An interesting, if one sided, article about the electric Sun Flyer. Focus is training, seems actually more viable than I expected.
https://spectrum.ieee.org/aerospace/avi ... is-at-hand

Tim

Article written by the owner of the company. Not one-sided, but self-serving. Grain of salt.

Remember that electric motors and Li-Ion batteries also need cooling. The cooling drag penalty for piston engines is not as high as most people think. This was demonstrated in WW2, as the radial engines won out over liquid cooling. At the time, many aero designers were thinking the same thing, that the cooling drag was pointing them to sleeker water cooled designs. It turned out not to be the case.

Article written by the owner of the company. Not one-sided, but self-serving. Grain of salt.

Larry, these are solid numbers for a decent sized, capable GA airplane. I agree that the state of the art is a long way and a technology leap away from electrifying that kind of airplane. The niche where the electric airplane can fit in is as a training airplane. It'll take some rethinking and it won't work in every flight school (local FBO or big operations).


Think of how you would run PPL training if you used a 100hp motorglider and you burned about 5 gallons of gas per hop... by the way the airplane has a 7 gallon tank.


- Economical cruise hp delivers about 60-75 knots; flight schools are used to transit times to the practice area being about 10-15 minutes each way
- The airplane's overall range seems to be around 150nm (no range in the specs, but endurance and speeds are on there)
- Plan ahead if there will be strong headwinds on the way home from the practice area and think about what happens to your endurance when you push the power up to make 100 knots

Max range on one battery means you'd think about PPL training a bit differently. Does a flight school pre-staging a battery at a student pilot cross-country destination sound weird? If this airplane can deliver on cost savings and knock even $20 per flight hour off the "realistic" price an FBO quotes to a prospective customer, I don't think it sounds weird at all. (Sunflyer is claiming $75-100 savings/hr and while we'd all love to see them achieve that...)

Just saying the concept is viable as a trainer, just some of the details would have to change.

I know gas engines are not very efficient. We convert about 20%, with 80% of the energy lost to heat/friction (mostly heat). To remove the heat, you add significant drag.
In addition gas engines are heavy, have high point loads, and significant vibration forces which require more structure.
So instead of comparing the energy requirements for a plane based on a gas engine, I would hope to see some engineer purpose building a plane for electric. Therefore they would hopefully used disbursed power to reduce point structure loads, a lighter structure, battery loads spread over a greater portion of the frame to reduce cooling requirements and again reduce point loads.

Once all this is done, I would thin the energy requirements are significantly reduced. For example, look at the energy the SunFlyer is going with. Much less then a C172 or SR20 for the same flight.

Tim

Has Tesla come up in the 16 pages of this electric airplane discussion? Another electric joke just like this airplane. If you want to run the air conditioner in your 100K Tesla in cuts your range in half.

Of course they have. How is Tesla a joke?
And you may want to look closer at the sunflyer and others. They are addressing a specific market, the training market.

Tim

Of course they have. How is Tesla a joke?
And you may want to look closer at the sunflyer and others. They are addressing a specific market, the training market.

Tim

Of course they have. How is Tesla a joke?
And you may want to look closer at the sunflyer and others. They are addressing a specific market, the training market.

Tim

Kevin, Luke,

ok, you are discussing the company, specifically the burn rate.
That has been beat to death in a few other threads.

From a tech standpoint, and from a product standpoint Tesla has lead the way in many areas. They have shown how to repackage existing tech and rethink the auto.

I think electric planes will do the same. I think they will be limited to flight training and the hundred dollar hamburger for the next decade or two. However, with those limitations they have the potential to make significant changes in aviation. Both around the cost, and around participation.

Tim

Tim,

Well, I am an engineer (not a licensed engineer, so I can't sign off your kitchen remodel foundation).

There's really nothing magical about airframe design. Everything that's applicable to low subsonic flight and aerodynamics was more or less figured out by about 1950. Since then, all that has really happened are advancements in materials and manufacturing, allowing production of better realizations of that knowledge.

The thing is, for any such airframe, the gasoline powered version is going to be built much lighter and less expensively than the electric version.

Why?

Because the combustion engine isn't really any heavier. Nissan built a 400hp racing engine that only weighs 88lbs. So it is entirely doable, has been done already and proven. Heck, a cheap little Rotax engine only weighs in at 65lbs.

Then we get to the weight of the energy storage, fuel vs. batteries and that's a total win for the fuel system, by an incredible long shot.

Is it interesting and neat these guys built an electric airplane - yes!

Is it going to change general aviation? No, at least, not yet, because it lacks practicality.

This little aircraft cruises on basically 25hp. How many useful 25hp aircraft are there? I just don't see it. The whole world of LSA's for example, nearly everyone who was in the market was looking for the most power allowed by law.

Look instead at self launched gliders, the majority of the one I have been watching use roughly a 50HP engine for initial climb, and can maintain flight on 25HP or less.

For training purposes, and to fly 50 miles for hamburger, this is good enough. Electric planes, I think in many ways are going back to the old/slow/low taildragger planes of a seventy five years ago in terms of mission. Look at a J-3 cub, 40HP.

For the next five years, I think it will mostly be early adopters whose spend more per hour if you include capital costs. But like any industry, early adopters benefit the rest of us.

Tim

Please quote properly.



It's true that Mike used the worst example in order to buttress his point. Here's what they wrote in a 2015 article at Qnovo:

"But for the added safety of the LMnO material, Nissan incurs some important penalties. First, the intrinsic energy density of the individual pouch is only about 320 Wh/L. Compare this to nearly 700 Wh/L for the Panasonic cells used by Tesla.'

In addition, the 2019 Leaf finally comes out with a 60 kWh pack. You know, here's your 8%, and they compound.

Unfortunately for the boosters of electric airplanes, Mike saved the best for last: show me the proof by designing an electric 172. No matter how much Tim talks about the efficiency and reduced power requirements, he just can't.

Electric power is used widely in gliders today. Its advantages are best used there. You get a self-launch airplane that only need a small amount of power, and is then recharged from solar panels for the rest of the flight, so you never even need to plug it in. This is very different from an airplane that needs to use power for 8 hours at a time.

The hate of Tesla is so precious in this thread though. Sure gave me a good chuckle.

I had a plane on leaseback to a flight school, I have also been involved in a couple of flying clubs. You can probably count on one hand the number of times any of those planes flew for an actual 8 hours in one day. Between pre-flight, taxi time, landing, refueling.... I often saw a tach time that was less than half of hobbs time, and hobbs was usually around 2/3 of reservation time. Most flight lessons are only scheduled for one to two hours.
Current battery tech is roughly one minute of charge for one minute of flying time, it has to be better than that for the very busy days, but not by much.

So for cross country flying, is an electric plane ready? Only a glider. Otherwise, for the hamburger run 50, maybe hundred miles away and flight training. Yeah, it is borderline now, but it is getting better.

Does it make economic sense yet? Not likely. But do not tell the early adopters this, I want them to fund the development to make life cheaper for the rest of us.

And for all those doubting electric planes: Electric cars have significantly lower operating costs than gas cars, even if the energy prices were balanced. The reason is they are mechanically much simpler. Now ask yourself the following, outside of an electric airplane, what technology of change is on the horizon that has the potential to lower costs for aircraft owners? Before answering, recall that most people say aviation is too expensive and cost is the major barrier to adoption.

Tim