Going Electric Solves Several Problems
The problem at the moment seems to be that people are unwary of the technology and switching, according to Pipistrel dealer Deepak Mahajan. We visited Deepak at his training school at Damyn’s Hall Airfield in November and were surprised to learn that he points to instructors as being the ones most reluctant to make the switch. The economics, he claims, are so compelling that flight school owners are often keen to get the new Velis Electro, while “customers” – the students and pilots out there — are also keen but mainly due to the environmental benefits. Increasingly, pilots are conscious that they should be doing their bit to stem global warming. Students, especially young ones, want to learn using clean technology — and all electric aircraft are if you use energy from sustainable sources.
Walking out to see the aircraft we first stopped at the charger, a large 32 Amp unit attached to a three-phase power supply in the main hangar. Deepak said you can do a ‘rest charge’ if not using the aircraft so it stays at 40 percent – keeping it fully charged is inefficient. While many owners and pilots don’t fly all the time, flight schools such as ‘Fly About Aviation’, the training school that Deepak runs, fly any time the weather conditions favour it. Lucky for us it was a foggy day with no flying, so Deepak was on the ground.
He’d just returned from visiting the Pipistrel factory, catching up new developments in the wake of U.S. corporation Textron acquiring the company last year. Deepak has been instrumental in working with Pipistrel founder Ivo Boscarel and his team to bring the Pipistrel Electro to the UK market.
So far ten Velis Electros are in the UK, the first being G-OGRN which is the aircraft we were introduced to in one of his temporary hangars. It’s done 100 hours in the last year, he said, often being used for training alongside a Rotax-powered Velis (which runs on Mogas i.e. unleaded petrol that you can get from your local petrol station in jerry cans). Other aircraft are located in Norwich (2), Wickenby (1), Humberside (1), and Shipmeadow Airfield (1), so far – with many more dotted around the world.
The Velis has the same structure as the Rotax-powered Velis. Deepak gave us a guided tour of the aircraft, including some rather ‘modern’ features borrowed from far larger aircraft – it has a stick shaker, for example, triggered by approaching the critical angle of attack. There is an angle-of-attack sensor on the pitot tube. The stick-shaker is both audio and ‘haptic’ and there is an alert on the screen also (though no display of AoA). The avionics are forward-thinking too, provided by Pipistrel’s fellow Slovenian company Kanardia plus a Garmin 695 navigation display.
So how do you as a PPL who’s probably flown pretty old aircraft most of the time get to fly the Electro? ‘ePPL’ differences training requires a minimum of seven sorties and takes around two days, says Deepak. Getting used to battery charge rather than fuel is one key difference, especially as the charge on current technology batteries last a maximum of an hour. The two battery packs – one in front of the fire wall behind the motor, the other behind the pilot seats – run down at the same time but provide the required redundancy (essential especially for a certified aircraft). The aircraft was certificated by EASA and this has now been endorsed by the CA – something that Deepak was involved with.
“The lowest charge I’ve even been down to is 7%,” he says, but he stresses what an amazing glider the Velis is anyway – just in case someone hadn’t managed things well. The training is aimed at ensuring your motor never stops in the air, though, and the system shows Yellow for 30% charge and Red when it gets down to 15%. For now, the Electro tends to be used for short hops and circuit sorties – Deepak says the most he’s done in a day is six. Sometimes he (and his fellow instructors) go to other airfields within range and has placed chargers there (e.g. Redhill) so he can charge up and fly back doing the second half of a lesson. Differences training for instructors and examiners is no different to that for any other pilot – you just have to learn to fly this aircraft. This was a major gain for Pipistrel when EASA was going through the certification process, and the CAA endorsed that too (politically, it would have looked very bad for them to go against EASA’s judgement in any case, says Deepak).
One of the main things to get used to is in fact the slippery nature of these little composite aircraft, for people that are not used to them. Deepak showed us the start-up routing, four ‘pull and up’ switches in a row from Master to Avionics to Battery (you hear the cooling pumps come on) to, finally, Power – and with that the props starts turning with almost zero noise. All so easy. Pre-flight includes a good look at the aircraft first, of course, checking things like coolant (there is an easy to see inspection window), with the batteries, motor and inverter being liquid-cooled, and control runs. The electronics take care of some things, for example if you try to start the motor it won’t happen unless the throttle is at idle. And it’s very easy to turn off after flight – just the four switches, off, from right to left. One of the things feeling the stationary propeller is that’s there’s negligible resistance – just the feel of the magnets as you turn it. This also includes the glide performance as the prop keeps windmilling no matter what. “With a failure you wouldn’t see the prop stop,” stressed Deepak. The POH says it has a glide ratio of 17:1.
Pipistrel Builds the Batteries
There is a ‘scoop’ on the left to help with battery cooling and the radiator gets ram air plus two cooling fans. The design of the battery is such that coolant runs in an array between the cells – Pipistrel buys the cells and builds the batteries itself. The batteries are ‘Lithium Polymer’ cells and there are 1,150 cells in each battery. EASA also required an ELT to be fitted, which is the large yellow box near the rear batteries. There are battery gas vents in the side of the aircraft, in case there is an issue where either of the batteries starts to generate gas. The holes are covered in stickers for easy inspection – if they are broken, there has been gas generated. If there is a battery cooling pump failure the avionics will warn the pilot to land as soon as practicable, says Deepak. The cold is one threat to the use of batteries as any Lithium battery below 10 degrees Centigrade will lose a lot of charge.
In the USA the Electro has not been certificated yet by the FAA – it is in the US Experimental category, but the FAA is working to validate the EASA certification under Part 23. So, it’s just a matter of time. “The FAA has been struggling to remove the phrase ‘reciprocating engine’ from the regulations, which EASA and the CAA didn’t have to deal with,” says Deepak. The reason it was inserted originally was to stop people putting rockets in light aircraft!
On the Electro the propeller pitch is ground adjustable – the prop speed is controlled via software “which is why the software had to be certified as well.” So essentially it is ‘power by wire’, like a FADEC on larger aircraft. One of the advantages, noted Deepak, is that a ‘schedule’ can be adopted to make the aircraft behave like, for example, a turbine-powered aircraft, or one with a constant-speed propeller. “This is great for training,” he enthused. This feature is not certified yet – having been left out of the first certification programme by Pipistrel and EASA to ensure there were no delays. “But it’s there,” Deepak added.
The highest he’s taken the Electro up to is 9,000 ft. “It took half an hour to get up there”. Coming down, the next exciting development will be to use the prop as a generator to recharge the batteries a bit — this feature is on the US Experimental versions already but is another ‘snazzy’ feature held back in the European certification, for now. But with better batteries and this kind of technology, the next generation of Electros will have twice the endurance. The other trade off with batteries is to have ones that charge faster, with a similar kWh (kilowatt hour) rating – “it’s different chemistry,” said Deepak, “You can’t have both”.
Being a quiet (max 60dB) training aircraft is a huge advantage due to the need to circuit at airfields. That’s great for maintaining good relations with the locals, and if you have a solar array to charge the batteries then that can also feed the local grid, which can lead to a discount on the electricity bills for households near the airfield. This is what is being offered by UK power supplier Octopus Energy, which only provides sustainable energy — Deepak has signed up with them and even has an electric car using their electricity. “The lady that complained the most before told me that she can now hear the birds sing. That to me is an amazing thing,” he said. The 60dB measurement is based on an observer 400ft below, and the aircraft at maximum speed – most of the noise being wind noise, of course.
For you pilots out there, there is no moving trim tab as the trim tabs are fixed, and the rudder has a fixed trim tab too – “to help keep right rudder”. The engine thrust-line ensures pitch-up when increasing throttle but sudden pitch-up is reduced. There is electric elevator trim to adjust the all-moving tailplane (‘stabilator’) and this is linked to the stick so it moves when trimming, by a trim motor.
To save charge, Deepak says he throttles back after takeoff – this “saves a lot of power and the aircraft still climbs very well.” For those that have flown small composite aircraft with Rotax engines, the power-to-weight ratio is excellent, and the Electro is no different with the motor having plenty of torque. With full throttle the aircraft will climb at 1000 ft/min.
For maintenance engineers there is a short course – maintenance is relatively simple with no moving engine parts to worry about. At the moment the course is based at Pipistrel but Deepak is looking for a partner training provider in the UK. They have to be a Part 147 school. The ‘Annual’ (annual inspection) takes half a day, officially, but really most of this is taken up in filling out paperwork.
Then with little maintenance cost, and running costs as low as £3.50 an hour, it can really make sense to get one of these aircraft on finance – and now Pipistrel is owned by Textron, its existing finance arm has come in to play to help customers acquire aircraft.
So how do we spread the word? Deepak is frustrated that it seems to be instructors that are resistant to change. He believes it has to be a “bottom up” process rather than “top down or “trickle down”. People need to learn about the aircraft and this comes from using it. “I can’t understand why more flying schools don’t take modern aircraft,” said Deepak. “You can lease them!” Or buy for €180k. If you can fly 10 hours a week, charging £150 an hour, and costs are only £10 an hour, then that leaves an awful lot to go towards that monthly lease payment! “We need to change the culture,” he concludes.
The final point is putting the aircraft on a trailer – it only takes an hour to disassemble and load on the trailer. So unlike most certified GA aircraft, this can be moved easily, and hangered easily. Even in a garage. But if you want to charge it, you’ll need a 3-phase supply. And if you want to swap in a new battery, it takes two hours – though in the factory they can do it in 40 minutes, they’re so adept at it now.
Meanwhile look out for the Pipistrel Pantera – now with hybrid and soon to go fully electric. And remember, said Deepak, that you are generating 3.3kg of CO2 for every kg of Avgas you burn in the standard aircraft piston engine. One kg of fuel burns with 14kg of air. And there is one cubic metre of air for every 1.225kg… so the volume of CO2 being generated by GA aircraft is huge – and around 18m3 of air is being burned per houre
Electro Key Facts:
The Electro is a full-electric derivative of the proven Velis SW121, powered by a Pipistrel E-811 electric powertrain. 57.6 kW max power delivery. Motor TBO 2000hrs (batteries initially 500hrs).
It is the first ever type-certified electric powered aeroplane, fully approved for pilot training in Day VFR conditions (EASA and CAA and others following, including the FAA). Also opens the door for commercial use (e.g. air taxi or ‘microfeeder’)
Powertrain is 345V DC, developed by Pipistrel with partners EMRAX and EMSISO.
Total nominal capacity 24.8 kWh
Two 75kg Batteries located in nose and other behind cabin.
A malfunctioning battery will disconnect automatically; remaining battery capable of supporting climb etc.
Pipistrel 3-blade composite propeller, ground adjustable.
Clean – no combustion gases at all. Can be charged from green energy.
First to support the SAE AE-7D charging plug. Charging overseen by main computer. Charge status displayed on Pipistrel EPSI 570C, 5.7in cockpit display.
Quiet inside the cabin and outside (60dBA).
Immediate power response to power request (throttle).
Can be used to form a Velis Training System with the Rotax-powered SW 121
Operate in cold, hot, rain…
High level of reliability and safety; fault-tolerant/dual redundant and crashworthy battery system with constant monitoring (DO-311A compliant). Demonstrated ability to withstand faults and battery thermal-runaway events.
Levers 12 years of Pipistrel experience in electric flight technologies.
Powertrain is liquid-cooled, including the batteries. Has a radiator and 2 pumps.
Simple user-interface (avionics) in cockpit.
Drastically reduced parts count reduces lifetime maintenance costs.
Charging from 35% to 95% State of Charge takes up to 1hr 20mins (up to 2 hrs if cold and battery older).
Pipistrel SkyCharge device comes with aircraft, can overnight charge on 240V AC or better on 380V three-phase AC quick charge.
Pipistrel partnered with GreenMotion to develop dual-use (car/aircraft) charger.
Simple start-up – 4 switches, no warm-up time required.
MTOW 600kg (1,320 lb) with 172 kg (378 lb) payload weight.
Vso 45 kts (Vs1 51 kts)
Cruise speed at 35kW: 90 knots. (max 98 knots)
Vy 75 knots.
Best glide ratio: 17:1 (stated earlier in text)
Best climb rate: 647 ft/min
Takeoff run over 50ft obstacle: 453m (1,485 ft) from grass, 409 m (1,342 ft) from asphalt.
Service ceiling: 12,000 ft. No loss of motor power delivered to prop with altitude.
Endurance: Up to 50 mins + VFR reserve.
Load factor max +4g/-2g.
Price: Approx €180,000 with Charger?
Electric aircraft produced by Pipistrel so far in Chronological order: Taurus Electro, Taurus G4, Taurus Electro G2, WATTsUP, Alpha Electro, HY4, Pantera Hybrid, Velis Electro, Alpha Electro LC.
Several publications have flight-tested the aircraft for articles, most recently Business & Commercial Aviation (BCA) which also had excellent drone drone footage of the takeoff. The Flying Reporter (see his YouTube channel), and Pilot magazine (Pilotweb). I’m sure there will be many more.