Why We don’t See Many Electric Aircraft Flying – Yet!
There have been some electric light aircraft out there for years. Years ago, there were not many – but now there are about 215 projects worldwide. They are all in different stages of development. None of them is ready for the market – yet.
And we, at MySky ECO, have one in development, too. It will be the MySkyECO MS-1e.
While we are not the earliest entry in the race, we have been working on it already for a long time. MySkyECO, Inc., was actually formed in 2015. The purpose was to bring an aircraft with an electric propulsion system to the market. After we spent some time on gathering information and learning about basic electrical engineering (after all, our primary knowledge was about aircraft and things related to aviation) we found that the time was not ready. Today the situation is different. Lots of progress has been made. There is only one area that is still lagging and that is keeping us from designing an all-purpose light aircraft right now.
Let’s look at the components of an electrical propulsion system and determine where we stand as of today:
The Motor
Electric motors are available from quite a few suppliers, some of them big names in aviation, like Rolls-Royce or Safran.
An electric motor weighs a fraction of what a traditional piston engine would bring to the scale. As an example, this is the Emrax 228.
It develops 109 KW, equaling 146 HP. That is almost the power of a Lycoming O-320. But while the O-320 has a dry weight of 244 lb., the Emrax weighs only less than 27 lb. When it comes to its size, the advantage is even more impressive: the diameter is only 9″ and it is just barely 3.5″ long.
That’s about the power we would want for the MySky MS-1e. But we might as well move one step up and decide in favor of the Emrax 268 with a peak power output of 200 KW. That’s more than 280 HP. We don’t even need or want that much. But the motor could run at reduced power output. The advantages would be easier cooling and low RPM. There would be no reduction gear needed for the propeller. The weight is still only 44 lbs. It looks like we will make up the weight difference by a lighter cooling system and lack of gearbox compared to the Emrax 228. Here is a link to the technical data of the Emrax 268:?https://emrax.com/e-motors/emrax-268/
The Controller
Besides the electric motor we need a controller which is even smaller in size and will weigh around 18 lb.
The Battery System
We are planning to use EPS Systems’ lithium-ion battery packs that offer high power and energy in a compact light-weight package – specifically designed for aviation applications.
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The system will be designed as a package of two individual strings with a mid-point disconnect. The disconnect can be triggered by the battery management system, whenever it senses that one of the battery cells has a temperature or performance problem. In this case the other string will take over. This would be reason to land soon and troubleshoot – but it would not lead to a power failure during flight. Both strings are redundant and either one can power the aircraft.
We are planning on having one string in each wing, close to the center of gravity (CG) of the aircraft.
The Wiring
To keep wiring reasonably thin, we will operate the electric motor at relatively high voltage. Somewhere around 500 V. The final decision has not been made yet. This way wiring is not a major weight concern.
The Cooling System
Both, the motor and the battery packs need cooling. We have the option to decide for air or liquid cooling for either one of these. It is too early to make this decision yet. We will carry out an extensive test program in the months to come to determine if air or liquid cooling is the way to go. Both have advantages and disadvantages. We will not make a decision until we have explored all options.
Weight and Balance
From the standpoint of weight and balance, a conventional aircraft design still makes sense. The motor, controller, and the propeller with FADEC (Full Authority Digital Engine Control) will be under nose cowling. There is no problem with the size of any of these components. They are, however, much lighter than the conventional piston engine that is now under?the existing prototype’s cowling. But that is not a problem. There is also some room left, and we will use extra batteries as useful ballast.
Regarding the main batteries, we are planning to line them up along the wing’s main spar. Thus they will be really close to the CG and their effect on weight & balance will be minimized.
One thing will be different compared to a fossil fuel driven aircraft: There will be no weight change because of burnt fuel during flight. That is more an advantage than anything else. Light aircraft typically do not have an MLW (Maximum Landing Weight). You can take off in a Cessna 172 or a Piper Archer with fuel fuel and turn around and land again. That would be a problem in larger transport aircraft. They are limited by MLW and would have to burn off (or jettison) fuel before landing.
Conclusion
All components are well developed and everything is ready to go for the electric aircraft. It is only battery capacity, more precisely the energy to weight ratio of the the li-ion batteries which is not sufficient for on all-purpose light aircraft. As of now, we are limited to an airplane that can be very useful in a commercial flight school environment. But this will be ready to go very soon. Thousands of bright heads in the industry are working hard to improve the battery technology to a point where we will be able to produce a real all-purpose light aircraft.
For larger aircraft, it will probably take longer. Although there are some promising developments, like:?https://www.zeroavia.com/
It looks like for larger aircraft a hybrid solution will be the way to go for the foreseeable future. But all in all: Electric aircraft are coming. It is not a question of if, IT IS A QUESTION OF WHEN.