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Siemens develops new low-weight, high-power electric motor for aircraft; enabling larger hybrid aircraft

Siemens researchers have developed a new electric motor that, with a weight of just 50 kilograms (110 lbs), delivers a continuous output of about 260 kW—five times more than comparable drive systems. The motor was specially designed for use in aircraft. Due to its record-setting power-to-weight ratio, larger aircraft with takeoff weights of up to two tons will now be able to use electric drives for the first time, Siemens said.

To develop the motor, Siemens’ experts scrutinized all the components of previous motors and optimized them up to their technical limits. New simulation techniques and lightweight construction enabled the drive system to achieve the weight-to-performance ratio of five kilowatts (kW) per kilogram (kg).

Since the new motor delivers its performance at rotational speeds of just 2,500 revolutions per minute, it can drive propellers directly, without the use of a transmission.

Motor and propellor. Click to enlarge.   Motor on test rig. Click to enlarge.

This innovation will make it possible to build series hybrid-electric aircraft with four or more seats. We’re convinced that the use of hybrid-electric drives in regional airliners with 50 to 100 passengers is a real medium-term possibility.

—Frank Anton, Head of eAircraft at Siemens Corporate Technology

The motor is scheduled to begin flight-testing before the end of 2015. In the next step, the Siemens researchers will boost output further.

In 2013, Siemens, Airbus and Diamond Aircraft successfully flight-tested a series hybrid-electric drive in a DA36 E-Star 2 motor glider for the first time. The test aircraft had a power output of 60 kW. (Earlier post.)



If they can get solid state or whatever batteries to go with it, the possibilities for flight are immense.


All we need is some decent batteries to go with this! :)


Interestingly the chief engineer at Mitsubishi said that the critical thing they needed before they could start series production of electric cars was the engine, that determined the time they started more than the batteries.

It would be nice to have both!


This is an amazing 5.2X e-motor or 5.2 KW per Kg.

How soon will we see 10X batteries and 10X e-motors.

Sometime before the end of next decade we may see both?

Extended range BEVs and small e-planes will become realities?


10X batteries - you might be waiting.
The larger electric motors are very interesting for a serial hybrid regional airliner. You could use them on batteries at the airport and on generator when the plane was off the ground, creating a very quiet plane which could be used day and night.

You probably need about 4000 Kw to match an ATR72-600.
So you would need 16 of these (or 4 1000Kw engines (!)).

It is quite a jump (a leap even !)- as everyone has said.


I wonder how much of the performance optimization of this motor relies on the abundance of cool air at the likely cruising altitude of the aircraft this would be fitted to.

It appears to contain a very clever integrated cooling fan, and a pretty small cooling line.

I agree with Davemart (ring a bell). A motor that small driving a four bladed scimitar propeller of that size is astonishing. The ability to create an ultra low drag nacelle will be a decisive competitive advantage.

This is really big news, possibly the most consequential breakthrough in aviation powerplants since the jet engine.

Bravo, Siemens!


I think the greater potential is decoupling of the primary powerplant and the fan systems.  A turbofan engine's diameter is limited by the need for ground clearance beneath the wing, and the Froude efficiency is limited by the diameter (and the amount of air it can handle).  If the engine core drives an alternator to power smaller fans running the span of the wing, the ground clearance can be increased while total fan area and efficiency also increase.

If power can be transferred across wings, engine-out operation need not cause asymmetric thrust.  With all fan elements still operational, drag is not increased from either dead fans or trim loads and performance improves.



A quick question for you, if you would be so good:
If the correct metric to use when considering the production of hydrogen for use in a vehicle the lower heating value?

I am assuming it is, and the figures which I have seen giving very high efficiencies may be based on higher heating value for the hydrogen, which may be appropriate in some applications but not vehicles.

I would be grateful if you have time to throw light on it.


Agree that decoupling provides additional advantages EP, but the application for this motor is replacing piston (and eventually turboprop) engines rather than turbofan.

Roger Pham

Why must it be a hybrid propulsion system? Why can it not be a purely electric propulsion, using a 150-kW Fuel Cell (FC) for a 4-seat aircraft? At 3kW per kg, a 150-kW FC would weigh merely 50 kg. Motor weight would be 30 kg and SiC-based power controller probably would weight about 5 kg. Total propulsion package would weigh about 90 kg (~200 lbs) vs 360 lbs for a Continental IO-360.

Hydrogen as a fuel is extremely light, and the carbon fiber H2 tanks/tubes can be load-sharing with the aircraft structures to save on weight and cost. Figure about 25 kg of H2 would be required at 5-6 kg per hour. At ~$4 per kg of H2 made right at the FBO's hangars' roofs from solar PV panels, this will be equivalent to $2 per gallon of AV gas, and will solve the near-future leaded-fuel availability problem as well.

For reference, look at the Pipistrel Panthera, a 4-seat aircraft capable of 198 kt TAS (227 mph) at fuel flow of about 10 gal/hr, or probably 5 kg per hour for the FC version because FC is twice as efficient.


The future of exciting and affordable personal aviation perhaps has just begun. Imagine no more engine noise and vibration, no more engine maintenance problem, no more engine's catastrophic failures, no more exorbitant fuel cost of $60-100 per flight hour...will be down to $10-12 per hour...no more exorbitant engine overhaul cost of 20-30 thousands of dollars every 1,500 or 2,000 flight hours...no more risk of carbon monoxide poisoning problem due to exhaust leakage...


Roger, both fuel cells stacks and storage tanks are life limited.

Without a refueling infrastructure on many airfields, it wouldn't fly.

It *could* happen. But with refueling facilities at $2.5 million each, it won't happen soon.

Almost every hangar has power, and most have 3 phase 208 or better. Solar is very easy to install on hangar roofs. At 400Wh/kg, electric flight becomes viable. It will be very hard for H2 to compete past that point.

Roger Pham

>>>>You stated: "Without a refueling infrastructure on many airfields, it wouldn't fly."

At ~$4 per kg of H2 made from solar PV panels right at the FBO's hangars' roofs, using trailerable H2 stations that can be installed in 2 days, this will be equivalent to $2 per gallon of AV gas, and will solve the near-future leaded-fuel availability problem as well. Data from ITM-Power indicated that the amortized cost of H2-station including electrolyzer amount to no more than $1 per kg, and the cost of the H2 stations will come way down with mass deployments and mass production, especially with cheap, non platinum catalysts.

Solar PV energy from the hangar's roof is better off to make H2 in order to allow for quick fillup, and fillup at any times, night or day, sunny or cloudy, something that solar PV for battery charging cannot do.

400 Wh/kg is nothing in comparison to H2's capability of 2,000 Wh/kg. The added advantage of H2 tanks are that they can be made load-sharing with the aircraft structures, thereby gaining more weight savings not possible with the battery packs.

At 5,000 psi, short automotive cylindrical H2 tanks are capable of 6% wt percentage of H2, but very long and thin H2 tanks designed for aircraft's are capable of 8% wt. percentage even before consideration of being load-sharing with the aircraft that can allow the aircraft's structural weight beside the tanks' wt. to be halved.


I'd love to see it. But the lightest carbon fiber tanks are about 200 lbs. and volumetrically very problematic for aircraft. Size means parasitic drag and frontal area. You can't put an extra 200 lbs in the tail even if you have the volume.

NASA did a design study and actually built an H2 GA aircraft a few years ago. They concluded that volumetrically it just doesn't work out.

Im sorry I don't have the link any more, but I'll post if it I come across it.


The only fuel cell plane that I am aware of is the Antares H2, with the H3 on the drawing board.
It is for missions like long range reconnaissance.

Progress for more general aircraft seems to me more likely through the gradual development of the ancillary power systems, which use on board reformation from jet fuel to provide energy to the fuel cells.

These have several advantages over using a diesel generator, including great reliability as proven in hurricane Sandy, where they did far better than diesel.
They are also more silent and vibration free, and since they do not combust the fuel have tiny comparative levels of pollution.

The development of on-board reformation is at an early stage, but since it is also a technology which is being used to eliminate idling pollution in trucks, is being vigorously pursued.

A quick question for you, if you would be so good: If the correct metric to use when considering the production of hydrogen for use in a vehicle the lower heating value?

If you're burning hydrogen in a combustion engine, you'd use the LHV.  I couldn't tell you what's appropriate for fuel cells and the like.

End-to-end efficiency for power-to-gas-to-power is the same in any event, as you'd incorporate the difference one way at production and the other way at consumption.

the figures which I have seen giving very high efficiencies may be based on higher heating value for the hydrogen

They'd more likely be based on the LHV, since the LHV is a smaller value and gives a larger efficiency when it's the denominator.

(note:  I'm seeing blockquotes boldfaced in the preview.  This is not my doing.)

the application for this motor is replacing piston (and eventually turboprop) engines rather than turbofan.

I prefer to think big.  Also think beamed power; if you don't have to carry your energy, you can do a lot more.  Think of an airliner which only needs enough fuel to reach its diversion landing sites en route, rather than the entire trip.


H2 may be an option for lighter than air vehicles with the addition of this type of motor. A British company http://hybridairvehicles.com/ is about to launch a commercial vehicle that was originally developed for the US military (victim of cutbacks) and is hoped to carry payloads of 1000 tons. Think how many trucks that could take off the road. Solar panels on the top surface of this airship could help drive the motors if they went on to replace the existing diesels.

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