Guy Leitch and Jason Beamish. Air to air Images Paul Ludick

We are thrilled to bring you the most significant flight test in the past twenty years: the first practical electric general aviation plane. Love them or hate them, electric planes are the future – and now they are here.

For the sceptics, a battery powered plane is an unlikely proposition. Batteries have a terrible energy density compared to Avgas and they are expensive and heavy – and unlike Avgas, batteries don’t get lighter as they are used up.

Yet Elon Musk has now sold six million Teslas. So no matter how big a sceptic you may be – battery electric power is a reality.  And nothing reflects this more than Textron, who make Continental and Lycoming fossil fuel burners, having bought Pipistrel for R3 billion in 2022.

Pipistrel’s Velis Electro

Which brings us to the subject of our epoch making flight test – the Pipistrel Velis Electro.

Battery technology has been around for hundreds of years. I remember our milk being delivered by milk float carts with lead acid batteries. Now we have the next generation of batteries –  with Lithium-ion cells. And there’s no doubt about it – they work in cars  – with many having 500 km plus ranges.

But aeroplanes are not cars. Cars very seldom use more than 25% of their max power output. Planes on the other hand are often expected to run at 75% continuous power – and that flattens batteries fast.

So the big question to be asked is: Is the Velis Electro a practical plane?

Let’s cut straight to the key numbers. The basic Velis Electro is limited to a 600 kg MAUW –  which gives it a payload of 378 pounds (172 kg) – which may seem light, but remember, it does not have to lift any fuel in that payload. Its maximum speed is 98 KTAS, it has a maximum endurance of 50 minutes, plus reserve, and can be recharged within one to two hours.

Bottom line; it’s great for flight schools doing circuit training, especially as half the circuit is done at almost no power.

The Velis Electro we have had the honour of being the first to fly in South Africa is the second Pipistrel all-electric plane to arrive. The first was a significantly less developed non-type certified version, registered ZU-TKD,  imported by the then agents, 43 Air School. Our flight test example, ZS-FSD, is EASA certified (and thus has a ZS- registration) and is more suitable for the flight school operators at which it is aimed.

In October 2024 we reviewed Pipistrel’s certified Explorer. The Velis Electo’s design and structure are essentially the same. So for this review I will focus on the power train with its surprisingly complex batteries, chargers, controllers, inverters and cooling systems.

Although the fuselage of the Electro is fundamentally the same as its siblings, the wings have a surprising difference. Unlike both the Alpha and Virus motor glider versions, there are no airbrakes and the flaperons’ maximum deflection is limited to just Flap 2, which is 19 degrees.

Like the Explorer, the pitot tube incorporates an angle of attack sensor for the haptic active feedback stall warning system. The elevator and full-span flaperons are pushrod operated and an electric servo motor drives a spring-bias system mounted on the elevator push-pull tube for pitch trim. The rudder is cable actuated.

An immediately obvious external difference to the internal combustion engine (ICE) aircraft is the air intake in the lower cowl. The electric motor’s thrust line is higher and very usefully for flight schools, there is even better prop ground clearance.

There’s a large air intake on the side of the fuselage behind the pilot’s door, and a small outlet in the belly. More about this later.

In the Cockpit

It’s the electric controls which are of interest, and they are unique so have been custom made by Pipistrel.

In the centre-right of the panel is the Electronic Propulsion System Instrument (EPSI). This is the main source of information about the operational state of the aircraft – most importantly, the health of the engine and batteries. The EPSI has multiple pages: for example, when connected to the charger it shows the state of charge in percentage and the temperatures of the batteries and inverter.

Another interesting feature, and again great for flight schools, is that Pipistrel are able to monitor the aircraft and its systems remotely, through an app which shows position and speed as well as take-off and landing times. The aircraft also has a sensor that logs events over a certain threshold, like a hard landing. It also monitors how many hours until the next maintenance check, and if anything out of the ordinary happens.

On the nose a 3-blade fixed-pitch prop is driven by an axial-flux electric motor which can produce 65kW (88hp) at takeoff. However, that maximum output is limited to 90 seconds.

Power is delivered by a 345 Volt DC motor built around a liquid-cooled high performance battery system, all developed and built in-house at Pipistrel.

A high-voltage H300C controller manages the three-phase AC supply to the motor. Maximum continuous current is an impressive 300 amps, and that’s a lot of juice – and a lot of heat. Both the electric motor and power controller are liquid-cooled by the same system, which consists of an electrically driven pump and a radiator.

The ‘fuel tank’ is two Li-Ion battery packs located in front and behind the cockpit. The battery capacity is 25 kWh, and they work in warm and cold weather, but are best at around 20°C. The batteries are liquid-cooled by two electric pumps, and the coolant flows through the large radiator behind the cockpit. Electric fans behind the radiator provide additional cooling when the batteries are being charged.

The external charger, batteries, pumps and fans are all monitored by the Battery Management System (BMS). The BMS performs myriad functions, including calculating the battery State Of Charge (SOC) and State Of Health (SOH). SOC is self-explanatory, while SOH is essentially the ‘age’ of the battery, which affects how much energy it can store and how much power it can deliver. As a rule of thumb, Li-Ion batteries have a guaranteed life of around 6,000 cycles.

As there is so much equipment crammed into the compartment behind the cockpit, there is no ballistic parachute nor baggage bay.

Naturally, but still unexpectedly, there is no dipstick to check the oil – and no fuel strainers to drain.

The controls are standard Pipistrel: the seats are fixed and so the rudder pedals adjust.  The two sticks are well located although the flap lever is slightly awkward and the trim indicator difficult to see. Inflatable lumbar support is a nice touch.

The power quadrant carries the T-handled power lever, while the pedestal that braces the instrument binnacle carries numerous circuit breakers and four silver toggle switches for the Master, Avionics, Battery and Power.

Pre-Flight

As the Velis Electro is still in its test phase and has to be operated from one airport, it was transported by Absolute Aviation Sales Director Justin van Tonder in a custom made trailer from Lanseria to the Coves Aero Estate at Hartbeespoort. Assembly was remarkably quick and easy, thanks largely to Pipistrel’s strong glider heritage.

Justin had fully charged both batteries so we were not able to experience what must be a light-dimming energy suction when the big three-phase charger is turned on to max. You need a 415V three-phase AC supply and the charger supplied with the aircraft can recharge at rates from three to 32 amps (the lower current helps keep the batteries cool, which is important on a hot day − but charging takes longer.)

When charging, the battery management system keeps things cool with coolant pumps and radiator fans. The risk of thermal runaway when the batteries are being charged is taken seriously, as lithium battery fires are self-sustaining.

To manoeuvre the plane on the ground you cannot push on the Velis’s prop as this puts a non-designed for load on the electric motor’s thrust bearing. Another interesting feature is that you can rotate the prop easily with just one finger, (just like an electric fan) so there’s little to no braking effect from the prop windmilling.

When you’re ready to fly, the Flight Page of the EPSI shows rpm and power in both digital and analogue formats, the all-important battery state of charge (SOC) in percentage and time remaining, the voltage in the main and auxiliary avionics battery, temperatures of the front and rear propulsion system batteries and coolant temperatures for the engine and battery systems. 

An annunciator panel has ‘Master Warning’ and ‘Master Caution’ indications for failures in the propulsion system. These are reinforced by aural warnings. There’s also a second, small warning panel which is specifically designed to warn about battery over-temperature. It is analogue and consists of battery temperature sensors and two warning LED lights (one for each battery pack) which illuminate if the battery temperature exceeds 58 degrees C.

There is a plethora of placards. Notably the limiting speed for Flap 2 is just 65 KIAS. Justin said that 60 KIAS was a sensible approach speed, so that doesn’t leave much room for a go-around.

Start-up

Working from left to right, you select Master On. The aircraft self-tests the ‘Batt Overtemp’ warning lights and haptic stall warning system.

‘Avionics’ is next. You check the propulsion system’s battery SOC and SOH and the auxiliary battery voltage. Radio and transponder on. Behind the seats the coolant pumps and radiator fans come to life. Check that the power lever is at ‘Cut Off’, select ‘BATT EN’ and then ‘PWR EN’ and the motor whirrs into life. Taxying on a hard surface requires very little power (less than 3 kW). Because the motor is so smooth and quiet you notice every creak from the undercarriage. 

Pre-takeoff checks

Pre-takeoff checks are simple: there’s no fuel pump, mixture, carb heat, mags and suchlike obsolete gadgetry.

The run-up is simple: set full power to ensure the system is producing at least 50kW, then power lever (it’s not a throttle) back to cut off, check motor and battery temperatures and that both batteries are ‘Active’ and you are ready to go.

Another interesting feature is it does not idle. When you pull the power back, the motor stops dead, like a modern car with auto stop feature at a traffic light. Move the lever forward and it spins into life again.

Flying the Electro

Jason Beamish writes; “Lined up on 36 at The Coves, I push the power lever to the stop and the engine whirrs enthusiastically. A quick glance confirms ‘airspeed alive’ and the needles of both the prop rpm and power are in the top of the green. Full takeoff power is restricted to a maximum of ninety seconds.

The acceleration is somewhere between adequate and brisk, and a lot less frenetic than the piston-engined Explorer. Rotate at about 45 knots and the Velis lifts off at fifty. At 300 ft I retracted the flaps and the Velis accelerates to 75 knots.

A scan of the panel shows power is steady at Maximum Take Off Power (MTOP) of 65 KW (88 hp). As the speed builds, the fixed-pitch prop creeps into the yellow arc and the colour of the digital rpm display also changes to yellow.

The big gauge registers remaining battery time. When we taxied out it said 55 minutes, but now it’s already down to 25, which isn’t very long to fly an air-to-air formation shoot and a full flight test.  However, when I brought the power back from MTOP to Maximum Continuous Power (MCP) of 25 kW the ‘Time Remaining’ doubled to a much happier 45 minutes.

On its website, Pipistrel says the aircraft is “optimised for local flights around the aerodrome, i.e. take-off and landing sorties”. The POH states that with a 100% charge, the battery would accommodate eight traffic patterns (defined as a 12 km circuit at 1,000ft AGL), with a 10 minute reserve.

Justin says a good rule of thumb is to calculate 2% battery discharge for every minute flown – without forgetting the reserves. That means that if your routing takes you beyond the traffic pattern, exact flight planning is a must.

Flying formation with the RV-7  cameraship was another interesting experience. Even though my dad is flying a super-smooth lead for photog Paul Ludick, holding position is not easy. Pipistrels are slippery, which is why the others have airbrakes. However, the Electro not only lacks airbrakes, but there’s minimal drag produced by the prop driving the engine on the ‘over-run’.

Flight characteristics are like its Virus siblings. The stability around all three axes is strongly positive directionally, positive longitudinally and neutral laterally.  Moving into slow flight confirms that the Electro is slow to decelerate, but the stalls are straightforward, either with flaps up or down, or with the power at either idle or maximum.

Pitch trim changes with flap are almost indiscernible. Adequate aileron authority is available deep into the stall, while a very curious anomaly (and something I’ve never encountered outside of a turbine powered aircraft) is the haptic stick shaker. As the stall is approached it shakes the stick vigorously.

The Velis Electro has been designed as a circuit-flying trainer, so cruise performance is secondary. But with the power set at 25kW it cruises comfortably at 70 KIAS and a quiet 1,900 rpm. The relatively high wing loading of 63kg/sq m gives a pleasantly firm ride, but the time remaining meter drops steadily, and all too soon we have to think about getting back on the ground.

On Downwind I pull the power right back and it’s a relief to see the time remaining jump. Because the plane has so little drag, a flatter approach at 60 KIAS and full flap is preferred. With the speed nailed to sixty and the power pulled back to the stop, the Velis still floats. Nevertheless, once down you can stop comfortably in 200 metres with light braking. 

The SOC indication was at 50% and this means that takeoffs are not allowed. As an indicator of how much energy is consumed at MTOP, if the SOC indication is below 15% an amber caution message stating ‘NO GO-AROUND AVAILABLE’ appears on the annunciator panel, which must concentrate the mind.  It helps to have glider pilot experience where go-arounds are not an option.

Conclusion

The limitations of battery technology mean an electric aircraft is not yet a practical touring plane to go places in. But it’s a great trainer thanks to being very cheap to run and at less than €215,000, is not excessively expensive.

The Electro is by design excellent for circuit training, but there’s more to it than that. It is possible that the electric powertrain will eventually be paired with a hydrogen fuel cell. And battery technology is steadily improving.

The big challenges for all electric vehicles are energy density and recharge times. As electric cars evolve it will be good for electric planes.  Consider the early jets−the Messerschmitt Me 262’s Jumo engines had a TBO of around twenty hours, and now turbofans remain ‘on the wing’ for over 20,000 hours.

The Velis Electro is hugely significant – Pipistrel have succeeded in building a practical circuit training aircraft that is quiet and cheap to run – and gets all sort of green credits. The future is indeed here.