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I can't wait for electric/hybrid aircraft.

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I can't wait for electric/hybrid aircraft.

Old 5th Jan 2010, 15:22
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I can't wait for electric/hybrid aircraft.

Half of the threads here pertain to safety and high workload related issues connected to the antiquated way modern aircrafts are made and propelled.

Just below is a thread about a C152 engine quitting because of either a rich cut or carb ice, depending on who's answering. Not even injection engines are commonplace even though the offer more security. Cessnas new 162 Skycatcher? Carb - check.

Just imagine if the above aircraft were hybrids. Until the new nanowire batteries get powerful enough in the meantime a hybrid solution with a small turbine APU would recharge a LiPo battery (like they've had and broken all records with in the R/C world for the best part of 20 years now). The battery runs a brushless electrical motor with 90% efficiency compared to the 20% efficiency of the combustion engine. Just imagine all the benefits:

1. No carb ice.
2. No need for complicated constant speed props (as electrical motors have linear power output and no sweet spot).
3. No TBO - only limited by bearing life.
4. No CO poisoning.
5. No shock cooling.
6. No rich cut.
7. No degradation at altitude, no need for turbos etc.
8. Built in Fadec (brushless motors you set a RPM setting and it keeps it through the controller, no matter what).
9. No need to check oil.
10. Much less weight - 15Kw (21hp) R/C brushless weighs less than 2kg. That means that a O-200 replacement would weigh about 10kg. That leaves a lot of weight for a battery..
11. No dirt.
12. No vibrations.
13. No noise.
14. No leaning at altitude.

I want to enjoy flying and the view, not manage a steam driven 100 year old system just looking to screw me up.

I can't friggin' wait.

Last edited by AdamFrisch; 5th Jan 2010 at 16:12.
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Old 5th Jan 2010, 15:29
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The Moni is available now with electric power.They are getting over an hr from a 40 min charge. OK not much use for cross country, but as a motor glider you can thermal all day and go home on power for less than $6 (they say).
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Old 5th Jan 2010, 15:53
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There was an article in one of the magazines (I think Flyer) about a year ago where they did the calculation for a two-seater. From memory, a Twister. Based on the latest technology, particularly battery, they calculated that they could rip out all the fossile fuel stuff, add in electric motors, controllers and so forth, and fit sufficient batteries in the aircraft, remaining within MTOW, for 40 minutes of flight. And they made some very generous assumptions to get to that number anyway. So, not enough for any meaningful x-country plus VFR reserves. Battery technology has to improve dramatically for this to work.

Gliders need only a few minutes of power to get to a height sufficiently for thermaling. I'd never heard of that Moni, but that sounds like a fair application.

As far as hybrids are concerned, well, they're nice for stop-and-go traffic, where kinetic energy can be converted into electricity and stored in the battery when the lights turn red, to become available again when the lights turn green. But this is not a typical usage scenario in an aircraft. Aircraft typically need continuous power and converting/storing that in an intermediate form is going to lead to efficiency losses in any case, and weight addition for no gain. If you want to use a light-weight turbine APU, just run the electric power from that APU directly to the propellor motor. Or even better, connect the propellor directly to the APU shaft.
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Old 5th Jan 2010, 15:53
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Interesting idea, although I suspect a truely electrical tourer is a while away.

On the hybrid idea, whilst an electric motor maybe 90% efficient, a small APU is not going to get any where near 20% efficient, so you would still be better off with a good old fashioned donk. If want rid of the nasty bits of a piston engine, forget the batteries, put a small APU in the aircraft, wire it up to an electric motor bolted to the prop and off you go. It won't be quiet, but you get around most of the problems with the old Lycoming. Plus you would have all the electrical power in the world for all the modern fancy nav kit. Mind you I wouldn't like to buy or maintain the APU, nor would I like to share a small airframe with one. 60,000rpm spinning just behind/infront of you? no thanks.
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Old 5th Jan 2010, 16:26
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I agree, while the hybrid thing makes a lot of sense on a car where weight is less of an issue, I would not want to carry two engines in an airplane (unless it's a twin)

I do however agree that the GA industry is hopelessly behind the curve and I find it hard to understand why we are still sticking to carbs and aircooling (even Porsche had to move on).

There are a couple of promising developments going on though, Rotax abviously being one well proven and quiet solution. Another (less quiet) are the new generation of small turbines such as this: PBS Velká Bíte?, a.s. ... Turbovrtulový motor TP 100

Sonex are mounting the jet version on their new sub-sonex
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Old 5th Jan 2010, 16:35
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The revolution has already begun. This will be the first certified electric LSA.

YouTube - Yuneec International E430 Electric Aircraft

But the beautiful thing with a hybrid is that you could take off on battery power, climb to your altitude and throttle back to economy cruise (which on an electric is probably below 50%). Now you start the APU. This ensures that the APU will be running at a higher altitude and consume less fuel. And all it needs to power is the economy cruise. It will also reduce noise considerably for take off. As you descend you windmill and generate electricity to top batteries up a bit. And should you really need to get down fast, you just regen more and make the prop/fan work as a speed brake.

But sure, there are still obstacles to be overcome for a pure battery powered tourer. But they're closer than many think. Battery capacity has doubled in just 5 years.

I've researched this quite extensively and what's important is power density, i.e. Wh/Kg. Newest LiPo batteries (like the R/C guys use) deliver about 400Wh/kg today. That means you could run a motor at full power of 400W for one hour. Or to put it in perspective of a C152 - a 182kg battery pack could make you cruise at 100% for one hour. In reality, you would never use 100% all the time on electric motors, so the endurance would probably be closer to 2 hrs for that weight. Not that far off - remember, you'd save not only on the weight of the fuel and the engine and that's gotta be an easy 150kg alone.

Now, here's the interesting thing - nanowire batteries that have just been patented and are getting geared up for production have a potential power density of 4500Wh/kg. If they can deliver on that promise, then it's all over for the combustion engine. Bye bye. Gone.

Obviously cost is also a factor for batteries, and to keep them healthy no more than 1000 charges are recommended. At the price of batteries today that would be a large sum of money, probably the equivalent to a TBO overhaul of your Lycoming. But the nanowire promise has the added benefit of dramatically reducing the price as well.

It's closer than we think. I wouldn't want to be Rolls Royce, General Electric, Pratt & Whitney, Lycoming or Continental in 20 years time.
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Old 5th Jan 2010, 17:46
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Unless one of the snap up the innovators while they are small and use their name, presence and experience to get the hybrid certified and into the engines

Reminds me a little of the Dynacam (or axial) engine that really makes a lot of sense in an aircraft and with Piper having plans to manufacture it for the PA28 range (late seventies I think, someone might remember).....and it all stranded on an disagreement over how rich the patent holder should be allowed to get

I think these guys hold the rights now: AVEC | Axial Vector Energy Corporation |
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Old 5th Jan 2010, 17:49
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I find it hard to understand why we are still sticking to carbs and aircooling
Carbs: Less sensitive to fuel contamination. Not that much less efficient compared to simple, pneumatic/mechanical fuel injection systems like the ones on an IO-360. More reliable than an electronic injection system; most significantly, an existing, well-tried carburetor design is far more reliable than a novel, untested (in aviation!) electronic injection system. Not dependent on electrical power for its operation. Development already paid for, thus cheap.

Air cooling: Light. Simple. Can not break (with a slight caveat for baffle seals and cooling flaps, which degrade gracefully, as opposed to a water cooling system that fails catastrophically). Sufficiently effective for a boxer engine, which happens to be the ideal shape for an engine that is to be mounted in the nose of an aircraft without a gear box or belt drive. Is the method used in engines whose development is already paid for, thus cheap.

Last edited by bjornhall; 5th Jan 2010 at 18:02.
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Old 5th Jan 2010, 17:56
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It's closer than we think.
Who is "we"? It might be closer than I think, but it is certainly not as close as you think!

For experimental designs it sounds interesting. Give the EAA members and their likes a couple decades to sort it out, and then we can start discussing it.

For normal category aircraft: No way this side of year 2035. We haven't even got the diesels sorted yet, despite their obvious theoretical advantages, and that technology has been around for a long time.

The development costs, including getting it certified, would be astronomical considering the tiny volumes of light GA today. The days when any significant technological advance could be paid for by users of light GA engines ended when taxi, business and light airline operators went turbine. What we can hope for today is reusing some parts of what the automotive industry comes up with, but since their operating environment and requirements are entirely different, most of their technology can not produce a light GA engine that is better than an IO-360.
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Old 5th Jan 2010, 18:17
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What we can hope for today is reusing some parts of what the automotive industry comes up with, but since their operating environment and requirements are entirely different, most of their technology can not produce a light GA engine that is better than an IO-360.
Actually, I don't agree with that statement. Electric motors are in use everywhere. From coffee grinders to trains. They're well proven and available in all shapes and sizes. Picking one off the shelf that's very suited to aviation use should be very simple. And since the motors have only very few moving parts and very predictable wear characteristics, getting them certified for aviation use should not be that hard as well. Compared to, say, a traditional piston engine consisting of upwards of 1000 components and god knows how many moving parts/bearings/friction surfaces and so forth.

It's battery technology that needs to make a giant leap for electric power to become feasible for aviation use (and automotive use as well, BTW), but the rest of the components you need for an all-electric airplane (or car) are already available, and well proven.
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Old 5th Jan 2010, 18:25
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Well, the energy inefficiencies in aviation are staggering.

It's taken 50 years of jet travel and APU-equipped aicraft to come to this (Delta starts using it this year) - you'd think that'd be day one that would have been sorted out, but no:

WheelTug plc

Regular long taxis with all engines running, complicated non-GPS approaches following antiquated flight paths that waste millions of gallons - the list goes on and on.

It's just very, very backwards and slow. I mean, the C152 I fly has 12.000hrs on it and was made in the early 70's.

Only in aviation.
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Old 5th Jan 2010, 20:28
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Good point regarding the electric motors themselves, but also regarding the batteries! And once you have the motor and the batteries, the hardest part remains: Systemization and system integration, taking that engine and those batteries along with all the other parts that will be needed and turning it into a practical, economical, reliable (both in terms of safety and dispatchability) and generally well functioning power source. Add certification standard development, certification (both aircraft and pilots; what differences training will be needed?), and so on and so forth.

Those are not reasons why this isn't a good idea, but they are reasons for why it will take a good long while and be expensive.

Again, in the experimental world it is a different matter entirely. This is exactly the type of thing the experimental category is intended for! Best of luck to them!



AdamFrisch:

Backwards and slow...? Slow, yes. Backwards, really?

There is a difference between stagnation and maturity. By the 1950s (some would say the 1930s), airframe and engine technology for light aircraft had reached sufficient maturity for designs based on that technology to be "good enough" for many purposes.

Once that stage is reached, a new design is not automatically much better than an old one. Taking into account aspects like reliability, maintainability, customer base, market positioning and so on, the older design can be better than the newer one. Or more commonly, the newer design is better, but not so much better that it really matters much in practice. When that happens, you will not see much progress in that particular field, but that is not stagnation, it is maturity. Stagnation would be when progress stops before the field is mature. Maturity allows one's efforts to be spent on other areas, in fields that are not yet mature and where progress really matters.

The progress made in GA in the last 10 - 15 years is quite tremendous IMHO, and I think it is accelerating rather than slowing down. But the results are not seen on the outside, or in performance specifications; a C172B looks deceptively similar to a glass panel C172S, from the outside. The difference is found on the panel, and in terms of the functionality provided by the systems on that panel. As in so many other fields of technology, capability growth takes place in software, not in hardware.

You may well be right that power plant technology will be an area of strong progress in a not too distant future, say the next couple decades or so. But I do not think it is fair to say that aviation in general, or GA in particular, is backwards or has been standing still in recent years. Avionics is not a mature field of engineering, and that is where most current progress is made.
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Old 5th Jan 2010, 21:40
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Add certification standard development, certification (both aircraft and pilots; what differences training will be needed?), and so on and so forth.
Well, look at companies like Rotax, Thielert (not the best example, I admit) and Diamond themselves (Austro) and you'll find that getting a brand new engine plus the surrounding systems (FADEC, amongst others) certified actually is feasible for a not-too-large company in not too much time.

Then consider that the potential savings of an electric engine over a Lycosaurus vs. the potential savings of a Rotax or diesel over a Lycosaurus are much greater, consider that once you have the basic integrated systems certification in place, you can just swap in and out larger or smaller motors, or add more batteries as desired, and consider the environmental angle. It's a great business opportunity, better than that faced by Rotax, Diamond or Thielert. For starters that means more investment money available to go through the certification process.

And as for differences training: the UK CAA already has this covered by introducing the category of "Single Lever Power Control" (SLPC) aircraft, for which they indeed require differences training by a suitable instructor, but no specific exam.

If Adam is right and those nanobatteries are indeed going to deliver energy densities (kWh per kg) approaching that of fossile fuels, for an interesting price from a TCO perspective, then I think the rest of the story (the other components, and the certification of the integrated system) is probably sorted in zero time flat.

Oh, and then we'll probably run into the same problem that the automotive industry is already deeply aware of: where are the Amps going to come from to charge all these batteries? The power grid is going to need a serious upgrade to be able to supply even a fraction of the energy that's currently being consumed by road and aviation consumers in the form of fossile fuels.
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Old 5th Jan 2010, 22:02
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Apparently the power contained in aircraft fuel amounts to the equivalent of 12000Wh/kg, so even with the new batteries fuel has more energy. However, a combustion engine only turns 20-30% of that into power, whereas an electric motor will turn 85-90% of into power, so you'll never need to reach those power storage levels.

If the car industry is anything to go by, then the shift will happen pretty quick once things start getting in place. Just remember how quick the hybrids went from the car nobody wanted to the car everybody wanted. The Prius is a massive seller for Toyota and every manufacturer has some type of hybrid on the go.

Fast forward 30 years. A board is going to have to be pretty convincing and persuasive if they want the shareholders to approve the costs of a gas guzzling Gulfstream G650 when they could be riding in an electric or hybrid bizjet that might not be exactly as fast or have exactly the same range, but get you there for a fraction of the cost. Imagine the badwill. Not to mention that the carbon excesses imposed by government on fossil fuels by then. They're never gonna get cheaper, that's for sure.

Backwards and slow...? Slow, yes. Backwards, really?
No, on avionics I agree - there it's been pretty fast lately. Construction? Not so much. Remember, the first composite aircraft was way back in the 70's and it was an experimental. You'd think the military and the big corps would lead this, but in fact without EAA and enthusiast tinkering in garages worldwide, there would be no 787.

Last edited by AdamFrisch; 5th Jan 2010 at 22:15.
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Old 6th Jan 2010, 02:30
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Carbs: Less sensitive to fuel contamination.
Is that really the reason most planes still use carbs? I have never heard of fuel purity being an issue. Cars have had FI for many years. I fly a FI plane and would never ever buy one with a carb. I thought that carbs, with their lethal carb ice issues, are still used only due to tradition / certification inertia.

Re electrics, as stated, the motor is not an issue. I have worked with model plane brushless motors and some bigger ones and 250HP is easy to achieve with a unit weighing perhaps 30kg i.e. ~ 1/10 of an IO-540 engine. The batteries are the problem...

But even if suitable batteries are developed, you have to charge them from somewhere. We don't have the infrastructure to charge them in cars, and are not likely to have for many decades, which is why all mainstream-usage electric cars will be hybrids, perhaps with a small turbine to charge the battery. The power would all have to come from power stations and there won't be anywhere near enough of those about, for the foreseeable future.

Airfields will never get the infractructure to support electric planes - who would pay for it? Most can barely afford to fill potholes in the runway...
1. No carb ice.
2. No need for complicated constant speed props (as electrical motors have linear power output and no sweet spot).
3. No TBO - only limited by bearing life.
4. No CO poisoning.
5. No shock cooling.
6. No rich cut.
7. No degradation at altitude, no need for turbos etc.
8. Built in Fadec (brushless motors you set a RPM setting and it keeps it through the controller, no matter what).
9. No need to check oil.
10. Much less weight - 15Kw (21hp) R/C brushless weighs less than 2kg. That means that a O-200 replacement would weigh about 10kg. That leaves a lot of weight for a battery..
11. No dirt.
12. No vibrations.
13. No noise.
14. No leaning at altitude.
A lot of the above are actually non-issues, especially in cruise where one spends most of one's time. Leaning is done at all altitudes, BTW, otherwise you have a massive waste of fuel.

I'd like to see electrics too (I work in electronic & mechanical engineering) but the economic case has to be present.

They will also need to address battery safety issues. I know fuel is not that safe but it goes off only if you set fire to it. LIPO batteries often go off by themselves if damaged, overloaded, etc. and they release an awful lot of heat when that happens.
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Old 6th Jan 2010, 08:58
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Is that really the reason most planes still use carbs? I have never heard of fuel purity being an issue. Cars have had FI for many years. I fly a FI plane and would never ever buy one with a carb. I thought that carbs, with their lethal carb ice issues, are still used only due to tradition / certification inertia.
You are probably right that the main reason why carbs are used is because the old engines still in use happen to have carbs. But I am rather certain carbs have the advantage of being less susceptible to fuel contamination than fuel injection systems, since the latter have much more narrow passages internally that could be blocked by contaminants. That is one reason I have heard for why Cessna went from 3 fuel draining points to 13 (!) when they fitted a fuel injected engine in the C172.
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Old 6th Jan 2010, 10:28
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More likely it is because of a bad fuel system layout which created many points at which water could settle, and since they had to recertify half the plane due to the FI, this was a reasonable juncture at which to implement changes which had been "pending" for many years but which they did not want to introduce alone because it would be an admission of a bad design
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Old 6th Jan 2010, 10:34
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TBH, on the car side I tend to view the current craze for the hybrid as a triumph of marketing and legislation over basic physics. At the end of the day all the power to drive the car has to come from the petrol or diesel engine. The only difference is that some of the time the power to drive from the car comes from the batteries but that pwer has to have been put into the batteries by the ICE. Just like if I pay for something with a credit card, my bank balance does not change but when the statement becomes payable my bank balance does change.
Against that the hybrid has to lug around a lot more weight, has to be more expensive to manufacture and as the batteries will have a finite life in terms of time and/or cycles will have periodic big replacemnet costs.
In the case of the pure electric cars at the moment I suppose that for someone who only does short trips they might be practical but you will still need to either own or hire a different car for any longish journey. Same problem as the hybrid as regards bettery life cycle. Not emmision free as they just move the emmisions from the tailpipe of the car to the chimney of the power station except possibly in France as they have a fair bit of nuclear.

But lets say that new battery technology, nanowire, ultra capaciter or whatever, becomes available, and it probably will. The electric car should now be practical as should the electric light aircraft, provided enough money is thrown at it.

However I can see one huge potential snag both for cars and aircraft. For it to be pracical the batteries have to have really high energy storage capacity. What happens when you do any physical damage to such a battery? That energy is going to go somewhere and not in any controlled manner.
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Old 6th Jan 2010, 10:46
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Have a look at this. Here's your dream come true (albeit in a Wrightish brothers kind of duration), Adam

Interesting to note that they set their record with battery power but are moving on to fuel cells. Discuss!
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Old 6th Jan 2010, 11:18
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Interesting to note that they set their record with battery power but are moving on to fuel cells. Discuss!
More specifically, hydrogen fuel cells.

I don't know what the energy density of hydrogen storage is these days (in kWh/kg) but if it's better than what batteries can deliver these days (400 Wh/kg for LiPo according to one of Adams posts, above) then it makes sense to use hydrogen as an intermediate energy storage solution, instead of batteries.

You do have the added weight of the fuel cell (converting the hydrogen into electricity) but I don't think they're that heavy. And hydrogen requires more infrastructure on the ground, both for production and storage, vs. an all-electric solution.

Oh, and at some point in time the general public will remember that the Hindenburg was also filled with hydrogen. That may become a significant psychological barrier to widespread adoption of hydrogen technology.
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