Save the earth - fly for £1/hour!
- Credit: Pipistrel
With reduced noise, a low carbon footprint and electrical ‘fuel’ costing just £1/hour, the Velis Electro will usher in a new era of flight training
It’s probably a typo. I had heard that electric motors would bring down the cost of flying, but this must be wrong?those fickle Excel tables... I check the column again, but it’s correct. All the entries are there?and the numbers stack up. One pound an hour? That can’t be right, my moped is more expensive to run! I ask Taja at Pipistrel to check the data she just sent me. “No mistake,” is her answer. Maybe in Slovenia they have super-cheap electricity? I check that too but no; it turns out that their electricity price is similar to the rest of Europe. So, am I really going to fly an aircraft that uses £1 of ‘fuel’ per hour?
Tailored for electric propulsion
“Benvenuti!” Speaking in Italian, company founder and CEO Ivo Boscarol welcomes me and my video crew to Pipistrel’s Gorizia plant, just across the Slovenian/Italian border. We’ve come here to fly the Velis Electro and to visit their factory and, as per protocol, we are initially led on a tour of the facilities. But?I can’t help it?very soon I find myself in interview mode, talking about this unbelievable £1-an-hour figure, and end up asking bluntly “How is it possible?”
“We started working on electric flying twenty years ago...” is Ivo’s understated, matter-of-fact response. I must say if I had designed an aircraft that flies for such an incredibly low cost I would probably be shouting it from the rooftops?but Ivo’s demeanour is actually quite subdued, almost as if the achievement was no big deal. “The point was to design an aircraft for a very specific task, for which electric propulsion is advantageous,” he says. And that’s exactly what Pipistrel did. The Velis Electro is not a jack-of-all-trades aeroplane: it does one thing, but it does it very well, and extremely cheaply. It is, plainly and simply, the least expensive circuit training aircraft in the world.
Ivo explains Pipistrel’s business case: “Electric propulsion has two main disadvantages for aviation. First, the low energy density of batteries, which means that you cannot fly too far. Second, the limited industry experience in electric flying, which creates obstacles to certification.” In this scenario, Pipistrel simply connected the dots. On the one hand they had many years of experience with electric flying, so that they could design a pack consisting of two relatively small batteries that would pass the EASA certification process. On the other hand, they designed an aeroplane that could make the best use of those batteries. And that is how the Velis Electro, a circuit-flying trainer and the first certified electric aircraft in history, came to be. “In the history books this aeroplane may end up sitting together with the Wright brothers’ aircraft, and the first jet,” Ivo states, highlighting how aviation propulsion actually has not seen many radical changes in its 117-year history.
Once you pass the hurdle of certification, and find a market that can make use of an electric aircraft, the natural cost advantage of electric propulsion shines through. For every hour of flight the Velis Electro uses about 25kWh of energy, which in Slovenia costs about £1, and in the UK (depending on your provider) only slightly more. All of the other operating costs are roughly similar to an equivalent piston engine aircraft?and electric motors are inherently fairly simple, which has a positive effect on ease and cost of maintenance. The biggest running cost is overhaul of the battery packs, which currently needs to be done every five hundred hours (a limit that will be extended as the technology develops). Overall, including all expenses, except insurance and hangarage, Pipistrel cites a cost per flight hour of around £64, of which just £1 is the cost of ‘fuel’ (that is, electricity).
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Fully charged in one hour
Of course, operating an electric aircraft has its peculiarities compared to combustion engines. The biggest difference is range: when fully charged the Velis Electro has enough battery energy to fly for one hour, which is more than enough to conduct a full circuit flying session. A few things should be noted regarding this specific point. First, the certification allows the aircraft to fly with only ten minutes of reserves, provided that you keep the airfield in sight?which is what you typically do when flying training circuits. Second, the one hour figure refers to actual flying time, not block to block. That is because, when the aircraft is stationary on the ground (say waiting for takeoff in a long queue of aircraft), it hardly uses any energy. So, if you are concerned about running out of battery while waiting for takeoff at a busy airport, you really don’t have to worry.
Another important issue with electric propulsion is the charging time of batteries. Here Pipistrel quotes a one-to-one ratio of flying time to charging time: fly for one hour, spend one hour recharging the batteries to full capacity (this is a compromise in the interest of utility, as slower recharging would extend the battery’s life). Thus ‘quick charging’ (an option for electric cars) is the default mode of operation. One hour on the ground in between flights is not an inconvenient break, considering briefing and de-briefing times before and after flight lessons.
A further point to consider in the Electro is that, once you go below fifteen per cent State Of Charge (SOC) the batteries’ reduced discharge capacity will limit maximum power output to 50kW and not the usual maximum of 58. However, you would normally be ending your flights before reaching 15% SOC remaining, as at anywhere below 20% SOC you start to eat into your reserves.
Finally, the motor must be ‘throttled back’ during the initial climbout, as the maximum takeoff power of 58kW can be maintained for no longer than one minute, after which you must come back to 49kW, the maximum continuous power. But that seems to be plenty: on my demonstration flight, in ISA conditions plus five degrees Celsius, the 49kW setting yielded a respectable 700fpm rate of climb (and keep in mind that many piston engines, including the Rotax 912, have similar takeoff/maximum continuous power restrictions).
It’s not just cheaper to refuel...
So, while a few minor adjustments are needed if you want to transition to an electric aircraft (just don’t plan, as yet, a Shoreham to Prestwick flight) there are a some distinct advantages to mention, in addition to low operating costs. Besides lowering your environmental impact, the other big advantage of the Electro highlighted by Ivo is the reduced noise of the aircraft. “There are over one hundred airfields in Europe where flight training is prohibited over the weekend because of noise,” he points out. “This is a major limitation for a lot of flight schools, and specifically for all those modular students who can only afford to fly at the weekend because they work during the week.” The Electro’s official noise rating is a very low 60dB, matching the interior sound level of a luxury car. During my flight I repeatedly took my headset off to assess how loud the cockpit was?my impression was that the Electro is about thirty percent quieter than an equivalent piston aeroplane.
Being somewhat of a newcomer when it comes to alternative propulsion systems, I also found some encouraging numbers when I compared electric and combustion powerplants in specific scenarios. You will often hear, for example, about the problem of ‘power density’ in batteries. That is, one kilogram of fossil fuel gives you a lot more power than one kilogram of batteries. Research reveals various estimates for the ratio of power density between batteries and fossil fuel – the highest I have seen is forty to one, the lowest five to one. Even under the best of estimates, then, with current technology a battery appears to only do one fifth of the work that the same mass of fossil fuel does. This is not good for a technology that is supposed to save the world! Everything changes, however, if you make the comparison within the context of an actual flying sortie, and if you include mass of the engine (or the electric motor) in the analysis. In this case, you discover that, to fly for one hour, the Electro needs 120kg of batteries to supply a motor weighing 20kg, which is a total of 140kg. To fly the same sortie, its piston engine sibling?the Virus?needs to lift less mass than that, but not much less: a total of 100kg, divided between engine and fuel. That means that in the case of the Electro the true weight penalty of electric flying is not the abysmal forty to one ratio mentioned above, but a much more palatable seven to five.
Electric flying also brings other advantages that are more of interest to the pilot (rather than the operator). For instance, you effectively have at your disposal a flat-rated powertrain: not using oxygen, the motor will in theory deliver the same power at high altitude on a hot humid day, as it would at ground level on a cold dry day.
The preflight is also a bit simpler: the electric motor and batteries have very few components, and I have the impression that, if something was amiss, an inexperienced pilot would more easily spot a problem in an electric aircraft than in a piston-engine one. And you obviously do not have issues with carbon monoxide.
The market response to the Velis Electro has been good so far, Pipistrel rolling out around five aircraft per month at the moment (the first buyers placed orders as far back as 2014). But, I say to Ivo, I suspect that some schools will hold back a potential purchase of the aircraft until the technology has been tried and tested. After all, this is a brand new aeroplane that was certified only in June. “Yes, that is likely,” answers Ivo. “It’s normal to be cautious with a newly certified aeroplane. The solution, we suggest, is to integrate the Electro gradually into your fleet. We actually encourage schools to try it alongside other piston trainers, and then assess their relative performance. While one can obviously buy the Electro as a stand-alone aircraft, our suggestion in general is to buy a package of trainers comprising both electric and piston, because the two will cover different phases of training”.
I also ask what’s in the future of electric aviation, since some experts believe that increased adoption of electric propulsion will lead to economies of scale, which in turn could trigger a semi-exponential improvement of batteries. But, despite leading the company that achieved the first major breakthrough in this field, Ivo takes a conservative view. “The rate of improvement of batteries is not great,” he says, “about three or four per cent a year at the moment. For instance, I believe we can double the range of the Electro by 2023, but developments beyond that range will be more difficult. That is why we need to look at all types of alternative propulsion for the future of aviation and to power larger aircraft, developing for instance hydrogen propulsion.”
As our visit draws to a close, I can’t help but see the Electro in a more long-term, historical perspective. Normally, when there is a historical ‘first’?the first aircraft, the first train, the first jet?what is really emerging is something with potential, not a market-leading product that is immediately usable (generally because it costs more than prevailing technology). As a first, the Electro represents quite an oddity, historically. On its début the aircraft was already the most competitive (that is, least expensive) circuit trainer on the market. It also just happens to be the first certified electric aircraft in history.
Everybody at Pipistrel, from Ivo down, is modest and almost dismissive about their achievement. but I think the Electro is actually a big deal.