You might wonder what electric aircraft has to do with ebikes, but…I believe it is worth taking a look at because they are at the cutting-edge of solid-state battery tech, so here’s what I found.
Oshkosh is a city in the state of Wisconsin. Since its near Canada and Lake Superior, it is super cold in the winter, but in the warm weather of July, it has become famous for hosting the Experimental Aircraft Association meet (EAA). If you think EU ebike regulations are restrictive and slow to improve, the aircraft industry is so “lawsuit averse” that improvements are very difficult to implement, except…when it comes to “experimental” aircraft…
Aircraft people love new tech, and they usually have money to spend on cutting-edge toys. As much as environmental activists love to hate rich people, it is often the wealthy who finance the advancements we all want, and that’s why electric aircraft are worth watching.
Also, the city of Friedrichshafen (In Germany) hosts the “Flugzeugbau” in April, which in German means “flying stuff construction”. Like EAA, it’s also a convention where manufacturers and aviation businesses meet to see what’s new. So…between EAA and Flugzeugbau, lets see whats new…
The 2-seat aircraft in the header pic above is the Aero-Electric “Sun Flyer” demonstrator, using a single Siemens SP70D motor. Siemens is a very old and large German company, located in Erlangen. Although they are a global corporation that is very diversified, they have a long history of being a major player in the electrical components field. In fact, they built an electric trolley for public transportation in the city of Munich…in 1881.
The “70” in the SP70D name means that it can provide a continuous 70-kW, which equals 93-HP. The Siemens line of aircraft motors are permanent magnet inrunners, and they all have liquid-cooling via a thin synthetic oil. They also have yoke options that are hollow, to allow certain hybrid designs to use a shaft down the center from a second power-plant.
The horsepower figures for the examples in this article are deceiving, because electric motors provide significant torque across their entire RPM range, and not just at high-RPM’s, like a gasoline engine.
Another major feature of the Siemens family of electric motors is that they all have yoke options that make the motors “stackable”, since some manufacturers want redundant motors on a single propeller.
The kV of the SP70D shown is optimized to operate with a battery nominal voltage around 350V-400V, which is similar to the Tesla cars, and the Nissan Leaf.
Siemens has many different sizes of motor for aviation applications, and their stackability gives designers even more flexibility. The pic above shows the SP260D, which provides a continuous 260-kW of power (348-HP), and of course, much more power as a temporary peak during takeoff.
The sport-plane in the short video above is the “Extra 330LE”, and the kV of this motor provides full power up to a low 2500-RPM’s using 570V. One of the major benefits of these electric drives is that they can provide full torque directly at the propellers optimum RPM range. Top speed is 340 km/h (211-MPH).
Most lightweight aircraft gas-engines must run at a very high RPM to attain max power, and then run their power through a large reduction (PSRU) to get the RPM’s down to the optimum propeller speed. Electric drives don’t need a PSRU, which eliminates complexity and one more potential point of failure.
The Alpha Electro from Pipistrel achieved first flight in February of 2019, (a year ago as of this article). There have been over 50 made and sold around the world. The company is marketing them with optional dual-controls as an affordable trainer for pilots to achieve an “electric aircraft” rating.
In the pic below, the Alpha Electro has the power plugged-in at the Fluegzugbau convention, and the cover has been opened to show the weather-proofed charger control panel.
A three-bladed propeller in the pic above is more expensive than a basic 2-blade. But by using three blades, you can have have a smaller-diameter propeller with the same thrust, and that smaller diameter lowers the propeller-tip speed.
That is one of the ways to dramatically lower the noise of an airplane, and the quietness of electric aircraft is a huge feature for plane owners who want to use a small community airport, and they typically have severe noise restrictions.
If you look closely, you can also see that the angle of the blades is adjustable (variable pitch). Most piston engines provide an optimum power-to-efficiency performance in a narrow high-RPM range. However, electric motors give you high torque in a wide RPM range, so a E-plane owner has the option to adjust the propeller blade angle for high thrust at lower RPM’s, for those small regional airports where low noise is needed.
The Italian company Efesto is the lead partner with Ashot-Askelon, and CFM Air. They have developed and are flying a hybrid system where an electric motor is squeezed in-between the propeller and a very conventional air-cooled flat 4-cylinder Rotax aircraft engine (a similar system is being developed by UC3M / Axter in Spain).
The standard way to get more power than a naturally-aspirated gasoline 4-cylinder aircraft engine, is to add more cylinders, or swap-in a turbocharged 4-cylinder. 6-cylinder engines are expensive, and every time the engine needs a rebuild (which is frequently on an aircraft for safety), it continues to be expensive again.
The problem with turbocharged engines is that the pilots sometimes get the engine too hot. They can dial-in the wastegate for more power on takeoff, and then dial it back for better fuel economy during the cruise, but mis-management sometimes leads to a damaged piston or melted exhaust valve.
The FAA doesn’t want to be too overbearing with regulations, but they still need to set reasonable limits. Certifying this 70-HP motor to be added to a standard 4-cylinder seems to be something that will be widely accepted. It provides a serious boost on takeoff, it is MUCH more reliable than a turbocharger, and in the event of a failed engine, the motor and battery provides 15 minutes of electric-only flight for a controlled landing.
Comco Ikarus C42/CS “Elektro”
The German Comco Ikarus C42 is an existing well-designed 2-seat aircraft. The “Elektro” version is a gas-electric hybrid conversion that is currently being marketed by them.
The Ikarus Elektro is an interesting drivetrain. Its a gas-electric hybrid, with dual redundant electric-drive. This suggests to me they hope to attain commercial certification for the system, and they can then scale it up to transport passengers.
In this system, it flies as a pure electric drivetrain, using two motors (in tandem on the same shaft), two controllers, and two batteries. Cruise power is provided by one motor, which is alternated between the two. Take-off requires the power of both motors.
The gasoline engine is a serial-hybrid. It is located behind the cabin, and it’s sole job is to run a generator as a range-extender. The stock battery packs can provide 45 minutes of electric-only fly-time, and when solid-state-batteries become available, the manufacturer anticipates upgrading to a 2-hour electric fly time, rather than using a smaller battery for the same range as before.
The two electric motors together provide a continuous 50-kW (67-HP), and roughly double that for take-off and climbing for 15 minutes. The range-extending Helvenco Swiss engine is an advanced single-cylinder 4-stroke in order to save weight while providing low emissions. It is fuel-injected, has 4-valves, and liquid-cooling.
Of course, the big question becomes, what is the payoff for such a complex system? The engine burns 7-Liters per hour (1.85 gal/hr), so the 35L fuel tank provides six hours of flying time, and of course the ability to re-fuel very fast. The manufacturer mentioned that an extended range 70L tank is also available for 12 hours of flight.
Using gasoline in a serial-hybrid configuration may be less efficient (than simply using that same amount of gas to directly drive the propeller), but the benefit is that the speeding up and slowing down of the propeller is accomplished by the electric drive-train. This allows the engine to run at the optimum continuous RPM’s, which benefits the emissions. When the 2-hour SSB pack becomes available, this will become a “plug-in hybrid” with the gasoline engine rarely being used at all.
The noise and exhaust from small aircraft may not currently be a huge concern at the small regional community airports scattered around the US, but the EU is embracing an increasingly restrictive set of rules that require planes, trucks, and buses to be clean and quiet in the cities and towns, but…they will continue to allow “reasonably clean” engines to be used out in the wide spaces between cities.
MagniX Tech is owned by the Clermont Investor Group, based in Singapore. The MagniX Tech headquarters are located in Redmond, Washington, along with their main development facility. They have a second facility in Queensland, Australia. They develop and install electric conversion systems, and they are on the forefront of what works.
Harbour Air is located in Seattle, Washington, and they shuttle customers all over British Columbia, Canada. They operate a fleet of De Havilland DHC-2 “Turbo” Beaver aircraft, which can carry six-passengers each. This rugged aircraft has a long history when using a piston engine, and also using floats to enable water-landings.
Harbour Air logs a LOT of flight time, so they have always previously used the turbo-prop version. That type of engine uses a small gas-turbine “jet” as the core, and it drives a reduction to spin a propeller. They are more expensive to purchase compared to an equivalent piston engine, but piston engines in commercial aircraft have to be frequently overhauled (Time Before Overhaul / TBO). Therefore, if you log a lot of hours of flight-time, the turbo-prop ends up being more affordable over time, due to its long TBO.
“The Magni500 electric motor that is used in the Harbour Air flights is rated for 750 horsepower and offers a 60-minute range, more than twice as long as Harbour’s average flight, Ganzarski said, allowing for a 30-minute reserve on the batteries.”
This company is based in Israel, and their “Alice” 9-passenger electric airplane is probably the most ambitious style here. It has been designed from the ground-up to be electric, rather than a conversion. The body makes extensive use of composites to save weight, since the weight of batteries directly affects the range. So, the lighter the plane, the heavier the battery can be. The unusual tapered cross-section of the fuselage reduces buffeting by cross-winds.
For redundancy, it uses three motors and propellers, with all of them in the “pusher” configuration. Although it needs all three motors for takeoff, it can fly and safely land on any two of them, in case of some failure (in spite of how reliable electric drive-trains have proven to be). The three motors are the Siemens SP260D’s shown earlier, and MagniX has an optional motor system for carriers who want that.
One propeller is located in the centerline at the very tail of the craft, and the remaining two are at each wingtip. A feature of having propellers at the wingtips is that when the craft is flying through cross-winds, it can use differential thrust to maintain its direction, rather than using a hard rudder control, which causes significant drag.
As bold as the styling of this airplane is, this is real, and it flew at the Paris air show in 2019. Eviation now has an order with Cape Air for ten units, at $4-million each. The purchase price may sound expensive, but the flight testing has shown the nine passengers (and two pilots) have a flight cost of only $200/per hour. For carriers who fly short range and 24-ours a day, the savings in fuel can add up quickly. If fuel prices increase (and they will), then the fuel savings will become even more pronounced.
The Airbus company is a consortium of companies in four EU nations…the UK, France, Germany, and Italy. They pool their resources to develop aircraft that they will all use, and this allows advancing tech to be adopted at a more affordable price.
I really like this plane, but it is unlikely to ever be sold to the public. It is a test-bed and technology demonstrator. It has two seats in tandem for a sleek cross-section, but the outstanding feature is the two drive units. There are two for redundancy, and they are closely mounted to the fuselage so a failure in one of them does not have a major effect on steering the craft.
It uses a type of propeller called a “ducted fan”. By enshrouding the tips of the blades, a smaller propeller can still provide the same thrust. Also, by using multiple wide blades, adequate thrust can be achieved at much lower RPM’s, resulting in a very quiet operation.
This demonstrator is intriguing, and Airbus’s plan is to use the data gathered by it to produce an aircraft with four ducted fans that are each much larger than these, with the goal of having a regional commercial aircraft that carries at least 12 passengers. Advancements in autonomous controls are anticipated to reduce the cockpit burden to using one pilot, instead of two.
Joby Aviation is based in Santa Cruz, on the California coast. They are backed by JetBlue and Toyota, and they are working on a five-seat aircraft with a 150-mile range. Rather than making a product for personal use, they are focused on producing a commercial air-taxi.
At first glance, the prototype looks like a scaled-up toy quad-copter, but the physics involved are sound. The six rotors allow for a fairly quiet vertical take-off, and then they pivot to provide a forward flight that is as efficient and as fast as possible.
$394 Million dollars has been invested in Joby by Toyota. Over a dozen other companies have partnered with Joby, and current funding is over $700-million. The Joby Air-Taxi can travel at speeds up to 200 miles per hour and can fly more than 150 miles on one electric charge.
Solid State Batteries, SSB’s
Toyota, Honda, Nissan, and Panasonic have partnered to form the Lithium Ion Battery Technology Evaluation Center (LIBTEC), and Toyota has announced they will debut their SSB at the Tokyo Olympics in 2020. Also, BMW is partnering with Solid Power in Colorado, and VW has invested over $100-million in Quantum Scape, in partnership with Stanford University.
SSB’s have been the buzz-topic for the last few years. They are much more fire-safe than the current state of Lithium battery packs, but the feature that is most exciting is the promised increase in range-per-volume. There are some applications where a smaller battery could provide the same range, and hopefully a lower cost of purchase. However, if a vehicles’ battery volume is set, then upgrading to an SSB can double the range.
As much as some observers will claim that a doubling of range is a game-changer in every application, not every new Tesla Model-3 buyer is paying the extra $10K for the extended range battery. However, when it comes to aircraft…every electric airplane manufacturer has stated that the switch to SSB’s will be used to extend range to as much as is possible.
Potential electric aircraft purchasers do not want to be stuck with this years batteries when the SSB’s come out, but…when the SSB’s arrive, no aircraft builder wants to be sitting on the sidelines without a tested electric aircraft design that is ready-to-sell.
SSB’s may not be the huge change that some observers claim for cars, motorcycles, and ebikes, but…when it comes to aircraft, people with millions of dollars to spend say that 2021 will be very exciting indeed…
Written by Ron/spinningmagnets, January 2020