An Electric Airplane Virgin No More

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I came, I saw, I flew. After three years of trying, frustrated by weather, schedules and airplanes that just weren't ready, I flew my first electric airplane this week, Pipistrel's Alpha Electro. And? From the inside the cabin, it was underwhelming. Listening to it whistle by on the ground was quite another thing, however.

As we've reported, Pipistrel announced the Alpha Electro at Aero Friedrichshafen in April, hoping for actual deliveries of real electric airplanes later this year or sometime next. The Alpha Electro is a conversion of the company's otherwise Rotax-powered trainer that's a popular seller. Pipistrel worked with Siemens to develop the airplane's brushless DC motor and inverter package; it developed its own battery technology in-house and having looked over what's involved in doing that -- making it work and making it safe -- I'm beginning to get a sense of how difficult it will be for companies to industrialize this technology at a scale that can be profitable.
As for the Electro itself, it has about 120 kg of lithium polymer batteries evenly divided between a front compartment just behind the electric engine and a second located behind the cabin. The cells are arranged in three quick-change, removable boxes each weighing about 20 kg or about 44 pounds. The motor itself weighs a fraction of the battery weight, at about 11 kg for the power-generating part, plus the weight of the inverter system that's basically a motor controller. The complexity of the additional technology to string together the batteries, the motor and the charging system is a bit more complex than there's time and space to describe here, but Pipistrel deserves credit for investing in its development. Company founder Ivo Boscarol told me that none of this hardware exists as off-the-shelf product and the motor itself is actually the easy part. I can see why.
As for flying it, between rain showers and a developing Burja wind, demo pilot Nejc Faganelj and I flew two short hops, both with fully charged batteries. Pipistrel engineered the Electro to perform and behave identically to the gasoline-powered version and it does, with some exceptions. Because of its short legs, it's intended to spend most of its time in the pattern, teaching students how to land and take off. You certainly can venture away from the airport, and we did, but you have to keep a sharp eye on the battery monitor, which tracks remaining energy. Pipistrel has said the Electro will have a one-hour duration, with 30 minutes in reserve. I don't think it's quite there yet, as least based on my flights. More on that in a moment.
What's odd about it is that when you flip on the switches controlling everything, you're basically ready to fly; no warm up and no run-up. Everything is more or less automatic. Pipistrel's Tine Tomazic said at the Electric Aircraft Symposium in April that anyone expecting an electric airplane to be whisper quiet and smooth as glass will be disappointed. He's right. Once the throttle is moved off the stop, which you can do instantly without fear of anything bad happening, the airplane feels and sounds indistinguishable from its gasoline stablemate. I didn't measure the noise level, but it seems comparable to the Rotax; there's still a little prop tip noise and the pulsing prop wash still hits the windshield and other parts of the airframe. That's the underwhelming part, which Tomazic says Pipistrel is happy with because the Electro is supposed to integrate into a flight school setup with gasoline-powered airplanes for other training and cross-country work. Get out of the gas model and into electric and there's little difference.
The Electro's climb rate and cruise speed are comparable to the gasoline version and so is everything else, right down to the switch placement. In place of the Rotax version's engine monitor, there's a battery monitor system that tracks overall battery health and remaining energy in a lucid, easy-to-read display. For our first flight, we did some landings and a low-altitude tour of Ajdovscina, Slovenia, where Pipistrel is based. Twenty one minutes of flight left 51 percent of remaining battery capacity, according to the monitor. On our second flight, we stuck to pattern work, which Faganelj said has delivered the full hour of endurance with a small reserve. But it wouldn't have on the day I flew. After nine landings and about 30 minutes in bumpy boreal winds, battery capacity was down to around 40 percent. Then it occurred to me that obsessing about the promised hour is somewhat beside the point. After 10 touch and goes, the typical student will be ready for a break or the end of the lesson and the Electro is probably capable of 15 or 16, with adequate reserve, albeit probably not 30 minutes. If it's meant to be a landing trainer, it has sufficient endurance to do that. 
Then came the real eye opener. I got out of the airplane and Faganelj spent eight minutes beating up the well-manicured runway with high power passes, a couple of which were 10 feet over my head. The airplane isn't quite perfectly silent as perceived from the ground, but it's close. You don't hear much of anything but a whoosh as it passes overhead with just a hint of prop tip noise. Pipistrel says the measured flyby noised is about 54 db, about the noise level in a typical office with AC running. Flyby noise isn't much of an issue in the U.S. and even in some parts of Europe, but in Germany and northern Europe it is. I suspect on that count alone, the Electro will get -- and is getting -- serious buyer attention. At the end of our landings -- 10 total -- and the flybys, total flight time was 38 minutes with 25 percent capacity remaining.
There were a couple of surprises about the Electro. For one, the engine is geared, not direct drive. That's because the motor is adapted from another application that Boscarol says he wasn't at liberty to describe. I suspect it's automotive, however. Future iterations of the motor for this airplane will be direct drive, which means the motor will be lighter yet. Second surprise: It's water-cooled. Because the motor is so power dense and physically small, heat buildup is an issue, so it has a small circulating pump moving a glycol/water mixture through the engine. That means it has a cooling inlet and a radiator about the size of the oil cooler in a Rotax. Although cruise speed isn't the Electro's forte, Pipistrel still had to model the cowling to minimize cooling drag, so electric propulsion isn't quite so divorced from the gasoline world as we might wish. Interestingly, when you flip on the motor switch, an electric pump comes along and that sounds just like a priming pump, but is in fact the circulation motor for the coolant.
Right now, the Electro is priced at about 100,000 Euros or $113,000 at current exchange rates. It would be less expensive but the motor currently costs as much as the rest of the airplane due to low-volume manufacturing. Boscarol says motor prices are expected to drop sharply as volume increases and he expects the Electro, or whatever model is the next iteration, to sell for about $80,000 Euros or the same as the gasoline model. Speaking of which, if we had made the same flight in the Rotax airplane, the fuel cost would have been about 23 Euro or $26 at typical European fuel prices. In the Electro, the freight was 2 Euro or $2.26 at Slovenian kwh rates. The dedicated smart charger the airplane is equipped with provides this information during the two-hour charge cycle. In the U.S., the gasoline/electric Delta would be less due to cheaper gas in the U.S., but the electric airplane would still be cheaper. Later on, I'll post the full-up numbers including battery replacement costs; at a glance, they're comparable to Rotax overhaul costs.
For the time being, the Electro isn't a player for the U.S. market because the FARs don't define a light sport/ASTM-type airplane as being electric powered and Pipistrel doesn't seem to be looking at a primary category certification. Further, it wouldn't be competitive with a Cessna 152 beater running on avgas simply because the Cessna is cheaper to buy. The Electro is, not unsurprisingly, getting a lot of attention in Europe where it will be significantly cheaper to operate and quieter, which matters. The looming unknown is this: Can a flight school integrate into its operation an airplane that may do only one thing, teach takeoffs and landings? And can it do so profitably? And how will students take to flying an electric airplane, which represents the bleeding edge of what electric propulsion technology can do? The fact is, Siemens is still tweaking the motor technology and there's not much competition yet. But it will come. Similarly, Pipistrel is seriously on the edge in developing advanced battery management technology and I suspect the next iteration of this equipment won't be long in coming. I was shown some research that leads me believe Pipistrel is further along than many might imagine.
To judge the Electro fairly, we'll have to see how it performs in the environment it's intended for: flight school training. In my view, there's a sufficient early adopter market to make Pipistrel's investment worth the effort. Whether it proves a hit or not, I have to say I'm impressed with the technical creativity Pipistrel applied to this airplane. If electric flight has legs -- and Boscarol is convinced that it does -- Pipistrel won't be caught at the trailing edge of it.

Comments (14)

Clearly not ready for prime time, but it shows progress. Eagerly awaiting your follow-up report(s).

Posted by: Tom Yarsley | June 19, 2015 7:43 AM    Report this comment

If they can overcome the regulatory hurdles, improve battery life and shorten charging times a bit it could easily be a 152 replacement. I can see flying for 2 hours stopping for 2 to recharge and continue on for a long cross country or use it for training, recharging between flights. I think it would need a genuine 2 hour endurance between charges with reserve and a 1 hour charge time would be great. As it is it could be viable. When they can fly one from Florida or California to Oshkosh it will have arrived. (they can give me one and I will be happy to make the flight.)

Posted by: RODNEY HALL | June 19, 2015 2:05 PM    Report this comment

It's obviously in the infancy of electric airplane technology, just like electric cars were not so very long ago. It used to be that 20 miles was normal, now 80 is normal, and some are claiming a much longer run as well. So maybe in time--but not yet. I agree that a 2 hour plus half hour or 45 minute reserve and a 1 hour charge time just might do it. Then, of course, FBOs across the country would have to have the charging stations set up, and that might be one of the bigger impediments--hard to justify a couple thousand dollar investment to sell the occasional $3 worth of electricity.

Posted by: Cary Alburn | June 19, 2015 9:05 PM    Report this comment

Electric airplanes are not efficient unless solar powered. The net propulsive energy loss can be up to 90% or more. If one looks at just the cost of the electricity, they look very efficient, however, when the total energy required for propulsion is considered, then one should calculate the losses in generation, transmission and distribution. Add to that the efficiency of the electric motor/propeller combination, it is a different story. Electric motors are efficient, however, the fact that this one needs water cooling, is telling us that a lot of the energy is lost as useless heat (maybe not useless on a cold New england night). Sound familiar??

In the electric utility business, many people tout the efficiency of fuel cells. What they don't explain is that the efficiency levels are only reached when the installation is able to use a majority of the system waste heat. Internal combustion systems when installed in such systems, are almost as energy efficient.

It will be great to have electric propulsion units for certain missions, but can the small specialized market support yet another specialized capital investment?

Posted by: Leo LeBoeuf | June 20, 2015 7:03 AM    Report this comment

"Non-beater" C150 or a C172 Remain as contenders. VFR/IFR, night and day, good 4 hr cross country trainer at $30,000 to $40,000. It seems to me that buying a flight time challenged electric "landing trainer" for about $120,000 is just not a good flight school investment.

On down-time. It takes 15 minutes to top-off a C150 or a C172 or any other similar craft. Not the case with the electrical. So the electrical "fuel" cost savings adjusted for down-time is a questionable matter. The Pipistrel may be limited to a couple of short flights in a day in closed traffic. Electrical airplanes, as they are presented today, seem to me like incomplete product. Too expensive and too limited.

Posted by: Rafael Sierra | June 20, 2015 8:42 AM    Report this comment

Their day may come. I remember when an electronic calculator cost more than a weeks pay and it could only multiply, divide, add and subtract. It was about 8x the cost of a slide rule. How times have changed. Someday, electrics will be viable, but for now they are in alpha mode but some folks will pony up the $ to buy one.

Posted by: Leo LeBoeuf | June 20, 2015 8:36 PM    Report this comment

Leo, I agree. In the early 70s, I and millions of other individuals, bought the electronic type calculators you mentioned. Electronic technology developed a proper product in a very viable market. Millions were sold allowing for profit then investment and growth into newer, better and cheaper items. Mass production facilitates all. Not the case with the electric airplane. Presently, the aircraft power systems lack energy storage capacity, endurance, reliability, versatility (IFR/VFR, DAY/NIGHT) and a viable market. Battery system weights need to be cut by 60%, capacity and endurance needs to be quadruple. Until then, I would think, the C150 or C172 type aircraft will rule.

Posted by: Rafael Sierra | June 21, 2015 8:21 AM    Report this comment

In sci-fi stories the energy source conundrum is resolved by a few keyboard strokes: A mini-fusion plant resides in the back somewhere; a superconductor box stores a few weeks' worth in (we presume) an incredibly dense magnetic field; or perhaps the protagonists find a "zero-point module" conveniently left by some previous civilization.

If only it were so simple.

Posted by: John Wilson | June 21, 2015 8:43 AM    Report this comment

Yes unfortunately, that is the story for GA any more. The numbers are too small. Perhaps, a new transportation mode such as electric small motorcycles or even for the geriatric set, electric scooters will spark some innovation advances. It's just that this older pilot may not see it happen. meanwhile, the aging C172s and PA 28s are the only economically practical solution. Hopefully, a new design will emerge to counter the coming supply demand curve inflection of affordable basic airplanes.

Posted by: Leo LeBoeuf | June 21, 2015 9:34 AM    Report this comment

Leo, I sense you pain.

Posted by: Rafael Sierra | June 21, 2015 9:53 AM    Report this comment

Electric motor, gasoline (or diesel) engine.

Posted by: JEFFREY GORSS | June 21, 2015 11:36 AM    Report this comment

Leo - it's not true that fuel cell powerplants are no more energy energy efficient than internal combustion engines. According to most current research actual vehicles sold, as well as the US Dept of Energy most IC engines are only about 25-30% efficient (tank to wheels), and that is only when operating at peak (75%) power while significantly less than that at lower power settings ... while fuel cell vehicles range from 40 to 60% at all power settings.

The latest FCVs such as Honda's 2015 FCX are at the very top of that range (60%). Honda increased the fuel efficiency of its 2015 FCX by 20% over its 2014 model, and further increases are expected as the R&D continues. Honda also reduced the size and weight of the fuel cell stack substantially, with their latest model being about the size of a typical desktop computer case at a weight of about only 200 pounds. The current FCX has a driving range of 240 miles, vastly better than any EV on the market.

Substantially longer ranges will be available on fuel cell vehicles with the latest in ammonia catalytic converter fuel systems, due to the much lower weight of the low pressure ammonia fuel tanks.

Fuel cells today are the only feasible power source for electric motor-powered aircraft if one wants to fly beyond the local pattern, as this subject aircraft of this post is limited to. With fuel cell technology vehicle (including aircraft) range is comparable to that of gasoline IC engines.

Posted by: Duane Truitt | June 22, 2015 8:52 AM    Report this comment

The Honda hydrogen fuel cell vehicle uses gaseous hydrogen as its fuel. So, when looking at the energy efficiency, one must consider the amount of energy used to generate the H2. This could be from cryogenic air compression or electrolysis. All use a bunch of energy to get the usable gas. So when factored in, the efficiency is not as great as advertised. Also many other fuel cells depend on natural gas i.e. methane as a fuel source. Again there is a lot of energy loss dissociating the CH4 in to C and H2. Then the C combines with oxygen to give CO2.
Fuel cells show promise, but we have been working on them since the Apollo days and they are still not in volume production. Fuel cells do not throttle well, so are best used in a constant output situation. Great fro cruise, but what happens in the pattern? Charge batteries or super capacitors (weight) or dissipate the excess electricity through a resistor bank? Eventually, solutions will be found that make economic sense. When that will happen is somewhere in the future.

Posted by: Leo LeBoeuf | June 23, 2015 9:53 PM    Report this comment

Leo - the same "energy in vs. energy out" also applies to gasoline. Do you not realize the tremendous amount of energy and costs expended to produce one gallon of av gas from crude oil in the ground?

You can play that game with any energy source and thereby render any effective comparison of energy worthless because the definitive analysis of net energy gain for all potential energy sources has yet to be written and accepted as established economic science ... many PhD dissertations remain to be written on this subject, as it's complicated and changes constantly with development of new technologies for exploring, producing, and processing various fuels in various parts of the world.

In any case, the "bottom line" is the bottom line. What is the cost of av gas today vs. the user cost of the least efficient means of hydrogen fuel generation?

Well, as we all know av gas today sells for a very wide range of prices here in the USA as well as world wide .. from a low of something around $4 per gallon in some parts of the USA to as high as $20 per gallon in foreign nations. The average cost of avgas in the USA today is probably $6 per gallon.

The cost of hydrogen fuel to the buyer at a pump, where one kg of hydrogen gas is approximately one GGE (gallon of gasoline equivalent) in the USA ranges from about $1.00 to $1.80 per GGE - about half the cost of auto gasoline and about one quarter the cost of avgas.

Therefore, it is pretty apparent that hydrogen as a fuel source is much cheaper to produce than gasoline, which takes into account ALL of the internalities and externalities of energy production to get it to your tank. When we start producing ammonia-fueled catalytic fuel cell vehicles, both the cost of fuel and weight of fuel for a given range will decrease substantially more.

Then, once that cheaper fuel gets to your vehicle or your aircraft, the fuel cell uses that energy much more efficiently than does any IC engine use its gasoline or diesel fuel.

Fuel cells are much more fuel efficient, inherently by the virtue that they do not waste nearly as much of the energy through waste heat that internal combustion engines waste, and fuel cells, unlike any mechanical engine, have negligible internal mechanical losses

Finally, Honda has also developed its own "home hydrogen generator" that produces hydrogen fuel using a small portable steam reformer working off natural gas as a feedstock. Natural gas is extremely cheap right now. You could put one of these in your aircraft hangar along with a gas tank for the natural gas and fuel your aircraft that way very cheaply. It will also power your home or hangar with electricity too.

Posted by: Duane Truitt | June 26, 2015 9:15 AM    Report this comment

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