Bye lands orders for nearly 300 electric planes
aopa.org
aopa.org
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
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).
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...
Enjoy your 20 mile finals :)
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.
For a VFR aircraft I don't mind an iPad-type device for nav. I did my initial training on a 6pack 152 and I was fine with that.
I'm mostly interested (and they've remained silent) on their choice of avionics for the IFR eFlyer4. I'd kill for a G1000...
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!
One bad thing for manufacturers is that they won't be able to segment their market by adding a turbo :)
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.)
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.
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.
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.
However, I really doubt they would certify an electric with a higher takeoff weight than landing weight.
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]
[1] https://www.pipistrel-usa.com/alpha-electro/
[2] https://sustainableaviationproject.com/
[3] https://www.pipistrel-aircraft.com/wp-content/uploads/2019/0...
[4] https://www.pipistrel-aircraft.com/aircraft/electric-flight/...
But also LSA-approved-for-training, I think. There's a flight school in the US using them.
> 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.
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...
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.
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.
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.
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.
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.
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.
It is possible to use hydrogen or kerosene based fuel cells instead of batteries http://figures-of-speech.com/2018/04/fuel-cell.htm.
Another advantage of electric airplanes is that for them it would be much easier to takeoff and land vertically.
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.
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 :)
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!
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.
(Obviously rocket powered airplanes don't need air intakes but that's not what we're discussing here.)
As someone else mentioned, if the batteries get too cold you run into other issues.
Me too, but it's pretty chilly at >35,000 feet up, where most commercial jets fly. Batteries really don't like the cold.
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.
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.
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...
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.
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.
Flight schools could still make this work depending on those ratios.
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).
On the other hand, the discontinued Cessna 162 sold for $150k and is more similar to the eFlyer’s capabilities.
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.
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).
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 tradeoffI imagine a big challenge would be keeping the batteries at a happy temperature.
A quick google search shows the Solar Impulse team ran into this problem: (https://www.theverge.com/2015/7/11/8933295/solar-impulse-sus...)
Edit: The above in regards to providing reliable electric power. Disregarding this, the main downside by far is energy density of currently available batteries.
From https://en.wikipedia.org/wiki/Energy_density, a kilogram of gasoline has about 53x as much energy as a comparable 1 kilogram lithium ion battery.
Gasoline 46.4 Lithium-ion battery 0.36–0.875 (MJ/Kg)
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.
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.
[1] https://en.wikipedia.org/wiki/Power-to-weight_ratio#Examples
The issue will always be that fuel is consumed and causes the aircraft to be lighter the longer you fly.
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.
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.
https://emrax.com/products/emrax-268/
Up to 98% efficiency. Up to 10kW/kg. Pretty impressive motor, and few electric motor makers like to compare their motors to this high of a standard.
Doesn't seem to be true.
The motor is a Siemens SP70D[1]
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.
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.
There's a lot going on with DIY electric flying craft as well. For example:
https://www.youtube.com/watch?v=J7ykW4zk-Hk
Fascinating to see this problem attacked from the top and bottom of the market at the same time.
After using my phone for a few hours, the remaining battery will be down to 25%. And in 5 mins, my phone will be off due to the dead battery.
Once it happened to my EV. The battery was down to 50%, and then suddenly drop to 10%. Luckily, I was very close to my home.
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.
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.