This is cool indeed, but don't get too excited - this is a puff piece touting (220, not 300) preorders that aren't yet real orders and might never be.
The plane is not FAA certified yet (the first and only prototype flew in February), and the 4 seater (which accounts for half of the 220 preorders) won't fly until 2022, and then will have to seek FAA certification too.[1]
Electric motors and batteries have a long way to go to even come close to power density and weight of kerosene or gasoline aviation engines.[2] Batteries also don't get lighter with reduced charge - something most aircraft rely on with designs and efficiency (ie. 500lbs of batteries weigh the same when nearly empty).
It's also notoriously difficult and extremely expensive to certify new engine types for general aviation commercial pre-built's - which is part of the reason majority of modern GA aircraft still use very old engine designs (just not worth the investment from the manufactures). You can't just show it works... it has to be proven to work in a number of extreme situations and for very long duration with extreme reliability.
Getting a new engine type into an Experimental Type Aircraft is much, much easier...
I'd also hope the motor electrical system is fully isolated and separate from the aircraft's other electrical systems (maybe I missed it, but I haven't seen anything discussing this so far). Electrical problems happen, and losing all systems plus the motor at the same time would seriously jeopardize the safety of this aircraft.
I wish Bye and his company the best, but I'm skeptical.
1) General aviation doesn't rely at all on the weight difference from fuel burn for flight planning (I am IFR certified and fly Cirrus SR22s). My fuel not burning in my wings wouldn't change anything, as I'm constrained by takeoff weight not by landing weight, and I don't climb into the flight-levels high enough for my current weight to matter (that would require FL22 or above, and I like my breathable oxygen).
2) General aviation certification, while expensive, is far from the cost of commercial cert, especially for VFR aircraft. There is no reason why they can't certify an electric aircraft, and they have funding from Subaru's investment fund. Pipistrel (electro) did it for their ultralight.
3) Of course the motor's electrical system is separate from the aircraft's other electrical system, that's aircraft certification 101 (being able to through the master switch deactivate alternator but not battery power). On top of that 12v instrumentation is (obviously) on a different power level than an electric engine, so the batteries will be different.
IFR certification will require 2 instrumentation power source backups (like BAT1/BAT2 on my cirrus) which really isn't a problem, when you've put a 92kWh battery on a plane you can put 2 0.5kWh batteries as redundancy.
(for what it's worth, I'm currently waiting to buy an eFlyer 4).
1) Ignoring actual question, electrics will likely benefit from flying extremely high as the motors don't care about atmosphere. Fuel burn won't really matter here though.
2) GA certification has sunk so many companies it's become a running joke. It's entirely fair to question their approach of using a heavily modded Lancair Legacy with an ipad for EFIS/EMS.
3) Yea, but again, they said they want to use an iPad as primary EFIS. Seems like a good way to piss off the FAA to me...
Motors rely on air for cooling, so they do care about atmosphere. Propellers rely on air density to "push". I don't know how this plays out in the real world, but atmosphere matters.
Motors came be 99% efficient, compared to ICE at 20%. Cooling isn't that huge of a deal. If a wing can operate at a given altitude you can design electric propulsion that will also work there. The U2 operated on a turbine at 70,000ft. A turbine is just a very complicated prop at the end of the day so in theory a large cord/diameter prop or a high speed ducted fan would also work. The actual altitudes were're talking about for GA are far lower though. Most GA aircraft top out below 18,000. Electrics will likely prefer operating at 20,000+.
Not sure if the 99% figure is correct, but it is certainly above 80%. Electric motors run quite cold compared to motors that are burning things. Cooling is unlikely to matter.
Now, wouldn't the cold air at higher altitudes present a much bigger problem for the battery? FL20 and up you can easily reach temperatures where current batteries are no longer usable.
I imagine the electric "bonus" at higher altitudes would be similar to a turbo prop's bonus. You can get more efficiency at higher altitudes, but it all goes away if you climb further.
Just finishing a decathlon checkout. They're awesome :)
The ipad could be fine if they have some simple steam backups (compass, ASI, altimeter). IFR it would not be a good idea though. G1000 would be awesome though!
> Ignoring actual question, electrics will likely benefit from flying extremely high as the motors don't care about atmosphere. Fuel burn won't really matter here though.
One bad thing for manufacturers is that they won't be able to segment their market by adding a turbo :)
Batteries not getting lighter with reduced charge is relevant in that it's not uncommon to trade reduced range for increased payload by carrying less gas. With batteries having a fixed weight, you don't have the ability to make that trade-off in an electric aircraft.
These battery systems are usually designed to be modular so you can add/remove/quickly swap them. Think server rack like trays full of battery packs that you can chose to partially or fully populate scattered around the airframe
Eh... are you going to be able to do that without an A&P? You can only do that at the start of your trip (unless you want them shipped to your destination, I guess).
> On top of that 12v instrumentation is (obviously) on a different power level than an electric engine, so the batteries will be different.
I wouldn’t count this as “obvious”. The Tesla Roadster, for example, operated its low voltage system using a DC-DC converter that was supplied by the HV system. Tesla decided this was a mistake in the Model S and added a 12V battery.
(Sadly, they seriously flubbed the charging logic for the 12V battery, and the Model S destroyed 12V batteries quickly. It took a couple years before the firmware was fixed to solve that problem.)
>> My fuel not burning in my wings wouldn't change anything, as I'm constrained by takeoff weight not by landing weight
I realize every pilot's job is different...but it's routine where I've worked(not as a pilot, but as a LIDAR operator), to skimp on fuel so we could still make weight & balance with our equipment on board. I've never heard(same as you) of anyone counting on that decrease in weight from fuel consumption though.
My memory is a bit vague, but I do seem to recall that there are some older GA twins where the maximum takeoff weight can exceed the maximum landing weight. Therefore, if you have an engine out immediately after takeoff with full load, you need to circle around for a bit to burn fuel.
I'd have to dig around to find out exactly which aircraft this refers to, but I'm going to take a guess that it's something like a Piper Apache or Aztec.
A Cessna 182S has a max takeoff weight of 3100 lbs and max landing of 2950 lbs. If you take off right at max gross you need to burn 25 gallons of gas. At 14 gph, that's about 1h45, minus a bit for the increased fuel burn in the climb.
This is something that can be designed for though (mainly stronger landing gear) and I would argue all the benefits of electric far outweigh the drawbacks aside from battery life/range.
Emergency situations give the pilot essentially unlimited powers to safely land the aircraft. In a ‘no time remaining’ type of emergency such as a fire you’re just landing the aircraft over weight. It will be fine.
> Pipistrel (electro) did it for their ultralight.
The Pipistrel Alpha was the aircraft I immediately thought of when I saw this AOPA press release. A Light Sport Aircraft (LSA) already FAA certified.[1] The Sustainable Aviation Project currently uses a few of them.[2]
Edit: Actually in the US the Alpha is only certified as Experimental.[3] Other jurisdictions have different certifications.[4]
Not all planes are Cirrus. Not all have the same takeoff and landing weight requirements.
> I don't climb into the flight-levels high enough for my current weight to matter
Isn't density altitude a thing? Haven't you ever filled up your tanks with less than their full capacity in order to carry more payload?
> My fuel not burning in my wings wouldn't change anything
Range? Do they weight the same if they are half full? Of course they do not.
> General aviation certification, while expensive, is far from the cost of commercial cert, especially for VFR aircraft.
If that too much of a hassle, they can be in the experimental category. The bigger problem is not the aircraft, it is the engines. There is a reason even your Cirrus SR-22 is using an old engine design. You CAN certify anything. Do you have the funds to do so is a better question.
> Of course the motor's electrical system is separate from the aircraft's other electrical system, that's aircraft certification 101 (being able to through the master switch deactivate alternator but not battery power). On top of that 12v instrumentation is (obviously) on a different power level than an electric engine, so the batteries will be different.
Yeah, but on a 'normal' plane, you can shutoff the entire electrical system. The electrical system that matters for continued flight is in the engine itself (the magnetos). Many aircraft do not even have a separate electrical system.
Electrical fires are deadly enough as it is, add a high voltage electrical bus and it is a much bigger deal.
Again, it can be worked around. And it again requires money.
Heck, Cirrus itself almost got bankrupt trying to release the Vision Jet. And that's based on 'proven' tech.
GA aircraft is not as big as a market as it once was. It certainly cannot compare with commercial aviation, so there's a limit on how much companies can invest.
Don't get me wrong, I think we need to stop burning fossil fuels as soon as possible – I drive an EV myself. And aircraft are a huge contributor to that (GA still spews lead around for the most part). If we want to change this, we need to start now.
But it is a hard problem, we shouldn't be so dismissive of the issues these manufacturers are facing. Or the drawbacks electric airplanes have.
I was unclear in my weight explanations. The OP’s point was that one of the advantages of fossil fuel aircraft was its ability to shed weight during flight from its fuel source burning away, and I claimed that was irrelevant for GA ( which it is ).
Completely agreed on the avantages of fuel for weight adjustments before takeoff though.
To be fair however the eFlyer specs of 440pounds of useful load for the 2, and 800 for the 4, are quite generous when you compare to fuel equivalent aircraft with realistic fuel loads.
The real insane drawback is the limited range at useful speeds...
Would hybrid (specifically series) make sense for GA fixed-wing? I'm pretty excited about it for VTOL, especially since it gives you a lot of redundancy in the electrical part and thus allows far lower reliability in the main engine-generator.
Electric trainers (initially) and short-haul passenger aircraft (in a decade or so?) will succeed simply because operating cost savings make them extremely compelling. Not just fuel savings, but reduced maintenance costs and increased reliability.
As for electric isolation? Yes, if electric aircraft work like electric vehicles, the high-voltage system that powers the motors is completely separate from the low-voltage system that powers the electronics.
Increased reliability isn't a big deal for modern commercial carriers. Engine reliability is very close to 100%, with little gains to be made. The real increase is in getting the same near-perfect reliability at decreased maintenance costs.
Sure, they’re very reliable in flight. But it’s likely that electric motors will significantly increase service intervals (lowering maintenance costs) and increase dispatch reliability (ie: delays because service/maintenance is required).
> losing all systems plus the motor at the same time would seriously jeopardize the safety of this aircraft
The 2-seater is VFR only, assuming with conventional mechanical control surface linkages. So if you lose thrust, you're basically a glider at that point, needing only backup steam airspeed and altitude, and maybe a yaw string, to land safely. The electronics don't buy you much at that point.
VFR is the most dangerous situation to lose all systems in your aircraft. You're low to the ground, and relatively slow... and may or may-not have radar following or even be near a controlled airport. You'll have a pretty short maximum glide distance, and won't be able to communicate your emergency nor intentions.
Engine-out's happen in GA, sure, but a total loss is pretty rare. Bye and his company will have to prove beyond doubt his design is at least as good as existing decade's old, super-proven designs.
VFR has got nothing to do with altitude. You can fly VFR in the US in most places at any altitude below 18,000 feet. Its premise is to remain clear of clouds.
Radar following has very little in general to do with safely landing if you have an emergency. While they can advise you of nearby runways, a significant part of the pilot's job is maintaining situational awareness, which includes knowing the nearby points to land at.
Being near a controlled airport has got nothing to do with safely landing an aircraft, even during an engine out emergency.
I don't understand why you conflate the loss of the engine to loss of radio. You have no idea how the aircraft is configured electrically.
> VFR is the most dangerous situation to lose all systems in your aircraft. You're low to the ground, and relatively slow...
I disagree. You don't have to be low to the ground to fly VFR. You could be at 10,000 feet. You don't have to be slow to fly VFR. You could be flying VFR in a turboprop twin and pushing 250 knots.
If I was going to lose all systems, I'd also prefer to be flying in VFR conditions where I can see the ground and have a chance of choosing somewhere to make an emergency landing, rather than, for example, over mountainous terrain in cloud.
Every GA pilot is taught and needs to practice engine out emergency landings in order to pass their bi-annual flight tests.
I would WAY rather lose my engine and instruments in VFR conditions (where I can see the ground and see where I'm going) compared to IFR, where I can't see where I'm going and I'm relying on my instruments to navigate.
This is why IFR certification (more dangerous and skilled) is an addon that takes dozens of hours to complete initial training for, and then requires Instrument Proficiency Checks every 6 months to keep current on.
> (ie. 500lbs of batteries weigh the same when nearly empty).
Would better solar-powered charging help, to charge the batteries while they're being used? I imagine it would be perfect for planes since they almost always have relatively unobstructed access to sunlight.
I left [2] unexpectedly excited for fuel cell flight perhaps with some form of battery or capacitor boost for takeoff. If it's a cap, you could even charge it while the plane taxis if an electric hookup was onerous.
Don't get your hopes up until you see Experimental Amateur Built kit-planes running electric motors. There are already electric trainers on the market but FAA certification is a bitch...unless you're Boeing :)
These are small, low-altitude, low-capacity planes - because this is a hard problem and you have to start small.
I wonder though - does Bye have ambitions in creating larger ones that fly at higher altitudes? I've thought about this ever since Elon speculated that high-altitude electric planes could be insanely efficient: they don't require the intake that normal jet engines do, so they can fly in thinner air and thus require less power to overcome air resistance.
The main problem being battery density, IIRC. I wonder how that has changed since the ideas were floated some years ago.
I want the super-fast, high-flying, supersonic electric planes please! That could do more to alleviate greenhouse gas emissions than even electric cars might!
Battery energy density hasn't seen any large improvements in a few years. High-flying, long-range commercial passenger aircraft are probably not coming very soon. An aircraft like the Bye eFlyer could help trigger a resurgence in general aviation, which has been on a decline, I suspect in part due to costs. I expect the fuel and maintenance costs for the eFlyer will be substantially lower than those of aircraft typically used for initial training.
The relatively short endurance and range of the first model makes it most suitable as a trainer, but Tesla's first car wasn't what most people would want to use for a long road trip. Refinement of present-day technology might well result in an electric airplane in which four people could reasonably take cross-country trips.
The part about air intakes doesn't make any sense. In order to move the airplane forward it has to suck air in at the front and accelerate it out the back. That's just basic physics, regardless of whether the power comes from batteries or liquid fuel.
(Obviously rocket powered airplanes don't need air intakes but that's not what we're discussing here.)
I presume whatever Musk said was referring to something legitimate, but to put a finer point on your comment: in normal jet engines, only a fraction of air actually goes into the combustion chamber. The rest is just pushed out the back (faster than it came in) by turbine blades that are driven by that combustion. Indeed, modern jet engines are "high by-pass" which I think means that the large majority (>80%) of air isn't part of the combustion.
Performance of internal combustion engines varies greatly depending on altitude due to thinner air. This is even worse on hot days. That's not the case with an electric motor. As you get higher, you need to push more air, but since the air is thinner, it's easier to push. Most likely and electric motor with a variable pitch propeller would be extremely efficient. Electric planes would get all the benefits of high altitude flight (namely thin air means less friction) and none of the downsides.
As someone else mentioned, if the batteries get too cold you run into other issues.
I think the point is that combustion engines require the thicker atmosphere to oxidize the fuel in combustion. The electric planes just need inertial reaction, they don't need oxygen.
No that's not how it works. Turbine engines can and have been designed to run fine at very high altitudes (>100000ft). So electric propulsion holds no particular advantage there.
Another problem with aiming for very high altitudes is that you need to have several hour long flights to be able to reach those altitudes and really gain anything.
A typical climb/descent rate for a passenger jet is 1500 to 2000 feet per minute. So for a normal flight, going up and down to 35k will take close to 40 minutes. Going to 55k will take an hour.
So this means you can't start small and focus on cityhoppers with the fancy high-flying electric planes, you have to go straight for competing with the heavy jets.
It's not very difficult to put batteries in a heat controlled chamber.
A lot of RC guys are doing it with high altitude long range RC planes. Distances over 500km at 15km are already happening on 10kg planes.
Wind and temperature aloft forecast includes the note: "TEMPS NEG ABOVE 24000" and omit the minus sign.
With normal lapse rates (3.6℉/1000 feet), you're gonna need a heater in any general aviation airplane.
Single engine airplanes tend to use exhaust heat to heat outside air as a heater, so no fuel consumed. For airplanes that use a combustion heater, fuel use needs to be considered in flight planning. Therefore I'd expect the same for electric powered airplanes.
You also gotta spend more energy going up higher, though. If you take the idea to its conclusion you just end up with the solution of taking a rocket from China to SF.
A propeller works by pushing off of the air. A jet works by exploding fuel. It's not clear how you'll get super-fast in thin air without the exploding fuel part?
That’s not true. You’re describing a rocket, not a turbofan or even a turbojet. Fundamentally, modern high bypass turbofans are just shrouded propellers. Could reach supersonic speeds in the same way using electric.
Lift to drag is about half as good at low supersonic speeds as transonic, so cut your range in half, but fundamentally there’s no reason you can’t achieve supersonic electric flight. Just need good batteries to get that range...
Well actually...modern jet engines tend to be high-bypass turbofans, with the PW1000G geared turbofan achieving a bypass ratio of 12.5:1.
In a turbofan, as the name suggests, the (vast) majority of thrust actually comes from the fan in front, and the turbine is really just used to turn the fan. That's what the bypass ratio means.
I thought that most commercial jet engines derived most of their thrust from the turbo-fan pushing air through the engine, not direct thrust from the fuel combustion?
With one or multiple ductfans in a row you can create enormous pressure differences and thrust.
Its less efficient than a regular propellor, at least at low altitudes
Ion thrusters? Not sure if they're at all practical yet, but that seems like a decent solution, especially if you can ionize the air you're flying through.
Air-breathing ion thrusters for aircraft are not at all practical yet. The first demonstration flight of a self-contained unmanned non-payload-carrying aircraft using one took place last year.
Spoiler: These aircraft are almost entirely useless outside of limited pilot training applications. You might get 1-1.5 usable hours of flight time per charge. Battery density is not there yet and this is another fake it till you make it play.
To further expand, these will cover about 90% of the hours needed for a part 61 private pilot licence and and another 80-90% for instrument and commercial. The issue is you'll still need a ICE aircraft for some of the XC flights which complicates training somewhat.
Edit: Also, 3.5 hours is at barely-staying-aloft airspeeds riding the bottom of the drag curve. If you're maneuvering, doing practice landings, or actually trying to go somewhere you will not get anywhere near those numbers. The FAA also requires minimum 0.5 hours of reserve upon landing.
61.87 has quite a few solo requirements in make/model for student pilots, so getting them dual trained in two airplanes seems potentially not worth it. There's an out clause "or similar make/model" essentially leaving it up to the CFI or the flight school to decide what is similar. But heck I wouldn't sign off a student trained on a Cessna 152 for a solo in a Cessna 162. They'd have to be really similar like Cessna 150 vs 152 similar. If the company produce the same plane with electric and fuel power plants it might work. But that's two airworthiness certification processes the manufacturer has to go through.
Don't get me wrong, these will be great for schools, but I don't think that's what the average HN reader is thinking about when looking at these. Bye is not publishing the important numbers so this whole thing looks a little too much like an attempt to say they're changing the entire aviation landscape when they're just another electric trainer (in a market that already exists and has more realistic contenders).
Huh? "Battery density is not there yet." "Fake it or make it" You know, it'd be helpful if you didn't accuse them of fraud without grounds.
Battery density is only half the issue. The other one is efficiency. Half-century-old cessnas fly like a brick. State of the art aerodynamic performance can allow you to get two or three times the range you'd get just swapping out their engine for battery+electric.
This aircraft can probably do about 400km range. With reserves, maybe 350km. That's not nothing, about Bakersfield to San Jose. And this thing is not fully optimized. If you REALLY wanted distance, you'd pressurize the cabin, use even higher aspect ratio wings, retractable gear, blend the body into the wing a bit, etc, and you could do up to about 1000km range with today's batteries (you'd be mostly battery by weight).
You think so until you look at TCO. A used 172 equipped for a superset of the training scenarios can be had for 1/5th the initial investment. You can buy a lot of operating costs with the savings.
Indeed, which is part of why most flight schools don’t buy new planes at all. I was mostly trying to refute the grandparents assertion that it was a “perfect plane for flight school.”
On the other hand, the discontinued Cessna 162 sold for $150k and is more similar to the eFlyer’s capabilities.
Let’s also not forget that not everyone lives or has time to deal with a full size airport. I can imagine a future where it’s feasible to offset commute times with these instead of other options.
I am curious, the aero-engines are know to be reliable but electric engines are considered to be good too. What kind of complexity variation does a battery introduce in providing reliable power vs gas tank. What can be possible weaknesses if any with electric planes?
These are some differences that I can think of after mentally running through a C172SP checklist.
In a gas plane, checking fuel level during preflight is a matter of direct observation. It's at a certain level, it's the right color, and it doesn't have any gunk in it. In an electric plane, you can't directly observe a battery's state of charge; rather, you can measure the voltage using a device of some kind, and then extrapolate range/capacity from that. That's not hard to do correctly, but it does involve more moving parts than just looking at the gas.
Batteries don't change their weight based on state of charge, which is nice for flight planning that normally has to take into account a heavier plane at takeoff than landing. But it is nice to be able to trade off range for performance by fueling to different levels in a gas plane, and you can't do that in an electric one.
Batteries perform worse in the cold. Gas engines don't (though normally aspirated/carbureted engines do). The eFlyer is a pretty small plane, though, and it probably won't go high enough to reach altitudes that are consistently very cold.
If your gas engine catches fire, there are a bunch of things you can do to put it out without killing yourself. But I'm not sure what you do if your batteries catch fire, except hope you're very close to a surface you can land on.
Liquid fuel is volatile, but generally does not catch on fire on its own. Batteries can catch on fire if over or under charged. Batteries can catch on fire if punctured - liquid fuel can as well, but batteries do not need an external source. This means you need thermal management for your energy source and your power unit.
It's not as applicable for this class of aircraft, but batteries do not get lighter as they are expended.
Liquid fuel provides the same amount of unit energy until it is completely gone; batteries lose power over time, leading to lower horsepower at the end (this is a simplified point of view).
The per-unit energy is the biggest issue. It's true that fire is a problem for batteries, but that is manageable with very small sensors and casings.
There are many more systems required to deal with the many failure modes of internal combustion engines:
- Heating systems to address carburetor icing. Typically manually activated by pilot since they have a performance cost.
- Fuel pumps since gravity cannot always be depended upon especially in acrobatic airplanes.
- Fuel sump systems which must be checked before every flight to address water in the fuel tanks & lines.
- Lubrication systems which require pre-flight fluid level checks.
- Magneto system to ensure that sparks can be generated independently from the electrical system.
- Redundant magneto system since carbon tends to build up and prevent proper sparking.
- Possibility of an engine running rough/cylinder firing out of sync due to carbon or other issues.
- Fuel/air mixture control so that the optimal mix can be selected based on altitude. Requires pilot intervention.
- Extreme thermal stresses on the engine, requiring engine run-up checks before takeoff.
- Radiators, and airflow rediretion to address cooling issues resulting in loss of performance and weight.
- Exhaust system, and noise vs. weight tradeoff
Outside of combat, fuel fires are very rarely in the fuel tanks (TWA 800 being a notable exception, and there are ways it could have been avoided), and a for a fire in an engine, the fuel can be cut off and fire extinguishers used. On the other hand, liquid fuel is probably much more dangerous in a crash.
Electric engines have a number of properties that are great for aviation, namely the ability to provide torque at low speeds and easily handle high rotation rates, which removes the need for complicated gearboxes and simplifies design. They have been proposed a number of times over the years, the historical problem has always been getting the electricity to drive things: batteries are heavy and diesel->electric converters (eg. hybrid trains) are too large to be practical.
It's worth pointing out that piston aircraft engines usually don't use gearboxes. Instead, they drive the propeller directly, which dictates very low engine speeds relative to where car engines usually produce their peak power since any part of the propeller blade nearing the speed of sound results in a loss of efficiency.
I wonder if progress being made in micro-turbine generators would one day allow them to be used in planes. Having a bank of generators inside the fuselage could making flying a lot safer. I imagine planes can be made much more aerodynamic as well.
Turbines are more efficient with larger sizes due to the fluid mechanics, and they need air, so then you end up at gas turbine engines externally mounted.
I imagine the primary weakness is the rather low energy density of li-ion batteries vs gasoline. This means less energy per kg of battery/fuel, which means lower power (speed/payload) or range or both.
Off the top of my head, both lithium polymer/lithium ion cells are much more temperature sensitive when compared to most liquid fuels. When flying fpv quadcopters in cold weather, (speaking from a anecdotal hobbyist experience here), I get a much lower maximum current for the first minute or so until the individual cells warm up due to the internal resistances. This translates to less total raw wattage. Total battery capacity is reduced as well.
I imagine a big challenge would be keeping the batteries at a happy temperature.
Edit: The above in regards to providing reliable electric power. Disregarding this, the main downside by far is energy density of currently available batteries.
I remember reading that electric motors are much lighter than gas engines for the same amount of power. This difference can at least partially offset the added battery weight.
Also, it's possible to have multiple, small electric motors with no loss of efficiency. That isn't possible for a gas engine. Multiple motors could add some redundancy, and therefore reliability.
I think we're going to see a lot of interesting designs over the next few years.
> electric motors are much lighter than gas engines for the same amount of power
That varies wildly based on what kind of engines and motors you're talking about; it's not consistent enough to be applied as a generalization, especially when it comes to aircraft (turbines are some of the most power-dense engines available). See here [1] for examples.
Something else to keep in mind: a plane gets lighter as it burns fuel. Electric batteries don't get lighter as they expend energy.
Chip Yates flew a few experimental electric airplanes a few years back. The last I heard, he had devised some sort of battery hot-swap system so he could fly from NY to England in one go. I don't think that one ever made it off the drawing board.
Cold weather operations might differ. It's not uncommon to heat a fuel powered engine in the winter, whereas with battery it might be mandatory.
Also, cabin heat affect on range will need to be well understood and incorporated in performance and endurance charts for flight planning purposes.
For pressurized airplanes, the power cost of pressurizing and cooling. I'm not sure what that cost to endurance would be, but it would need to be accounted for.
It IS true for the prototype. Siemens is really good at grabbing these orders for production aircraft and getting their name in press releases, but the actual motor used for the prototype according to the FAA (who I don’t recommend lying to) is the EMRAX one.
EDIT: And EMRAX motors have shown up on lots of other electric aircraft. My day job is making novel electric motors, and their motors are incredibly tough to beat. I have much respect.
Interesting product. All the discussion about training airline pilots makes me wonder if their value add is they can tune their fly by wire system to have the flight characteristics of a larger jet for familiarity with takeoffs and landings. That might make up for the relatively limited air time the plane can achieve (you don't need a lot of time for training flights per say). Turn around time would become an issue though in terms of how many you would need to sustain a full training day for a given number of students.
The majority of flight training in the beginning is learning the basic ‘stick and rudder’ flying skills. This is the basic characteristics and relationship of pitch, power, roll, and yaw. Those basic skills and relationships help a pilot learn how to get out of unfortunate situations. Training in an aircraft artificially more similar to an airliner would not be productive as they tend not to be as forgiving when pushing the envelope.
These aircraft may work as trainers because training aircraft come back to home base the majority of the time. This doesn’t solve any type of GA point to point transportation though until infrastructure is built out to accommodate charging. Land at any FBO today and they’re going to laugh you away if you ask for an electrical cord that charges these large batteries in any meaningful amount of time. Your product may be killer (Tesla Model S) but don’t expect any kind of uptake without the support infrastructure (arguably Tesla’s number one strategic move).
Battery swapping and offline charging has not been successful in the automotive realm, but it might be a pretty reasonable alternative for aircraft. Even cheap aircraft are so expensive that the overhead of having two sets of batteries wouldn't make that much difference on the overall price, and you could probably rely on a shared pool of batteries anyway, since a lot of light aircraft aren't flown that much.
If battery swapping works then that also opens up some interesting possibilities like aluminum-air batteries that have much greater energy densities than lithium-ion batteries but which aren't rechargeable.
I don’t disagree that there are many solutions to the problem. The issue isn’t a lack of solutions though. It’s a lack of implementation. Swappable batteries sound great but does say Million Air FBO at Chicago MDW have swappable batteries for my aircraft? If someone wants to really make a dent in this market they need to follow Tesla and build out the product and the infrastructure to make it practical. I have yet to see anyone come up with big enough investment to do that.
that’s because for those cases the power draw is hard to predict. in case of your phone, the BMS might be lying and also the state of health of the cell might not be accounted for, but it’s more likely that some apps are juat power hungry.
as for the EV, it’s doing the same thing as an ICE car, it predicts the range based on your last x kilometers, if you step on the throttle your range will deteriorate as you reach higher speeds and drag increases. a traditional car will start reducing the estimated range as well.
I imagine that the aviation industry is much better at predicting and controlling the power draw, therefore the range won’t be so unpredictable.
it’s not the cells that are unpredictable, it’s their end user.
Negative. 3.5 hours is at max endurance airspeed, probably 50-60 kts and only 3 of those is usable since the FAA requires you have 0.5 available upon landing.
If you have a headwind, which is very commonly 30 knots or more, then in this plane you are barely moving. So, it would be hard to reliably get anywhere at all.
Training flights are mostly in the vicinity of the airport so speed and range matters less. But you do still have to get places (eg the practice area and back) and a really slow plane is going to make a difference in the number of flight hours you need to accomplish the missions.
It's unlikely you'd be moving at max endurance speed if you're going for greatest range. Max lift to drag speed is probably higher, on the order of 70-120knots depending on altitude.
At maximum endurance speed, sure, but that's not likely to be the maximum lift to drag speed. The maximum lift to drag speed of the eflyer2 is 20.6.
If we assume 35% of the in-flight vehicle's mass is batteries and the batteries have a 168Wh/kg specific energy at the pack level (same as the Model 3's battery pack), operating at the EMRAX motor (used for the prototype)'s peak efficiency with a high efficiency propeller, that gives about 400km range.
The plane is not FAA certified yet (the first and only prototype flew in February), and the 4 seater (which accounts for half of the 220 preorders) won't fly until 2022, and then will have to seek FAA certification too.[1]
Electric motors and batteries have a long way to go to even come close to power density and weight of kerosene or gasoline aviation engines.[2] Batteries also don't get lighter with reduced charge - something most aircraft rely on with designs and efficiency (ie. 500lbs of batteries weigh the same when nearly empty).
It's also notoriously difficult and extremely expensive to certify new engine types for general aviation commercial pre-built's - which is part of the reason majority of modern GA aircraft still use very old engine designs (just not worth the investment from the manufactures). You can't just show it works... it has to be proven to work in a number of extreme situations and for very long duration with extreme reliability.
Getting a new engine type into an Experimental Type Aircraft is much, much easier...
I'd also hope the motor electrical system is fully isolated and separate from the aircraft's other electrical systems (maybe I missed it, but I haven't seen anything discussing this so far). Electrical problems happen, and losing all systems plus the motor at the same time would seriously jeopardize the safety of this aircraft.
I wish Bye and his company the best, but I'm skeptical.
[1] https://en.wikipedia.org/wiki/Bye_Aerospace_eFlyer_2 [2] https://aviation.stackexchange.com/a/26919/2294