Pipistrel's Alpha Electro II trainer holds appeal for ab initio training schools, but adjustments are needed to deal with the new technology. Steve Hitchen was introduced to electric power over the Yarra Valley and reports on how the type is being integrated into flight training.
Korum Ellis whipped off his headset, and prompted me to do the same. We had a sensible conversation without competing with the ambient cockpit noise, something I haven't been able to do airborne since the last time I went gliding.
That's what you get when an electric motor is swinging the propeller.
But quieter cockpits are just a side-effect of electric aeroplanes; the main event comes in lower operating and maintenance costs, with simplicity of operation thrown in on the side. That's the reason why my local flight trainer Lilydale Flying School (LFS) added a Pipistrel Alpha Electro II to their fleet.
The Alpha Electro is the classic composite airframe that characterises both the Sinus and Virus range, but the Rotax has been dispensed with and replaced with a 60-kW Emrax electric motor drawing from two batteries totaling 21 kWh. It makes for a very different machine that has been tailored to the basic requirements of ab initio training: short duration, two people, close to the airport and carrying not a lot of bags.
That was a claim that I thought needed testing, and the only way to do that properly is in the air. Hence, I met Ellis at Lilydale on a good flying day when a gap opened in the Electro's dance card.
Taking it on
LFS Operations Manager Jonathan Merridew was impressed with the Alpha Electro from the beginning, and quickly saw the sense in using the platform for training.
"LFS sees that the Alpha Electro really is proving itself to be a viable commercial aircraft," he told me. "A significant portion of our flying are relatively short training or air experience missions within the Yarra Valley – for which it is perfect."
"We expect that the Alpha Electro will open up a new market of flyers who understand and are enthusiastic about electric vehicles – on the ground and in the air!"
All new types added to a training fleet bring about a change in thinking from the instructors and pilots, but Merridew says his team has made the leap to electric power without much fuss.
"Operationally, our team have found it quite easy to adjust their thinking to the particular requirements of the Electro which largely revolves around battery management, in flight and on the ground," he remarked
"There's been a lot of interest in having a go from both new and existing students. Pipstrel airframes have been around a while and been developed to fly very nicely, so the Electro is not hard to fly.
"The main challenge for existing RPC holders is to get their head around how to best manage their energy usage to have the maximum possible fun!"
I gave Alpha Electro II 23-2091 a quick walk-around as it was tethered to its charging device, then sat down with importer Korum Ellis from FlyOnE to get the low-down on the ethos behind building an electric trainer.
"This is the first electric trainer and recreational aircraft to hit the market, built by Pipistrel," Ellis told me. "Pipistrel has a long history of making very good aircraft and you can see that all coming together in this new airframe. It's nicely made–all carbon composite–and is in the LSA category.
"The reason Pipistrel has created this plane with these performance characteristics is to keep the price down to get some early uptake. They could definitely have made a plane that flew twice as long, but it would have cost four times as much, and it wouldn't have been in the LSA category, which would have made it more difficult to certify.
"The endurance is perfect for flight training and for recreational consolidation as well."
With electric power still in infancy in aviation, Ellis admits to getting some awkward looks when people encounter the Alpha Electro for the first time. Much of that derives from not understanding exactly what is under the cowl and how it all comes together.
"It uses an Emrax motor, which is the first certified electric motor in the world," he explained. "Pipistrel use it on the Velis Electro and it's now being used in the USA on some military electric aircraft as well. It's also being used on the AMSL Vertiia that's being developed in Australia.
"It's lightweight with high efficiency, and is super reliable. The service interval is 2000 hours. It weighs about 12 kg and sits in the nose right behind the prop. It takes up very little space; it's about the size of a mud cake.
"It has 60 kW output, which makes it similar to the 100-hp Rotax engine, but it's in a sportier airframe; low drag and very nimble. You do notice that power delivery with the Emrax is instant, so when advance the lever you're at full power in a fraction of a second."
The powerplant itself is an axial-flux motor that measures 188 mm across and 113 in depth. When added to the front battery's mass of 57 kg, gives a combined weight 6 kg above that of a Rotax 912.
Detractors of electric aeroplanes are usually quick to nominate limitations as the biggest objection, and for sure the Alpha Electro's capabilities have a relatively small envelope. The endurance is about an hour depending on how you run it, the batteries are heavy, there is no storage space in the cockpit, and given that the MTOW is 570 kg, the useful load is only 190 kg, which is just enough for two large people.
On the plus side, the usable load is all usable; there's no fuel to be added to the wings in order to run the engine.
But that in itself caused a design issue for Pipistrel. The weight that would have been the fuel has been taken from the wings and added to the fuselage in the form of the battery weight. That transfer of load is what limits the MTOW of an airframe that can carry 600 kg in Sinus or Virus form.
Charged up and rolling
I followed Ellis out to the front of the flying school, where 23-2091 was loading up on electricity from its charger, a box on wheels about the size of an old gas heater, that was in turn hooked into the 240 V mains.
Ideally, the charger is best plugged into three-phase power for faster charging, but on this day, the 232 V flow was enough to get the aircraft back in the air in reasonable time.
The charger feeds the front battery, which lives beneath the cowling neatly tucked in behind the motor. The second battery is located behind the cockpit in the space that would have been the baggage compartment in a Sinus or Virus. At 57 kg each, they needed to be placed apart to keep the centre of gravity in a reasonable spot.
Converting the electricity into traction is a Pipistrel-branded three-blade prop. This is a fixed-pitch unit with a wider RPM operating range than the average propeller, designed specifically for the electric motor.
"[the operating range] starts much lower because our idle is effectively off," Ellis explained. "When the throttle is right back the prop is not spinning at all. It become effective from the moment the throttle lever is moved forward. It doesn't have a low-drag idle setting."
I slid myself into 2091 using the classic Pipistrel ingress technique: backside first, then hook your leg up and over the stick. Nice and easy. Like the Virus, it doesn't have a lot of space around the elbows and the wing spar carry-through within worrying proximity of the crew's foreheads, but the leg room permits the occupants to stretch out a bit.
However, any other similarities between 2091 and any Rotax-powered Pipistrel ends there.
The panel has a stylish polished-carbon look to it and is fitted out with only the essentials needed for the type of flights the aircraft has been tailored for.
On the left is an unconventional tacho with a large digital read-out complementing the dial and an obtrusive trim indicator. Topping the next column of gauges is an ASI, again with digital display, and beneath that a digital AI.
Dominating the panel are a GPS unit and a Pipistrel-branded EPSI570 engine management system. The EPSI570 shows RPM, battery levels, power output in kW, estimated flight time remaining at that power, temperatures at critical parts of the powertrain and visual warnings.
This is the instrument that you will need to take notice more of than perhaps any others. It tells you the health of the battery and therefore the remaining energy available that can be converted into flight time.
On the far right is a conventional altimeter and glider-style vario to provide the crew with rates of climb and descent.
Below everything sits a rather large balance ball. With limited energy at your disposal, there's no point burning it off wastefully by flying out of balance, so Alpha Electro pilots quickly learn to keep the ball centred. It would be a focal part of the test flight I was about to undertake.
The console is home to the master switches and two others: BAT EN and PWR EN. These are the energiser switches, first for the battery and then for the power. Between the seats are the power lever, brakes and flap, which are the normal slots for many LSAs including the Pipistrels.
Things get unconventional when it's time to start. After the normal cockpit checks and a howl of "clear prop", Ellis flipped on BAT EN and PWR EN, resulting in nothing visible happening at all, even though the aircraft was now considered started. It wasn't until he slowly advanced the power lever that the prop started turning.
Departing
Ellis taxied 2091 down the south end of Lilydale Airport ready for a 36 departure. I noted the available power went from 85% to 81%, drawing 3-5 kW as we went. That was a fair bit, so I wouldn't recommend a 34R departure from Sydney International in an Alpha Electro; you might be out of energy before you get to the holding point.
The vital actions were somewhat truncated due to a lot of things missing: TMPFISCH became TFISCH and there was nothing on 2091 to run up. That has us lined up and ready to go in just moments.
With full power set on the take-off run, the Alpha Electro behaved like any other LSA. It didn't use a lot of runway and was in the air briskly. During the climb, Ellis set the RPM at 2310, which drew 46 kW from the batteries and gave us 70 KIAS and a 400 fpm climb. However, those settings dropped our available flight time back to an alarming 18 minutes! It was clear we couldn't continue that way.
Ellis leveled out at 2500 feet, which prompted me to ask how high he was planning to take us.
"You generally don't climb too high," he replied, "because climbs use a lot of energy, so it's a great plane for flying low and slow. You'd probably stick at around 2-2500 feet; maybe get up to 3000 if you want to do some stalls."
With the RPM hauled back to 1920, the power draw came down to 21 kW, which extended our flight time out to a more respectable 36 minutes, and returned a TAS of 71 knots. There is some skill needed to cruise an Alpha Electro, and it comes in the form of managing the available energy.
"In cruise you bring the power back, and then you're on efficiency watch to try to extend your air time as much as possible," Ellis said as he watched the EMS like a hawk. "Typically you watch the speed and feather the power up and down to target your most efficient speed, which is about 66 knots.
"Around 65-70 KIAS is a sweet spot where you're getting low drag off the airframe, the controls feel nice and you can get the power back to about a one-third setting if you at low weight. That will give you nice air time; you can fly for about 45 mins on that power setting."
Hands on
It took the stick when it was offered to me and swung 2091 to the south. Ellis was right about the nice feel on the controls. I found the Alpha Electro response sprightly and well balanced in pitch. I tried to concentrate on keeping the ball centred, but having significantly more time in GA tricycle that any other aircraft, sinned repeatedly with my feet.
It was in the steep turns that 2091 displayed an unexpected characteristic given its sweetheart handling in the cruise. It needed lots of back stick in the turns and keeping the ball centred taxed my leg more that I thought it would, given the mass ahead of me was about the same as a Sinus or Virus.
After a couple of turns and a short cruise for the headsets-off test, Ellis pointed out that we probably should think about returning to base. We were only 10 nm east of the airport, but the journey home was going to take longer than normal, and pilots of the Alpha Electro need to constantly monitor and manage the energy state.
At the time we turned back, the available energy in the batteries was down to 47%.
Ellis showed me how to set up a cruise descent: set the RPM at 1560 and trim for 81 KIAS. That returned a 250 fpm rate of descent, but slashed the energy usage back to 3 kW. Remarkably, the windmilling prop was actually regenerating the battery. In contrast to ground operation, when the throttle is closed in the air the prop doesn't stop, so it acts like a wind generator to put some electric energy back into the batteries.
The approach and circuit are normal; there's not a lot that needs to be changed because the aircraft is electric. On final, however, the Alpha Electro II has the advantage of instant energy change when more power is needed. Should the pilot get a bit low on final, power lever movement prompts instant action from the Emrax motor.
The end of it all
Ellis taxied 2091 back to her tethering point and hooked up the charger, regenerating the battery for its next mission. In all, we had flown for 38 minutes and reduce the battery energy from 85% to 35%. If you do some quick mathematics, had we departed with the batteries full, we could have stayed out a lot longer.
I would have preferred that; getting my head around flying by electricity would take some doing. In contrast, Ellis says some people immediately shine to the concept.
"Some progressive people, like here at Lilydale, have had a look and found that very few of their flights in RAAus registered aircraft are over an hour," he told me, "so an electric aircraft just fits. If you have a look at it unemotionally, yes it's limited, but it fits perfectly in the case of most basic training flights.
"People get familiar with the aeroplane very quickly, and it's such a nice flying experience, like a very powerful motor glider, and there's less faffing around when you get to the airfield and are ready to go flying. You're in the air in about seven minutes because you don't have to do so much stuff to the aeroplane.
"When they look at that, the emotion swings around and they think 'I'll find a way to make this work.'"
On my test flight, our time was limited and therefore the full envelope couldn't be explored. However, I came away with the impression that the benefits of an Alpha Electro would become more obvious the more you flew it.