Sure, let's take the most energy efficient aircraft and compare it to the least energy efficient passenger vehicles??? I mean, how can one even pretend that is a fair comparison.
More generally for energy efficiency, it is well known that the most efficient trip is a shorter one or one never taken. Many fans of these technologies are people who dream of living 90 miles away and fly into town in half an hour. Or as you described "this would replace a two hour trip across a city in traffic with a fifteen minute flight". Comparing MPG when your technology is designed to encourage more miles is a flawed approach.
There's a popular perception that all aircraft burn energy like an oil refinery on fire. The reality is that small piston aircraft are approximately as fuel efficient as the vehicles around you on the highway (at least where I live) while getting you there a whole lot faster.
A Cirrus is a good comparison stand in for the KittyHawk aircraft because it has a similar design and construction style (ignoring the dodeca-props), four seats, and is the most common general aviation aircraft not designed in the 1950's. A Cirrus isn't even close to the most energy efficient aircraft - that would be more like 60 mpg, nor is it the most efficient in its class.
This is just objectively wrong.
Before taking wind into account, a Cessna 172 travels 120kts on a good day and at altitude and appropriately leaned can get down to 8 gallons an hour.
120 nautical miles in 140 miles (less, but benefit of the doubt and all). That's 17.5 miles per gallon. At cruise altitude. Leaned appropriately. You can tack on another few gallons for the climb, and you're going mixture rich on descent so you're back up to 10-11 gph for the last 20-30 miles of your trip. You're lucky to get 10mpg overall for a flight, and that's using gas that costs $5 a gallon.
There are a LOT of benefits to GA flight in order to get around. Fuel efficiency is definitely not one of them.
Also, it may be worth taking into account that airplanes travel in straighter lines.
I fly a Cherokee 140. One of the most common aircraft, as with the Skyhawk. My fuel consumption is 8.4gal/hr at 75% mixture and 5.6gal/hr at 50%. Assuming I'm doing an average ground track of 100mph (for easy math), that's 12-18mpg (not counting that I'm 100% rich at TO and LND).
I wouldn't exactly call it fuel efficient, but it isn't burning like an oil refinery on fire either. I also don't pay $5 for gas ($4.09 today, but it isn't uncommon to see it at $3.50). But you do have to consider speed and time to destination if we're going to compare to cars.
One thing to also consider is that avgas is still leaded. And for anyone interested, here is the POH for the Skyhawk[1] and Cherokee[2]. Note that fuel consumption will be in hours or gal/hr when discussing aircraft. Mpg doesn't make as much sense.
[1] https://www.flyingd.net/documents/N739EF_172N_POH_000.pdf
[2] http://wilgroveairport.net/files/Cherokee%20140%20POH.pdf
Disclaimer: Use the POH provided with your aircraft.
Really all depends where you fly.
If you exclude GA aircraft not designed in the mid-20th century, you exclude 90% of GA aircraft and 99% of certified GA aircraft. We can make that distinction if you want but it ignores reality.
That's been true up until now, but this vehicle doesn't need to do that.
Also, most e-planes have a small motor in the wheel for taxiing.
>I'm talking about overall miles traveled so I'm not sure the straight line thing matters. Yes for the same trip you will travel a shorter distance in a plane.
I think you just answered your own question.
81% of energy produced in NZ is renewable. Complex terrain would make such vehicle a saviour. Plus, in any terrain planes almost always travel less, so savings are intrinsic.
Finally, using "taxi" name here is awful. At the most it's going to be an entertainment device initially (tourism and extremely expensive attractions are insane in NZ), method of access remote places later.
Your conclusion that we must have different value systems only shows where you stopped thinking.
We differ in the timescale on which we consider the betterment of human lives.
And we differ in the subset of human lives we consider the betterment of.
If you remain convinced we have different value systems, then it's not about energy or the betterment of human lives (or straw lives), but about placing a low value on short-sightedness and egotism.
It may be possible that this is something of a politically difficult problem in many areas, though. Until San Francisco actually allows itself to become a real city, we may be stuck looking at workarounds. It's very, very, very far from ideal. Exactly as you say. But it may be the best we can do for now.
Solar is becoming so cheap that an excessive amount of generation will be installed, so adequate generation will be available in morning or evening, or with clouds. During peak sun, excess power will be basically free, so any battery can be charged during these periods at little cost. Wait and see if skeptical.
I don't think anyone would stop a human-rights march because of energy efficiency concerns. And who cares about energy efficiency when the energy is clean? It's well-known that the US is trending greener and this electric taxi is years away from widespread adoption.
Second- I have a hard one understanding how this could approach the aerodynamics of a Cirrus. All those fans will be drag monsters.
And a little side fun note on rooftop landing pads- ideally, a high rise has expose cooling towers on the roof, taking up most available space. Any rooftop landing facility would have to be constructed over that, at phenomenal cost per foot. Developers expect to get repaid handsomely for that kind of capex. If you aren’t landing rooftop, you are landing at an alternate location X blocks away, which could be a real drag of the other kind..
There is DEFINITELY a market for this plane, and it’s bigger than current heli, but it’s probably not ubiquitous air taxi service
A chunk of a GA aircraft's operational cost is annual maintenance. By flying more per year, the operational cost of an aircraft goes down. I think you can get the operational of a Cirrus down to $100/hr if you fly it 500 hours per year.
However, operating this aircraft at scale would seem to have some real maintenance advantages beyond what you would typically see for General Aviation:
- There's only one moving part in an electric motor, vs all the complexity of a [edit: 6 cylinder] piston aircraft engine.
- You can specialize your people, procedures, and facility around a single aircraft type.
- You can swap out engines and avionics and work on them while the aircraft returns to flying.
And yes, this won't be as aerodynamic as a Cirrus, but it should be similar to a GA single engine aircraft, rather than either a quadcopter or a helicopter.
- I was just looking at the cost for me to take Uber across town. My experience has a lot of 30 minute trips in different cities, which has equated to $50 rides on UberX, and that is always between urban centers and airports (i.e. ideal connecting points). My assumption would be that Uber gets as close to operating cost as feasible, if not cheating on the backs of the drivers, plus Uber hasn't actually made money (but thats a different discussion!). So thats my $100/hr for an Uber. Never mind the fact that personal car ownership is far cheaper.
- With very limited experience with general aviation, I have chartered a few private flights- for around $4000 for a day trip on a late model KingAir. Not worth much for this comparison. But thats why I looked to Uber as the absolute low end, because the best economics of air travel will probably only approach the best economics of surface travel.
- I just don't know why Cora's aerodynamics wouldn't look a heck of a lot like a quadcopter. My background is Civil engineering (im a static kind of guy!) so i dont know much here. All those extra surfaces add a lot of drag, no way around it. I wonder if they could turn the props and feather them up so they all align and provide lift with forward flight? I'm sure Eric Allison (engineering lead) is on top of it.
Dont get me wrong, I think its great stuff and I look forward to its development. However, there are a lot more problems to solve than just perfecting the actual aircraft. Its a whole ecosystem, not just an air shuttle. Recent history has given us a few great entrepreneurs who have overcome a multitude of problems in their space, but i definitely wouldn't bet too early on something like this without a little more to show for it. The New Zealand partnership will be a good prooving grounds.
EDIT: im happy to be wrong on all this!
Transportation accidents are the leading cause of "unintentional injury" deaths (i.e., not disease, suicide, or homicide) [1]. Although the absolute rates are somewhat low (7.28 fatalities per billion miles for cars and light trucks), you are approximately 100 times more likely to die while driving than flying (table 2 in [1]).
Getting safer seems like it could be possible, but it's going to be an enormous amount of work.
But someone flying commercially, even in a Cessna is going to have quite a bit more training than Joe Pilot who flys 10 hours a year. A commercial and IFR certificate at the very least, and will also have to pass more stringent and more frequent medical exams.
But just because you aren't doing those things, doesn't make you any less at risk from other people doing those things. You are still on the road, surrounded by, in some areas, hundreds or thousands of deadly machines operated by people who are generally almost capable of handling them.
I just finished an excellent book on this, "A Deadly Wandering", which examines distracted driving specifically but also touches on a few other related subjects. In the primary case that the book follows, and in the few others it mentions, distracted drivers walked away from wrecks where they had killed innocent other passengers or motorists.
Being in a car (or bike, or motorcycle) on the road is one of the most dangerous things the average person does on a regular basis.
I understand that some people have very dangerous commutes, but for some it's literally 10 miles of traffic moving at <10mph 99% of the time. If that's your "driving" then the risk of having a life destroying accident is almost nil and it's probably safer than walking or cycling at that point(you basically sit for an hour in a metal cage that's barely moving, surrounded by other barely moving metal cages).
Yes, there is still a chance someone else around you could be drunk or speeding or distracted, but if you are sitting in an 8-lane jam that's not really going to do much damage.
Still not saying I'm narrowly avoiding death or anything, but man, the sheer volume of people going to work on the interstate every morning and night causes so many wrecks.
The operating costs for my SR20 with all things taken into account: Oil, Hangar Costs, annual inspection and averaged annual repairs, engine overhaul allowance are close to being conservative $160/hr fuel included vs. about $70 about it being fuel alone. From my calculations, if I went with a NA SR22, I'd be closer to $200/hr for a non-turbo, and about $260 for a SR22T.
Keep in mind, those hourly costs don't take into account the capital costs, depreciation and other training expenses required to operate the vehicle.
It's hard to compare costs of a vehicle to an aircraft. To drive to the airport, pre-flight the plane.. file a flight plan and deal with being re-routed the terminal area trying to get into a busy airport often undermine the time savings of just driving, unless i'm flying out of the state. I don't fly because it's convenient or faster. I do it because the feeling of watching the earth drift away from you when the plane is leaving the runway never gets old. I love flying. :)
One, comparing one of the most fuel efficient ASEL aircraft compared against one of the least fuel efficient passenger vehicle categories. Nobody uses pickup trucks for taxis. Nobody uses large SUVs unless you specifically request them (and they typically have a surcharge).
> Once it is in cruise mode, it is as safe as a regular small aircraft.
Well landing and taking off are the two most dangerous phases of flight. "Once you ignore the two most dangerous phases of operation, operation is as safe as you'd expect."
Not to mention that small aircraft/general aviation is not safe. Most life insurance excludes it. If you're under 140 hours TT and not instrument rated, life insurance that explicitly includes GA is prohibitively expensive (I received a quote at 80 TT and pre-IR for nearly $300/mo for a 10 year term on an otherwise healthy 30 year old male, comparable policies with a GA exclusion are $10-12/mo).
The most optimistic figures put GA roughly on par with riding a motorcycle without a helmet.
> An easy target for making these at scale would be $500,000 per aircraft.
Look up the cost of a new Diamond DA-20 or Robinson R44. There is no way you can build one of these things for less than $750k+ at cost so you're going to need to sell them at 1.5-2x that or more. And that's at scale.
And speaking of scale, what do you think the market for these things is? You're not going to be selling millions of them. Cessna sells a shitload of planes compared to the rest of the industry and they sell one factory new plane a week, almost exclusively to large institutional flight schools.
> Operating costs at scale, max $100/hr
I know "lol" is code for "I breathed through my nose a little louder," but this actually did make me laugh. Operating costs will be the 2-3 times this at scale. And 5x+ now.
I fly a single-engine plane with over 30,000 units in production (PA-28-181). They're everywhere. The lower HP version is a very popular trainer aircraft, and as such need to have low costs of ownership and maintenance, and high reliability. I fly this plane as part of a non-profit club and still pay $100/mo and $100/hr to fly a 45 year old plane with no autopilot, steam gauges and a carbureted engine.
Right, because the actuator disk loading[1] goes up, meaning that you're "throwing air downward" faster, with thrust scaling as v (momentum) while power scales as v^2 (kinetic energy). This is why propulsive efficiency decreases as exhaust velocity increases (for rockets this is simply exhaust velocity, while for air-breathing engines it's the change in velocity caused by the propeller/turbofan relative to the original airstream velocity).[2]
So bigger props are more efficient, because the actuator disk has more area. But the other way to add area is to add propellers. This has 12 props, so the disk loading is 1/12th as much.
The equation for hovering power is:
P = (mg)^3/2 / sqrt(2 A ρ)
>You also need laminar air for rear props to be efficient. The drag on the wings should create a ridiculous wake behind the aircraft. I would love to learn how KittyHawk are trying to mitigate these problems (which are huge constraints even for major players).
They showed CFD in the video, so apparently that combined with test flights and scale model flights (both shown on their website).
Notice that the propellers are rotated slightly inward, but the outer propeller (that rotates in the opposite direction) is angled outward. I suspect they're managing the vorticity of the propeller wakes, using it to lower induced drag (effectively creating a longer "virtual wing").
Also, it looks like they transition to horizontal flight and then shut down the rotors (or at least, dramatically lower the power). The video shows the hovering system shutting down and self-aligning the propeller blades into the airstream.
[1] https://en.wikipedia.org/wiki/Disk_loading, https://en.wikipedia.org/wiki/Actuator_disk
Energy efficiency is not all or none - it's a question of how efficient it is. Whichever way you dice it, the final result of the combination of energy density, thrust, weight lift, drag, is a plane is efficient enough to have a claimed range of 100km. If it were more efficient, it would have a longer range.
So an electric plane could be twice as inefficient in other ways (e.g. extra weight for batteries) and still come out ahead overall. And that's before taking carbon and pollution into account.
If a city takes two hours to cross in traffic, that's a clear sign it needs a subway or monorail.
I could understand why say, Lagos wouldn't have effective mass transit. But it's hard to see why major developed-world cities can't justify the investment.
Do we need more subways? Heck yes! I want one in my hometown. Do we want air taxis at the same time? Well, why not?
But it may find a niche market by being faster, cheaper, and easier to fly than existing light helicopters.
And as others have pointed out, helicopters are perfectly capable of autorotating in case of power loss.
Well, there's beaches near some coastal cities that afford survivable landings, but may be risky for others.
Last year there was a tragic case near Lisbon where two people on the ground died. It was a flight lesson with an experienced instructor, who followed protocol and landed on sand at the water's edge. (My understanding of the discussion at the time was that hitting water with fixed landing gear is an almost certain death sentence for the plane passengers, because it flips over instantly.)
Unfortunately, without power, the pilot missed a more deserted stretch and ended up in a section of the beach with quite a few people enjoying the summer at the seaside.
One of the reports in the Portuguese press: http://observador.pt/2017/08/02/avioneta-despenha-se-na-prai...
In my layman understanding: the heuristic amounts to - at low altitudes you flare and cushion, and at high altitudes you enter autorotation.
However, they've got a far better starting platform for doing this than anything else I've seen. It's made out of simple pieces with a lot of good options when things go wrong.
1) 15 minutes? If you flew in a small aircraft regularly, you would know it takes 40-60 minutes to prep a plane from park to airborne in zero traffic.
2) Estimating what the fuel consumption of a small aircraft will be is much, much harder than a surface vehicle. Consider 90% private aviation disasters are a result of pilot error. And 90% of pilot error is in fuel consumption estimation.
15 minutes? If you flew in a small aircraft regularly,
you would know it takes 40-60 minutes to prep a plane
from park to airborne in zero traffic
If there is unavoidable time consuming checking, you could do that in advance and provide the plane as an autonomous taxi. So it shows up, picks you up, drops you off.
Yes, but...
Things like "check your propeller for cracks", or "verify that the control surfaces are actually moving when the controls say they should have moved" should not be skipped.
But you can skip a lot of things just by virtue of this being an electric vehicle - like "visually verify fuel level without using the gauge", or "check oil level", or "test carb heat" or "verify dual magnetos" etc.
It takes 10-15min (max!) to check a Cessna 152, start, and call for departure clearance. Add on another 10-15min for taxi via the pumps & power+pre-take-off checks, you still have 30min left to play with.
I do agree with your main point that you don't just hop in and turn the key, just think that an hour for all that is taking your sweet time.
Also, with a computer flying, you can do something less extreme: actively and continuously manage the compromise between speed and efficiency. If your confidence of reaching your destination drops below the required threshold (say 99.999%), slow to whatever speed is required to achieve that confidence.
R22
Range 240 miles
Speed 110 mph
Price $250k
Range 60 miles (1/4 that of the R22, 1/20th of the SR22)
Speed 93 mph (half that of the SR22)
Price ???
Their first try: zee aero made a barely flyable contraption that was nuked by American FAA, and rightfully so.
http://wap.business-standard.com/article-amp/international/l...
This time, I don't see this being much better. My early childhood aspiration was aeronautics. I believe as somebody who built a semiflyable motoglider as a 15 years old in 2006, I can comment on technical soundness of this. Biggest red flag in the design are fans in front of the wing. Turbulence from them will be randomly stalling the wing, and most likely asymmetrically - which leads to a corkscrewing risk, especially with that huge elevator.
As for the noise, if it can land vertically, I can immagine it making a steep descent on top of a tall building, unloading passengers and then autonomously taking off to pick somone else some other place.
Imagine what you will, reality still exists. Some places have similar restrictions, some don’t - there are helipads all over Los Angeles for example.
A safer, quieter ‘air taxi’ is more likely to reduce restrictions than add to them.
I hear they have trains that can do this in far away lands. Trains that go 180 mph. Not in my backyard.
Electric cars have a long enough range and are mostly single family so swapping is less useful.
Reserve is a much larger issue, aircraft want to keep ~1hour of reserve these things are starting with less than that.
I am also wondering about the ergonomics for people who are mobility challenged.
On the plus side, their launch material successfully has gotten me past thinking that they are building quad copters for people into thinking about what they might be used for. The numbers pencil out for relatively short commutes.
Let's talk energy efficiency first. Once it's up in the air, it's has a similar profile to a normal single engine airplane. A Cirrus SR22 can go 1,200 miles on 80 gallons of gas. That's roughly speaking 15 miles per gallon - better than many pickup trucks or large SUVs. And that's while going 180 mph. Slower is more fuel efficient.
This aircraft is definitely going to make noise on takeoff and landing, but it's not going to make much noise while cruising.
The Dodecacopter/regular aircraft hybrid solves a lot of problems. Once it is in cruise mode, it is as safe as a regular small aircraft. Importantly, unlike a quadcopter, it does not crash immediately on loss of engine power - it can glide to a landing somewhere, or use a parachute, or land with its Dodecacopter rotors.
Unlike a rotor craft, this aircraft is very energy efficient while cruising.
The Dodecacopter side lets it take off and land in even more places than a helicopter. It looks like it has redundancy for any two rotors/motors to go out. If this happens on takeoff, you fly to an airport to land. If this happens on landing, you leave the aircraft on the ground until someone comes and fixes you. You skip all the transmission and cyclic complexity of a helicopter. This is going to cost a whole lot less to maintain than a helicopter.
In short, this has potential to be way better than either a helicopter or a small airplane. Even ignoring the air-taxi business, there's a market for this aircraft.
So let's flip to the business side. An easy target for making these at scale would be $500,000 per aircraft. (Might be able to half that, but lets be conservative). Operating costs at scale, max $100/hr, could be one quarter that.
On the revenue side, this would replace a two hour trip across a city in traffic with a fifteen minute flight. Unless you've flow small aircraft before it's hard to appreciate just how much faster it is not to use roads. There's definitely going to be some market for this - that's worth money.