Taurus Electro

49′ 1½” wingspan
Glide ratio 41:1
Electric retractable engine and propeller
Unique side-by-side seating – perfect for training
Retractable undercarriage
Perfect for thermaling or slope soaring
Comfortable training or pure sports aircraft

So, what does an owner think ? 

Here are a few comments from owners Terry and Kim.

Our Taurus is the first G2.5 and our solar trailer is the first G2 in the USA.

The Taurus is based at our home airfield, Boerne Stage Airfield (5C1), Boerne, TX. The airfield is about 20 miles north of San Antonio.

After 17 flights and 19 hours, Kim, my wife, and I have confirmed our Taurus Electro is the best motorglider for our soaring profile.

  • The cockpit is the most comfortable, roomy, easy to get into and out of, and has the most awesome visibility of all the 28 different gliders we have flown.
  • The conventional landing gear means we can taxi to and from the runway by ourselves. Since we live on a mostly power airfield and are retired, we can blend in with the powered aircraft and also fly on any day of the week without the help of anyone in our soaring club.
  • The hottest day we have flown on so far has been 94F. With my wife and I in the glider, we were airborne in about 600 ft and climbed 500-550 fpm. The Taurus climbs so good that, if the motor fails at any altitude, we will always be able to land into the wind on the active runway.
  • The Taurus is a very nimble glider in all three axis. The flight controls are well balanced, very crisp, with light stick forces.

The Taurus Electro G2 was the first electric 2-seat aeroplane in serial production available on the market. It offers complete freedom and independence thanks to the retractable electric engine, dual retractable main landing gear, excellent gliding performance, inexpensive maintenance and a well ventilated spacious cockpit. Furthermore, Pipistrel believes it is the only truly useful electric aircraft out there, because the electric drive is applied to the glider airframe, where battery capacity is not a limiting factor in performance/endurance. Taurus Electro G2 represents a leap forward in performance, safety, functionality and user friendliness.

Can electric perform better than conventional? Absolutely!
For the first time electric power outperforms its gasoline-powered counterpart – the Taurus. Taurus Electro G2 can use a shorter runway, climbs faster and is performs much better than the gasoline-powered version when it comes to high altitude operations. All this is possible thanks to the specially-developed emission-free Pipistrel’s 40kW electric power-train.

The tailor-developed Lithium-technology batteries come in two configurations, capable of launching the aeroplane to 1200 m (4000 ft) or 2000 m (6500 ft) respectively. They are placed in self-contained boxes, monitored constantly by the super-precise Pipistrel battery management system (BMS), compete with data-logging and battery health forecasting.

The propulsion motor weighs an impressive 11 kg (rather than 16 kg) and generates 10 kW more power, resulting in a total of 40 kW. Due to this 33% increase in power and 40% decrease in weight we developed a whole new propeller, which has proven to be more efficient than the version flying on the Taurus Electro Prototype.

The motor peaks at 40 kW for take-off and allows continuous climbing at 30 kW power. It is controlled by a specially developed power inverter/controller and governed by the cockpit ESYS-MAN instrument. All components are networked via CAN-bus, feature proprietary multi-layer protection logic and produce a true throttle-by-wire experience.

The result is a full featured maintenance-free electric powertrain, that can be retrofitted into existing gasoline powered Taurus gliders and will be offered for integration into third party platforms as well. With Pipistrel, it is all about safety, more performance and fewer emissions.

The Taurus Electro G2 conforms with EU microlight standards as well as FAA ASTM standards for the airframe. Pipistrel is working with authorities to obtain full certification for the electric engine systems.

The Taurus Electro G2 made its first public appearance at AERO 2011 Friedrichshafen, where it won the Berblinger prize registered as D-METD. Numerous other certifications, including France, South Africa and USA were completed by the end of 2011.

Also at AERO 2011, Pipistrel is unveiling another World’s first – the concept of Flying For Free. Pipistrel developed the Solar Trailer, which can charge-up the Taurus Electro G2 in as little as 5 hours absolutely free of charge and with zero emissions! Furthermore, when the Taurus Electro G2 is stored in the trailer during the week of bad weather, it will still be charged and ready to fly by the weekend. The Solar Trailer and Taurus Electro G2 are perfect companions and demonstrate how it is possible to fly for free, quietly and with absolutely zero emissions, with today’s technology! This changes everything, again.

More than just a touch of Innovation!
With the Taurus Electro G2 we are introducing a World’s first – a full set of on-board networked avionics providing for a fly-by-wire powertrain management with built-in multi-layer protection logic. Let us tell you that this represents a great improvement over the system used in the Taurus Electro prototype, where everything was handled by the pilot.

State-of-the-art battery system that uses information from the past to see into the future.
The first element of this networked system is the state-of-the-art hybrid battery management system which was developed entirely in house to be able to function with tighter tolerances than commercially available systems, yielding better performance and longer battery life. The Battery Management system monitors the batteries, which were specially developed to be used in the Taurus Electro G2.

These batteries represent the absolute pinnacle of today’s battery technology, combining low weight, high power and high energy density to levels that seemed impossible as recently as 2009. The batteries are placed in aluminum boxes with dedicated power and signal connectors. Each battery cell’s performance is monitored, temperature measured and future performance predicted.

The system is able to forecast when a battery cell is not performing and signals the need for a premature replacement. All parameters are also logged in the on-board flight data recorder. The four battery boxes are removable and replaceable.

Power controller
The second element is the power inverter/motor controller. It’s location has been moved into the aircraft’s fuselage, it has become more efficient and features self-protection logic against current spikes, over temperatures and other potential abnormal situations. In other words, the controller is not only driving the motor, but also providing for the low-level protection of both itself, the batteries and the motor.
Introducing the ESYS-MON cockpit interface instrument!
The most noticeable addition to the networked system is the color-display cockpit interface instrument. The screen is really bright, in fact brighter than most displays out there, and is readable in the strongest of sunshine! It indicates the drive mode and important parameters to the pilot and provides the interface for engine retraction and extension. Everything is operated via two (2) toggle switches and a rotatable knob. The first toggle switch is the power on/off switch and does exactly that – powers up the motor controller.

The second toggle switch is the motor position selector »up/down« i.e. extended or retracted. This process is fully automated – the propeller is positioned and held in place while the motor extends or retracts. The pilot only selects the desired mode with the toggle switch. The rotary encoder acts as the throttle selector.

The beauty comes from within…ESYS-MON is much more than just a display.
Due to the nature of electric propulsion system, we decided to employ the computational power of this cockpit interface instrument and gave it the role of the master on board computer. This means it not only displays data to the pilot, but also »talks« to every other powertrain component on board via CAN bus and makes everything sing together. It is able to detect overheating of individual components and reduce power gradually in order to maximize the climb potential with the given system status. Not only that, it provides systems diagnostics and all necessary warnings to the pilot.

Combining all elements, we have developed an aircraft which offers more performance and an almost care-free use of this revolutionary technology.

Taurus Electro is made in highest technology composites (epoxy resin, glass fibre, carbon fibre, kevlar fibre and honeycomb structures). The airfoil used on wings is ORL 170, (F. Orlando).

Motor High performance synchronus 3-phase electric outrunner with permanent magnets
Power 40 kW for takeoff, 30 kW contionus
Propeller 2 blade Pipistrel 1650 mm diam special for Taurus Electro G2
Wing span 14.97 m
Length 7.27 m
Height 1.41 m
Wing area 12.33 m2
Rudder area 0.9 m2
Horizontal tail area 1.36 m2
Aspect ratio 18.6
Positive flaps 5 deg, 9 deg, 18 deg
Negative flaps -5 deg
Center of gravity 23% – 41%
Empty weight (includes standard battery!) 306 kg
Minimum pilot weight 60 kg
Maximum total pilots weight 220 kg
Max take off weight (MTOW) 550 kg
Weight of std battery system 42 kg
Weight of optional battery system 59 kg
Stall with flaps 63 km/h
Stall without flaps 71 km/h
Manoeuvring speed 163 km/h
Max. speed with flaps extended 130 km/h
Max. speed with airbrakes extended 225 km/h (extend at or below 160 km/h)
Max. speed with powerplant extended 160 km/h
VNE 225 km/h
Min.sink 0.70 m/sec
Min.sink speed 94 km/h
Max. sink with airbrakes 6.0 m/sec @ 100 km/h
Best glide 1: 41
Best glide ratio speed 107 km/h
Best glide at 150 km/h 1: 33
Best glide at 180 km/h 1: 23
Max towing speed 150 km/h
45°- 45° roll time 3.9 sec
Take off run MTOW 160 m
Take off over 15 m MTOW 245 m
Best climb speed 100 km/h
Max climb rate (MTOW) 3.1 m/sec
Relative climb (elevation independent!) 1100 m (4000 ft) / 2000 m (6000 ft)
Max load factor permitted (x1,8) +5.3g -2.65g
Max load factor tested + 7.2g – 7.2g

Pipistrel reserves the right to revise the above data whenever occasioned by product improvement, government/authority regulations or other good cause. The design basis follow the strictest EASA CS-22, CS-VLA and CS-23 (sections), as well as rules applicable to ultralight/microlight aircraft (LTF-UL 2003, etc.)

I wish to know more about the batteries used in Taurus Electro G2
Battery type is a special-made Li-poly battery, 10 Ah capacity per cell, 25 C discharge rate. The system includes 4 boxes where the batteries are located, the BMS also. The standard battery configuration is 128 cells, optional are 192 cells. They fit in the same 4 boxes in both cases.

The basic option gives you total capacity of 4.75 kWh, from which it is sensible not to use more than 80% due to battery cell life. Effectively you end up with 3.8 kWh of useful energy. This version fully meets European microlight standards regarding the empty weight! The battery pack weighs 10.5 kg per box, there are 4 boxes, totaling at 42 kg.

The optional pack adds capacity to reach 7.10 kWh total, again by taking 80% »sensible discharge level« you are effectively at 5.7 kWh of useful energy. This battery pack weighs 13.9 kg per box, there are also 4 boxes on board, totaling at 55.6 kg.

What is the endurance of the Taurus Electro G2 in real life?
In terms of endurance the following margins apply for the basic battery pack:
20 kW power output: 11 min 30 sec
30 kW power output: 7 min 40 sec
40 kW power output: 5 min 40 sec (theoretical, expected is 1 min on 40 kW, then reduced power)

The data may change because of ambient temperature. 80% sensible discharge level is taken into account.

In terms of endurance the following margins apply for the optional battery pack:
20 kW power output: 17 min 10 sec
30 kW power output: 11 min 20 sec
40 kW power output: 8 min 35 sec (theoretical, expected is 1 min on 40 kW, then reduce power)

The data may change because of ambient temperature. 80% sensible discharge level is taken into account. Please note that in horizontal flight only 7 kW is needed, so theoretical endurance reaches 1 hour.

What are the variables influencing the top-of-climb capability?
There are a lot of factors for this, from cockpit load, runway condition (how much energy you burn for the taxi & take-off), ambient temperature, thermal properties of different components, controller parameters, etc. Ambient temperature is the most important factor of all.

What maintenance is required for the powertrain?
The maintenance is virtually care-free!
Battery system takes care of itself but needs to be recharged to full charge at least once every 90 days to keep them »healthy«.
Controller maintenance: nothing, just clean the cooling duct.
Motor maintenance: check main bearing for axial free play and tighten main bearing every 10 hours of motor operation.

Is it mandatory to wait a long time until engine is hot before start?
Absolutely not. The colder – the better for the engine. It will not be recommended to apply full power however if the batteries are below 5 deg. Celsius.

How does the Propeller stop and the engine retract? Is it all fully automatic?
Yes. Fully automatic systems include the brake, which is all electric, and positioning via a magnetic 16-bit hall-sonde encoder. When the propeller is correctly positioned, it can retract. The stopping, positioning and retraction of the propeller work flawlessly at the press of a single button.

Is engine and controller cooling adequate even in the summer time Australian conditions?
The cooling is proving to be sufficient. In any case, there is a protection logic built in which will slowly reduce the power on the system if it will be picking up temperature too fast (considers also temperature gradient, not just limit temperatures!)

Is it possible to retract the engine right after stopping it, or is it mandatory to wait while the batteries cool down?
Batteries essentially do not become over 50 deg.C hot. It’s not necessary to cool them down – you can retract immediately at any time, mid-flight or on the ground!

Is it possible to extract and restart the engine mid-flight?
Of course. As with the retraction, it is all automatic.

Is there a recommendation »don’t take-off when the remaining power is under a certain percent« ?

The system will not allow you to do that. If less than 3 minutes of battery endurance is indicated, it will not go to take-off power and it will produce a warning.

How long does it need to charge at 220V?
3.5 hours for the standard battery configuration, 5 hours for the optional configuration. This is when the batteries are completely empty! You can monitor all this via the ESYS-MAN instrument. Charging is also possible form the Pipistrel’s Solar Trailer.

Is charging with 380 is recommended?
No, the charger is a single-phase 220V or 110V.

Is there any built-in safety in case of too high temperature or controller dysfunctions ?
There is a multi-layer logic in place. The controller takes care of itself. In case of too high temperature it will first reduce power (up to 5%) and then switch itself off in case of severe over-heating. BUT BEFORE THIS OCCURS THE FOLLOWING WILL HAPPEN:
We have an on-board computer now. It measures not only the temperatures of all components of the system (motor, controller, 4 temperature probes per battery box etc), but also a bunch of other parameters and has the limit temperatures as well as limit temperature gradients programmed inside. For example, if the motor is heating up more than a certain amount of degrees-per-minute, it will reduce power to track the maximum permitted temperature gradient (slope), in order not to reach the limit temperature at all. The same goes for the controller, as well as for the batteries. Manual override is possible, of course. There are warnings which display on the screen, too.

Will parachute remain usable in case of battery overheat / fire ?
Thanks to the super-precise Battery Management System, which was specially developed by Pipistrel just for Taurus Electro G2, battery issues are extremely unlikely. Furthermore, the batteries are placed in self-contained metal boxes in the fuselage. In event of an overheat/fire, the parachute remains fully functional.

How is throttle control executed?

The system uses throttle-by-wire concept. The throttle input is received at the ESYS-MAN, filtered with protection logic and the reference for the RPM is then sent over to the motor controller via CAN bus. It is all very elaborate, not via a simple potentiometer as it is common with other aircraft.

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