Electric aeroplanes...
 

...anyone here flown one?

Nope, but they were building a nice twin electric down the road near Royan. AirBus were funding, but pulled the plug (oh dear..not deliberate pun). Aimed at the training market with a 45 min endurance. Tandem seating in an all composite airframe. Good reports until the idea stopped. They had previously build a carbon Cri Cri with electric power that worked well, but it was just a stepping stone to the trainer.
DW

An electric powered CriCri was the coffin of a strongly reputed aviator and aircraft builder round here - I still miss him, and still distrust those smallish boxes storing huge amounts of energy; forever, probably. Oh yes, I know, of course, tomorrow's haircut will be for free... ;) Everything will be better tomorow, yes, of course, but today and tomorrow I'll still fill two 20 litre jerrycans at the village petrol pump, to go flying.

Have a hard enough time keeping my phone charged up, would have no chance with an electric airplane.

Had a quick look on you tube, there are quite a few videos so I think that one day some of the smaller aircraft will be powered this way.

I was asked to participate in design and approval of an electric conversion for a 172. Though it seems to have gone quiet, I learned quite a few peripheral things while I studied the concept. A big one was charging batteries. The problem is that either you have to swap heavy and expensive batteries to keep the plane in service, or it's down for hours charging after a half hour flight. Training aircraft don't generate revenue while they're parked charging. Swapping several hundred pound batteries will involve heavy lifting, and probably a dented airframe at some point. Putting the batteries in place of fuel tanks in a Cessna would be difficult to impossible. It's a logical place, but hardly an easy do. A whole bunch of screws for a 152/152/172 fuel tank cover, but not possible for a 180 and on.

The authorities were very eager to support the concept with regulatory flexibility. For example, at present, an "engine" must be type certified to be eligible for a certified aircraft. I can't certify a motor to the engine design standard, so I can't use a type certified powerplant in the installation. Previously a project stop, but the authority really wants to give on this point, among others.

It'll happen, and I look forward to it, but it's a ways off for commercial application just yet.

A lot of "resistance against them!

This link, and the links to other sources within that thread, may be of some interest...

FP.

Thanks - still very little though. Have been chatting to Pipistrel, but they're coy about how many electric aircraft they've actually sold.

Fascinating stuff, and clearly the future, but still some (mainly weight of batteries) issues to solve.

There is so much R&D going on in the car industry that the concept of batteries being big heavy boxes that have to be constantly lugged about to be recharged will be overturned. For example Toshiba have developed a new titanium niobium oxide battery that gives cars a 200 mile range and can be recharged in 6 minutes.
This will give rise to much more innovative installations such as batteries with unusual shapes to fit in dead spaces and the use of distributed battery installations (lots of smaller batteries spread about).
When the current push to electric cars was first mooted, my immediate thought was that "refuelling stops" would consist of pulling up and swapping battery packs (bit like the old coaching inns swapping horses!) ..........how wrong I was?

You're right, but of course weight/bulk is still less important to cars than to aircraft.

I love the 'change horses' analogy, very apt!

10 years ago, electric cars were a dream, now I drive one every day, it is fully charged every morning in my garage and drives better than any other car I have had. Prices of batteries are coming down exponentially, capacity to weight ratio goes up. It is the beginning of the end for internal combustion engines.

I don't know about being worried by "smallish boxes storing huge amounts of energy" (presumably you're thinking of Lithium ion batteries?). Just try calculating the energy in two 20L jerrycans of petrol!
I used to fly a petrol powered DG808, 20L of petrol 4 inches from your right shoulder; now I fly an electric Antares with cables carrying 280V DC immediately behind your neck (but with the batteries in the wings). I feel safer in the Antares. In both these gliders the pilot wears a parachute.
The MCR01 I used to fly had 80L+ petrol immediately above your knees and no parachute system.
None of them feel safe to me.
So to return to the original question: no I haven't flown an electric airplane and yes I've flown several hundred hours in an electric powered sailplane but with a typical powered launch time of 6 minutes and an absolute engine run time of about 11 minutes my experience and range is very limited!
On the plus side the batteries are now over 10 years old and only 4 of the 72 cells are down to 97% of their original capacity. Their predicted life is about 20 years, probably just as well as their replacement cost is the same as buying a new Lycoming...

Um!

Not an aeroplane.

:)

Short answer: no.

Long answer, actively studying them and hoping to first fly one this summer as part of working into a flight test programme.


So I'd class myself as knowledgeable, but for the moment, mostly second hand knowledge. Nonetheless, very happy to discuss what I do know, and my opinions on it.


In very short term - I'm a fan, I think that they are definitely part of the future, but probably not all of the future.

G

And whilst you're online - thank you for the 'electric' tip. Really excited about it...

May not be around to see if this really is the future, IMHO this is a non-starter for anything outside of pure private short hop flying returning to the same airfield/charging point.

While there is funding available for these "fantasy" projects they will aways be promoted as "the clean, green future" until the reality sets in and the cash dries up.

NO one is ever going to fly the atlantic or even as far as Benidorm on an elec aircraft with hundreds on-board.

It ain't goin' to happen.

I always love it when someone says 'NO one is ever...'

That someone can believe with absolute certainty that something will fail...

For the record, I believe this is all coming way faster than we realise - and that this is a good thing.

Slight thread drift, but I met one of the senior controllers at Belgocontrol last month. He confirmed that pilotless planes (and equally automated airspace/airfields) cannot come soon enough (from a flight safety, not job security, point of view).

Certainly do.

Well when an electric A380 with 450 PAX flies to Hong Kong I will say "you were right" however as I am on that BA flight next month I will stick to an oil burner for now.

Unfortunately a lot of this electric aeroplane hype is too tangled up trying to compare car/bus/truck elec technology without accepting the harsh realities of leaving the ground with a stack of battery's. There are no lay-bys or hard shoulders..:)

Just taking into account the amount of chemical energy in hundreds of ton's of avtur then translate to storage capacity of battery's no matter how good Mr Tesla can make them, is going to let you fly with dozens let alone hundreds of other pax.

Ah for the days when electricity was becoming too cheap to meter. https://en.wikipedia.org/wiki/Too_cheap_to_meter

Predictions are hard, but the energy in a couple of jerry cans still takes a heck of a lot of battery power. Let alone A380s.

I think there are some great changes to come in light aircraft design in particular now that the electric engines are so small and light and the fuel (ie batteries) can be located wherever you want and won't change the C of G as the power is "consumed".

But sitting on the terrace at Atlanta airport a few weeks ago looking at the sheer number of flights taking off and the huge fuel compound, I didn't feel a need to rush to my broker and dump my Shell shares.

(old stock market adage: Never Sell Shell)

I used to be able to work this out but what sort of power supply does one need to do that?

I always thought electric propulsion, assuming enough power was available, would be good for aerobatic flight. Short duration with time on the ground in between sequences. No problems of inverted fuel or oil systems.

Alternative is this Part 103 home built example.

I don't believe this "It will never happen" notion.
I do subscribe to, "We don't know what we don't know".
If someone had suggested 100 years ago that you could cut grass efficiently with a piece of plastic string, they would have been laughed at.
If someone were to tell the gunnery officer on HMS Victory that one day you could put an explosive shell into a target 600 miles away to within a yard, what would he have said?
Battery technology is making leaps and bounds in the motor industry and it won't be too long before power density--weight--size will fit aviation.
Suppose the entire wing of an A380 could be one battery weighing the same, and rechargeable in seconds by a man made bolt of lightning, taking 5/10 hours to discharge at cruise, then what?
Who can say with certainty "it can't be done".
Not today it can't, but-------

I agree with you that electric and/or hybrid aircraft will become widespread but I disagree that we don't know what we don't know, at least in broad terms.

Batteries of various types have been around for a long while; the main issues with them are longevity and energy density. There are physical limitations on the energy density of the Lithium Ion cells that are currently used to power aircraft and they'll never compete outside the training/microlight/powered glider markets. There are chemistries such as Lithium-Air that could be practical in terms of energy density for longer range aircraft but thus far they've been hard to develop. Ditto for fuel cells. Will they become practical? Maybe. But the basics of electrochemistry are well understood and there are hard limits on what the technologies will be able to achieve.

I am also highly sceptical when someone says, "it can never be done,"

I am the proud possessor of a pile of 'Flight' magazines from 1912 to 1918. In one of the articles a professor of medicine from Birmingham University (England) states that it is physically impossible for a human to fly at more than 250 miles an hour as his chest will cave in.

Unless you are dealing with a law of thermodynamics, the future can be anything the human imagination can conceive.

At Freidrischhaven this year there will be a good selection of electric motors and aeroplanes, many more than even five years ago. It is happening now.

For those who want to do the math. An A380 takes approx 253 tons of Jet a-1, this produces 11.3 kWh/Kg. As the aicraft fly's this fuel is burnt so becomes lighter and more efficient. Battery's retain their weight. Not sure of the limitations of top speed of propellors, assuming that is how elec propulsion is delivered? if this results in a lower max cruise speed then more fuel will be needed. I'm sure someone will be able to give more accurate predictions, but i still stick to the idea we will never fly as we do today commercially with elec but except for some very limited small private operations and limited short hop commercials it will not be the norm.

Problems to be solved...

- Energy density
- Crashworthiness of any battery technology used.
- Best practice in power system management
- Pilot training and qualification
- Ground infrastructure for charging, battery swappover, etc.
- Design practices

I don't see any of that as insoluble, it's just that the solutions seem likely at the moment to primarily favour small, short duration training aeroplanes. That seems unlikely to be the permanent position and touring light aeroplanes and regional airliners may just happen in my lifetime, if not necessarily in my flying career.

However, I'm quite happy to also say that some things I'm regularly reading are complete cobblers. I am getting to the point of wanting to shout abuse at the authors every time I read of yet another "flying taxi" project offering an electric, autonomous flying car that will be delivered within 5 years, operate from outside people's houses and cost a fraction of the price of a new Cessna 172 - having been developed invariably by teams with little or no aircraft design, flight test and certification experience. There is just so much snake oil there that the people who are peddling this rubbish should be facing public ritual humiliation, not having their fanciful artists impressions spread all over the internet.

G

I would agree that, currently, the technology favours the light end short duration stuff.
But taking that list of problems to be solved.
Energy density.
Would make the personal single/two seat VTOL device possible using current drone technology.
What is this story about Toshiba developing a battery giving cars a duration of 200 miles, recharged in 6mins? True or krap?
Would this be possible with a row of 240volt sockets at the local pumps?
Crashworthieness.
I watched something recently where a battery was hit with a hammer, smashed in half and still delivered power. Whether that was practical or a set up I don't know.
What is the crashworthieness of a can of Avgas by comparison?
The rest, training, etc will follow as reqd.

As I said Crash - they're all solvable problems, just not overnight, and not necessarily in a way that permits a straight swap with the technologies we're flying at the moment, or at the same scale.

For example - a major issue may be unattended charging - if you rummage around YouTube you can find plenty of examples of people who seem to be determined to blow batteries up, and the most exciting seem to be where they've deliberately overcharged them. That's solvable too - but is a problem that just doesn't exist at-all with present technologies.

Another for-example. Train a new PPL on an all-electric, then they want to go and fly a Piper or Cessna conventional product. What differences training will then need in a new aeroplane that has a fuel system instead of an electrical system, can change CG position with fuel/energy state, and requires familiarity with a mixture control and carb heat. Again, all solvable - but does need to be solved.

G

I think we (private flying pilots) will be the first to use battery powered airplanes regularly. Some are in the market already, and two seat planes with about 1 hour endurance are getting close to where a training aircraft needs to be. If performances were doubled to around 2 hours things start to get interesting for flight schools. Service and maintenance costs are very low, except for batteries but that is a quite predictable write-off with time.

Conversion to piston or turbine should not be more challenging than conversion between piston and turbine today. Regarding things like carb-heat, I was actually shocked to meet pilots at my current club that had never flown a plane with carb heat, only new 172SP's with injection engines, so there we have a challenge already today.

Scratching head... Many unknowns... bit of assumption here and there.

Drive 200 miles ~ 320 km at (assume, on the optimistic side) 3 l/100 km => burn 10 litres of petrol. There's 13 kWh in a kg of petrol so one litre holds 13 x 0.8 (density) ~ 10,4 kWh. So those 10 litres burned are equivalent to 100 kWh or a bit more. To charge 100 kWh in one hour takes 100 kW power (and that's assuming a 100% efficient charge process) - to do so in 6 minutes = 1/10th of an hour requires 1 Megawatt. Not something to take from a 230V~ socket or you would need VERY solid cables. And a power plant VERY near by.

Someone please check my maths? It is getting late. The 13,0 kWh/litre is from en.wikipedia

To each their own :) To me it is shocking that there are pilots who do fly with such paleo-primitive technology.

I see where you're coming from there Jan, but I think you're missing a fundamental difference in efficiency. An electric powerplant on an aeroplane is around 70-80% efficient, whilst piston engine powerplant is around 15% efficient. So you only need to store for an electric system about 1/5th of the total energy you do in a fuel tank. I'm guessing that there's a similar difference on cars.

The other side of that - and the fundamental problem for electric flight is that the energy storage density of petrol is about 46 MJ/kg, whilst for the very best Li-Ion batteries it's about 0.9 MJ/kg.

So you need 1/5th of the energy (thus allowing sensibleish charging times and very low energy costs) but because energy storage density is about 1/50th - you need 10 times the mass to store energy to do the same amount of work.

On a car, that's bearable within reasonable limits. But the 70L = 50kg of fuel you'd need for an hours flying plus sensible reserves in a PA28 requires around 500kg of batteries. The 450kg difference is all of your available payload, and then some.

G

I used A123 batteries in my electric helicopter a decade ago. They're still going strong and you could charge them in 8 minutes. They were unfussy and the combination of batteries/motor gave a better power to weight ratio than an IC engine. It was only in energy density that they fell short.

The obvious solution to the fast-charge problem is to have a large battery on slow charge from the mains. If you take somebody for an hour's lesson then charge in 10 minutes from the ground-based battery then you will only need a 17kW mains supply - assuming you need 1/5 the energy of petrol for an equivalent flight. Expensive, but probably cheaper and easier than trying to swap batteries in and out of the aircraft which is the other solution that has been proposed.

The electric motor is a lot lighter for the same HP output as an IC engine, making up for some of the weight penalty of the batteries. Plus, it runs efficiently at very low RPM, making more efficient and lower noise propellers possible.

@GtE: thanks, there had to be a flaw somewhere. Still, if only 20% is required of what I calculated, it still takes a 200kW power source to recharge in 6 minutes - only slightly less unrealistic. And @abgb, "only" a 17kW power supply? How many m2 of solar panels does that take? Or a 40+ amp cable from a 400V outlet? Or would you produce those 17kW from a diesel generator ;) ? And mind you, that is only for one aircraft. If, on a sunny weekend day, your field wants four planes in the training circuit than you'll need four of those 17 kW power sources, too.

On a more general note, I agree that the evolution is not to be reversed - but I remain highly cautious, there's too many tell-tales around, and the technology does need time to ripen.

There is an electric motor fitted to a glider that seems to have some advantages over the lawnmower engines that are currently used when a glider runs out of lift but these have had problems with battery fires so there is currently an AD to fit a fire detection system.

The Question Of do I use the parachute or do I try to land the glider after a fire warning is the current hot topic in gliding clubhouses when the weather prevents flying.

Even Elon Musk hasn't been bold enough to promote electric passenger flying and the likely reason is the Laws of Physics. Here on planet earth we have things like gravity and wind resistance to cope with and a vehicle is never going to sustain long periods of motion from battery power alone, particularly at high speed.
To do that will need an entirely new and yet unknown power source,

Kryptonite...

... or nuclear fusion, said to be 99% ready for operation 50 years ago. O no, wait, it still is at 99% - reminds one of an aircraft homebuild project... ;)