One of the things that helped Southwest dominate in the short-haul space, particularly in the Texas Triangle, was optimizing "turn-time" with a target of less than 10 minutes to both deplane and board passengers (10 minutes!)[0]
I wonder how lengthy charge cycles will affect the viability of fast turn times, especially for the short-haul segments that they're targeting for these new airliners. It seems like they'll need to either have extremely fast charging or be prepared for significant downtime between flights; where will the planes be stored while they're charging?
It's important to both invest in and appear to be investing in the future, but even a soft commitment of 100 planes seems like quite a bit, especially in the very competitive and cost-focused short-haul space.
Battery swaps could be viable, barring some complications in gate infrastructure and airframe design. Obviously this would be impossible if airframe designers incorporate battery cells in structural members, as some suggest to offset the weight penalty.
I've said for a while that electric planes are the perfect use case for aluminum-air batteries. Aluminum-air batteries have up to 8x the energy density of lithium ion, but are not rechargeable, so using them only makes sense if you have a system to recycle the used batteries. This doesn't make a ton of sense with cars, because cars are constantly going from random place to random place, and having to include a stop at a battery recycling center every ~1000km or whatever would be impractical.
But planes go between very limited sets of known points, with huge amounts of infrastructure. Adding in the capability to do Al-air battery swaps / recycling would be easy, and the benefits for the use case (huge weight savings, faster turnaround times by swapping vs charging) are big.
Small tertiary airports often served by short regional flights don't have a lot of infrastructure. They have a couple of fuel trucks and a gate agent/security screener/baggage handler who might all be the same person.
So instead of a fuel truck you have a battery swapper.
You'll have to ship the batteries somewhere they can charge/reprocess, but you also need to ship fuel, so it's a 1-to-1 tradeoff (you can ship the batteries by land).
Not that much more (theoretically) - Al-air batteries could reach up to ~8kWh/kg, which is in the same range as jet fuel's 12ish. Aluminum is also denser than jet fuel, so per unit volume it could be even closer.
From wikipedia[0] "it is possible to mechanically recharge the battery with new aluminium anodes made from recycling the hydrated aluminium oxide". I've found a few papers regarding recovery of aluminum from aluminum oxides, but I don't have the background to interpret them with an eye towards that process's impact on the overall efficiency of the battery.
Production of aluminum metal from aluminum oxide is hugely energy-intensive. Aluminum plants often have an on-site utility-size power plant to provide the electricity. Is this same energy needed to recycle the oxide from the batteries? If so it seems like a non-starter, maybe unless it could be done with solar generation.
The real question here is the ratio of energy delivered over the life of a fresh anode as it is fully converted to aluminum oxide, to the amount of energy required to turn that same aluminum oxide back into a pure aluminum anode.
And that must and is changing. Green transport is predicated upon a green grid.
Additionally, a “wasteful” process, like electrolysis of water to make hydrogen, can be usefully inserted at onsite wind generation sites for when the grid isn’t requiring/buying vs sitting idle. When you see large wind turbines stopped and you know that there is a constant stream of wind at 50m above that ridge line it’s simply because the grid is not buying atm. I’m positing that aluminum air batteries are viable for aviation for the same reason.
There is no "recharging" an aluminum-air battery, you add the energy back through recycling (smelting) it.
One of the big synergies is with renewables: With the right industrial process, you can treat this smelting process as a way to dump excess energy in peak production times.
It's the same idea of green hydrogen. Only hydrogen allows you to use pipelines instead of physically hauling everything. You also don't have to worry about the battery physically gaining weight as you fly.
I remember 20 years back, hydrogen was going to be it. There were prototype cars manufactured, calls for hydrogen fueling stations to be built, everyone scrambling to get on the hydrogen train. Then it all just fizzled out. It was probably one of the promised techs I most wish had lived up to the hype.
Because aluminum-air batteries are not rechargeable, they're fundamentally inferior to hydrogen fuel cells (which work in nearly the same way!). At least with hydrogen you can refuel the airplanes with a liquid instead of having to use a physical battery swap. Also, even higher energy density that doesn't gain weight during flight.
The "more info" page on their website says they are ruling out battery swaps, at least for now, since a battery swap would require a mechanical certification every time it was done.
They are swappable though: they explain that used battery packs can be replaced and that used packs can be used for a second purpose with less stringent requirements. For example, an energy storage facility at the airport.
"Obviously this would be impossible if airframe designers incorporate battery cells in structural members, as some suggest to offset the weight penalty."
Why not do both?
Swap one part and charge just the internal batteries. But internal batteries does not sound so clever with limited lifetime anyway.
- the power you can get from the charger to the batteries
- the power the cells can accept
You can reasonably easily fix the first point with custom infrastructure, so the second point will be the limiting factor, and that one means that it always takes e.g. 20 minutes to charge your batteries, regardless how many you're charging (because with a bigger battery, you're simply charging more cells in parallel, at the same speed per cell).
That's part of what made high speed rail so compelling. When done well you can be on the train, sat down and moving in just a few minutes. No airport security, long ticketing lines, baggage check-ins or fuss at the gate. Just walk in, bags in the overhead, sit down and away you go.
I think high speed rail is compelling because of the speed and accessibility (which if built right -- looking at Japan) becomes an easy option for commute and transport between cities that is vastly more accessible than airports (Narita airport is FAR from Tokyo central)
The security check in, long ticket lines, etc. are all byproducts of security theater that has come through and honestly in the US, with TSA Pre, I'm pretty sure I spend more time sitting at the gate than ANY other process (check in, 5 min, security, 5 min, walking to gate, 5 min, sitting at gate waiting for boarding, 40 min)
100% agree that the ability to walk straight into a train, find your seat through multiple doors (even the wrong car) feels pretty good.
Well said though to clarify the reason why you wait 40 minutes at the gate is probably because you have to calculate some extra per each step leading to it. You can't be sure you'll make it in 5 minutes per check in, security and walk to the gate. Also, the added cost in time and money of missing a plane is quite high compared to missing a train e.g. in Europe, so that further increases the buffer you add to the process.
I've been reluctant to get precheck because I hate to give up my fingerprints. There have been a few infamous mistakes where they messed up like the Oregon lawyer thought to be involved with the Spanish train bombers. Being in software, I know many immigrants to the us and they all have precheck and the border check version - while me and many of my natural born citizens don't have it, at least partly for that reason of fingerprints. I solved that problem for now by not flying during covid ;-) Am I unnecessarily paranoid? Probably.
Applying for a US work visa or residency involves writing down so much about yourself (inc. getting fingerprints), that pre-check afterwards feels like just re-providing a subset of the same paperwork
Yeah this is a good point... I definitely don't want to miss my flight and now I have a really good and predictable handle on how long security and check in takes, but I never seem to have a good handle on how boarding will go (I usually just abide by the "domestic gates never close till 30 min before the flight earliest" rule)
With all due respect, if they had built airports in the middle of cities, we would all be complaining about why we had to take a taxi to the train station miles from the city centre.
The big advantage of the train is being on the property ladder 100 years early.
ok so my conjecture: an electric VTOL aircraft will mean cities rebuild airports. Of course it means Kitty Pride will be flying a Electric VTOL ...
But this will free up enormous tracts of land - the railways don't just use land for stations, but the railtrack takes up most of the land (in long strips as it were).
Imagine cities in 50 years, with rail land reclaimed, with Tokyo-like laws that prevent on-street parking (a valuable gift to car owners), freer flowing traffic, more walkable neighbourhoods. There is a lot to unpick.
I think you're overstating how impactful railway land usage is, in total amount it's definitely a lot but per suburb or area it's not much and it more or less sits next to the rest of the suburb rather than dominating it. It provides far more value than an airport in my opinion. I can walk out my door and 5 minutes on to a train then into the city, there's no way to get a plane from my house to the city.
What you really want to reclaim I feel is roads from cars, we devote insane amounts of land to cars, car parking, and car travel..
The city of Adelaide is an interesting example if you're interested, it's a young city and built an airport 4km from the CBD, which means the CBD can't have tall buildings, the airport has a curfew, noise is a constant hot topic, and it takes up more land than our CBD and most prized suburbs do. It's likely sitting on hundreds of millions worth of real estate, while the train station takes up less than a city block and then the rails weave their way through the rest of suburbia. The most recent Southern Interchange, a car highway interchange, takes up more land than the train station does including it's convergence and junction yard, and all it does is connect two roads together.
The city also tore up all it's rail network when cars took over, and now it can't afford to put the rail back in now that it's proven to be the more sustainable and pragmatic option.
>>> there's no way to get a plane from my house to the city.
I think I was drinking too much coffee.
But railway is just another road. In fact i suspect that we will find self-driving cars are too hard to put into the mix with human drivers and pedestrians. So we shall build / cordon off roads and end up with railways without rails.
If they use them to fly to and from tiny airports they might fly only a few times per day with enough time to recharge in-between (because there's no demand).
Since the planes themselves are really small, they also won't spend a long time at the gate so they could be transported to a maintenance hangar to recharge.
I think it’s more important. A wide body long-haul plane takes a significant amount of time to turn around w.r.t. many other aspects — more passengers, cargo/luggage, fuel, food, etc. the bigger the plane, the longer this takes. I’ve been on small commuter planes that turn around in 20-30 min, landing to take off. These are the planes that turn around quickly as there are fewer passengers, they carry less baggage, and you don’t always need to refuel.
If anything, these shorter routes are more time-sensitive.
Even if they don't have super fast chargers or battery swaps, I'd imagine the cost of longer turn times might be offset by the substantially lower fuel costs.
Electric airplanes are increasingly just gadgetbahns of the sky. None of the are even remotely feasible, and reading the comments here it's clear that even if they did exist they'd be immediately disrupted by existing airplanes. I think it's time we stop giving them any more thought as they simply cannot work.
LNA, an aviation industry newsletter, recently came to a very different conclusion [1]. The biggest difference to Wendover Productions's numbers is a hugely higher estimate in the cost of replacing the battery every 5-10 years due to battery degradation.
That sounds like a ridiculous assumption. Airplanes are basically guaranteed to not discharge the batteries lower than 20% for safety reasons. I’m guessing they’ll also not charge to fully 100%, like some BEVs. On fixed routes they could charge only what they need to get to where they’re supposed to go plus the required buffer for emergencies. The batteries will probably also be cooled. So it could be an ideal scenario for battery degradation. There are 10yo Nissan Leafs on the road right now that was pretty much the worst case for battery degradation.
You can also imagine that planes will start operating longer routes and then move to shorter routes as the battery degrades. Since the batteries are large they could get a decent amount of money for them when they’re too degraded for airplanes. They should still be useful for energy storage.
I also think it’s likely that when airplanes go mainstream, they’ll use a different chemistry than the standard Li-ion chemistries we have today. Maybe solid state lithium (Quantumscape?) or sodium ion. So it’s very hard to say how big the degradation problem will actually be.
Sodium ion doesn't really have major advantages over lithium ion and is heavier. I am confident aircraft will use a lithium-based batteries. I agree some sort of solid state chemistry is likely. NASA is also working on solid state lithium battery chemistries for aircraft.
> they’ll use a different chemistry than the standard Li-ion chemistries we have today.
I somewhat doubt it. The characteristics that make a good battery for a plane make a good battery for a car. I think the only place there's a difference is airlines are likely willing to spend more on batteries.
The cost of replacing a battery is about the same cost as a turboprop engine overhaul, and depending on the battery type and other details, it may occur less often.
Turboprop engines like the PT6 have a Time Between Overhauls of about 3000 hours, maybe longer. At 240 knots, that's 720,000 nautical miles between overhauls. If your electric aircraft has a range of 500 nautical miles and a 1500 cycle life, that's the same time. For an electric aircraft with a 900kWh battery like the Eviation Alice, and a cost per kWh of $170-$300/kWh, that's $150,000-300,000, the same as a turboprop engine overhaul.
Cycle lifes well beyond that are feasible, though, and battery costs are reducing over time.
So, by that article, a fully-loaded turboprop (let's say 19 100 kg passengers, 4900 kg airframe, 320 kg fuel, 308 kg reserve fuel) flying 200 nm weighs ~ 7500 kg and consumes just under 4 MWh of fuel, of which 1 MWh is useful work.
The battery model will weigh at least twice that for the same useful work, so how the hell does it fly as far? Could it actually fly the mandated 100 nm + 30 min contigency*
One thing to consider is that you save a lot of weight on noise insulation. The wavy edges on the back of many new jet engines make the engines about 2% less efficient, but they let the plane save on enough weight to more than make up for it. Electric engines are probably about 20db quieter than equivalent power jet engines, so that can claw back some of the lost range.
Not unless they’re using magical 1000-3000 Wh/kg batteries. I expect practical transports will use electric motors with hybrid power. And as far as I know, the ONLY electric airplane currently for sale is the two-passenger Pipistrel Alpha Electro.
I don't think you can cite the technology that has advanced most dramatically out of all the technologies to support some kind of rule that all technology inevitably advances rapidly.
Yes they'll get better, but they might get 10% better over the next 20 years or something like that.
Historical rate of improvement is significantly faster.
50% improvement in energy density over 10 years would be more conservative than most estimates, which range considerably but none I could find were worse than that:
I would say that the poster you're replying to is more directionally accurate than you are.
I read them as saying "transistors have steadily marched toward the theoretical limit in size, batteries will do the same for power"— and that isn't a 10% improvement from where we're sitting now. I couldn't tell you offhand what it is, but it's at least double density.
And it really depends on the chemistry. Some chemistries can last 10,000-100,000 cycles and so the battery may never need to be replaced in the life of the airframe.
One thing short haul electric aircraft have going for them is the regulatory requirement to have a 45 minute reserve. That essentially means that the battery will never be cycled to anywhere close to 0% but probably maintain at least 20% almost all the time. Combined with most routes probably using just 80% of the max charge, and the batteries could last an extremely long time.
Also battery prices continue to fall. Some industry analysts still use battery cost estimates from five or 10 years ago for something that will happen in 30 years (battery replacement).
Edit: looks like they’re using extremely high costs for battery replacement, comparable to costs about a decade ago and about 2-4 times current costs for mass produced batteries, let alone 5-20 years from now: “ The cost of replacing such a battery can be projected to reach around $400 to $500 per kWh mid-decade.”
The FAA regulations don't require just a 45 minute reserve. They need to be able to fly a missed approach at the destination airport, then fly to the alternate airport and land, plus still have a reserve.
Fuel isn’t. Jet fuel is basically no more expensive than diesel and sometimes cheaper (no road tax). You can consider batteries basically like jet fuel.
In Norway jet fuel costs like 3 times less than gasoline due to absence of taxes. For these reason some amateur flight school use small planes with jet engines, like DA40NG, to get much lower operational costs. It can be even cheaper to fly such plane than drive a car.
ridiculous quote of $/kWh of batteries, poor analysis of degradation which is way more complicated than they assume, also you should understand that soon carbon will have a price, airlines won't have a freeride forever
Anyone get a weird feeling about Wendover? I used to think he was a decent authority until I watched his channel Half As Interesting.
Maybe he hires a writer, but his sarcastic joking nature comes off as extremely sincere and authoritative. This makes me question how solid his Wendover points are. He has a commanding voice and we believe him.
I suspect it was in jest, but the reason why is that he is obviously immensely passionated about aviation and logistics. He makes really, really good videos about both, I'd recommend his channel to anyone.
PS, I had to vouch for your comment to reply, as it was dead. Had a look through your profile… I think there's often a lot of value in asking simple questions, but a lot of your comment history is just extremely low value (eg. correcting people's spelling). If you don't have anything meaningful to add to a discussion, maybe consider not replying at all.
It was indeed in jest! Wendover's videos have been consistently increasing in quality over the years. The amount of research that goes into each one is phenomenal. So much so that lately if I ever come across any aviation topic on the internet, there's already a Wendover video about it. :)
The only reason I pay for youtube premium is for creators like Wendover, Extreme Engineering, Smarter Every Day, etc. There are a lot of independent science, economics, and history channels there that are too good for YT but depend on the traffic for survival. Some have made attempts to switch to other platforms like Nebula but they dont have the mass yet.
I do have a Nebula subscription, and Wendover is part of it. I like the fact that Nebula is partly owned by the creators themselves, and a significant part of Nebula's revenue goes directly to them.
I had a Gell-Mann amnesia moment when their video about electric car charge infrastructure made some major errors about electrical engineering. But their videos do generally feel exceptionally well researched, especially by YouTube standards.
Small aircraft on short routes are quite a niche market right now, but electric aircraft have a very good value proposition there, reducing both fuel and maintenance costs drastically.
Depending on how things work out, in 10 years we might see a lot more flights in 10-30 seat electric aircraft, e.g. as connecting flights to tiny airports.
For me only if we figure out how to shorten airport time. Otherwise train in europe is easier - and usually located directly downtown or close instead of an hour in a car with traffic.
Small aircraft can operate from regional airport which are much, much faster to board and disembark from then the large airports that behemoths have to use. I really don’t understand all the hate for a smaller electric aircraft. There are tons of advantages, and the difference in pilot labor costs are practically trivial. (I think a big driver for larger aircraft had been reducing number of engines per passenger as jet engines are expensive to maintain and the larger ones are also more efficient, but this isn’t really applicable to electric motors.)
If? Spain has security checks on major train stations which makes it slower than in other countries but still way faster than airports. Trains have way more doors for example and it is easier to get a timeslot to leave than it is to get one to taxi.
Trains take a lot more time, even HSR. I'm going to Madrid in the near future and I don't think I'll take a train, it's at least 6+ hours, and most of it is HSR.
How long is the flight in comparison? And have you factored in the airport time into that?
I was looking at taking the Eurostar from London to Amsterdam, and a friend was dismissing it as it took 4 hours where as the flight is ~45 mins. Except its not, the flight its self maybe 45 mins, but you have to get to heathrow (which is further away than St Pancreas) plus get there an hour early. Then we would have to deal with Schiphol and getting to the center of Amsterdam. To me the prospect of spending 4 hours sat down on the train and arriving directly in central Amsterdam, all the while with more space than a plane is much better than the prospect of 4 hours of that.
Now obviously that's a very niche case, and for most people it doesn't make as much sense, but I think people get scared off by the long train times but ignore the extra time needed around the flight.
I don't know, but my city airport is small, so it's pretty much arriving and boarding. Now barajas is another history but I doub't ill be there for much more than 30 mins.
It also depends on train stations being accidentally close to where you depart/arrive. Most people don't live closer to a large train station then to an airport, I'd think.
The train station in my city has 80 million travellers per year compared to the airport which only has 27 million. And while I do not think many train stations have been built since the 1950s many have been expanded.
Definitely not in Germany. There are lots of medium to large cities without an airport, but every one has a large-ish train station with decent connections.
Due to the nature of the two, train stations are usually in the center of cities, while airports have to be quite outside.
Also, in my experience there are usually more than one train station in larger cities but even smaller ones have them. While airports are only a few even at a country level.
I don't know what you mean by "large" then. In the context of this discussion, I meant train stations served by high speed rail and airports with regularly scheduled commercial service. The former vastly outnumbers the latter in continental Europe.
I dont think that's true at all. Train stations in Europe are far, far more common than Airports. You may have to change rather than a direct train, but chances are you can get around pretty easily.
Trains are great in many cases, but there’s some limit to tunnels and bridges: you can go from Stockholm to Berlin directly, but Stockholm to Helsinki is harder (that’s actually the destination that the plane is likely to cover); Manchester to Amsterdam is feasible by train in theory, but given the constraints around London and the Channel Tunnel, unlikely to loose its flight connection. Same for Aberdeen to Oslo.
Many of those are over seas, so an ekranoplane would make sense, if you want to lower the energy output, but a tradition train won’t work for many cases.
Manchester to Amsterdam is further than the distance targeted by these first electric aircraft, getting between a runway and a gate at Schiphol is probably beyond their range too.
Helsinki - Stockholm has too many travellers for a 19-seater. :)
Planes like this will most likely be used for routes from very small local airports to larger regional ones. I'd guess it's more likely to cover things like Rønne - Copenhagen, or Mariehamn - Helsinki.
I wanted to love ekranoplanes, but although they have greater lift for a given span, they don’t have superior lift to drag ratios, which is what limits efficiency.
You could imagine a propulsion or even a lift mechanism closer to what is used for a hydrofoil. Modern sails or kites could improve the propulsion and handle the drag better.
I feel like we can make fast trains really worth it, but it makes the few connections I mentioned under-supported if you want to remain below a certain carbon footprint.
That certainly limits their universality, but you can imagine a network of fast trains when there’s ground and boats, or something faster on sea, when there’s none, to substitute to flying.
Ekranoplanes use the ground effect, which requires to be close to a flat surface, indeed, but the larger the place, the further you can be. Something the size of a 747 could be a couple dozen meters above the waves and fly smoothly above moderately rough sea.
Every time someone points out how we “have trains already” it makes me think:
It’ll take less time to have operational electric passenger flights than it would to build a new high speed rail route. Particularly in the US (Europe is admittedly much better than the US in that regard).
Small electric planes do not fly as fast as the current passenger Jets, theor speed is going to be comparable to a high speed train.
In fact i'd say europe could avoid airplanes entirely if it could sort out it's rail network, but, alas, going from Londom to Prague I'd have to change like 6 trains. You have to cross many different national signalling systems, gauge sizes and ticket offices.
Track gauge is the same all over western and central Europe. And Europe is slowly but surely moving towards ERTMS/ETCS() for train control. Different voltages and frequencies are a problem but less than in the past thanks to modern electronics.
That seems irrelevant as that electricity could be collected and used whether or not it is used for planes. So while that may be a good idea it has little if any influence on whether or not it makes sense to use electric planes.
But they could equivalently sell the electricity and buy jet fuel with the profit. Sure, the margins are slightly worse but it doesn't significantly change the equation.
Potentially they have about the same cost profile as a taxi over the same distance long term. Low noise also means access to smaller and more conveniently located airports. Initially, the novelty value will mean high demand, pricing, and relatively low cost compared to flying a small traditional plane. So great business opportunity if you can get a few planes.
I recently had a pie-in-the-sky business idea and I would love for someone who knows more about the industry why it will definitely fail. I assume it's unworkable for a lot of reasons, but it is just plausible enough to be a fun idea for a sci-fi novel.
Get a fleet of 2-4 seater unpowered glider planes [1]
Get a bunch of rural properties spaced ~100km apart.
Put little glider landing and launch strips on each property. Use a powerful electric winch to launch the gliders.
Develop software that can fly the planes autonomously from strip to strip (I assume this is the really hard part, but I am under the impression that autonomous flying is a much easier problem than autonomous driving?).
You now have the ability to shuttle passengers around your network of airstrips at ~200kph for the cost of electricity used by your winches and maintenance of the glider fleet.
My thought is that the electricity of the winches is pretty minimal and could be served with some locally installed solar panels and batteries, and the maintenance is super low since the gliders don't have many moving parts onboard.
The main use-case would be city-to-city short hops that are currently poorly served by rail. It's far easier to build a string of small airstrips than a whole rail corridor.
This idea came to me when thinking about SpaceX's recent plans to catch their Starship boosters out of the air instead of having landing gear on them. The reasoning is that you can have essentially unlimited mass for ground support equipment, but mass on the booster is precious. So you offload the landing gear from the booster to the ground support equipment, even if it's big and complicated. This idea is like electric aircraft, but you've offloaded the propulsion and batteries to the ground support equipment.
Here's a simple test I use on startup ideas. I call it the reversion test.
Let's suppose for a moment that air travel today worked the way you described it, with gliders, 60 mile range, electric winches etc.).
Then someone comes along and invents the motorized plane and now all of a sudden you can start and land a plane pretty much anywhere you want, you're no longer dependent on weather and, in addition, you multiply your range by a factor of 5x to 10x.
To me that sounds more disruptive than the other way around, so your idea would unfortunately fail the reversion test.
A winch gets you maybe about 1/3 of the cable length (and thus strip length) at best. A typical cable length is between 1 to 2km long. Let's say you can gain 500 m height. A glide ratio around 50 is probably on the higher end of what's achievable, so you're looking at 25 km of range. That's before you account for wind, that the world is not flat or the fact that you don't start your landing at 0 m, but more like 200/300 m from the ground.
Honestly, for short ranges, you're much better served by electric planes, or gliders with a self-launch motor. Small strips and winches don't go together.
You can get almost infinite range on hot days by riding thermals.
This assumes thermals are available in the area (some days are better than others, as are some locations), and the s/w knows how to ride them.
But that is a much harder problem than just launching and gliding.
Also, gliders that could carry even a handful of passengers + baggage would be huge, and likely far too heavy for a simple winch lift.
As for the automation - airliner flight is more or less a solved problem, for flights in good weather that don't suffer any emergencies.
It hasn't been taken further because most passengers don't want to fly without a human in charge. And also because the edge cases - unexpected turbulence, difficult weather, mechanical failures, unruly passengers, software failure - happen often enough to be a problem, and they need someone trained on board to take over.
For context I have a pilots license and have tooled around in a glider a few times as well.
Some problems with this scheme come to mind quickly but these are the first few:
1) Weather. It exists and basically makes this plan totally unworkable on any practical level.
2) Physics. An unpowered glider would have at best 1/100th the potential energy to fly distances like the ones you describe assuming perfect weather. Remember there are hard limits on altitude (due to oxygen) and speed (need to not rip the wings off) and those plus weight are the variables in your equation that tell you how far your glider can get unless it’s able to exploit unpredictable thermals.
3) Refundancy, or lack of it. The failure mode for the slightest miscalculation is certain death for your passengers and maybe a few on the ground. Unpowered flight leaves essentially no margin for error which makes it a non-starter.
Not familiar but like the spirit of the idea. At first glance from just the material you provided it'd have to be a lot closer than 100km apart, 30:1-40:1 seem to be typical ratios with 70:1 being cutting edge and winch launch height seems to top out at 3000 ft (less than 1km). Not to mention for a lot of travel the ground isn't flat which can be problematic even in the direction there is an average decrease in ground height.
Flying in good conditions may be an easier problem to solve than driving in good conditions but the issues seem to move towards what happens in the bad conditions. It's not like you can just hit the brake or park on the side of the road and continue later when the system detects a current or upcoming problem. Even if you get it so 99.99% of flights are in favorable weather and wind without piloting issue a 1 in 10,000 chance your glider is going to make an emergency landing or worse is not good enough odds, especially if it's multiple flights each way. And that ignores the problem of the service being unavailable if certain weather conditions aren't met, so the backup transportation option is still needed at a moments notice in full force anyways.
Then, much like self driving, there are the regulation issues https://www.ssa.org/glider-pilot-ratings/ which would be their own challenge to change and require you solve them before the business can even get it's chance to get going.
That being said I like the concept, just not sure it's really any easier. Perhaps we should just build the missing rail instead :).
> Develop software that can fly the planes autonomously from strip to strip (I assume this is the really hard part, but I am under the impression that autonomous flying is a much easier problem than autonomous driving?).
As a software developer, this part is what I don't like.
We're still quite a ways from fully autonomous driving cars (as in: don't rely on a human taking over for backup). A bad bug in an autonomous car could drive you at high speed into a wall, but there can at least be an "emergency stop" button that disables the main processor and jams on the brakes.
Planes have no such ability to just "stop". At best, they could deploy a parachute, but even then landing safely is by no means guaranteed.
I think we need a decade or so of fully autonomous cars being accepted into daily life before this can be attempted with anything that flies.
We're (much?) closer to Fully-Self-Flying planes than FSD cars because the problem space is - perhaps counterintuitively - MUCH smaller to tackle. And we have a lot more experience tackling it.
Additionally there could easily be remote pilots as backup in case of catastrophe (See remote piloted military and border patrol UAVs)
As an industry leader on this specific subject matter... I agree: the problem space is much smaller, in theory.
However, certification requirements and safety assurance needs will drive both cost and time into realizing fully autonomous aircraft. They will be here, but we are 10-15 years away.
The problem is in how to certify machine learning code. Today, you can't. Existing AMCs (accepted means of compliance) are incompatible with the nature of ML. (The breakdown is specifically with assurance architectures focused on code traceability and coverage.) A new architecture for demonstrating safety assurance with AI/ML is needed, and is being built, but is still 1.5-2 years away from being released, and then it will take another year or two before a CAA (civil aviation authority, like the FAA or EASA) will certify a component with ML code--and that will not be an autonomous pilot. That will come in time, but the industry is conservative--especially on safety-critical matters--and it will take years to develop trust in both technology, human factors, and methodology to work up to autonomously flown passenger aircraft.
From the regulator perspective, EASA has taken poll position in thought leadership. Google their AI Roadmap or their Concept Paper for Level 1 Machine Learning Applications.
Point of information; certified autoland systems appeared on airliners in 1968. Yes, we're a ways off from the level of automation for a fully pilotless system as proposed here, but I think it a matter of a few years, perhaps a decade.
You know what they say- the last 20% of the problem is 80% of the effort. I think that these percentages probably understate things, but the point is that getting something to be mostly functional in ideal circumstances really isn't much of an achievement.
-- I don't know of any glider mass-produced after WW2 that seats more than two individuals, ± a water/sand ballast tank, ± a range-extender or self-launching engine.
-- Have you ever experienced a winch launch? Try it. It's about 3g of acceleration, sometimes more. I quite like them. Most normal people probably wouldn't.
-- At the top of the winch launch, you pretty much need to immediately find a thermal and gain some height before flying off cross country. You've got about a minute or two to do so, before entering the circuit and needing to re-launch and try again.
-- Replace "200 kph" with "about 80 kt IAS". Remember that gliders fly beneath the weather 99.9% of the time and the winds in clouds are strong -- although the only youtube videos I've seen of an aircraft landing "backwards" on a runway are of a Russian high-wing aircraft, it's entirely plausible that you could end up getting a negative tack speed in a cloud.
-- Cloud flying, or flying in inclement weather is insanely dangerous for a glider. They're relatively light, have large aspect ratio wings, and don't usually have a whole lot of instrument navigation equipment on board. If the wings are wet, their coefficient of lift goes down...which would have very bad consequences for your business model. There's a reason that cross-country glider pilots have a friend with a land rover and a trailer, and train to land in fields, after all.
-- You have absolutely no opportunity to make a go-around in a glider landing. Zilch. Nada. Screw it up and Plan-B is a well placed field. This is less likely to be acceptable commercially.
The problem is rural areas are not cities by definition. So you'll drive out 30 minutes to a rural airstrip, fly out to another rural area in a 30 minute flight, then presumably rent a car in the rural area (build an Avis there I suppose), and drive 30 minutes to the other city. Including time for transitions, checking in, and paperwork, it's maybe 2-2.5 hours for 100 km of travel. You could maybe take rideshare, but if this is truly "rural" that might not be an option. Have you ever tried getting an Uber to take you 30 minutes outside of a city? I regularly drive such distances on the weekend in 1 hour. The overall idea of travel between cities is what air taxis were for: https://en.wikipedia.org/wiki/Air_taxi but it was for distances of 200-500 miles.
The energy would probably be better spent on a bus, with even a gas-powered bus being more efficient per passenger-mile than a 4 pax aircraft. It could also go city to city and skip the rural areas altogether.
This has a lot of physical issues, not least of which is air resistance (drag). Simply launching a plane off the ground does not impart enough energy to make the full trip at high speed, and airplanes must continually burn fuel to counteract drag and gravity.
Gliders are able to bypass this limitation in certain scenarios (such as updrafts) but this only works in specific cases. It also usually takes more than a launch to bring them to sustainable altitude, and they are slow.
Electric aircraft (not necessarily gliders) could use a tethered assisted take-off and ascent as a way to save on the initial power draw. You probably would want to use another assistant plane (not a ground station) to pull the passenger plane to altitude and speed and then return to a runway while the other continues on it's longer flight.
Gliders don't launch by winch. They are towed up to launch height by powered planes.
Also, gliders are not really able to handle emergencies that well since they are unpowered -- if there's a need to divert or something, they're completely at the mercy of their own gravitational energy. Gliders are usually very safe to fly in because they're very light and maneuverable, and crash-landings are usually OK. That safety net completely evaporates with thousands of pounds of human cargo.
>Develop software that can fly the planes autonomously from strip to strip (I assume this is the really hard part, but I am under the impression that autonomous flying is a much easier problem than autonomous driving?).
I guess it could be easier in some ways, still the idea of passenger UAV(?) seems insane for some reason
This me reminds me of Canada's joke political party : the Rhinoceros Party.
They proposed stuff like putting steroids in water supplies to make Canadians stronger. One of their propositions was to build an inclined bike road across Canada so you could "coast from coast to coast."
Totally possible, though I was under the impression that the UAVs used by the military already land autonomously. But I agree that the autonomous flight part is almost certainly the hardest part here.
I am mainly curious if the general physics and economics of the idea are remotely feasible, assuming the software is solvable.
I would expect handling all of the edge cases is the hardest part. For example, there is an emergency of board and you have to land immediately, what do you do?
Digging through their website[1] trying to figure them out. Seems to me that the whole business proposition depends on their understanding that Norway, Sweden, (and I guess they expect others to follow) will mandate all short flights being electric in the next decade.
They also say turboprops are higher maintenance and this expense reduces the viability of short flying routes, and I guess their implication is that electric will be cheaper. I am not sold on that one. 95% of the maintenance cost is the routine inspection. You'd have to do a routine inspection on electric propulsion as well. This is all just speculation until you see it in action.
Gas turbine engines have critical components which can have gradual failure (fatigue particularly, and creep) which need regular inspection to catch small defects before they grow to critical size. They also have large numbers of high-temperature, stressed components.
Electric motors are generally much simpler in construction and wouldn't need nearly as much mechanical inspection.
The difficult/expensive part is the battery, but that's going to have more onboard condition monitoring and will be simply replaced periodically, not subject to regular teardown inspections. The cost of ongoing battery replacements might be significant, though.
95% of daily maintenance costs. Overhaul costs of jet/turboprop engines are considerable, several hundred thousand dollars per engine. A reasonable operating budget is about 1000$/hour per engine. Electric engines should avoid overhaul costs, and the fuel costs would be practically zero.
Interesting that the routes they name are 119 and 78 miles.
Kinda surprised Americans have flights so short. But then again the aircraft might beat CAFE for a vehicle with a single driver in it, plus aircraft usually carry a load of cargo too, as the passengers pay for the plane to go somewhere and the cargo is the profit. Wonder how much cargo this elegy plane can carry.
It's all connecting to bigger flights. Plus 78-119 miles means either paying a lot of money for a cab, paying gas & parking fees for the duration of your trip at the bigger airport, or asking a friend/family member very nicely to take that trip to drop you off/pick you up. The smaller cities in question for these routes aren't going to have any sort of usable bus service for making a flight on time.
To answer your cargo question: probably not much. The distance is within a normal delivery range of some rural UPS/Fedex/DHL routes. Making people in these smaller cities go to the airport to pick up boxes just makes a lot of work for them.
source: my own experience taking loud proppy planes between Roanoke VA to Charlotte, NC to connect to a larger flight
> Plus 78-119 miles means either paying a lot of money for a cab, paying gas & parking fees for the duration of your trip at the bigger airport, or asking a friend/family member very nicely to take that trip to drop you off/pick you up.
A small city would be essentially destroying its own airport by authorizing a convenient rail connection to a nearby bigger city’s airport.
Example: there is a train between Milwaukee and Chicago and it stops at MKE, but it will never stop at O’Hare, because that would be the end of MKE.
Technically you can take the Blue Line from O’Hare to downtown, making dozens of local stops, and then walk a few blocks with your luggage to Union Station, but by the time you get downtown you could be in Milwaukee already on a connecting flight. And those few outdoor blocks are a big deal in winter, dragging soft sided luggage through the slush is not fun.
This. People tend to grossly underestimate the expense and effort to build new rail tracks in an industrialized country. Most land is owned by someone already, there are environmental concerns, other (rail-)roads and generally obstacles must be crossed, and -worst of all- you have to repeat the process basically for every single town you want to connect.
Side remark: The same holds for roads, of course, with the notable caveat that roads form a flexible network automatically. Planes are just superlinear in their flexibility: If you have n airports and add one more, you get n new connections.
A a route that serves a few hundred passengers a day is also potentially profitable for an airline while a train would likely not be unless there's existing infrastructure that can be leveraged. Also, if nobody needs that route to be served any more, just send the plane elsewhere.
Edit: I'm an idiot and missed that these are 19 seat planes. No, a train that only serves 19 people a day, one way, has a zero percent chance of being profitable, and I doubt it even makes environmental sense if you have to lay 70 miles of track to support it.
For 19 people on a 100-mile route, they may as well schedule a bus.
(For example, my parents would take a direct bus a similar distance to Heathrow or several other airports. It saves parking costs and driving while tired.)
Also there are a fair number of smaller cities that have physical obstacles (mountains, bodies of water) between them and a major airport. I used to fly with a connection between Chicago and Grand Rapids, MI regularly. That's a 50 minute, 220km flight, or a 3 hour 315 km drive (assuming no traffic). Plus, embarking/disembarking at a smaller airport lowers total time as well.
I actually think you the cargo aspect will be somewhat significant as well- The regional airports I checkout on flightaware appear to have several fedex/UPS feeder flights a day.
True, but if you don't have a car and are going downtown to downtown, it's probably faster to take a train or bus, given that it takes almost an hour to get from downtown Seattle to SeaTac by transit and a shorter-but-still-nontrivial amount of time into Portland on the Max on the other end, plus ticketing, boarding, etc. I think it really only makes sense if you're connecting.
There used to be commercial flights from United from OXR to LAX. It’s only an hour drive but they still managed to have service for quite some time and there’s been talk about bringing it back. Little connector flights like that could help reduce congestion at LAX. I could easily seeing electric flights returning and even being subsidized.
They talk about regional flight. Does anyone have any sign that battery-powered planes carrying a hundred people will cross the Atlantic, Pacific, or the U.S.?
I originally thought since we engineered from the Wright brothers to 747s, aren't we just at the Wright brothers stage now, but am starting to conclude it's not possible.
I don't have such a sign, but 100 passengers is still smaller than what current jets do, so it might be possible.
It would be a radically more efficient design than what we currently have, though.
Before we can even think of long-range flights, let's consider mid-range:
A 737-300 has a range of ca. 4000km from 20,000l of fuel. But that's not flying with full tanks all the time. It has a payload capacity of 17t (on top of passengers, I think) and carries up to 149 passengers.
If we cut the payload to 10t and passengers to 100, our "comparable" electric plane has 10t free payload for batteries (3t for the 50 passengers and 7t from the reduced payload). If we, generously, assume that we can add another 10t as "structural batteries" (basically, building the airframe out of batteries, because, why not, but also smaller and lighter engines), we end up with maybe a total capacity of 40t for our batteries (assuming 1kg/l for the jet fuel). We need the energy for a mid-range flight, say 1000km. That would be about 5000l of kerosene, in a 737 (not completely true due to weight loss during the flight). Fortunately, our electric propulsion is probably much more efficient (thermally) than a turbojet, so we might only need about 2/3 of the same energy. That puts us, very roughly, to the equivalent of 3.333l of kerosene, or about 86GJ. Hence our battery would have to offer 3.6MJ/kg.
This is inside the theoretical realm of a zinc-air battery. So with this very rough calculation it does not seem to be impossible to achieve mid-range battery electric flight. And this usually means it is going to happen whenever it is economically sensible.
For long-range flight, though, we would need even better batteries. Like, at least 4 times better. This is not on the horizon, currently.
The Youtuber Real-Engineering (aerospace engineering background) has a good video discussing the viability of electric aircraft. Barring some dramatic revolution in battery energy density, electric aircraft beyond a certain range are simply not-feasible. They are very feasible for short-range routes though.
I think the caveat here is "battery powered electric aircraft." Fuel cells have much higher energy density IIRC.
It's not inconceivable that fuel cell electric planes could become a thing as well, especially if these early BEV show other benefits around maintainability, noise reduction, etc. I think its a long shot though, as jet fuel + carbon capture will probably be price competitive before fuel cell airliners become a thing.
As others have mentioned, the energy density is a big deal because those planes' fuel accounts for A LOT of their take-off weight. To both illustrate this and point out another potential problem: when a fully fueled heavy, long-haul / high-capacity airliner needs to make an emergency landing shortly after take-off, one of the first things they do is start dumping fuel to reduce the weight (make it more maneuverable) and reduce the fire risk of a crash. Not sure what a comparable procedure for batteries might look like.
An A380 at MTOM has about 15% payload (pax, cargo) and about
40% airplane, so a full 45% fuel. And kerosene has about 30 to 90x the specific energy (energy per mass) as current batteries, so for an electric airplane the numbers would be much worse. (Plus the Airbus doesn't have to carry the fuel it has burned, while an electric plane does have to carry the empty batteries.)
TLDR: Long range air travel with batteries is a long time off.
For sure, you're right that compared to a jet engine there are fewer parts. The caveat is you're comparing a large engine (and aircraft) with a much smaller one. Electric aircraft of today can't go anywhere near the range of jet engine powered aircraft, and hence the engine sizes are similarly sized. It's not a fair comparison, but you are right.
It highlighted a few Bay Area startups. Sounded like smaller commuter planes would be first. There were also hybrid designs, which reduced fuel use significantly.
Green aside, this was an interesting video explaining that for short flights electric planes are extremely lucrative https://youtu.be/aH4b3sAs-l8 [wendover]
vs. ejecting batteries turns the aircraft into a bomber. The Air Force drop fuel tanks from some aircraft but I have no idea how much trouble they get into for doing that. [1][2]
Good point. The Dreamliner has such problems in its Li-ion batteries to the point that the weight savings due to composite construction was subsequently nullified by metal retrofits to contain battery fires (https://en.wikipedia.org/wiki/Boeing_787_Dreamliner_battery_...). Additionally, IATA has put strict limits on Li-ion cargo due to Lithium being too reactive, so any plane with Lithium batteries must consider that.
That could be more of a problem. Regardless of the height, dumping a battery means a projectile falling, which could injure someone or cause property damage.
If fuel is dumped high enough, it pretty much evaporates and doesn't fall to the ground. If the plane is low when it dumps fuel, it can hit the ground and bystanders; but, it's not going do much, if any damage. (Assuming it doesn't hit someones barbecue or a smoker.)
Batteries could be used as part of the structure itself (similar to the transition we made from separate fuel tanks to simply putting fuel in the wings). That saves a lot of weight.
Note that they have agreed to buy them "conditionally… once the aircraft meet United's safety, business and operating requirements." The 2026 number in the title is probably without meaning. Nobody's meeting those requirements just yet.
Someone is. What is very interesting about Harbour Air's approach is that they are not creating new aircraft but rather retrofitting electric propulsion onto their existing fleet. This is not an electric engine filling a niche application. Rather, this is electric replacing combustion engines on very longstanding commercial routes.
"After the successful first flight of the Harbour Air eBeaver powered by magniX in December 2019 and the ongoing flight tests since then, the companies have teamed up with H55 to bring their shared vision of clean, efficient and quiet commercial aviation to life by 2022. H55 will provide its proven modular battery technology to expand the eBeaver’s balance to weight ratio and endurance. The company’s battery modules have one of the highest energy densities on the market and will provide the entire energy storage system and redundant battery monitoring at the cell level for the eBeaver. "
The eBeaver is about as relevant to conventional air travel as the existence of electric milk floats and forklifts was to ground transport for the past 50 years.
I take it that you have never been to Alaska. Or BC. Or Washington. Or anywhere else with more trees than people. Without bushplanes the entire resource extraction industry would grind to a halt. The conversion of a Beaver to electric follows on the past turbo-beaver conversion. It matters and is being watched by the industry.
In the 1990s, the idea of electric RC planes were ridiculed as well. I am moderately optimistic that 1:1 planes will eventually follow, as RC electric cars became "good enough" and 1:1 electric cars are a reality now.
I had an electric RC plane in the mid 90s. It wasn't much, just a styrofoam body and pair of electric motors (no flight controls) but it was a cheap and functional RC plane.
Nice info, P and GP!
I built a RC buggy car with lipo batteries; it's amazing how quickly it goes, and how well we've suspension etc works. Sadly most of the time was spent on the build, too hard to get to the local track with family and such, but still a great experience. It's just so quiet compared to the nitro ones too.
Goes to show if you want to get somewhere, first you have to start. The other top trending thread on making a bit of progress every day comes to mind, it's amazing how far we can get over a long period of constantly making small improvements.
This means much less efficient flight, because lift costs energy, or much slower flight. But it's more plausible for these very short flights than for longer flights.
Solar-powered synfuel seems like a more likely mass alternative for the near future (02030-02050).
I was professionally close with an engineer who used to work on a (rapidly dwindling headcount) team responsible for the programs and related QA for mission critical flight safety systems. Think one of the big manufacturers.
The eng dealt with:
The standard was scripts with mutable variables such as `G == , B == , C == , redefine G as something else later` responsible for the processes around pretty critical airplane innards.
QA down to 1 or 2 headcount, and those 1 or 2 also doing the above program writing.
Zero hand-off once leaving the job on the mission critical QA the eng was responsible for, not for lack of effort on the engs part. Managers not aware the eng was leaving until day-of.
I could go on and on, but the point: I'm not sure how I feel about the safety of airplane travel after the above, but at least the engines were internal combustion so somewhat tied to physics vs. programming logic. A future with electric airplanes scare me a bit though. The software in them is aggressively, poorly done. I know airplanes are designed w/ fail-safes on the fail-safes and that eng had their own limited view of a complex system. But, it was bad.
Most of your point is well made, but electric engines are just as tied to physics, unless I'm missing something? Doesn't mean quality of the control software is still not concerning.
I think what they're trying to say is that the types of electric motors used in vehicles (like switched reluctance motors[1]) typically require a computerized controller that someone has to program, and therefore has an additional point of failure from a software standpoint.
However, I'm pretty sure any modern internal combustion engine will have a highly advanced ECU computer too, so this is sort of a non-issue (though I'll admit I don't know much about aircraft engines specifically).
Gist is going from internal combustion with a ton of supporting or fully necessary tech to fully electric, fully SW-driven, really skeeves me out given the above testimonial and others like it.
I openly allow it's quite possible that airplanes can't fly these days but for software though.
Modern turbofan/turbojet/turboprop (really, any engine) has a ton of SW involved. Engine controllers [1] literally control the engines. Your point is completely wrong, I've worked on this software and they go through many forms of verification for things to work. Look at the failure rate of avionics and compare that to other industries.
Sure you or your friend may have had a bad experience at that company, but the big players generally won't let software bugs through.
Eh,I did say it was only that eng's view of the world, but the big players certainly do let bugs through.
Boeing code leaked in '20 [1] and it was ugly, however it was ~network vs. app layer so unclear how it worked at the engine level.
Add in the track record of CAN bus security difficulties and knowing airplanes use similar tech, "generally won't let bugs through" when paired with the footnoted security leak is a gross overstatement.
My assumption was modern ICE's also had software controllers. You could go with a fully hardware controlled electric motor (electric motors significantly pre-date computers!), but that of course would come with the same kind of trade-offs as fully hardware controlled ICE's (a couple I can think of off the top of my head are inability to change and inconsistent or degrading behavior over time).
I wonder how lengthy charge cycles will affect the viability of fast turn times, especially for the short-haul segments that they're targeting for these new airliners. It seems like they'll need to either have extremely fast charging or be prepared for significant downtime between flights; where will the planes be stored while they're charging?
It's important to both invest in and appear to be investing in the future, but even a soft commitment of 100 planes seems like quite a bit, especially in the very competitive and cost-focused short-haul space.
0. https://www.npr.org/2015/06/28/418147961/the-man-who-saved-s...