Battery powered Skyhawk

[flysebi]

It has been seldom in the history of aviation that a single technology has revolutionized the way we fly by addressing multiple problems facing the industry and solving them all. The most important such event was the widescale adoption of the turbine engine in the 1940s. Turbines, as you know, remedied (and continue to remedy) commercial, military and business aviation problems of reliability, cost, range, speed and power, while also bringing with them a number of infrastructure advantages associated with using a single fuel type. Though it’s still in its infancy, electric propulsion seems to promise to solve a similar range of problems in light GA. But in the case of the electric motor, the potential advances might be more sweeping and more compelling, though almost certainly on a smaller scale economically.
The most visible electric airplane project these days is Bye Energy’s Green Flight Project. The man behind the program is George Bye, an engineer whose background as an Air Force transport pilot and instructor doesn’t seem to lend itself to his new role as a high-tech entrepreneur and self-described futurist, the head of a company that is trying to do no less than bring electric power to the mainstream of light general aviation.
Bye has even bigger ideas for Green Flight, but the first step for his company is nevertheless an ambitious one: to convert the most popular airplane in history, the Cessna Skyhawk, to electric power. On Bye’s team is a guy who certainly knows Skyhawks, former Cessna CEO Charlie Johnson. Bye and Johnson gave a product update on the Green Flight Project at a press conference during the AOPA Summit in Long Beach, California, in November. There was much promising news, including endorsements and partnerships with several industry heavy hitters, such as Jeppesen and Cessna. Now nearly done with the detailed engineering phase of the project, Bye Energy could be flying the first electric Skyhawk soon.[...]


A Battery-Powered Skyhawk - Pilot Magazin (http://pilotmagazin.ro/2011/03/a-battery-powered-skyhawk/)

[Jan Olieslagers]

Sorry, flysebi, but this is all too reminiscent of the novel "Lijmen" by my countryman Willem Elsschot, translated into English as "Soft Soap".

Of all construction materials, steel is the noblest, the most....

("steel" replaced by marble, glass, wood, cardboard, or whatever fitted the new victim)

[xrayalpha]

Why get a Skyhawk electric powered?

No-one in their right minds is trying to get an existing motor vehicle made all-electric.

No-one would put a turbine on a Spitfire.

New powerplants mean new airframes.

And airframe technology has leapt ahead huge amounts since the days of the SkyHawk!

[znww5]

Having been on the receiving end of this sort of PR-speak drivel for the past 30 years, I had almost lost the will to live by the tenth word.

By the way, I'm currently working on a new engine design which works on rice-pudding, sucks carbon dioxide out of the atmosphere and turns it into fresh spring water with a hint of lemon - all I need is to get some industry big hitters on-side and I can start the ball rolling.

Gimme a break :rolleyes:

[FlyingKiwi_73]

i'm just worried about the size of the extension cord!!! surely the battery weight renders this idea useless?

[K_9]

i'm just worried about the size of the extension cord!!! surely the battery weight renders this idea useless?
Yes, because clearly 45 gallons of fuel, associated tanks, two gallons of oil, a 320 cubic inch internal combustion engine, two magnetos, an alternator, a starter, and a heavy prop have no weight whatsoever. :ugh:

I think it's a marvelous idea. Purchase and maintenance costs on an electric motor are going to be hugely reduced over those of a gasoline engine, necessary electricity costs will be drastically lower than fuel costs of gasoline-powered Skyhawks, and once all the teething issues are solved, an electric motor will be much more reliable than an internal combustion engine.

Those of you bucking over this because it's different need to accept that progress requires setting aside some things we've grown to be comfortable with and moving onto newer and better things.

[FlyingKiwi_73]

I know a leetle bit about this technology and i think the weight and size of any 'fuel cell' would be prohibitive to the design, the amount of charge you would get from a series of solar cells would not nearly be enough to power a 134KW engine, it may run your glass panel nicely though.

Putting the technology in a new airframe designed around this technology is a new ball game, i think the detractors are talking more about using an existing inefficient airframe design.

If you look at electric or hybrid cars you can see the amount of space taken up by the fuel cells not to mention the weight, on the ground this is not an issue, in an light Aircraft, these things are at a premium.

Solar power is useful to a point, i know its limitations it powers a bunch of my instruments (weather sensors and station) but its not nearly enough to power my irrigation systems which has much less draw than 134 KW!!!!

[K_9]

I know a leetle bit about this technology and i think the weight and size of any 'fuel cell' would be prohibitive to the design, the amount of charge you would get from a series of solar cells would not nearly be enough to power a 134KW engine, it may run your glass panel nicely though.

Putting the technology in a new airframe designed around this technology is a new ball game, i think the detractors are talking more about using an existing inefficient airframe design.

If you look at electric or hybrid cars you can see the amount of space taken up by the fuel cells not to mention the weight, on the ground this is not an issue, in an light Aircraft, these things are at a premium.

Solar power is useful to a point, i know its limitations it powers a bunch of my instruments (weather sensors and station) but its not nearly enough to power my irrigation systems which has much less draw than 134 KW!!!!
I only skimmed the article so if they addressed the solar cells I must have missed it, but I would have to think the solar cells are there more for charging on the ground and providing a very small increase in endurance in-flight. An array that size would probably get less than 1000 watts on a good day.

Also, how often do most of us fly with more than 1 passenger in a 172, or for the full range of the airplane? For the type of flying most weekend pilots do, I think a weight and range penalty would not be much of an issue.

In any case, this is a stepping stone toward better, more advanced aircraft that build upon this technology.

[AdamFrisch]

Electric has a great future for aviation. It solves virtually all the problems we have with propulsion whilst delivering more power-to-weight than any other prime mover (much more than turbines).

It's the energy storage that's still the bottleneck, as you know. But it's advancing in leaps and bounds. Already today, weight for weight, you could get 1 hr endurance out out of an electric 172. That's pretty impressive. With a lighter airframe and advances in energy storage, you could see 3hrs pretty soon.

You might want to look at a thread I started a while ago on the subject:

http://www.pprune.org/private-flying/400967-i-cant-wait-electric-hybrid-aircraft.html

[FlyingKiwi_73]

I know a leetle bit about this technology and i think the weight and size of any 'fuel cell' would be prohibitive to the design, the amount of charge you would get from a series of solar cells would not nearly be enough to power a 134KW engine, it may run your glass panel nicely though.

Putting the technology in a new airframe designed around this technology is a new ball game, i think the detractors are talking more about using an existing inefficient airframe design.

If you look at electric or hybrid cars you can see the amount of space taken up by the fuel cells not to mention the weight, on the ground this is not an issue, in an light Aircraft, these things are at a premium.

Solar power is useful to a point, i know its limitations it powers a bunch of my instruments (weather sensors and station) but its not nearly enough to power my irrigation systems which has much less draw than 134 KW!!!!

[gasax]

Electricity has no future in aircraft until the storage issue is sorted. The shear energy density of combustible fuels is orders of magnitude greater than the best (read very very expensive) storage solution we current have.

Specialist airframes - such a self launching gliders - can use what we presently have - until the cells get old and then their replacement costs make overhauling a Lycon seem like small change.

It all looks a very long way off unless there is a major break through in storage technology.

As for converting a Cessna 172? Why on earth would you pick that airframe for a technology which is challenged on payload, endurance and power?

[dublinpilot]

The first post seems like an advertisment for a magazine with that article in it.

I like the thoughts of electric aircraft, but have some reservations.

Energy storage is one that has been mentioned. An endurance of <3 hours isn't enough. Any electric aircraft that I've heard about has a relatively slow speed (100mph or less). I would never be comfortable planning a flight with less than 1 hour reserves, which means I'd be limited to <200 miles.

On top of this, electric motors seem to slow down as fuel supply gets lower, rather than running normally until exhaused like combustion engines.

A second issue is shrinking fuel tanks! We all know that our laptops run for shorter and shorter periods on batteries as they get older. I don't know if aircraft batteries are the same technology, but I'd be uncomfortable with 'fuel tanks' that were getting smaller as time goes one.....exactly how much fuel do I have before I take off?

However the biggest one for me would be refueling. If I want to go somewhere beyond 100 miles, and return home afterwards, or go further than 200 miles in a single day, then I need to either exchange or recharge the batteries.

Recharging the batteries will take hours, which isn't really acceptable.

Exchanging the batteries means that you are taking on a battery of unknown quality, and unknown fuel content (back to shrinking tanks...how much has this one shrunk by?)

If you never fly more than 80 miles away, then most of these problems aren't for you, but would you really buy an aircraft with such a range limitation?

dp

[chrisN]

gasax wrote:

---------------
"Electricity has no future in aircraft until the storage issue is sorted. The shear energy density of combustible fuels is orders of magnitude greater than the best (read very very expensive) storage solution we current have.

Specialist airframes - such a self launching gliders - can use what we presently have - until the cells get old and then their replacement costs make overhauling a Lycon seem like small change.

It all looks a very long way off unless there is a major break through in storage technology.

As for converting a Cessna 172? Why on earth would you pick that airframe for a technology which is challenged on payload, endurance and power?"
--------------
I have an electric-powered modification on order for my glider.

Battery life is estimated as 1000 recharges before they deteriorate to 80 percent capacity. Say 100 per year for 10 years. I don't know the future cost of replacement batteries, but say £10,000 in 2021. So I am calling each use of the batteries as costing £10 per flight on which they are used. Not unreasonable. Electricirty recharge cost is negligible by comparison – but say £1 for a 1-hour usage.

Other marginal costs of flying with the FES (Front Electrical sustainer) include higher insurance and maybe some maintenance costs, but I doubt it comes to another £9 per hour of use, so my total “powered” cost is probably going to be below £20 per hour.

Previously, it was an unpowered pure glider, so this is all extra. If I were taking out an IC engine and replacing it with electric, it would be closer to a breakeven – maybe even cheaper, but I will never know.

For heavier aircraft and/or needing more endurance, I would agree that it needs a leap in storage technology. I have no idea how practical that is – but history suggests that tech improvements in future are unforeseeable, though they eventually yield increases of hundreds, or even thousands, of percent in performance.

Chris N.

[dublinpilot]

Battery life is estimated as 1000 recharges before they deteriorate to 80 percent capacity. Say 100 per year for 10 years. I don't know the future cost of replacement batteries, but say £10,000 in 2021. So I am calling each use of the batteries as costing £10 per flight on which they are used. Not unreasonable.

Will a battery really last for 10 years, irrespective of the number of recharges?

[chrisN]

I am not an expert, but I am told they will, if properly looked after (recharged after each use by a correctly designed balancing charger).

From:
Future of gliding - Front Electric Sustainer (http://www.front-electric-sustainer.com/technology.php)

----------------
“A 1200W programable Li-Po charger is used for charging, together with active balancer unit. Balancer monitors the voltage of each cell in the pack and balance them all the time during charging, so that all cells are at same voltage with precision of 0,005V. Balancer could be used even when charger is not turn on. With active balancer, balancing is more precise and faster.

Charging time of one pack of batteries is only 2,5 hours if they are fully discharged. If you used only 50% than charging time is also 50% shorter. LiPo batteries are without memory efect, so you can charge them also if they are not fully discharged!

Unlike lead acid batteries, Li-Po batteries can be stored for months without significantly losing charge. Self discharge rate is less then 1% per month at room temperature!

At 1C rating (horizonatal flight) life expectancy of batteries is around 1500 charging cycles of maximum alowed discharged cells. After that the battery will still have 80% of the original capacity.”
-------------


Chris N

[IO540]

Electricity has no future in aircraft until the storage issue is sorted.

I agree.

The best anybody can do at present is chip away around the edges, addressing specialist applications. There is no way to make even a practical electric car.

Also there is no apparent way to make a battery which is recharged quickly.

The best brains around are flat out working on this issue and have been for many years.

[AdamFrisch]

Well, I think it's unfair to immediately demand higher speed, less cost, more endurance from this new technology out of the gate. Of course it will take many years, just like it took 100 years of combustion technology to get to here (well, if you're Lyco or Conti, just 50 years, as nothing has happened to their engines since then...). And in the meantime, we'll probably see many bridging hybrid solutions.

Electric will of course first start in easier applications - such as self launching gliders. There it already makes much more sense than anything else. After that it will be local training aircraft that depart and return to the same airfield, probably with exchangeable fuel cells for speed. What's wrong with cheaper flight instruction?

Once again, you just have to look at hybrid cars - 10 years ago it was something nobody wanted. Now show me a single manufacturer who hasn't got some kind of hybrid in the works? Even Ferrari and Koenigsegg have them in development...

[spernkey]

I like the idea of a "Hybrid" system which uses the electric motor on take off to assist the (smaller?) engine. Loads of torque. No need to carry heaps of stored energy just for a take off/go around.
The real aviation benefit would be the redundancy offered by the electric motor should the engine fail in flight, sure would be nice to be able to maintain airborne for even 15 minutes to make a precautionary landing rather than a forced one!
With some clever technology might it even be possible to let the descent phase recharge the battery a bit? A bit like regenerative braking?
It would be a start, and i believe in starts!

[K_9]

Well, I think it's unfair to immediately demand higher speed, less cost, more endurance from this new technology out of the gate. Of course it will take many years, just like it took 100 years of combustion technology to get to here (well, if you're Lyco or Conti, just 50 years, as nothing has happened to their engines since then...). And in the meantime, we'll probably see many bridging hybrid solutions.

Electric will of course first start in easier applications - such as self launching gliders. There it already makes much more sense than anything else. After that it will be local training aircraft that depart and return to the same airfield, probably with exchangeable fuel cells for speed. What's wrong with cheaper flight instruction?

Once again, you just have to look at hybrid cars - 10 years ago it was something nobody wanted. Now show me a single manufacturer who hasn't got some kind of hybrid in the works? Even Ferrari and Koenigsegg have them in the development...I think you hit the nail on the head.

Any new technology is not going to be perfect right off the bat. Cars made huge changes in their first 100 years. Computers made huge changes in their first 50 years. Airplanes made huge changes in their first 100 years. Television... Trains... Wind Turbines... Solar Cells... Jet Propulsion... Elevators... Etc...

New technologies take time to grow and improve from the initial concept/prototype phase, but without a first step you get nowhere.

[FlyingKiwi_73]

Hands up now all those who bought a Prius, do you feel like a tit?

The biggest have in automotive history.... with the exception of the PT Cruiser (hey want an older looking new car... heres one we mangled earlier) you burn exactly how much less fuel a year... a thimble... well done:D, unless you just bimble to shops it useless... I'm all for planet saving gadgets but don't put a pigs ear in a box and sell me a purse.

When you can do a X-country land and 're-fuel' at a remote airfeild- (an extension cord will do) then i'd be interested.

but why oh why put this technology into and airframe designed 50+ years ago. take advantage of the advances in composites and aerodynamics, build somethign really slippery, then you'd save a lot more power than dragging an in-effecient airframe through the sky.

[K_9]

Hands up now all those who bought a Prius, do you feel like a tit?

The biggest have in automotive history.... with the exception of the PT Cruiser (hey want an older looking new car... heres one we mangled earlier) you burn exactly how much less fuel a year... a thimble... well done:D, unless you just bimble to shops it useless... I'm all for planet saving gadgets but don't put a pigs ear in a box and sell me a purse.

When you can do a X-country land and 're-fuel' at a remote airfeild- (an extension cord will do) then i'd be interested.

but why oh why put this technology into and airframe designed 50+ years ago. take advantage of the advances in composites and aerodynamics, build somethign really slippery, then you'd save a lot more power than dragging an in-effecient airframe through the sky.
I average 24mpg city and 33mpg highway with a conventional 2.5L 4cyl 4 door compact/midsize. EPA says the 2009 Prius gets 48mpg city and 45mpg highway. That's a significant difference. Since even the most fuel efficient of conventional cars get crap mileage in city driving (constantly accelerating and then braking means most of the energy you burn to go just gets turned into heat by the brakes right afterwards), that's where the Prius really shines. What are you trying to get at by calling Prius owners tits?

A new airframe is a high risk development. A new mode of propulsion is a high risk development. Put them together and the whole program is just asking to fail. Better to try out the new propulsion technology on a proven platform than to try to design a brand-new airplane around what is effectively a prototype. History shows us that, for the most part, the big successful companies have tried to avoid putting a brand-new engine on a brand-new airframe in order to avoid putting too much risk in the program. An example of what happens when you try to put a new engine on a new airframe: 787. Boeing took a huge risk on that program, and while they're about to finally get it finished up (it's turning out quite well, too), it's been riddled with delays.

[AdamFrisch]

I'm willing to bet an efficient gas turbine running a generator and having an electric motor drive the prop, would be much lighter than any combustion engine.

Let's aim for 160 hp. A brushless motor for a C172 would weigh about 15kg (yes, the deliver about 7-10Kw/Kg). A generator that could provide such power would weight about the same (as a motor is a generator in reverse), so add another 15kg. Add electronic controls for both and you have maybe 10kgs on top of that. How much does a gas turbine weigh that can produce about 160 shaft horsepowers? Well, the venerable helicopter turbine the Allison C18 delivered 317 shp on 70kg (140lbs), which would make it a fair assumption that half that power output could reduce the weight to about 50kgs. Let's add it up: 15+15+10+50=90kg. Now, that's less than any combustion engine.

So why isn't this available?

Well, you could as well ask yourself why a PT6 costs 10 times more than a combustion engine when it's simpler and cheaper to manufacture? Nothing makes sense in aviation, that's why. No normal amounts of logic apply, because the regulatory organs have a stranglehold on the market. It's an oligopoly. Want an alternative to that PT6 in your TBM? You're out of luck - it's been certified with that engine and that engine only and now they have you over a barrell. They can charge whatever they want.

They will fight electric tooth and nails. GE, RR, P&W will bring out everything they got and the FAA and EASA will listen. The revolution will not happen within the "big" industry, military or certified planes, it will happen with the grassroots, EAA, homebuilts and nutjobs in sheds. Just like it's always done - you look at most big inventions in the flying industry and it's almost always from the small enthusiasts and tinkerers in garages. There would be no composite 787 Dreamliner without the Windecker, there would be no B2 Stealth Bomber without the Horten brothers etc, etc.

[gasax]

Adam - there is no such thing as an 'efficient' gas turbine. They are used in aircraft due to very high power to weight ratios - exactly the opposite to electrical power!!!!

The specific fuel consuption of gas turbines is terrible, the numbers give you a clue gas turbine around 0.8 lbs/hp hr, a petrol engine 0.4 and diesel 0.32 - the basic thermodynamic cycles that these engines use predetermine these 'efficiencies' and wishful thinking will never outdo physics.

People who actually understand these things are the main reason why some of these outlandish ideas have not seen the light of day.

LArgely I~ would agree that the 'Pious' is largely a confidence trick. If Toyota had genuinely wanted to advance the state of the art it would have been diesel powered. But it was aimed squarely at the US market - where cars are petrol powered and so the marketing people waved its partially green credentials and the somewhat gullible public bought them - giving them fuel consumption almost as good a a standard diesel car........

Why do turbines cost so much? Try the engineering and materials. There will never be a 'cheap' turbine. Removing them from the aeronautical industry would help but in essensce most of a turbine needs to be made from very high specification materials and the slightest design or operational error reduces them to scrap - a massive difference to cast iron and standard aluminium alloys.

[IO540]

Any new technology is not going to be perfect right off the bat.There is a big difference however: short of some amazing invention, there is no known way of storing the electricity required.

Maybe somebody will invent something but you are looking at totally blue sky research. It might happen tomorrow, in 100 years, or never.

The electric motor drive train has not been an issue and could have been done decades ago (brushless motors with AC drives have been around for yonks, with the electronics gradually getting a little better). The obvious formula is a motor per wheel but mounted inboard of the drive shaft to avoid the unsprung weight. The rest is just straight electronics.

The lesser issue is that the electricity grid would not be able to cope if all normal cars suddenly went electric. But at least there are obvious (if hugely expensive) ways to solve that one... but I bet you that electricity prices would go through the roof; they would have to increase by 5x to 10x to match the cost of petrol or diesel, and that would be done by sticking a huge tax on it. But this would be tricky because it would make household electricity very expensive. But the govts would have no option because they need the tax from people driving around.

The Prius is a crap car and a straight diesel car would be every bit as economical, and a lot cheaper to make and buy.

[sunday driver]

The piston engine will never be viable in an aeroplane until we solve the issue of carrying and storing the coal and water ... as George Cayley probably said :=

[AdamFrisch]

I know they're inefficient, but the way things are going with 100LL availability and pricing, it will end up being cheaper. Any hybrid solution is going to involve some sort of turbine until power storage gets there.

[Jan Olieslagers]

a SMALL 275 HP engine? You US'ans really must have a different vocabulary. My BIG campervan has a BIG 2,8 litre diesel engine producing just a meagre 128 HP - how's that for small?

[Lone_Ranger]

Wing tip generators re-capturing the vortex energy and turning it into electricity.....yea right, something for nothing, perpetual motion sir?, well of course, please invest 10 million and we guarantee your place in the future fantasy-marketing cr@p, americans just love it

[FlyingKiwi_73]

My problem with the Prius is not the MPG savings, urban yes it maybe better, highway MPG theres bugger all difference.

The issues is ethos around the thing, its the idea that its planet saving technology. its bollox the Prius is a giant marketing ploy pulling on the guilty heart strings of over consumers.

The Nickel used to make the battery is far more harmful to the environment than the emissions from a diesel! it would be more environmentally sound to buy a Hummer. and what do you do with it when the cars life is over, leave out in the rain to dissolve like a berocca? give it to the magic recycling pixies?

Totally off thread but people really need to experience the pitfalls of things like like solar energy before evangelising it. i deffinately use it it and i know its limitations.

[K_9]

My problem with the Prius is not the MPG savings, urban yes it maybe better, highway MPG theres bugger all difference.

The issues is ethos around the thing, its the idea that its planet saving technology. its bollox the Prius is a giant marketing ploy pulling on the guilty heart strings of over consumers.

The Nickel used to make the battery is far more harmful to the environment than the emissions from a diesel! it would be more environmentally sound to buy a Hummer. and what do you do with it when the cars life is over, leave out in the rain to dissolve like a berocca? give it to the magic recycling pixies?

Totally off thread but people really need to experience the pitfalls of things like like solar energy before evangelising it. i deffinately use it it and i know its limitations.
While much of what you say is true, keep in mind that many of these new green technologies are in their infancies. There's only one way for them to really grow up, though. If nobody had been interested in airplanes, we wouldn't have gotten much farther than the Wright Flyer. Airplanes have been lucky enough to have their research development heavily subsidized and catalyzed on taxpayer dollars for national armament in both hot and cold wars.

Also, car batteries are recycled (and all batteries should be recycled).

[atpcliff]

Hi!

The electric Skyhawk is planned to fly for 2 hrs, seat only two people, and be used almost exclusively for flight training. In flt training, most of the flights are out and back, and ususally .9-1.5 hour sorties.

The batteries will either be able to be recharged in the time it takes to debrief and brief a student, and/or they will be set up for a battery swap, which will take about 10" or so.

The electric motor, and associated accessories, are MUCH less weight than the comparable ICE equipment. The electric plane won't need the tanks and fuel. It, obviously, will need a battery. The solar cells on the wings, which won't be on the earlier models and/or will be an option, will help recharge the battery.

They picked the -172 because it is the most popular trainer. When you need to overhaul the ICE powerplant, you swap it out for the electric motor.

For those of you who feel it is a pipedream, there were many, many carriage and horse-type people who knew that the new "horseless carriage" would never take off: For example, they were too difficult to operate, they were loud, dirty and stinky, there was no where to drive them (not enough suitable roads), there was no where to maintain them, and there were no places to refuel them. Because of the lack of infrastructure, and the fact that it was a new technology, many, many people were 100% sure that the automobile would never take the place of the horse carriage.

cliff
KGRB

[gasax]

I think the evangalists need to be careful with their historical 'learnings'.

The reason technologies like the motor car and internal combustion in general advanced as rapidly and as far as they have is because technology 'savvy' people could see those nascent technologies offered great potential.

They meant that greater power, less weight, more speed etc were potentially on offer.

The situation with all 'green technology' is fundementally different. In the vast majority of cases large costs and other significant disadvantages means that the 'green' version will under perform the present situation until there is either a massive technical breakthrough or legislative or some other external influence.

In short it is the Prius argument - it looks good for the planet but actually it is not green, it promises fuel economy but does not delivery, it is not genuinely sustainable - it is marketing.

I know a chap with an electric glider - it is a thing of beauty - the best our technology can offer at the moment. It self launches and can climb to 3000m - once. It can give full throttle for 13 minutes - after which it can 'self sustain' for maybe another 10 - if the cells recover. He has had some problems with the cells but loves the idea of the machine.

List price is just short of $300,000 so it carries some pretty significant downsides. Incidentally the manufacturers say there is no point in using solar cells to increase the self sustaining mode - too heavy, too little power......

[IO540]

A battery powered C172 may well work for 1hr training flights in the battery endurance sense.

However the overall economics will be a different thing. Nobody has got anywhere near 1000 cycles especially with rapid charging. Anybody with experience of laptops, model planes, etc, will know this. You get 100-200 cycles out of a LIPO battery and it is going downhill. And this battery won't be a £100 LIPO :) It will cost many thousands. The real life will be a major cost factor.

The motor and control electronics are relatively trivial and could have been done 20 years ago in pretty much the same way as today. But even there, the reliability won't be 100%. It could be very high indeed, but there is very little electronics expertise in GA today. It looks like the combined might of Lycoming manages to knock up an electronic ignition box not incomparable to ones I used to build for Yamaha bikes in the 1970s.

If I was running a school I would look at this seriously but only on a "pay per flying hour" basis so the vendor would be forced to back up his battery life and other claims. After the Thielert fiasco, I can't see any flying school owner doing much else...

[ZeBedie]

Battery technology is predicted to continue to increase. Boeing believe this and have scetched out some ideas for an electric motor assited turbo-prop, subject to a massive step change in battery efficiency.

[IO540]

subject to a massive step change in battery efficiency.

You and I could do that too :)

A 1000HP 3-phase brushless motor is tiny. At a guess, about 1ft long and 2ft diameter if you want a low-RPM direct-drive solution. Weight perhaps 50-100kg (i.e. a fraction of a PT6).

The controller would be about 1ft cube; weight about 10kg.

Just need a battery................ ;)

Oh BTW you will need one other thing in the long term, to generate the electricity if this idea becomes popular:

Nuclear fusion :)

Actually that will prob99 come, within our lifetimes. It already works, for a short while.

[BackPacker]

A battery powered C172 may well work for 1hr training flights in the battery endurance sense.

I just ran a few numbers.

Assume a C172 that's normally running on a 160 HP engine, at 70%. One HP = ~750 W. So in one hour, this aircraft uses 160 * 70% * 750 = 84 kWh. (Maybe a little less because of increased efficiency. But that doesn't change the discussion significantly.)

This energy needs to be replenished somehow. A typical European circuit can deliver 240V at 16A, which is 3.8 kW. This means that recharging that aircraft using a normal circuit will take a little over 22 hours.

So in essence, with that setup, the flight school can squeeze a single flight out of that airframe on any given day. Assuming they max out the 240V circuit for the rest of the day to recharge the aircraft.

Of course that's not a setup that's practical. But you need the equivalent of 22 average household circuits, all maxed out, to get a more-or-less workable charge rate of about one hour for each flight hour - assuming your batteries can charge that fast.

10 aircraft charging simultaneously and you're looking at values approaching one Megawatt. That's the unit that we normally express powerplant capacities in. (Fukushima Unit 1 was 460 MW, to give you an idea.)

As others have said, before electric flight really takes off, there are a few things that need to happen:
- Battery storage capacity needs to improve significantly
- The power grid needs to be upgraded significantly

And even then I think automotive technology is going to reap the rewards first, and aviation last.

[astir 8]

Just a thought for those who equate electric power with milk floats and mobility scooters.

The fastest lap time round the Isle of Man TT course on an electric motorbike is I believe 94.7 mph.

And I've got a little £40 battery powered model helicopter which I'm sure would have been impossible to build at any price 25 years ago.

Electric devices are getting much better very quickly. But where will all the "clean" electricity come from? Errrrrrrrrr......

[24Carrot]

So I fill up my electric C172: 5 hours x 84kWh = 0.420 MWh.

Then I crash.

What happens to that 0.420 MWh when the battery breaks?

[IO540]

A typical European circuit can deliver 240V at 16A, which is 3.8 kW. This means that recharging that aircraft using a normal circuit will take a little over 22 hours.

Correct; however it is not hard to get a hefty 3-phase supply put in. Years ago I had a big house (my ex's house now ;) ) which I wired up for a 3-phase swimming pool heat pump, and some other stuff. The company charged about £800 for bringing in 3 x 35mm2 cable which was good enough for at least 100A per phase, so that's 72kW. In fact I recall allowing for a 40kW 3-phase pool heater, and some other stuff; on Economy 7 this was not much dearer than oil which was the only other option. They installed a 3 phase electricity meter for free. The quarterly rental was the same, as Seeboard did not have a 3 phase domestic tariff :) The cost per kWh was the same too (they obviously hoped you would buy lots of them :) ).

So I think, in a city scenario, 100kW is really easy.

Out in the sticks, miles from nowhere, it would be expensive (5 figures+ perhaps) but not much training takes place from remote strips.

[douglas.lindsay]

I recently saw some marketing material, presumably the sort that has been used to persuade my very own government of the value of electric cars. I seem to recall that it suggested there is a payoff in favour of electric cars if you assume that the regular sort get about 35-40mpg at best.

(Let me at this point say I'm a total amateur in this area, so treat my comments accordingly)

I drive an unmodified 2005 Peugeot 307 HDI Sport. I'm one of these nerds that actually knows what mileage I get, and keeps a close eye on it. I get 54mpg in the city, and at least 63mpg out of town - yes, it beats a Prius by a substantial margin in both environments :-)

Not that I don't like the idea of electric transport - I do, and I'd love an electric car and matching aeroplane. I just think the hype is a bit ahead of reality at the moment.

[BackPacker]

Not that I don't like the idea of electric transport - I do

Me too. But if we ever get electric transport (and I don't mean trains or anything else with a "live rail" or something like that) the first application will be relatively light and low-intensity. Electric scooters that are used for inner city traffic for instance. Followed by electric city cars with limited range for commuter traffic. But not high-intensive stuff like airplanes used for flight schools, that need *at least* four hours usage out of them on an average day and maybe as many as six on a good day.

I've done the calculation and by far the most of my car trips are < 200 km per day. In a pinch, I could probably even live with even less range than that out of a full nights charge. If somebody would come up with a light two-seater (say a Mazda MX-5 or similar size/shape) that's electrically-powered and would be available for a reasonable price (not much more expensive than an equivalent petrol car), I guess I'm not going to need a whole lot of convincing. Throw in a rental plan that gives me relatively easy access to a diesel estate for the few days a year that I need the range or payload, and I'm sold.

And yes, I'm one of those nerds that tracks mileage too. My 2001 VW Golf Estate TDI does 19.5 km/l average over the last ten years.

[K_9]

I drive an unmodified 2005 Peugeot 307 HDI Sport. I'm one of these nerds that actually knows what mileage I get, and keeps a close eye on it. I get 54mpg in the city, and at least 63mpg out of town - yes, it beats a Prius by a substantial margin in both environments :-)

Don't forget about the difference between imperial gallons and US gallons.

[24Carrot]

How on earth is the Prius piece of this thread still going?

The Prius is extremely good in congested traffic. I drive one, and have the mis-fortune to drive at least an hour a day at an average speed well under 10mph. Queuing in traffic, the petrol engine seldom runs. The occasional movement comes from the battery and electric motor. Occasionally the petrol engine kicks in and, at efficient revs, re-charges the battery. The efficiency is obvious.

At the other extreme, on the motorway, the battery and electric motor are a waste of space and weight, you just have an under-powered over-heavy car. The inefficiency is obvious.

Because the efficiency varies so much with the conditions, there is no point in comparing individual's mpg achievements. Indeed, the compelling case for Londoners to buy a Prius used to be exemption from the Congestion Charge, not the petrol consumption.

[MG23]

For those of you who feel it is a pipedream, there were many, many carriage and horse-type people who knew that the new "horseless carriage" would never take off: For example, they were too difficult to operate, they were loud, dirty and stinky, there was no where to drive them (not enough suitable roads), there was no where to maintain them, and there were no places to refuel them.

And they laughed at Bozo The Clown too.

Electric 'horseless carriages' are nearly two centuries old; they're not some new invention that just became technologically feasible. They were abandoned when the ICE car became viable because in comparison electric cars sucked. They still suck for the same reasons, while the ICE has improved dramatically.

Which is not to say that electric vehicles aren't a good idea in specific markets where the benefits outweigh the disadvantages, or that an electric training aircraft is a bad idea, but absent massive improvements in electrical storage and recharging technology, or some kind of external power supply, they're not going to replace the ICE.