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This is wrong on many levels:

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...

Enjoy your 20 mile finals :)

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.

90% is the usual assumption.

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.

Hehe I also fly a super decathlon for aerobatics. 0.3mile finals! ;)

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...

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.

https://www.law.cornell.edu/cfr/text/14/91.15

Sure dropping objects is another option, but arguably that would work in an electric plane too.

However, I really doubt they would certify an electric with a higher takeoff weight than landing weight.

> 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]

[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/...

> Actually in the US the Alpha is only certified as Experimental

But also LSA-approved-for-training, I think. There's a flight school in the US using them.

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.

> batteries have a long way to go to even come close to power density and weight of kerosene or gasoline aviation engines.

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.

> (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.

At 10 watts per square foot it’s not going to offset the weight cost, let alone appreciably charge the batteries.

Depending on budget and amount of engineering involved: https://en.wikipedia.org/wiki/Solar_Impulse

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.

This.

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 have seen experimental amateur built kit planes running electric motors.

The things Peter Sripol does on youtube are amazing. He built an ultralight electric aircraft using model-building techniques.

You've probably seen a couple... but it's super rare still for all the same reasons listed above.

Almost nobody uses them outside of some niche designs and gliders.

Not with that attitude you won’t!