Was Wrong Solution for Lack of Runways

The Airbus A380, the double-decker, super jumbo, 500+ seat airliner program has been canceled after only twelve years in service. One of the original rationales for the A380 was that you can’t build more runways at the major airports – which is true – so having larger aircraft was one way to maximize the use of existing airport concrete.

But with the A380, Airbus missed an epochal, transformative turning point in air travel—which means that smaller is actually getting better. This has been proven by the success of Airbus’s own A350 and of the Boeing 787. Their superior adaptability to the needs of airlines and their passengers’ travel demands has also prompted Boeing to retire the 747, the “Queen of the Skies,” after fifty years of dominance. 

That’s why I am leading the team, building the next generation of regional air travel with the concept that smaller is better. Transcend Air is on the verge of taking the next inevitable step. By going smaller yet, and by taking advantage of our high speed VTOL aircraft, we can relieve the “you can’t build more runways” problem by having an airliner that doesn’t need runways.

We calculate that we can take 16% of the passengers out of conventional single-aisle airliners in the U.S. We will move people in and out of the city centers directly with a distributed network of vertipads using our Vy 400 aircraft that seat four or five passengers. That’s 73 million passengers a year who won’t have to sit in traffic to an airport, or stand in line after line to get to their seats. Our aircraft is built for speed (400 MPH) and will get people from door to door three to four times faster.

This revolution in air travel looks familiar. In the computing world, we went from giant centralized mainframes, to PCs, to iPhones in less than 30 years.

When I started out as a programmer in the 1970s, it was just at the beginning of the personal computer industry, and the mainframe still ruled computing - just as the 747 still ruled the skies. People would line up with their deck of punch cards to be processed and stack of printout to be returned. The PCs meant no time wasted waiting. What Airbus didn’t realize in 2000 when it launched the A380, is that, like the computer business, the mainframe was not the future.

Once you get your data and programs onto a mainframe, it’s still a super efficient way to compute – but only if you don’t count all the time lost by users who have to queue up to get access and then wait a long time for their results. Big airports and airliners are the same way. Once the seats are full of passengers, the A380 is super efficient at getting them to a distant runway – but only if you don’t count all the time lost by passengers who have to sit in traffic to and from airports, and stand in long lines to get on and off the giant aircraft.

But people don’t care about efficiency of the computer or the airliner. They want their computing or travel needs met in the least expensive, least time-wasting ways, while maintaining the the highest level of safety.  A350 and 787 mean more direct flight options with no time wasted making connections.

We all know what the next step in personal computing was. Most of us now carry glass computers in our pockets that have nearly become the second halves of our brains – barely more than a single decade after Steve Jobs unveiled the iPhone.

 We are looking forward to doing the same for air travel. 

“I’ve seen things you people wouldn’t believe.” – Roy Batty,  Bladerunner

Ridley Scott's 1982 dystopian sci-fi classic Blade Runner takes place in 2019, so the obvious "how much came true?" stories are flooding the Internet. The basic plot, if you need a review, is that a group of fugitive, rogue "replicants"- enhanced humanoids - escape back to Earth and cop Harrison Ford has to track them down.

I'll spare the rundown of comparisons to the real 2019, and leave that to the folks at Filmspotting (one of the best movie review podcasts, btw). Except to say that this weekend I got a preview of Sony's new Aibo, and that thing is frighteningly close to being a real dog, except smarter and it'll take photos of your home while you're gone, and probably upload them to all your friends. So maybe we're close to a "replicant" dog.

Ford's character zooms around in the slums of Earth in the ultimate sci-fi vehicle, a flying car that doesn't blow over the trashcans on the street. So is the dream (nightmare) of flying cars here yet? Of course not. But realistic goals of new urban mobility and regional mobility are now at least in the sphere of legitimate conversation.

Numerous companies - some of greater credibility than others - are promoting VTOL aircraft designed for short-haul within-city transportation. Even Airbus, the world's largest aircraft manufacturer, has pitched its fanciful design. CNET calls it for what it is: "wacky". Uber, which has never built anything other than an app, actually says it will have a flying electric VTOL ready for testing in Dubai next year. There's also a bridge in Brooklyn I could sell you.

The race for actual, practical, economically and environmentally viable VTOL aircraft will be won by the doers, not the dreamers. And several start-up companies are doing the hard work of engineering prototype aircraft, to be followed by manned prototypes, to be followed eventually (they hope!) by certification from regulators. They are working, simultaneously, on building the necessary infrastructure (where will these things land and takeoff from?). And working on gaining pubic acceptance of new aircraft.

We need new ideas to solve the urban and regional mobility crisis. Sci-fi movies give us the spark of imagination, but not the actual blueprint to get it done. The immediate future of real VTOL aircraft glitters brighter than C-beams in the dark near the Tannhauser Gate.

All the hoopla over VTOLs (Vertical Take Off and Landing aircraft) have many asking “isn't this just another helicopter?” That would be the same as asking Igor Sikorsky, the father of helicopters, if his invention was just “another airplane”?

Just as helicopters proved to be a dramatic leap forward in aviation (despite helicopter buffs' sarcasm that they fly by “beating the air into submission”), the nascent VTOL industry will take us on another giant leap. Helicopters have been limited to the wealthy when it comes to transportation, but VTOLs could finally be everyone's transportation of the future - and solve some of our infrastructure problems along the way.

The key differentiator, by just looking at a VTOL, is, of course, how it takes off and flies. In the most efficient form, it takes off like a helicopter (mostly straight up) and “transitions” into an airplane, where it does most of its work with its wings. It then transitions back into a helicopter-type design to land straight down.

That technology exists today, and full-scale VTOLs are flying in the military. But the V-22 and its derivatives themselves adopted the most expensive and complex parts of helicopters – and them connected them together in even more complex ways. Only the U.S. military can afford that! Even traditional helicopters are expensive to operate, because their complexity requires a lot of maintenance for every hour they fly, and since they don't move as fast as airplanes, those hours don’t get you very far. That’s why helicopters end up costing so much more per mile to get you places.

VTOLs under design are promoted as flying up to speeds of 450 miles per hour, about three times faster than a similarly sized helicopter. That means they can do a trip from Manhattan to Boston in half an hour. The direct cost of a VTOL flying to Boston from Manhattan would be just $449, compared to twice that in a helicopter. And many VTOLs are designed with whole aircraft parachute systems, providing a level of safety few aircraft have today (only the Cirrus aircraft family boast factory-installed parachutes).

What about all-electric aircraft? Many would-be players in the VTOL space are pushing all-electric vehicles. They are coming. But not yet. Just take your toy drone out for a spin and you'll notice how little battery life there is. That problem only gets worse with bigger aircraft.

The proof will be in the pudding, of course. But once jet-powered VTOLs are commercially flying the more expensive, exclusive helicopter market will see some rapid changes – and if you are an air traveler, you'll get to experience them.

The Consumer Electronics Show in Las Vegas has always been about the here now, the aspirational, and the fantasy. It's what makes the yearly, epic show so much fun. And it's a good analogy for the aviation industry as a whole.

Sometimes, we don't really know what is aspirational and what is never going to happen. A number of years ago, I saw a demonstration of the self-parking car. Who would want a self-parking car? But that is now a thing and available. We witnessed the same thing happening as drones went from the flashy future to the more mundane now.

I wasn't at this year's CES, but the reports highlight the continued move towards electrification of aviation and aircraft. You will be hearing a lot about electric powered VTOL aircraft (vertical takeoff and landing) that are designed for urban mobility. Bell (formerly Bell Helicopter), while not exactly a consumer product manufacturer traditionally, has made a move in that direction and  unveiled a full-size, hybrid propulsion VTOL air taxi that it says will be available in just a few years.  Unlike some other VTOL manufacturers, Bell recognizes that an all-electric VTOL is unrealistic because battery power just can't take you that far. My friend and colleague, Peter Schmidt, the COO of VTOL start-up Transcend Air, has written extensively about how all-electric VTOLs are simply not realistic because the basic physics of extending battery life isn't moving that fast. You can read one his blog posts here. The problem is that many VTOL start-ups are promising all-electric aircraft that they will never be able to deliver (or deliver before they run out of investor money). By the way, this is why Transcend is going to market with a VTOL ready for production now, with a traditional jet engine.

There's little question that mobility is moving towards electric powered solutions. And aviation should follow the auto industry's lead. I had the privilege of seeing the original EV-1 from General Motors more than a decade ago. But each car cost hundreds of thousands to build and long range mileage wasn't great. GM abandoned it, and with that surrendered the narrative to Toyota-- which produced a mass-market, hybrid vehicle, the Prius. In essence, a compromise car between oil and electricity. It would be years until Elon Musk- who may be as brilliantly nutty as his company's namesake- would unveil the all-electric Tesla.

The one area in manned aviation where all-electric airplanes are actually flying now, is in the 2-seat, fixed wing market. Bye Aerospace's Sun Flyer2 now has a range of 3.5- 4.5 hours and is nearing certification. Siemens is making Bye's propulsion system, and the German company knows a lot about both engines/motors and mobility. (And it would be nice as a pilot to not have to calculate fuel load, since that number is always the same with an electric airplane.). It would be great to see that range tested in real life.

This is the path we in aviation should follow. Start with a realistic VTOL that could be produced now (so we can improve urban mobility) and evolve to the all-electric version. The only thing that moves fast in aviation are the aircraft. Not the building of them.

Besides my role at Hopscotch Air, I'm the Vice President of Marketing for Transcend Air.

Those Parachutes for Small Airplanes Really Do Save Lives -- Air & Space Magazine, May 2018 

Boris Popov is not a household name, not quite even in the small world of aerospace - yet.

Boris introduced his Ballistic Recovery System for small aircraft in 1980. It's a parachute, not for you the occupant, but for the whole aircraft. Imagine that!

Actually, you don't have to imagine it, because through tireless development and refinements over the past thirty-eight years, Boris and the good folks at his company BRS Aerospace have made it real. As you can see in the pictures above, way back in 1998, BRS used NASA grants in partnership with Cirrus Aircraft to develop a system for Cirrus's SR series of five-place GA airplanes.

It has been a great success, as this study shows:

Injuries were shifted from fatal to serious or minor with the use of CAPS and postcrash fires were significantly reduced. These results suggest that BPRS could play a significant role in the next major advance in improving GA accident survival. 

Other research shows that emphasizing the use of the parachute to their pilots has made the Cirrus fleet more than twice as safe as other GA aircraft. 

That's why our full size Vy 400 has had a BRS Aerospace whole-aircraft parachute designed in from the start. It's why Boris was one of the very first industry suppliers we met with. And it's why the Vy can deliver a $283 ticket price between Manhattan and Boston, something that would not be achievable if we had to rely on a second engine for safety.

We're so convinced of the value of whole aircraft parachutes, we've built one from Fruity Chutes into our 1:5 scale prototypes. This is also for safety. It makes sure we can bring the aircraft down gently if anything unexpected happens during flight test.

We tested the chute launching system just the other day. The result, as NASA has taught us to say, was nominal - check out the video! We are pleased to have joined the whole aircraft parachute club with that test.

Boris won the 2017 Joseph T. Nall Safety Award, and given the many lives already saved from his work and leadership in this area, I expect he will continue to be recognized for his tremendous contribution to the safety of all who fly in parachute equipped aircraft.

It Don't Mean a Thing If It Ain't Got That Swing!

--Duke Ellington/Irving Mills

https://www.youtube.com/watch?v=zhQHGEfbP5k

The music is Catgroove by Parov Stelar.  Please check him out, he is one of the pioneers of Electro Swing, and his music is terrific!

* music used under license

Daring Cycles - on Electric Tires

(Paris, early eVTOL concept, c. 1897)

I had the honor of joining Rob Dumovic and Matt Juszczak on their Plane Talk Podcast in July - and they introduced Transcend Air as a "very interesting company that we think is going to revolutionize travel." 

Revolutionize travel?

It was kind of them to say, but running as we are at or near the peak of the Urban eVTOL/On Demand Mobility hype cycle - as attested by the Executive Director of the Vertical Flight Society himself - I'm getting as tired as you are of overheated rhetoric.

This is far from the first time the brazen hype trumpets have blown for travel innovations. Even the humble bicycle excited people so much that we actually got the first eVTOL concept from it, 121 years ago. (shown above)

Sadly, bicycles didn't give us wings any more than RedBull does.

Yet ... bicycles DID prompt the paving of inter-city roads, roads that had fallen into disrepair after trains disrupted horse-drawn carriage service.* And paved roads made the automobile a no-brainer, accelerating its mass adoption. That was a revolution in travel.

And, at the same time that ad was painted, two successful bicycle entrepreneurs decided to take to the skies themselves - wearing somewhat less revealing flight suits. We all know what the Wright brothers accomplished a mere 6 years later at Kittyhawk. Worldwide mass air travel also started, in part, from bicycles. Another revolution.

Our aircraft design is going to let us offer cheaper business travel from city to city, while reducing door-to-door travel times by 60% to 80% and providing a super roomy and comfortable experience. Plus no congestion on the roads or in airports to deal with.

I can claim this because, math.

From the details of our aircraft design, to the resulting performance specs, to the economic models we've built, we have dreamt through careful mathematics - not overheated imagination.

And yet, we are poised to finally deliver on the vision so psychedelically rendered above, because technology has continued its march.

I don't know if it will ultimately be judged a revolution, but I do know I can't wait to Vy to Manhattan in 36 minutes.

And what the heck even are electric tires, anyway???

* https://www.theguardian.com/environment/bike-blog/2011/aug/15/cyclists-paved-way-for-roads

“Doc, back up — we don’t have enough road to reach 88!”

“Roads? Where we’re going, we don’t need -- roads.”

 

     — Marty McFly and Dr. Emmet Brown, Back to the Future

Doc Brown didn't reinvent the wheel - or the car, for that matter. He built his time machine into a car - a stainless-steel bodied DeLorean, in fact. And when he came back from the future, it wasn't just a roadable time machine anymore, it was even cooler. It was a VTOL aircraft as well!

Like Doc, NASA has invented some pretty cool tech over the years. In the process, they had to come up with a way to figure out if it was ready for its mission. Flying the air- or spacecraft in question is always the ultimate test, but if you're wrong about its readiness, you end up with a crashed vehicle, and possibly harm to people. While the risk of those is impossible to elminate entirely from test programs, neither is particularly desirable, so minimizing them is key.

Thus NASA came up with the concept of TRL- and that’s not Total Request Live on MTV. It’s Technology Readiness Level. And it’s an engineering geeks’ dream chart.

As you can see in the diagram, TRL Level 9 is reserved for components or systems/susbsytems that have flown successfully. Level 1 is for concepts and ideas.

The higher the TRL, the more proven. Doc used a TRL 9 vehicle - the DeLorean - as the major subsytem in his VTOL time machine. The flux capacitor was probably at TRL 4 when he installed it. It was smart of Doc to add just a single unproven susbsytem to the DeLorean, since it substantially increased his odds of a short duration and low cost test program.

Sadly for what I am sure was a carefully crafted test plan, things got a little rushed for him and Marty. They jumped right to a full prototype demonstration, which is normally a very bad idea, but the test did work - thereby bumping the whole vehicle to TRL 7. (Phew!)

Doc and Marty just had to cope with machine-gun wielding terrorists. With our Vy 400, we have to deal with a far more powerful opponent: the FAA.

We will have to prove to their satisfaction that the Vy is safe. It's a challenging road, but we are partnered with people and organizations that have traveled it successfully before, so we know what needs to be done.

The most important thing is, don't take unecessary risks. That starts with our design.  

From our flight control system to the BRS parachute, and throughout the vehicle, our components have all been used with success in other aerospace applications. Even our basic aircraft shape was proven by the CL-84 in the 1960s. Industry experts who have reviewed our design consistently tell us they think it will work.

Amusingly, they say that with some surprise. I know they've all also been looking at other programs in the eVTOL/Uber Elevate space, and in the electric commuter space. I look at those aircraft, and I see a lot of TRL 1s around energy storage, aircraft planform, and autonomous flight. I gather the surprise comes from the fact we have a high TRL design. Who knew we're as smart as Doc Brown?

And even if Doc Brown showed up today with a Mr. Fusion and a flux capacitor, we wouldn't modify the design. It would add too much risk and cost to our certification effort. Besides, since it cuts four hours off the current five hour NYC to Boston trip time, the Vy is already a time machine...

Thanos: Stark. 

Tony Stark: You know me? 

Thanos: I do. You're not the only one cursed with knowledge. 

Tony Stark: My only curse is you.

As I've mentioned before, our aircraft, the Vy 400, is NOT an e-for-electric-powered VTOL. It IS a VTOL, meaning a Vertical Take Off and Landing aircraft, but by our numbers, electric is not yet ready for our needs, so we are going with jet engine power.

But if you spend any time around aviation these days, you can't help noticing there are a lot of electric aircraft designs being touted. One colleague said he'd counted over 200! This page at eVTOL News lists 131 programs, almost all of which are electric - and there are additional non-VTOL electric aircraft projects out there.

People ask us, why this proliferation all of sudden? 

Short answer: a set of technologies have come together now to make it easy to design electric aircraft with potentially interesting economics.  A technology window has opened, due to

• Moore's Law and it's inexorable march to give us ever-cheaper and more powerful computing. For $100, you can buy a playing-card sized embedded computer with the raw power to run an entire vehicle, with cycles left over.
• GPS in aircraft letting them know where they are in space, which is a crucial ingredient to building a self-flying vehicle that flips the pilot seat from expense to revenue.
• Smartphones - yes, smartphones! They have sophisticated sensor suites built into them, with accelerometers, compasses, cameras, heat detectors, light detectors ... and they are built by the literal billions.  That means those suites can be built into other gear for dirt cheap.
• Military drones and their compelling advantages have led to advances in remote operation, autonomous aircraft systems, electric actuators, sensor integration, and more.
• DJI and other brand consumer drones have taken the dirt cheap sensor suites from smartphones, plus some of the control techniques from military drones, to become a whole new class of consumer goods now produced in the tens of millions. This has driven down the cost of related flight tech, including high power and light weight electric motors, thereby driving demand for the last enabler...
• Li-Po and Li-Ion batteries. Not just drones, of course, but smartphones and other personal gear have helped create a global industry that is producing comparatively low-cost batteries that can power all sorts of useful (small) gadgets - and even electric cars.

So, basically, a lot of people have looked at the drones they got for their birthdays, and have said, "Saaaaay ... if I just make this bigger, it could FLY PEOPLE!"

And then there are the execs at Uber, who apparently said, "You know, if someone makes people-flying drones, WE CAN SELL RIDES IN THEM!!" Uber then leant their considerable brand power to the encouragement of aircraft makers, with significant success.

But unlike in the PC world, you can't just grab the latest tech, slap some software on it, ship it fast, and let your customers be your testers. Buggy OSes and malware-ridden laptops are an annoyance; buggy aircraft ... cannot be allowed.  The FAA will see to that.

So a reckoning is coming for the infinitude of electric designs.  Certification will not be a snap - we'll see how many make it.

Dunning and Kruger's 1999 study, "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments," derived in part from the cognitive bias evident in the criminal case of McArthur Wheeler, who robbed banks with his face covered with lemon juice, which he believed would make it invisible to the surveillance cameras. This belief was based on his misunderstanding of the chemical properties of lemon juice as an invisible ink. -- Wikipedia

In 2017, after a competitive evaluation process, Transcend Air was admitted to the CONNECT Springboard startup accelerator program. We were honored to be accepted. The whole basis of the program is that people who apply need help — lots of it. And while it’s true that my co-founder Greg Bruell and I are experienced, successful, serial entrepreneurs, we don't think we know it all. We have a healthy respect for our Dunning-Kruger limitations, and really don't want to screw up the company by running around with the aerospace equivalent of lemon juice on our faces.

CONNECT has provided us with a team of mentors with terrific experience: a former military aircraft manufacturer CFO; a marketing consultant with a background selling private jets; an IP attorney who is also a pilot; an entrepreneur-pilot who was an early investor in the Very Light Jet hype cycle and learned much from how that all went down; a serial entrepreneur-pilot who has taken two companies public. Their feedback on multiple topics has made us better advocates for the vision we have for Transcend.

But we are blessed with expertise beyond our CONNECT team. Because Greg and I are skeptics ourselves, we didn't launch Transcend until we had numbers for the aircraft and the business model that we had scrubbed intensively via feedback from family, friends, colleagues, consultants, and advisors - a process that continues.

Our aircraft design has benefitted from input from the former chief test pilot for the V-22 and the Honda Jet; from the world's VTOL experts at NASA Ames; from both sides of the team who took a business jet prototype from concept to Oshkosh flight demo in 25 weeks; and from professional aircraft and propeller designers with literally hundreds of aircraft designs under their belts.

Our certification plan is being led by a fixed-wing/rotary-wing/VTOL test pilot with 13 years at the FAA Rotorcraft Directorate, including as test-pilot for the AW609 civil tiltrotor.

Our airline business model has been improved with help from the former head of flight operations for Delta and Jet Blue, and from two CEOs of startup air taxi operators.

Why have all these incredibly talented and experienced people wanted to help?

Their advice and support have enabled us to mature a good, solid concept into a great one - and now they want to keep helping to see it make its impact on the world.

Imagine if he'd gotten to work with a team like ours - Wheeler would have had the world's biggest chain of lemonade stands by now!

When the lights go down in the city / And the sun shines on the Bay / Ooh, I wanna be there in my city / Oh ooh woh... -- Journey, "Lights"

Our Vy 400, VTOL aircraft uses a jet engine. It isn't battery powered, for a very simple reason: Jet fuel has 50 times the energy of current batteries. 50 times! What does 50 times more look like? (See graphic above.)

The journeys we want to take people on are measured in hundreds of miles. San Francisco to San Diego in an hour and a quarter - with no waiting in lines, because we won't use airports. We need jet power to do that.

Batteries have been improving at 3% to 5% per year for decades. As Dr. Don Hillebrand, the Director of the Energy Systems Division at Argonne National Laboratory - which is the national lab tasked with working to “answer the biggest questions facing humanity”- said last week in his talk at the Lindbergh Innovation Forum, it'll be about 2045 before battery-based powertrains can match jet-engine-based ones. So, where will you be in 2045?

With today's best batteries, a VTOL aircraft carrying four people has a range measured in single-digit city blocks. That's not even enough to get you across the San Francisco-to-Oakland Bay Bridge.

It's not until 2030 that, per Roland Berger's projections, batteries will have improved enough for eVTOL aircraft to get just across Silicon Valley. It'll be 15 years or more after that before they'll be able to complete the trip down the California coast.

Pretty as the sunrise over the Bay is, we don't want people to be stuck watching it for another 27 years when we can use tech that is available today to get them down there - and back before sunset. (!)

So don’t stop believing - just believe in viable technology. 

“Mind the gap … Mind the gap … Mind the gap" —London Underground subway warning

The Vy 400 is a single-engine turboprop that can fly regionally from city to city, just like other turboprops. But it takes off and lands vertically. Those other conventional turboprops don’t. The Vy400 is not an eVTOL. eVTOLs are powered by batteries — and battery-powered aircraft that can actually fly somewhere won’t be ready for who knows how long (see my post on that). 

So it follows that we are often asked about another VTOL: the XTI Trifan 600. I wanted to point out a few differences, but first, there are similarities: Both have jet engines, both have six seats, both have three propellers, and both will be built from lightweight carbon fiber.

One big difference is price. Our planned Vy price is $3.5 million. XTI’s literature says the Trifan will be nearly twice as much: $6.5 million.

But the Vy is also faster. It will fly up to 405 mph. The Trifan is limited to 345 mph. 

The Vy can also carry more passenger weight. The Vy design allows for five passengers, each weighing 200 pounds, and their bags, averaging 50 pounds each for a typical business traveler. That’s 250 pounds total per passenger. The corresponding weight per passenger in the Trifan is 150 pounds, and therefore it can’t fly VTOL with adults in all five seats.

Then there is size. The Vy is a full 7 feet, or 17%, shorter than the Trifan, yet XTI says the Trifan will weigh a lot less, both empty and full. Since aircraft weights follow their lengths pretty closely, that really puzzled me. We have top flight (pun intended) aerospace design engineers on our team, but could XTI’s engineers be that much more clever? More than half a ton more clever?

So I got some data. The chart above shows the most popular current single engine turboprops, along with the Vy and the Trifan. The aircraft are graphed from smallest to largest by length. The Vy falls pretty nicely* on the trend lines for both empty and max weights, while the Trifan has a 1,430 pound gap empty, and a 3,430 pound gap full. That is, given the 41 foot length of the aircraft, comparison with all the other aircraft suggests it should be heavier, a lot heavier: over 40% heavier empty.

Perhaps their design is just that much superior to ours, and to Piper’s, Cessna’s, Daher's, and Pilatus’s. But there’s a reason Londoners are warned about the gap: you don’t want to put your foot in it.

INIGO: You keep using that word.  I do not think it means what you think it means.

-- The Princess Bride

Recently, Ashish Kumar, the CEO of Zunum was quoted* in the Economist:

Zunum claims that its plane will have a CASM of 8 cents. Oliver Wyman, a firm of aviation analysts, reckons that the average for American airlines in 2016 was 11 cents.

Sounds great! …but what does it actually mean?

CASM, or cost per available seat mile, is calculated by dividing the operating cost of an airline schedule by the available seat miles that schedule provides. Talking about the CASM of a single aircraft gets tricky. CASM includes non-aircraft operating costs like pilot pay, ground crew, insurance, amortization, landing and terminal fees, and maintenance. On none of those cost categories does Zunum’s hybrid-electric design have an advantage, so the claimed CASM savings cannot be found there.

But surely fuel savings amount to something?

The batteries Zunum plans to equip its plane with are heavy, with a much lower energy density than jet fuel, resulting in a loss of efficiency versus a pure turbine design. Running their jet engine at its most efficient speed may make up for it; confirmation awaits real world operational data. 

So, on the chance that the hybrid-electric design does result in fuel savings, what might that mean for ticket prices?

It turns out that jet fuel represents just 20% of the total costs for an airline flying a passenger on an aircraft of that size. Therefore, the maximum possible savings - if energy became free! - would be around 20% of current prices. 

Since there are no regular scheduled services on any comparable aircraft today, I got a charter price quote for a round-trip for nine passengers on a Pilatus PC-12 from White Plains, New York to Richmond, Virginia, making use of the reliever airports those cities have adjacent to NYC and DC, respectively. The price per passenger today is $1,647. 

So, if Zunum’s aircraft design could somehow use no fuel or energy at all, the price would drop to … $1,318 per person.

I think the word for mass market flying at those prices is, "inconceivable."

* https://www.economist.com/science-and-technology/2017/11/30/small-hybrid-electric-airliners-ready-for-take-off

Image: The forseeable future for batteries for eVTOL aircraft.

VLADIMIR: Did you not hear what the child said?

ESTRAGON: No.

VLADIMIR: He said that Godot was sure to come tomorrow. (Pause.) What do you say to that?

ESTRAGON: Then all we have to do is to wait on here.

VLADIMIR: Are you mad?

        — Samuel Beckett, Waiting for Godot

With battery-powered aircraft, energy doesn’t come from pounds of jet fuel, but Coulombs of electrons. A few tens will get a toy drone airborne, but to safely fly people … you need roughly a million times that much. That’s enough to impress even old Charles-Augustin de Coulomb himself.

When will batteries be that powerful? Keep waiting: eminent consulting firm Roland Berger guesses not before 2030.*

So, it’s fun to dream about catching a battery-powered Uber air taxi and zipping across town to catch a ball game.

It’s also fun to dream about zero-calorie desserts and warp drives. But right now, we don’t know how to make any of them.

Uber’s bravado in espousing an all-electric vision for city-hopping has earned them a ton of press, and industry attention. But I notice they aren’t developing their own vehicle.

To get people in the air, it’ll take more than an app. It’ll take an unknown breakthrough in battery chemistry, happening at an unknown time, likely more than a decade from now.

We’ve built 14 electric VTOL (eVTOL) prototypes. We love the advantages of electric propulsion, and can’t wait for batteries to improve by a factor of 10x or so, when we plan to equip our aircraft with them.

In the meantime, we are very happy to design-in the most reliable jet engine ever built, and look forward to zipping you not just across a city, but from one city to another.

Uber can keep on waiting for Coulomb, if they like...

*https://www.rolandberger.com/publications/publication_pdf/roland_berger_aircraft_electrical_propulsion.pdf