Will 2015 See Deliverable Electric Airplanes?

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When I was a little kid riding in my Dad’s Oldsmobile across the plains of Texas at night, we would spot the lights of Amarillo in the distance and two hours later, we’d get there. An exaggeration of course, but it reminds me of covering the electric airplane industry.

We’ve reported periodically about this company or that, this new battery development or breakthrough motor controller yet…nothing. I visited Europe twice last summer with a topline agenda item of actually flying an electric airplane. Almost accomplished it in Slovenia, but got blown out by the bora winds common in that part of the world.

This spring, however, the first electric airplane you can actually buy looks like it will emerge at Aero in Friedsrichshafen next month. It will be announced by—who else?—Pipistrel, the innovative Slovenian company that’s been bullish on electric flight for several years and five projects. They’ve been selling an electric motorglider which is now just beginning to get some sales traction. That was the airplane I was supposed to fly last year, the Taurus Electro.

This year’s announcement, if it goes off as planned, will be the Alpha Electro, which was just going into the conceptual testing phase when I was in Slovenia last year. The Alpha is basically a variant of the Pipistrel Virus, a light, all-composite, highly efficient two-place airplane that sells in the U.S. as a light sport and as a microlight in Europe. Its light airframe makes it an ideal choice for an electric and what Pipistrel envisions is a straight-up electric version of the Rotax-powered airplane: same airframe, generally the same performance, but less payload and, obviously, less maximum endurance.  

Siemans AG, the giant German electronics and electrical firm, pitched in to develop the motor, which is a 31-pound unit a little bigger than a ceiling fan motor and about the same shape. The prototype’s motor is capable of 85 kw or about 114 hp, but Pipistrel’s Tine Tomazic told me the production version will have the same output as the gasoline airplane—about 80 hp or 60 kw. The light little Alpha does well with that power, hardly lacking for climb rate.

But how much battery weight does this puppy have to haul around? A lot. Where the gas version tankers 78 pounds (35.5 kg) of fuel, the Electro needs 277 pounds of LiPo cells or 126 kg. Saving it is what electric propulsion taketh away in battery weight, it giveth back in far lower engine weight. So all in, the Alpha Electro will have an empty weight around 377 kg or 829 pounds compared to 631 pounds (287 kg) for the gasoline model I flew last year.

The electric version will have a useful load of 380 pounds. That’s 190 pounds each for student and instructor except in those cases where both the CFI and student are people of girth, in which case I suspect it will be flown overgross, just as Cessna 152s are now. (I know this a shock, but then so was finding out about Santa Claus and the Tooth Fairy.)

By comparison, a typical Cessna 152 has a useful load of about 480 pounds (218 kg). Down fueled with half tanks, it’s good for 402 pounds of payload or a little less. With full fuel, a 152 can carry about 350 to 370 pounds. The 152 can, of course, be down fueled to balance the weight; the electric airplane can’t, at least while retaining useful endurance. Speaking of which, how much of that will the Alpha Electro have? Pipistrel says its testing is on target for about an hour, with 30 minutes of reserve, including a cabin heat budget. Is that even useful?

Based on discussions with its customers, Pipistrel is marketing the airplane as an “airport” trainer, the ship that stays in the pattern to do touch and goes and landing training. I’ll get to the economics of that in a moment. They don’t see it as cross-country trainer, for obvious reasons, and maybe not even a maneuvers trainer. So to work, the Electro has to be placed in a school whose business model supports an airplane dedicated to one purpose. In the U.S., that would be a tough sell; in Europe, apparently not. In any case, if the Electro finds buyers—and Pipistrel says advance orders on it exceed any other model they’ve introduced—I predict it won’t be limited to the pattern. Schools will find a way to build it into their regular training doctrine, just as early adopters of VisiCalc used it for store inventory. I think I can get out to the practice area, conduct a 45-minute lesson, and get back to the airport with safe reserves. Only operational experience will reveal if this is practical and safe. I’m looking forward to learning how schools actually use the airplane.

The batteries are in two modules, each with three enclosures about the size of an overnight bag and weighing 46 pounds each or 21 kg. They’re meant to be quick change, so you can rapidly unplug them, slide them out on rails, and stick in fresh charged batteries. There are three battery enclosures in the front of the airplane behind the motor and three more in the back. They aren’t cheap, either. A full set of batteries costs about $11,500 with an estimated life of 2000 hours, same as the TBO on a Rotax engine.

Pipistrel is modeling flight school ops using two electric airplanes with one set of spare batteries between them, another thing it says customers are interested in. Those that want a single airplane might choose to charge between flights, which will require just under an hour. Flight schools I’ve interviewed tell me if they put 100 hours on a trainer a month, they’re viable and based on a six-day week, the Electro could just about do that, if it has good dispatch reliability. And if it’s designed right, why shouldn’t it? Pipistrel also envisions pairing the electric with a gasoline Alpha to do cross-country and other training tasks. Having flown the Alpha, I think it’s different enough that I wouldn’t want to bounce a student from an Alpha to something else.   

What about the numbers? Electrics hover on the horizon as bright neon signs that say “game changer.” The definition of that overused phrase is technology that’s disruptive or completely resets the accepted paradigms. I can’t make the calculations do that, although I can support a less catchy, pedestrian phrase: does actually reduce operating costs.

Here’s the rundown, apples to apples with the two Alphas. The chart below tabulates it. The gasoline version sells for about $83,000, although check back tomorrow and that might be less, given the free fall in the Euro against the dollar. The Electro doesn’t have a precise price yet, but Pipistrel says under €100,000, so I used $100,000 for my calculations.

Add up the gasoline Alpha cost and divide by 100 hours a month and it comes to about $48 an hour composite operating costs. On the electric side, most of the costs are similar, but with obvious exceptions. Pipistrel is planning on a 2000-hour life for the major components, which are essentially the batteries. The electric motor has a 10,000/50-year projected life limited by the insulation on its windings. At 2000 hours, it needs a $400 bearing rebuild. The batteries are projected to have a 1500-cycle-to-full-charge life, which Pipistrel is also calculating as about 2000 operational hours. At the current favorable exchange rates, the battery pack replacement cost is $11,500 or about $5.75 an hour. Tomazic told me Pipistrel is considering all the costs across the board as the same as the gasoline version, except for fuel, so for my calculation, I added a fudge factor to the battery cost. Call it a budget for the unknown. There are inevitable unforeseens in a new type such as batteries that don’t last as long as projected or other unpredictable factors.

So where’s the savings? In fuel, or lack thereof. In the U.S., the Rotax will cost about $22 an hour in fuel; in Europe, make it $36 per hour, if not a little more. At typical Kwh costs in the U.S.—about 12 cents—a battery charge will cost under $2. At the highest prices in the EuroZone, $6 is more like it. Either way, if Pipistrel’s numbers are close to the mark, the hourly operational costs are about half what they are for the gasoline version.

So why’s that not a game changer yet? The airplane will be used for only a portion of the training, that part which remains in the pattern. Let’s say that’s about 35 percent of the typical 70 hours required for a private certificate—25 hours. For U.S. context, multiply that times a $22 savings and it comes to $526. OK, so maybe the pattern work is 40 percent of the hours, in which case the savings comes to $590. In the U.S., a private costs between $10,000 and $12,000 all in, so we’re talking about a 4 to 6 percent savings. Hey, I’ll take it. It’s better than an increase of that much. But a game changer it is not, at least in the U.S. At European gas prices, the electric looks much better because fuel is so much more expensive and thus a larger percentage of operating costs. Plus, in Europe, where airport noise is far more restrictive than in the U.S., they’ll like a quiet electric.

I suspect there’s a sliver of a private owner market that will buy an electric airplane for the novelty, for the greenness and tech-edge of it. I typically fly the Cub for less than an hour at a time, so it would fit my profile. I pine for the thrill of advancing an electric throttle to the sound of nothing but prop tips slicing air. But I wouldn’t spend $100,000 on an airplane to do that that has limited range. So I have no idea how robust such a market might be. Pipistrel’s healthy order book for the Electro indicates to me that there are enough schools intrigued by this technology to give it a go. They’re not all in Europe, either, Tomazic told me. Nor are they in the U.S.

Although I’ve applied U.S. economics to this analysis for the sake of context, the Alpha Electro won’t be a player in the U.S. as an LSA because the FAA hasn’t gotten around to defining light sports as capable of being electric airplanes. That’s part of the reason, I presume, that the U.S.-based Electric Aircraft Corp. is certifying its proposed Sun Flyer under the primary category. Once again, I’m afraid, the rest of the world may lead while the U.S. lags.

So where does this get us? As I’ve said before, the electric airplane evolution is not going to fizzle. Just as electric cars have made market inroads—with the trends accelerating, I might add—so will electric airplanes. Battery technology is forecast to decrease incrementally in price and increase incrementally in capacity, both curves that are going in the right direction. Unfortunately, we can’t say the same about the long-term cost of fossil fuels or the prices of the airplanes we’re building to burn them.

Electric vehicle sales trends. Source: ZSW

So at the expense of limited practicality, these early electrics show potential to at least lope the price spikes off the cost of training. To be the real game changers some think they are, I think they’ll need better endurance. I don’t know what that number is, but I’m not convinced it’s an hour with 30 minutes of reserve. To compete with gasoline, I’d want better range than that, maybe even in the training realm.

Right now, Pipistrel is plying the early-adopter market and it will be fascinating to see how schools, instructors and customers take to these airplanes. What we’ve found with LSAs is that in some schools, they are much preferred over conventional aircraft. One school I spoke with was flying the wings off its Skycatcher. But in other venues, older 152s and 172s are preferred; the LSAs molder and are often disposed of. Electric airplanes may show a similar pattern for the short term. I wonder if the novelty of flying a near-silent airplane will have such appeal as to overcome other shortcomings, some we may not even know about until electrics hit the field.

We will see soon enough. But so far, I like the direction it’s going. Now please, someone let me fly one of these things.

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Comments (56)

An hour in the traffic pattern, with reserves? I doubt it. That's about fourteen 1,000-foot climbs to pattern altitude, plus a little cruising, plus 14 (idle power?) descents - in one hour. That's a VERY different energy consumption profile, from the traditional one climb / one cruise / one descent profile that's been the typical endurance metric.

The good news is, "fuel" is a part of the vehicle's empty weight. The bad news is, "fuel" is a part of the vehicle's empty weight.

I'd love to attempt to put one to an hour's use in the pattern, here in sub-zero New England. I'd appreciate the quiet cockpit, and I've always enjoyed practicing emergency landings! Please, someone let ME fly one of these things, too!

Posted by: Tom Yarsley | March 15, 2015 1:53 PM    Report this comment

Electric battery-powered aircraft are an impractical novelty, with limited performance ... today, and likely also for the foreseeable future.

I could foresee, however, the potential of electric fuel-cell powered aircraft some day (but not today). One can store sufficient pressurized gas fuel (hydrogen) in relatively light weight cylinders to provide a range comparable to hydrocarbon-fueled internal combustion engine powered aircraft. And unlike battery powered birds, the technology is scalable to larger aircraft.

The economics of hydrogen fuel manufacturing, distribution, and sales, however, are not yet available to allow any kind of large scale adoption of fuel-cell powered aircraft. However, should the infrastructure eventually be developed, such aircraft would deliver virtually all of the advantages of hydrocarbon-fueled internal combustion power (long range, high power to weight ratio) with all of the advantages of electric battery powered aircraft (no polluting emissions, quiet operation, and long power plant life cycle).

Posted by: Duane Truitt | March 15, 2015 3:23 PM    Report this comment

Objection, your Honor! Lipol batts overheat and burst into flames. And..."They aren't cheap, either. A full set of batteries costs about $11,500 with an estimated life of 2000 hours, same as the TBO on a Rotax engine."

So my prediction for this item is that it won't succeed.

Posted by: Rafael Sierra | March 15, 2015 3:31 PM    Report this comment

If the Euro is falling in value, then the price for these aircraft will go up. It would take more money to make up for the loss of value. The price will not go down, contrary to what Paul asserts.

I'm not sold that electric cars are really trending upwards... At least not enough to really count as good gain. Even with the gov't subsidizing the rich here in this country to buy an electric car, they aren't selling that well. I only see them in urban areas.. Not out in the rural areas much.

So, some FBO will buy one of these things, and leave it parked outside exposed to the elements. I wonder how long it will be before one catches on fire out on the ramp or in the hangar. With how close we like to park our aircraft next to each other, I suspect others will catch on fire too.

Elon Musk is a pilot. I wonder why he never developed an electric airplane to help save the world? He sells the Tesla brand with gov't help... Why didn't he go the GA route too?

They should end that subsidy, by the way.

Posted by: Albert Dewey | March 15, 2015 9:49 PM    Report this comment

Albert Dewey, you are correct. The electric car industry is not gaining. Several manufacturers are discontinuing production as performance is poor and cars are expensive and impractical. Battery recharge is long with a decreasing range as batteries debilitate. Ranges have decreased from a 100 miles to 60 or even less than that. Expect then for the battery powered aircraft range to decline as batteries capacity declines. Not a good thing. Inversely, a C172 range is predictable and one can "recharge" in minutes.

Posted by: Rafael Sierra | March 15, 2015 11:30 PM    Report this comment

Another great back-to-back number crunching analysis (how do you keep your noodle from sizzling and overheating, Paul? Do you have time to eat and bathe, too?)

Not knowing much about this thing, I googled up a 19 minute YouTube video showing it's intro at Blois 2014 ... (do they pronounce that Blah?), France. Google WATTsUP at Blois.

In the video, Pipistrel CEO Ivo Boscarol is saying they'll be certified in the US LSA market. I guess he didn't hear that the FAA isn't real enthusiastic about electric motored LSA's yet?

And, Tine is saying that the prop is "special ... recuperating 13% of expended energy during each descent ... equating to one free pattern trip in every six." I like free. A green airplane and free patterns ... WOW!

Hate to tell ya, Yars, but Tine says the batteries only work down to -20degC ... so in sub-zero New England, you may want to rethink cruising the pattern in one of those things.

I absolutely do not understand the fascination with electric airplanes at THIS time. Current battery technology does not have the energy density necessary to be anything more than a fad. This thing loses 198 pounds of useful load on electric, too. And, as soon as anyone uses the word 'green,' the tree huggers come out of the woodwork like hungry termites at a carpenter's convention. Don't they "get" that anytime energy changes form that some is ALWAYS lost? By the time the juice jumps back into their batteries, they've polluted the world and angered Al Gore. They don't want nuclear power plants (like they have in Blois, FR), they abhor coal fired power plants like we have lots of in the US, they blame windmills for killing birds and blighting hillsides and yet they persist in electric cars and -- worse -- airplanes. Those people are just plain nuts.

An electric motor for part-time thrust in a glider ... maybe. An electric motor in an airplane I can't leave the pattern with ... fuhgetaboutit. But -- hey -- they're saving the planet, eh. Maybe Obama will give Pipistrel a subsidy?

Wait! It just hit me. The FAA commercial UAV operators must remain in visual sight of their machines. If we take the crew out of these things, maybe their endurance could be raised? An Alpha Electro UAV is in SOMEONE's future, I'd bet. In no time at all, KTLA in LA will be replacing their traffic and freeway chase helicopters with a fleet of Alpha Electro UAVs equipped with cameras.

Your gas and electric model analysis was good, Paul ... but you forgot the third column. Buy a reasonable used C172 in today's abysmal market and figure it's 2,000 hour total life cycle costs. And don't forget to factor in the RESALE value of each after that period. That'll open some eyes to the ridiculousness of electric airplanes.

Now then, I'm off to the shop to do some designing. I see a market for nifty 'green' battery carrying carts with racing stripes that Alpha Electro pilots can pull behind them as they prance back to the FBO. I'll be rich in no time.

Posted by: Larry Stencel | March 16, 2015 6:20 AM    Report this comment

OMG! Just as I pressed the 'send' button on my comment, the TV news flashed something about a George Jensen style flying car on the news. I'm not making that up, boys. So I googled it and ... I'm blown away ...

Another Slovakian Company -- Aeromobil -- has designed a flying car prototype in version 3.0 with folding wings that have VARIABLE ANGLE OF INCIDENCE. This thing looks like something Darth Vadar would be proud to own as he traverses the solar system. The cockpit is filled with Garmin everything and the video on their website appears to show the thing actually flying. It makes a Terrafugia look like a Model T next to a Maseratti. What a slick video they've produced.

Their Corporate development timeline shows that they started out with V1.0 in 1990 and now -- 25 years later -- they're in (finalised) V3.0 and will be ready for market by 2017. I'd better wait to buy because this thing might be just what I need. After 25 years, I'll bet the bugs are worked out of it. If ONLY it was electric (green), though. If it were an amphibian, that'd make it even better.

Wikipedia says that in March 2015 (that's now, today maybe), "Juraj Vaculik indicated ... that the vehicle is intended for "wealthy supercar buyers and flight enthusiasts (I think that's 'us' ?). Vaculik expects the aircraft will be available for sale in 2017."

Their specs are saying it'll go 435 miles as an "aeroplane" or 545 miles as an "automobil. It goes on to describe co-founder Juraj's experience as, " twenty years' experience of working as a leader with very broad experiences from political revolution to managing theatre or international media and advertising industry." Wow. Those Slovakians must be some pretty smart fellers. Now if they could just get with Siemens and Pipistrel and put one of those electric systems in it, they'd have a real "green" winner on their hands. Why ... the treehuggers and our EPA will go crazy over THIS thing. Why would anyone buy a Volt if they could fly, too? Maybe we could even turn it into a UAV?

Damn. I was just about ready to push the trigger on a RV-12 S-LSA when out pops the Alpha Electro and now the Aeromobil 3.0 flying car. The number of choices is getting ridiculous. I'm going to have to call Dan Johnson over at LAMA and have him add this thing to his burgeoning list of 150 LSA's with 2,000 sold, too. He may not know about it? I sure hope the FAA gives this thing a weight limit exception because all those avionics look kinda heavy.

Paul, when you go over to AERO next month, you'd better include a side trip to the Aeromobil factory in Bratislava, Slovakia. I'd sure like to know what you think about the thing. I'll hold off buying anything until you're back. Of course, if the FAA passes the Class III medical exemption in the meantime, all bets are off because I'll be keeping my Cessna and Piper.

Posted by: Larry Stencel | March 16, 2015 7:22 AM    Report this comment

Ladies and gents, now that's what I call an oustanding diatribe against the Bertorelli doctrine. Larry "The Terminator" Stencel for POPA Pope! And I thought you were hiding Larry. Oh man, what a comeback!

Posted by: Rafael Sierra | March 16, 2015 8:18 AM    Report this comment

Bertorelli, commence firing, fire at will!

Posted by: Rafael Sierra | March 16, 2015 8:42 AM    Report this comment

Bless you, my Son Raf ... Bless you. You may kiss my ring! :-)))))

As Pope, I am going to fundamentally change aviation (for the better) as we know it in the United States.

Stand by for further ... watch out, Mikey. Lead, follow or get out our damned way!

Posted by: Larry Stencel | March 16, 2015 8:47 AM    Report this comment

My old dad used to say "Son, the thing about as airplane is that you just can't pull over to the side of the road when something goes wrong".

But lithium batteries? Think about it; all that's standing between you and your future as a roman candle is a hair-thin layer of insulation inside the cell. Li batteries have been implicated in several aircraft fires. It's going to take a long record of service to find out if one should worry more about this risk instead of perhaps a UAV collision or maybe Larry's writing eclipsing Paul's. Of course, if the batteries were designed like drop-tanks near the CG, you could jettison the things if they started smoking...I just wonder why nobody seems to address this risk when talking about the latest greatest electric airplane.

Posted by: A Richie | March 16, 2015 8:55 AM    Report this comment

Make that "an" airplane

Posted by: A Richie | March 16, 2015 8:58 AM    Report this comment

Paul, I was wondering when someone would acknowledge the elephant in the room. Aircraft require considerable power to climb and cruise. Batteries available today cannot provide enough power at the aircraft payload restrictions. The result is aircraft are being offered as 'trainers' because that is all they may be useful for. Stay close to the airport. Going around the pattern. But that does not actually mean touch and goes. Cruising around the pattern at pattern altitude is more likely as the repeated climbs will drain the battery quickly. Pretty useless as far as training goes. However electric-powered aircraft do have a huge potential. And having been one of the few pilots actually flying one for a year now I am totally sold on the 'clean' side of it. But I am not referring to the global environment as much as I am the 'micro-environment' meaning what is affecting the pilot here and now: 1. No fuel and no oil. Nothing to clean up, no residue to scrub off. No smoke and smells; 2. No noise pollution affecting the pilot or those on the ground (prop noise remains but that can be minimized); 3. No or minimal maintenance; 4. No vibration to speak of. All this adds up to a very pleasant personal flying environment. If it happens to save the macro-environment on some miniscule way all the better.

I have come to the conclusion that electric power works with very light aircraft or very low-drag aircraft or very slow aircraft or a combination of the above. Self-launching gilders for example. Climb for 5-10 minutes then use sparingly for sustaining flight or extending glides.

My electric flights have been in the Zigolo motor-glider. The mission can be a 30-45 minute dawn or evening patrol as most ultralights are used for but with electric I am so much more comfortable flying low perhaps due to so many 2-stroke failures back in the 80's. Plus the low noise does not irritate the evening BBQ crowd even in shotgun range. Or a self-launch to a thermal and shut down without having to think about the restart (or not). Just spin it up like a ceiling fan.

I also believe there would be a market for a 'personal sport plane' meaning a single-seat low drag coefficient enclosed aircraft that would have a reasonable cruise of around 100 mph with low power consumption. Even better would be a hybrid that could engage a small 4-stroke engine; range-extender' during cruise which would result in an electric aircraft that could actually go somewhere and even get back.

Visit my booth at AERO in the E-pavilion and I will show you some aircraft along these lines. And perhaps at SNF this year you can have a chance to fly my electric-powered Zigolo. Per my plans 2015 will be the year that a practical (and legal) electric aircraft will be delivered and in the USA as well.

Posted by: CHIP ERWIN | March 16, 2015 9:00 AM    Report this comment

Interesting to see a discussion of electric vehicles that is dominated by commentators who keep their feet on the ground.

Electric car blogs are typically the province of True Believers who eagerly lap up every drop of the Kool-Aide dispensed by the manufacturer/developer. Dropping any negative posting into one of those is sure to trigger a blizzard of criticism directed at your total lack of intelligence or your failure to properly credit that miracle battery that is just around the corner.

My prediction is that commercially practical electric flight isn't going much beyond the self-launching motorglider for the foreseeable future.

Posted by: John Wilson | March 16, 2015 9:42 AM    Report this comment

Richie ... at the small Midwestern town/airport where I summer to escape from the epaulet wearing maniacs, one of the locals is a member of the local fire department. He tells us that the VFD has strict orders, if it comes upon a Prius or Volt on fire ... make sure no one is inside and let it burn. The Volt -- especially -- has a very high bus voltage because it's a pure electric machine which, by definition, requires all those batteries. Lots of people don't understand that when a Volt controller deems the engine is necessary, the engine runs the car by generating electrical energy which then parallels the battery pack to run the motors that drive the wheels. This is quite different than the series-hybrid engine arrangement in the Prius where the engine AND electric motor run in series, coaxially. If I understand it correctly, the Prius hybrid runs at a much lower bus voltage.

Anyways, good point. The Alpha Electro likely has six suitcased sized battery packs partly because it needs the capacity and partly for safety reasons ... but that's just a guess by me. I'd be willing to bet that the setup is series/parallel so that overtemp sensors can turn off a pack but the airplane can continue to produce power? Both cars can carry heavy battery packs because they're only overcoming the additional friction induced in the bearings. In an airplane, every extra pound has to be made up for in the L/D performance curve ... else gravity takes over.

Chip ... as much as you might infer that I am anti electric airplanes, I'm not. Much work has been done by many entities making more efficient motors and higher capacity batteries. But ... we are not at the point where the marriage of the two is ready for prime time to produce a viable electric powered airplane. In that respect, I agree with Paul's comment that, "...both curves that are going in the right direction." When the battery capacity - cost curves arrive at a reasonable eutectic point, maybe there'll be some success. But -- and again, as Paul points out -- we ain't there yet.

But ... you've hit on another of my 'peeves.' Why isn't anyone making more efficient single place designs, either in the gas driven LSA arena or electric arena. Or, better still, a family of airplanes. If I was presented with an electric single place airplane which could actually do 120 kts, whose MGTOW didn't exceed 1,320 pounds and which could be flown as Light Sport compliant with decent range and which didn't cost 50% more than its gas counterpart, I'd consider it ... maybe.

Finally, there's another elephant in the room. Insurance. After I test flew the RV-12 S-LSA, I investigated insurance. With MANY years of safe operating history behind me, the cost to insure the RV-12 was more than three times that of my C172. Nuff said.

Posted by: Larry Stencel | March 16, 2015 9:45 AM    Report this comment

Larry, I did not mean to infer anything about your opinion on electric aircraft. In fact I pretty much agree with all you have written.

Battery energy per pound (or technically Kw/Kg) needs to triple before electric aircraft are ready for prime time. That will most likely happen someday but most certainly not in 2015 or even in 2016.

I do plan to develop this single-seat personal cruising aircraft you identify. But it cannot be SLSA until the FAA allows electric motors. I did successfully petition the FAA to allow retractable landing gear on amphibious LSA aircraft which eventually lead to a rule change. I expect eventually the FAA will change the LSA rules to allow electric power someday as well. But for now I am working on aircraft that can be legally sold in other countries and in Europe. Then bring in quick-build kits for the USA market in the E-A/B class.

They will be LSA ASTM-compliant and will be morphed into LSA when possible.

And the price will be much closer to a nice motorcycle. Affordable aviation. Something LSA failed to deliver even with gas power.

Posted by: CHIP ERWIN | March 16, 2015 10:28 AM    Report this comment

My Mooney Bravo holds over 100 gallons. My plane partner or I will always say, "We're heavy when taking off with full fuel," but we're always lighter when landing. Not true with batteries--they don't get any lighter. Flew back from West Palm to Republic on Long Island two weeks ago. Stopped in Virginia to take on another 50 (not needed, but cheaper than home airport); anyway I was fueled up and back in the air in 15 - 20 minutes. I applaud Pipistrel in their efforts, especially the Panthera which is a thrilling design, but I don't see electrics making sense until battery technology improves significantly.

Posted by: Thomas Reilly | March 16, 2015 11:47 AM    Report this comment

Considering the infrastructure isn't really available for electric aircraft cross-countries (i.e. electric outlets on the ramps or charging stations in the FBO mx facilities) I suppose staying close to the airport is a requirement. Now some entrepreneur (maybe a retired tanker pilot) might want to consider in-flight recharging. Just drop the extension cord.

Posted by: Robert Mahoney | March 16, 2015 12:00 PM    Report this comment

I think there are a couple other factors that could skew the numbers.
Regarding the quick-change battery packs, will the FAA deem swapping them as a maintenance item, requiring log book entry, or will they look at that as the same as refueling, which we all do without logbook entries? They might have a lot of heartburn to view it as the latter if any tools are involved, and be hard pressed to allow it under the preventive maintenance items an owner is allowed to do, especially if more than one person is needed to get the battery packs in and out. Can you imagine a flight school having to make a maintenance log entry for swapping the batteries for each hour of flight?
Another monkey wrench is the insurance. Insurance companies are going to be asked to set a rate based on very little data, and you know they will skew that rate in their favor until a fleet history is established, so I think equating the per hour insurance cost with the Rotax powered version is optimistic at best.
On the other hand, you can count battery drain as close zero for any time where a gas powered trainer would be idling, either waiting for the oil to warm up, during runup, or waiting to take off. When you pull the power lever aft on the electrics, the prop stops. There is no 'idle'. Then the battery is supplying just avionics and lighting, not the prop motor. In a training environment at a busy airport, where you have to wait for landing traffic to take off, this becomes a non-significant percentage of operating time.

Posted by: Rob Norris | March 16, 2015 1:22 PM    Report this comment

About swappable battery packs...

If you need a "ground crew" to swap batteries, you've got a plane that you can sell only to flight schools who have trained personnel on hand at ALL locations where their planes will need a swap-out.

Excepting airliners, planes simply need to be capable of being "re-fueled" by ordinary pilots. I've long maintained that electric-airplane battery packs need to be compatible with the "cheerleader" model of a pilot - a 100 pound, 5'-5" female in reasonably good physical shape, and with representative upper-body strength. With that in mind, what would the weight limit be? 46 pounds? In Pipistrel's dreams.

Let's start with a common "Jerry jug" gasoline container - one of the newer blow-molded plastic ones. There's a reason that the biggest of these hold only five gallons of gasoline - anything that weighs more than about 30 pounds simply cannot be manipulated easily by an average adult human. Now, let's give our cheerleader a go at that (I actually have). No dice. Even if she can get it off of the ground, she can't also align it with a simple docking mechanism - not at 30 pounds. At 15 pounds, it's a very different story. Wanna go for 20? How often do you want your 20-pound battery packs to get dropped onto the concrete?

Of course, packaging batteries in 15-pound chunks exacts a weight penalty (20 little enclosures weigh more than, say, 3 big ones). But there are a lot of other good reasons to put Lithium Ion eggs in several baskets, not the least of which is to limit the critical mass of a runaway enclosure event. To the extent that multiple small battery packs provide an isolation mechanism and limit the fuel supply of a flaming pack, they represent a good trade-off against smaller quantities of large packs.

Cirrus likes whole-airplane parachutes. But an under-canopy descent of a flaming airframe is unfriendly to both the occupants and the parachute. When one of these large-format battery packs erupts, you're going to need a great firewall and an expedited descent and landing - or a personal parachute and a reliable means of egress. In the military, we call that inventory "an ejection seat." Oh, yeah - those things weigh a lot. Ain't design engineering fun?

Posted by: Tom Yarsley | March 16, 2015 2:50 PM    Report this comment

"Hate to tell ya, Yars, but Tine says the batteries only work down to -20degC ... so in sub-zero New England, you may want to rethink cruising the pattern in one of those things."

Exactly, Larry. That was part of the point that I was making. Keeping the cockpit and the batteries warm enough here in the winter likely would consume up to one-half of the batteries' charge. Electric airplanes are a temperate-climate beast - among other limitations.

Posted by: Tom Yarsley | March 16, 2015 2:57 PM    Report this comment

Yars, instead of an ejection seat, an ejection battery might be a more workable idea. The heavy batteries would probably already be designed on or near the CG, and if you make them flush/belly mounted (also an easy load by the cheerleader with a pallet loader) they could be dropped like a hot potato. Not sure what the protocol would be for the "drop event"; overtemp or smoke might be the indication. It would require breakaway cables of some sort...yes indeed design engineering is a never-ending tradeoff! (30+ years design EE speaking). But wait 'til the public hears about this idea, GA will definitely be the villain on this one!

Posted by: A Richie | March 16, 2015 5:08 PM    Report this comment


As if I don't have enough on my mind worrying about epaulet wearing maniacs spoiling my day in the traffic pattern in FL, or missing the hoardes of beer delivery UAV's when I'm buzzing my buddy's cows up north, or someone shining a laser into my eyes at night ... NOW I have to worry about a flaming LiPo battery pallet ejected from an electric airplane that's on fire unexpectedly knocking me out of the air without notice. Oh geez, I shoulda taken up boats back then ... and I better get my will in order now.

Good job, Richie!

BTW: The protocol for ejecting the pack ... your pants are on fire or your heinie is no longer providing 'seat of the pants' AHRS info. Sooner or later, some pilot will become a posthumous hero for staying with the "hot potato" pack to avoid dropping it on a housing area, as well.


Seriously, though ... I did additional research: The Sonex e-Flight Electric Sport Aircraft (ESA) concept vehicle used a similar power level setup. A 80HP (60KW) specially developed motor and a 270 volt, 200 amp adjustable total output power in separate packs cooled by holes that would also serve as fire ejection ports in an emergency. That's 54,000 watts potentially let loose inside the airplane, boys. SCARY!! Maybe ejecting such massive power -- if necessary -- isn't so far fetched after all, Richie?

The Beyond Aircraft electric Skyhawk did fly but without all four seats and only for short periods. Here's a statement by Panacis, maker of the batteries. "Airborne electric vehicles represent the most challenging environment for energy storage due to the increased need for reliability and lower weight, when compared to the simpler systems employed in electric cars. The power profile of electric aircraft is also more challenging than electric cars due to the extreme temperature variations as the aircraft climbs and the high power requirements during takeoff."

The last online info I can find for either is two years old ...

Posted by: Larry Stencel | March 16, 2015 7:26 PM    Report this comment

If we have angst over 5 pound UAVs crowing the sky, imagine the angst over having 20 to 40 pound flaming batteries drop out of the sky from pattern altitude.

Posted by: Leo LeBoeuf | March 16, 2015 7:27 PM    Report this comment

Designing a self-ejecting battery pack is pretty easy. Achieving comfort with dropping 15-pound incendiary bombs upon the landscape is far more difficult - for me, anyway.

The Germans operated the Graf Zeppelin (and others) for many years, in complete safety. Of course, there was that little incident at Lakehurst...

I've entertained visions of lightweight blow-molded battery enclosures; interior surfaces sputtered and post-plated with titanium, sufficient to withstand the duration and intensity of a full-charge catastrophic thermal event; equipped with a suitable pressure relief port, and nested between ceramic foam (think space shuttle tile material) barriers mounted between adjacent plug-in modules. A relatively simple fuseable-link-spring mechanism could provide on-catastrophe separation of the pack from the vehicle's "backplane" (required to break the thermal connection provided by the pack's blind-mate connectors), with a secondary-detent restraint to prevent ejection from the vehicle. For not a lot of money, we could do enough destructive testing to both entertain ourselves and validate the survivability of a runaway event.

Unless we want a repeat of the Hindenburg, I can't see much of any way around similar protections. Richie? Larry? Paul? Others? Has anyone asked the nascent manufacturers what their checklist procedure will be, in the event of a battery fire at 3,000 feet over Long Island Sound? Over a dry-woods forest? Over downtown Chicago? No matter how limited the range or endurance of whatever vehicle emerges from their imaginations, the fire threat still presents itself. Being unprepared for it seems awfully Hindenburg to me...

Posted by: Tom Yarsley | March 16, 2015 9:03 PM    Report this comment

Anybody remember how impractical the first personal computers were? What could you do with them other than play a few silly games? Even so, many of us laid down the $3000 for a 64K RAM machine and thought it was a great deal. Everything has to start somewhere; the Wrights didn't start with a 747, but something that was more in tune with the period knowledge and technology; and it wasn't a bit practical.

The Pipestral may be the place to start. The battery power may be impractical, but if people like the rest of the machine, better energy storage may become available as more people think about it. Chemical batteries may be reaching the end of their development, but supercaps or other methods could make electric power practical. Or maybe "practical" will be redefined as being an hour of local flying, if nothing else is affordable/available (yeah, we'll run out of 172s eventually).

Posted by: Stephen Phoenix | March 16, 2015 11:18 PM    Report this comment

Ejectable battery boxes? I'm sure that would get a warm reception from the regulators. Pun intended. Somehow, the prospect of flaming wads of LiPo dropping into the kids nursery room may not be the best way to make friends for GA.

Non-metallic lithium batteries have two significant failure modes--internal cell shorts and unbalanced charging. The Pipistrel boxes have internal fans and the usual electronics for cell balancing during charging. They are enclosed in a fireproof firewall material. I saw this stuff at Sebring in January. It's applied specifically for containing the high heat of lithium ion thermal runaways.

This is basically the same strategy Boeing has followed in the Dreamliner, whose battery pack has enough joules to melt half of whatever aluminum is in the airplane. Even before the Boeing battery fires, a source who works in both lithium and lead-acid technology told me their numbers showed Boeing would have high fire risk. They had two. Cessna lost a Citation on the ground due to a lithium battery fire. (By the way, there are hull losses due to lead-acid fires, too.) Yuasa lost an entire lab to a LiPo bench fire during testing.

I don't have a solution for this. Because of my personal perceived fire risk, I haven't put LiPos in any of my bikes. It's a tradeoff thing. I don't think the higher price is worth the performance gain. The fire risk, although probably slight, tips it into the negative for me. Price delta is about 3X; sometimes more.

I think the best you can do is test the thermal containment as thoroughly as possible, make the charging electronics reliable and then decide whether you accept the risk or not. But the risk will always be there. More field experience will shed light on how significant it is. And not all the chemistries have the same thermal characteristics on runaway. Lithium Iron Phosphate is supposed to be more containable, I'm told.

Personally, I'd still fly one of these electric airplanes. I think the risk is acceptable.

Posted by: Paul Bertorelli | March 17, 2015 5:12 AM    Report this comment

And by the way, on battery economics, the trends will be pushed hard by automotive. Contrary to what was stated above, EV sales are continuing to increase. The Volt has stumbled, Tesla has flattened, but overall sales continue to rise.

This data is from Centre for Solar Energy and Hydrogen Research Baden-Wurttemberg (ZSW): "In early 2012, there were almost 100,000 plug-in cars on the world's roads. A year later the report says, there were 200,000 vehicles. To date, there are now an estimated 405,000 electric cars globally, with the magic 400,000 barrier crossed some time late in 2013 or early 2014. If this trend continues, the report says, we'll see more than 1 million electric plug-in cars on the roads by 2016."

From Green Car Reports: "Plug-in electric car sales during 2014 rose above the 100,000 level, to total roughly 118,500. Last year's total represents a 27-percent gain over calendar year 2013. It's the third annual increase in full-year sales in the U.S. since modern electric cars first went on sale in December 2010; the 2013 total was about 93,000."

If I have time, I'll post the graph. It goes up, not down. Even if one million isn't reached next year, battery demand will continue rise, stimulating R&D and economy of scale. Bodes well for cost, if not energy density .

Posted by: Paul Bertorelli | March 17, 2015 5:58 AM    Report this comment

Automotive use certainly has been and will continue to be the largest factor in increasing demand for these batteries. At the manufacturing scales that Tesla envisions, costs should come down significantly.

More than one aspiring automobile manufacturer has publicly contemplated swappable battery packs - whole-vehicle implementations, at that. The entire vehicle would be raised up on a very-slightly-modified automotive lift, leaving its battery behind on a low-profile cart that had been wheeled into place under the vehicle. Reverse the process, with a fresh pack - voila! Thankfully, there's a dedicated battery-swap facility on every busy corner in America!

The cheerleader and the fire-containment requirements drive the battery-packaging considerations. And the true packaging weight has to consider the mating apparatus that's mounted in the hull, which increases with the count of battery pack interfaces. The installed weight per deliverable watt (attainable rate-of-discharge) becomes our useful load challenge.

Paul's comment about Pipistrel's consideration of the aviation-application duty-cycle is heartening. No automotive application short of a dragster offers as much battery abuse as would an hour of touch-and-gos.

Like Paul, I'd fly one tomorrow. But I'm not sure that I'd take the grandkids along......

Posted by: Tom Yarsley | March 17, 2015 6:35 AM    Report this comment

1. I'd already be driving an electric car if one was available at comparable pricing to a gas vehicle. It would meet the majority of my driving needs, with the remainder filled by the older "traditional" vehicles I own.

2. You don't see many single-seat aircraft on the market because adding one more seat doesn't cost too much (in money, materials, capability, etc) but adds a whole lot more value for customers. The majority of pilots want at least one more seat so they can take other people with them, even if they only do it occasionally.

Posted by: Bob Martin | March 17, 2015 6:37 AM    Report this comment


That second seat may not cost much to install, but the upholstery may be overkill if there's only enough useful load available for a hamster.

Posted by: Tom Yarsley | March 17, 2015 6:42 AM    Report this comment

Replace the CFI with batteries: make it an RPAS with the instructor on the ground. ;). Later, replace the student with a camera.

Posted by: Paul Bertorelli | March 17, 2015 7:12 AM    Report this comment

I wrote the second comment at the top of this thread, suggesting that fuel cell powered electric-engine aircraft make a whole lot more engineering sense than battery powered toys currently being designed and marketed ... and nobody bit?

Anyway, perhaps it is theoretically possible some day (some millennium?) to develop a light weight battery with enough capacity to power a medium to high performance aircraft in normal aircraft missions with range equal to or more than the typical four place piston-prop planes we have now (>500 nm), But it will be hugely expensive, most likely, if we ever get to that state of the technology.

In the meantime, hydrogen fuel cells have been marketed and used in all sorts of applications for decades, going back to the early days of the US space program, and are now being used in automobiles, submarines, and other vehicles with none of the drawbacks of battery powered vehicles. The fuel is hydrogen, needs a source of oxygen (typically from the air), the result is electrical power and the discharge of pure water. You can store as much fuel as needed to meet any range requirement, and it is scalable to any power need and any size aircraft.

The only drawbacks to fuel cells is that the fuel tanks - pressurized hydrogen gas cylinders - need to be protected from impact and fire (do-able with modern composite construction), and the fact that we don't at this time have a hydrogen supply infrastructure in place.

Hydrogen is typically produced either as a byproduct of hydrocarbon fuel refining (of which we have an abundant source right here in the good ole USA) or as the product of electro-hydrolysis. Indeed, non-steady power generators like wind turbines are excellent for producing a store-able fuel like hydrogen rather than trying to link them into the power grid and coordinate somehow with other on-demand power plants.

The weight of a hydrogen fuel cell system, including full fuel cylinder(s), fuel cell, and electric motor(s) will be comparable to if not lighter than internal combustion engines plus filled avgas or jet-A fuel tanks. Electric motors are more durable and far more reliable than internal combustion piston engines or even modern turbine engines.

Fuel cell powered aircraft will deliver vastly more capable performance than any battery-powered bird is likely ever to deliver. And fuel cell technology is already here, already well developed, and does not depend upon some future Star Trek scientific breakthrough to become a reality.

Posted by: Duane Truitt | March 17, 2015 7:51 AM    Report this comment

I'm still trying to understand why anyone would want a pure electric airplane. What's the point?

Do you think you're saving the planet because the thing has no measurable hydrocarbon byproducts? If so, you're deluding yourself ... where do you think the juice to recharge it came from. Do you think we're gonna run out of dead dinosaurs? Not gonna happen in our lifetimes. Do you like quiet? Maybe you could argue that one on the basis of sailboat vs motorboat viewpoints but nothing very useful. Do you think you'll get better performance than a small Lycoming or Continental or Rotax? What're you smoking? Do you think they're more reliable than hundreds of mechanical parts roaring around? Bounce that point against the numerous discussions above trying to figure out how to jettison the flaming LiPo battery packs. Do you think that 100LL is going away and your O-200 won't run on unleaded MoGas ... I have a dozen friends that'll prove you wrong.

WHAT's the point, here? Are you wanting to be different for difference's sake? Or, because it's a new technology that always seems to attract we pilots? OK, maybe you have more money than good common sense and just want to be different? If Paul won't put a LiPo battery in his bike, why the heck would he want to fly an electric airplane other than novelty? OR ... more poignant ... why would he want to PAY the money to buy one of those useless things? What's the point beyond a good Editorial byline?

With GA dying a slow painful death, the number of private GA airplanes (different from serious business machines) is nothing more than a pimple on an amoeba's heinie in terms of fuel consumption. We talk about that here. So -- again -- what's the point? We can save fuel other ways.

There are SO many ways to make an airplane more efficient ... even now ... if over-regulation and limitations of same weren't an issue and ingenuity were allowed to flourish.

As far as powering a small recreational GA airplane with PURE electric power, it's the dumbest idea I've ever heard of. Just go back up to the top of the blogs and re-read 'em.

Now then, if we're talking about cars and the REAL need to be transported from A to B ... that's different. But, even there, there ways to mitigate either fuel consumption or byproducts harming the planet on a large scale without going to pure electric. The Prius series hybrid proves that, as a start.

In the 50's as a young kid, I can remember that houses were all going pure electric because atomic power was going to make electric power so cheap as to be free. Yeah, how'd that work out?

1 gallon gasoline equivalent(GGE) = 33.4 KwH. That means the e-Sonex is carrying ~1.6 gals of equivalent avgas. Said in reverse, T. Reilley's Bravo is carrying 62 e-Sonex battery packs. Got any room to sit in there, Tom?

Like John Wilson said, "Electric car blogs are typically the province of True Believers who eagerly lap up every drop of the Kool-Aide."

At this time, NOTHING is more efficient than carrying fuel in liquid chemical format in tanks, burning it to make reciprocating parts whir and then enjoying the countryside move by 'neath us.

Posted by: Larry Stencel | March 17, 2015 8:25 AM    Report this comment

So, electric cars are on the increase.... And the taxpayer is footing the bill.

Tesla gets help from the taxpayer...GM gets help for the floundering Volt, and remember Fisker? They also took huge gov't loans, and they went belly up. Chinese investment is now trying to get production going.

The study Paul sites mentions global sales... What about here in the US? Does the study break it down?

Posted by: Albert Dewey | March 17, 2015 9:54 AM    Report this comment

Diesel-electric locomotives pulling payload vehicles that utilize steel wheels upon steel rails are the most efficient means of ground-based transportation that we have. Great concept; great execution. The biggest contributing reason is that it simply doesn't matter very much how heavy the damned things are. Aircraft lack that critical characteristic. They need energy to climb, to support their weight in the air at cruise, and beat that air into submission so they can get somewhere. Hell, we climb to crazy altitudes, just to take advantage of reduced air drag.

From a weight perspective, chemical fuels are wonderfully energy-dense. By comparison, batteries are woefully energy-sparse. Pound-for-pound, combusted hydrogen delivers about 3.2 times the energy of combusted gasoline. Unfortunately, a pound of hydrogen takes up an awful lot of space - unless you compress it to interestingly high pressures or, better yet, liquefy it.

Petrochemicals come out of the ground, almost ready to use. They're very cheap.

Which choice wins? Follow the money... As my Irish grandmother used to say, "If wishes were horses, beggars would ride."

Posted by: Tom Yarsley | March 17, 2015 12:17 PM    Report this comment

Good job, Yars.

I slightly challenge your statement that hydrogen delivers 3.2 times the BTU's of gasoline -- the chart I'm using shows 1 GGE = 114,000 BTU's for gasoline and one pound of hydrogen delivers 51,500 BTU / pound. Figuring gas weighs 6 pounds per gallon, the equivalent 6 pound WEIGHT of hydrogen would deliver 309,000 BTU's or 2.7 times that of gas. But ... we're splitting hairs, here. You and I are right on point. How'd you come up with 3.2 times?

Measuring how you'd CARRY that weight of hydrogen gets us back to the "how are we gonna jettison it" or carry it diatribe. Also a good point. The container weighs something BUT ... the higher energy density by weight likely trumps that problem?

And, I AM keenly aware that a locomotive is a superbly efficient way to move heavy stuff. Here's another. Do you know what the most efficient method of moving from A to B under human power is? A bicycle. So if all the tree huggers of the world were REALLY caring of the planet, we'd see more bicycle riders. But no ... they're riding around gleefully in their Volts and Leafs and other pure electric vehicles thinking that they're doing something good. During every convention of people demonstrating to save the planet, I'd LOVE to ask 'em how they got TO the demonstation. We ALL know the answer to that.

Here's another issue. There isn't enough raw materials on the planet so that everyone can HAVE an electric anything. Dead dinosaurs are easy to find, easy to refine, easy to burn and -- in more recent years -- fairly easy to burn completely so that we don't choke on carbon monoxide.

"Following the money" is also correct. Why do you think the price of gas went down SO precipitously in the last six months. Because certain Countries in the middle east want us to keep buying their dead dinosaurs and fear the Keystone pipeline.

One last point. There's a reason they invented the figure of merit called GGE ... because gasoline IS the relatively common way of measuring stored chemical energy. It's no different than water being used as the standard for density. Water and gasoline ... and beer ... that's all I need.

Now then, my BP is up and my flight physical is soon. I need to go do some of my alchemical duties before my brain explodes. Thanks, Yars. I at least feel better.

Posted by: Larry Stencel | March 17, 2015 1:06 PM    Report this comment

THIS JUST IN !! Again, I'm definitely not kidding here guys!

In a Time Magazine online article released today, here's the title, "NASA's Crazy 18-Engine Electric Concept Plane Could Be the Future of Flying" It goes on to say, "NASA says the unusual setup, called Leading Edge Asynchronous Propeller Technology (LEAPTech) could result in more energy-efficient and greener aircraft." They're saying they're testing it on a pickup truck but in just two short years, they'll put all that stuff on a Tecnam 2006T twin airplane sans Rotax's.

There's even a picture of the contraption wing on a strut on the NASA Armstrong website.

Has someone left the gate open to the insane asylum? If not, Jim Jones didn't die in Guyana, he's selling koolaid in front of the NASA center? The ONLY thing they have right in the title is ... "CRAZY." So I can picture it now, Paul will be writing about whether or not a single lever auto controlled electric motor'ed P2006T will require a multi-engine rating.

These "green" people are driving me insane!

Posted by: Larry Stencel | March 17, 2015 1:32 PM    Report this comment


I used the chart found here: en.wikipedia.org/wiki/Energy_density Check the values in the "Specific Energy" column. Hydrogen rated at 142 MJ/kg; gasoline at 44.4 MJ/kg = 3.2x. Just for comparison purposes, the same chart lists a wide range for rechargeable Lithium Ion batteries: 0.36 to 0.875 MJ/kw. If bringing gasoline along on your flight is like bringing coal, then bringing batteries along on your flight is like bringing the entire coal mine.

I saw the NASA story earlier today. With regard to requiring a multi-engine rating, I would point you to the FAA's desire to authorize commercial operations of a drone helicopter on the basis of possessing a private pilot certificate... wait for it... in airplanes (or anything else). Translation: nothing would surprise me.

Posted by: Tom Yarsley | March 17, 2015 1:57 PM    Report this comment

Years ago, people said "You idiot Wright Brothers--there ain't no engine ever gonna be light enough to power an aeroplane and you're nothing but a couple of fools to keep trying at it. Why don't you just go back to your bicycles and stop pestering the rest of us with your crazy schemes."

Posted by: jane zhang | March 17, 2015 3:22 PM    Report this comment

With apologies to the late John Hartford, I'd also like to fly a "Steam Powered Aero-Plane"!
Don't laugh; it was actually done in 1933 with a Travel Air biplane.

Posted by: A Richie | March 17, 2015 3:54 PM    Report this comment

Toyota (worlds largest auto company) is moving to fuel cell power with new technology.
They announced no pure battery electrics are planned at Toyota.

Posted by: Bill Berson | March 17, 2015 5:46 PM    Report this comment

I'm just a little confused about the implied simplicity of the battery pack and the ability of the hypothetical 100 lb. cheerleader/pilot will to swap 'em.

For comparison, the battery pack of the Tesla Model S is arguably the most complicated sub-system in the car; it's custom-shaped to consume otherwise-unused space and has a complete cooling sub-system including liquid coolant, pumps, fans, and requisite electronics, etc. (I won't even bring up the failure mode of the Roadster battery when sufficiently discharged...)

And a few "mere" 46-lb packs will suffice for a vehicle that, as has been pointed out, will impose repetitive max load events during climbs to pattern altitude?

While I certainly appreciate the in-depth reporting and comparison, methinks Paul hasn't been given the full story here...

Posted by: Unknown | March 17, 2015 6:29 PM    Report this comment

"While I certainly appreciate the in-depth reporting and comparison, methinks Paul hasn't been given the full story here..."

Methinks too.

The concept is good, the existing battery materials are not. The project needs more laps around the R&D circuit solving for safety, weight, efficiency and cost reduction.

Posted by: Rafael Sierra | March 17, 2015 8:43 PM    Report this comment

Unknown said: "I'm just a little confused about the implied simplicity of the battery pack and the ability of the hypothetical 100 lb. cheerleader/pilot will to swap 'em."

On the off chance that the remark was more than rhetorical, I'll offer some thoughts...

When designing a product, you take advantage of anything that's not precluded by provided constraints. Elon Musk elected not to be constrained by a requirement to make his battery packs swappable by a cheerleader. On the other hand, if your Tesla batteries run dry at any location where there's not a plug-compatible charger available, you'll need the services of a tow truck. Rah, rah!

So, other than our cheerleader, what are some of our likely design constraints? Blind-mate connectors are a must; cords always are a maintenance and safety nightmare. I'd offer air cooling as a basic constraint, both for charging and discharging. Hot-swap capability should be a required feature. Putting all of the charging electronics into the plug-in module will provide the ability to use a garden-variety (DIN) extension cord as a "charging station." Voltage-agile charging needs to be a given, if only because 120 vac power is unavailable in many parts of the world. Unspecified (here) is whether the battery modules should be gang-chargeable in situ (while installed in the aircraft) - a process that's tenuously analogous to a single-point fueling system.

I'd require a visual indication of charge level on the face of each module. I'd include a high-current two-pole female connector for battery output, with the conductive surfaces guarded by a finger-excluding gate that would be opened upon insertion into the airframe's mating backplane. You should have a Class D connection to announce insertion and removal of the modules in time for the module electronics to configure for the coming "hot" connect or disconnect, respectively. You should have a serial port connection for communications with related electronics in the aircraft.

Our cheerleader has only two hands, so the front-face grip handle should include an integral low-force button to permit un-latching of the module. Her other hand can go under the bottom surface of the module, for maximum support.

If temperature control of the modules is an issue, I'd try employing something analogous to cowling flaps on surface(s) of the aircraft that are adjacent to the heatsink surface(s) of the modules.

As I said earlier, the modules need to contain (or at least isolate) all of the carnage associated with a thermal runaway event at full charge. I like titanium for all of the usual reasons, but I wouldn't make it the primary structure. That needs to be something rugged, lightweight, and cheap. Probably a hybrid injection-molded / blow-molded rugged plastic enclosure - very much like our example red Jerry jug. The titanium could be sputtered and plated onto the inside of the enclosure, or it could be hydroformed a la a Zero Corporation metal briefcase. If the latter, I'd be sorely tempted to isolate the Ti enclosure from the primary structure with a fill of medium-durometer Sorbothane material - a choice that would pay for itself the first time our cheerleader dropped the module.

Speaking of which, integral G-metering would be a requirement - it would have to work even when the module is fully-discharged. There are lots of ways to do this; I've already bored you enough.

I could blather on, but you get the idea - we could design a robust battery pack that would be highly cheerleader-resistant, without resorting to rocket science. I say that as someone who actually has practiced rocket science. ;-)

Posted by: Tom Yarsley | March 17, 2015 9:38 PM    Report this comment

I agree with the person above who said "What's the point?" about electric planes. Like electric cars, it's a vanity project for people who want to show off how "Environmentally correct" they are, nothing more.

In contrast, Toyota got it right with the Prius. Use electric power and batteries to improve efficiency (especially in city driving), but rely on a conventional gas engine to provide the bulk of the power.

Posted by: Eric Gudorf | March 18, 2015 5:21 AM    Report this comment

A realistic takeaway is that the available electrical airplane motor driven resources are not meeting the basic and practical flight endurance criteria. Thus, demand will remain poor making for a non-viable market. And in turn, making for a tough sell to investors and consumers. Again, the concept is good, the existing battery materials are not. The project needs more laps around the R&D circuit solving for safety, weight, efficiency and cost reduction. The electric car industry innovations will determine the success or failure of the electric airplane industry.

Posted by: Rafael Sierra | March 18, 2015 7:34 AM    Report this comment


Thanks for your info on the relative energy density of hydrogen fuel vs. gasoline fuel, in which hydrogen is noted as several times more dense. There is also the matter of thermodynamic efficiency, which means, the ratio of the mechanical efficiency delivered to a motive device (prop, fan, wheel, etc,) and the chemical energy contained in the fuel tank, or the "tank to wheel efficiency rating".

For internal combustion engines, the typical range of tank to wheel efficiency, considering all thermal and mechanical losses, is only about 18-20% as compared to the energy content of the raw fuel.

For fuel cell vehicles, typical tank-to-wheel (or prop or fan) efficiencies including all losses (heat, friction, etc,) range from 36% to as much as 60% - two to three times the efficiency of internal combustion engines.

So your comparison of GGE values for hydrogen vs. gasoline of 3.2X should actually be more like 6-12 times when factoring all normal losses from tank to drive train.

As for storage of hydrogen, it is normally stored as a compressed gas cylinders at pressures of 4,500 psi or more. There is a risk associated with high pressure compressed gases, but then there is also a risk with highly flammable avgas too, which routinely kills a lot of aircraft accident victims in post-crash fires, and sometimes causes crashes even when in flight. The risk of a hydrogen leak is pretty minimal and easily manageable.

Hydrogen fuel cells are the most efficient, safe, clean, and high performance motive technology available. The only reason we haven't gone to fuel cells is that we don't have the infrastructure yet to produce and distribute the fuel, given that most of our infrastructure investment dollars for the last century has gone to hydrocarbon distribution.

The hydrocarbon production infrastructure already in place, and needed for a vehicle fueling network, however, is immediately convertible to hydrogen production. Indeed most hydrogen production today is derived from hydrocarbon feedstock, and most hydrogen produced is actually devoted to the refining of hydrocarbon fuel products and petrochemicals.

Oh, and by the way - electric engines last lots longer than internal combustion piston engines do, and require far less maintenance.

Posted by: Duane Truitt | March 18, 2015 4:51 PM    Report this comment


Larry's the guy with the GGE values, but your points about thermodynamic efficiencies are totally apropos to where this discussion has wound. Compressed hydrogen driving fuel cells driving electric loads is a very efficient way to power a vehicle - any vehicle.

Design and build-out of the required infrastructure needs to address both the transportation/storage/distribution considerations AND the hydrogen-generation ones. The true greenies won't be happy with anything less than hydrolysis powered by baseload solar - which itself doesn't exist, and whose own design and build-out considerations are nothing short of disruptive in every sense of the word. Other means of hydrogen generation pretty much miss the ultimate point - the elimination of the combustion (or conversion) of legacy hydrocarbons. Any process that pours carbon dioxide (and/or other "greenhouse gasses") into the atmosphere is a non-starter for the greenies. And I do understand their position - I'm just one of those evil realists.

But filament-wound tubular spars (a la baby Grummans) make a great place to store compressed hydrogen fuel in small aircraft. Not widely understood is that, in the event of a tank rupture, escaped hydrogen gas rises into the air - whether in flames or not. This hazard behavior contrasts very favorably with heavier-than-air propane, which spreads out along the ground from the scene of the rupture. Its risks include both combustion and oxygen-displacement asphyxiation.

Hydrogen is great stuff - if you can get your hands on it. Toyota's initiative can't hurt. Only time will tell if it's effective. Still LOTS of cheap petrochemicals out there, whose use does not require a fundamental overhaul of the nation's / world's energy infrastructure.

Posted by: Tom Yarsley | March 18, 2015 6:04 PM    Report this comment

Hydrogen fuel cells for vehicles are not as efficient as one would believe. The efficiencies quoted consider using the high grade heat that is given off from the reaction. In a stationary power plant this can be done. In an aircraft the heat will most likely be dissipated. Some heat may be used for de-ice or potable water heating and perhaps cabin heat but the majority will be rejected. So there goes 10 to 15% of the efficiency. Secondly, fuel cells work best in constant demand systems. They do not throttle easily. If used in an aircraft, the output may need to be stored, batteries again, or converted to heat via resistor banks when power is not needed; i.e. during descent or approach or TPA operations. So let's not get all misty over H2 fuel cells on the surface, they look very efficient, however, in actual operation they are not as rosy as the marketing hype would have you believe. Internal combustion engines used in combined cycle power generation and excess heat use, have efficiencies approaching those of fuel cells.
Remember the devil is in the details as any good rocket scientist or energy engineer knows.

Posted by: Leo LeBoeuf | March 18, 2015 6:04 PM    Report this comment

Paul, just go ahead and put a diesel engine on your Cub

Posted by: Richard Montague | March 19, 2015 7:17 AM    Report this comment

Deliverable hydrogen fuel cell technology and infrastructure for GA in the United States won't happen in this century. There's practially no interest or impetus for innovation in GA powerplants or their fuel in this country. (Unless you consider Lycoming's improved tappet coating as a bold innovation.) The GA community has been foot-dragging on unleaded hydrocarbon fuel for some 30 or 40 years, and it will be a good 10 years or more before a fuel becomes widely available. Even at that, I read nothing but grousing about abandoning 100 LL and sneering at "greenies" and "treehuggers". Imagine how much enthusiasm there would be for carrying around high-pressure tanks full of the same gas that filled the Hindenberg.

Any innovation in GA powerplants has to come from outside the U. S. GA industry. The electric motor and battery industries can improve their products and make an end-run around the conventional GA industry - like the glass-cockpit avionics companies did - but getting hydrogen delivered to FBOs in the U. S. is a non-starter.

Maybe in another 30 years when the current crop of GA pilots are no longer flying and the U. S. GA industry has been completely taken over by the Chinese, GA may be more open to innovation - if it survives. Until then, we're pretty much stuck in 1970.

Posted by: Rollin Olson | March 19, 2015 12:10 PM    Report this comment

Rollin, I disagree with your assertion that the infrastructure for hydrogen fueling for aviation won't be in place this century (we're only 15 years into it!).

For one thing, the infrastructure to PRODUCE hydrogen already exists, is in place, and it is producing large volume of H2 today. Most of today's H2 production is derived from processing hydrocarbon feedstocks (crude oil), and most of it is actually used in the refining processes for producing other consumer and industrial hydrocarbon fuels, and in producing petrochemicals.

Secondly, the infrastructure to TRANSPORT hydrogen to airports would be rather minimal - effectively, just fleets of liquefied hydrogen gas tankers, similar to the fleets of tankers you already see on the highways transporting liquefied oxygen and nitrogen gas. Getting liquefied hydrogen to all of your friendly corner C-stores would be a much, much larger scale endeavor, just because of the shear numbers involved compared to airports.

Getting hydrogen from the refineries to the airport vendors would not require nor could the volumes justify any pipelines, while the vast quantities needed to fuel private cars and trucks would undoubtedly require large scale pipeline development. Of course, most of the avgas and jet A dispensed in airports today is also delivered by tanker trucks.

For aviation, the infrastructure needed - and that we don't already have - is not that much, actually.

The biggest obstacle to converting aviation to hydrogen fueling is the same as it is in anything else aviation related - the FAA and its bureaucratic obstacle course designed to discourage any and all innovation in aerospace technology.

Posted by: Duane Truitt | March 19, 2015 12:34 PM    Report this comment

Duane, it seems to me that the biggest obstacle to converting aviation to hydrogen fueling is the market (i.e. airplane owners) that discourages any and all innovation in aerospace technology in airframe manufacture and especially powerplants. The big news in GA these days is about refurbishing planes designed in the 1930s to 1970s. I periodically read articles about this or that innovation that never went anywhere because "the market" didn't want it, e,g, Paul's report on Lycoming's findings about single-lever control.

As for the big bad FAA, people get the government they deserve. The GA community has been remarkably ineffective at working with Congress and the FAA to make regulations better fit our interests - with one big (and one small) exception.

The big exception came In the early 2000s, when the FAA played ball with GA to develop the light-sport category, with industry-standard ASTM certification rules. A whole slew of European airframe manufacturers and Rotax have been able to develop and market products under these rules. But rather than build on this momentum, it seems that most American pilots heap scorn on the whole LSA business. I see no indication that mainstream U. S. airframe and powerplant companies, and certainly not the pilot community, are doing anything get the FAA to ease its "bureaucratic obstacle course" for airplane certification.

The other exception is the push to eliminate the Third Class Medical. The AOPA et al are lobbying and getting legislation introduced in Congress to change this requirement. It will likely take several years for legislation to get passed, but this is how things actually get done in Washington. When pilots (and manufacturers) actually take an active interest in regulations, it's possible to influence them.

Sitting around and grousing doesn't get anything done.

Posted by: Rollin Olson | March 19, 2015 3:58 PM    Report this comment

So Chip Erwin

How did that amphibian you got (with support from a hundred pilots holding deposits) an FAA repositionable gear OK on turn out?
Sold none, right?
Despite faking production line marketing photos of it in your drive for deposits... some (most?) never returned to this day... and when you lied to everyone in sight about nearly everything.... especially your trusting sucker english kitbuilders you simply abandoned to seek certtification on their own after your faked Sport Cruiser load testing was revealed.
Settled all your Czech and UK fraud and negligence lawsuits yet?
You tried to suppress/ignore user and importer warnings on airworthiness defects in the early CZAW SC instead of immediately alerting owners... despite photo and design engineering evidence. Which I've seen.
Why does ANYONE pay ANY attention to you and why does Bertorelli keep letting you post when he bans those who factually warn of your history?
Like Dan Johnson (who crashed your improperly rigged only Parrot right in front of you departing Naked Lady Ranch) does he want a ride in your new scam THAT badly?
You make Jim Bede look like a Founding Father by comparison.
At least he was an actual engineer and never MEANT to screw anyone.

Posted by: Cheep Errwin | March 30, 2015 10:27 PM    Report this comment

Why would ANYone believe ANYthing former CZAW chief and still con man Chip Erwin says...except Bertorelli and Dan Johnson who shill for him? He screwed ALL UK SC kit buyers by abandoning them to fight for certifications when his fraudulent test reports were discovered. He shuffled SC delivery dates playing favorites. He faked Mermaid production line photos online and in other marketing and has yet to refund some of the deposits wasted when he pissed off Jabiru and got blackballed...then couldn't make Rotax usable and amphib essentially stillborn...125 deposits for RTF...one or none of those delivered Just company prototypes and couple US custom kits.. Then claimed Rotax SC had comparable performance to intended Jab 3300. Not even close ( as Farry S. proved). dozens more shady deeds and lawsuits galore but one thing ALL should condemn: hid known airworthiness defects from early CZAW Sport Cruiser acquirers. I discovered and tried to spread reports including secret photos BY HIS IMPORTER and others. Avweb blocked me and copy fast as they will delete this ASAP

Posted by: Cheep Errwin | March 31, 2015 12:24 AM    Report this comment

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