A Tesla model Y long range is around 4400 lbs. The heavier the batteries the heavier the structure required to carry them. Agreed for other than a few use cases like training or VFR air taxi from the outskirts of town we are no where near the energy density required with foreseeable battery technology. Hybrids make sense but at that point it may make more sense to use a generator to provide cruise performance taking advantage of multiple motors for redundancy or to allow unique aerodynamic improvements and use batteries for backup and takeoff performance increases (possibly vtol).

Recall that for every pound of jet fuel burned, a plane is pulling 3.5 pounds of oxygen out of the air, so you're really only taking off with ~30% of the "fuel" that you're going to need. Plus, once you burn it, your plane is lighter and goes faster/higher/better economy.

Sadly, this is also why co2 emissions are such a problem: each pound of burned jet fuel makes 3.2 lbs of co2. (Not to mention, nitrogen oxides, sulfur oxides, soot, ... and water.)

Electric aviation has some real challenges to overcome. Short range can work because the engines are lighter... but you quickly run up against fuel density issues. Training though is a great application as you need only one charger, and you get a ton of efficiency from pattern work (eg, prop can fully stop).

Subsonic aerodynamics has been well understood for a long time. Compare the performance of a new Cirrus G7 with a 1970 V35 with the same IO550 - the difference is barely noticeable - with 55 years of development.

Those planes fully fueled with ~80 gallons weigh considerably less than a tesla model 3. and have 2.5x the range of the car

A gas powered car of that size gets about 35 mpg. The bonanza / cirrus more like 10mpg. so with the range difference, the aircraft need 7.5X the energy that the car batteries provide.

I don't see any near term path to batteries with that increase in energy density, so I expect electric airplanes to either be very limited range, or highly optimized for efficiency at the expense of all sorts of other tradeoffs. There will be niche markets, but I don't see general purpose electric airplanes in the future.

And sport aviation. There has been a few conversions using Zero motorcycle motors, batteries and harnesses that put out about 80 HP equivalent. They are getting 1 1/2 hr range. The battery is forward of the firewall.

It is also suitable for launching a powered glider.

I am currently converting a Honda Pioneer 700-4 using a Zero motorcycle motor/battery and harness.

I think he’s suggesting that the high torque capability of electric motors would allow the prop to deliver takeoff thrust at cruise pitch.

There is one problem with that, angle of attack.

If the prop is pitched for 20 degrees AOA, it will be essentially stalled on hovering mode and produce poor lift.

If it is pitched to 10 degrees, it will produce great lift to hover, but will loose lift as speed increases.

So it isn't just about the motor load curve, it is also about the prop AOA versus speed.

Drones make this work because they don't go very fast and have a high prop RPM.

Mike C.

There is one problem with that, angle of attack.

If the prop is pitched for 20 degrees AOA, it will be essentially stalled on hovering mode and produce poor lift.

If it is pitched to 10 degrees, it will produce great lift to hover, but will loose lift as speed increases.

So it isn't just about the motor load curve, it is also about the prop AOA versus speed.

Drones make this work because they don't go very fast and have a high prop RPM.

Mike C.

Airplanes. The angle of the prop wants to match the speed it goes through the air so that it gets an optimal AOA. If you are going to run it at cruise pitch all the time (coarse), when you are moving slowly (say on take off and climb out) the prop AOA will be too high (less efficient). I'm not sure it would work any better than an ICE with a fixed pitch prop. Haven't thought about it much, but it is not obvious to me either way.

How do the marinas that handle larger boats like fishing boats handle this. They are large and have high demands for shore power. Tough environment . Do they meter electrical usage at large marinas. I never had a boat that needed this type of infrastructure but a Marina is about the closest business model to a GA airport.

Tugs could move the airplanes from the charge locations when needed. But yes probably specialized use only for a long time.

Is this what you call "controllable"?



Mike C.

You'll still need a CS prop if the airplane has a decent cruise speed and or you want the most efficiency possible (likely a big issue for any battery powered design).

That said, I do believe that a small turbo diesel powered alternator feeding a small, efficient electric motor would be an awesome combination, especially if a relatively lightweight and robust diesel can be made. Add 10 minutes worth of batteries and you've got some redundant power to make a landing if the diesel quits.

to add some data ....

Some recollections from conversation with demo pilot

Stall 80 (has no flaps)
Approach 90
Cruise 105
Max 135
Battery 2,800 lbs
STC in works for newer battery pack
thrust equivalent 600 HP
Can run 108% power if needed
5 blade fixed pitch prop
2,600 foot ground-roll at MGTW

A 80kt stall with a 135kt max cruise speed sounds like a fairly useless airplane to me. But with such a short range of usable airspeeds it probably doesn't need a C/S prop.