Electric Propulsion

Propulsion System

The foundation for the Antares concept was laid with the patented electrical propulsion system of the  Antares.

The electric motor EM42, with which the Antares 23E is equipped, is the only electric motor to this date, which is EASA certified as an aircraft motor. It is a DC brushless outrunner, which operates at voltages bet- ween 190V and 297V and currents up to 160A. In electric motors, high power is usually acheived by making the motor run at high RPMs. This is not what is desired for an aircraft motor that is to drive an efficient propeller. The EM42 generates a maximum of 42 kW of power while running at low speeds. In doing so, it generates a maximum torque of 216 Nm. The total efficiency of motor and controller is 90 percent.


A full charge takes approximately 9 hours to complete using the built in charger (optional 230 V or 110V AC). Needless to say, this requires the charger to be connected to the power grid.

[Translate to Englisch:] Bislang unerreichte Leistungsdaten sind das Ergebnis dieses Ansatzes: hohe Steig­geschwindigkeiten (ca. 4 m/s beim Start), große Startüberhöhung (mehr als 3.200 m bei ruhiger Luft) und ein nahezu lautloser Flug.

Hohe Leistungsfähigkeit ist die eine Seite des innovativen und patentierten Antriebs­kon­zepts der Antares. Doch Alltagstauglichkeit braucht auch Zuverlässigkeit, Sicherheit, Wirtschaftlichkeit und Bedienkomfort. Im Gegensatz zu Verbrennungsmotoren hat der Antrieb eine systembedingt hohe Betriebssicherheit und läuft fast vibrationsfrei. Damit werden Zerrüttungs- und Dauerfestigkeitsprobleme vermieden. Zudem kommen nur relativ wenige, dafür extrem hochwertige Bauteile mit minimalem Ausfallrisiko zum Einsatz.

Und, nicht zuletzt: Die Wartung des Antriebs erfordert einen für Flugzeugtriebwerke einzigartig geringen Aufwand.

Propeller

Developed and optimized especially for the Antares 20´3E, the propeller blades are mounted directly onto the outrunner electric motor. A propeller diameter of 2 m / 6.6 ft leads to low RPM, high efficiency and low noise emissions. The available motor power is independent from density altitude, therefore the propeller is the only altitude dependent propulsive component. An increase in altitude of 3.000 m / 9.800 ft results in an efficiency loss of only 4 percent

The higher the aircraft gets, the faster the propeller has to turn in order to deliver the required power. At very high altitudes the maximum available power will be limited by the max rpm of the motor. However, at 4500m (13123 ft) a respectable climbrate between 1.8 and 2 m/s (354 – 394 ft/min) can still be achieved.

This makes the Antares an aircraft very well suited for operating at high altitude airfields and for flying in mountains.

Propulsion Interface

All the propulsion system functions, i.e. positioning and holding the propeller, extending and retracting of the motor, as well as power regulation, are controlled easily and with a minimum of effort using the patented “Single Lever Control” at the left side of the cockpit. Propulsion controls controls are intuitive, and can be performed blind, reducing pilot distraction and minimizing the risk of performing a control error. 

System monitoring

The Antares 23E contains a number of subsystems, the most important ones being propulsion system, battery system, hydraulics and battery charger.

System monitoring is performed by the main computer, utilizing numerous sensors. All relevant propulsion system parameters together with some other flight data are made available on the display.

Should any parameter enter a critical range, then it will be marked with color coded text on the display, and a vocal audio warning will be issued.

In pre-flight, the display unit is used to display pre-flight checklists. After flying, the main flight data can be read from the electronic log book.

Experience has shown us that very little time is spent monitoring the propulsion system. The pilot assumes that, as long as no audio warnings are issued, all systems are functioning correctly, and can therefore focus fully on what is going on around the aircraft.

Where possible and beneficial for safety, the main computer will use available sensors to automatically check (but not override) pilot actions. Some examples:

  • An airbrake a warning will be issued if one attempts to go through the final checklist or applying power with airbrakes extended
  • A warning will be issued if one attempts to go through the final checklist with dolly still attached or landing gear switch in position “retracted”
  • A landing gear warning will be issued if one attempts to extend the airbrakes with the landing gear retracted

Communication between the different aircraft subsystems run over 2 serial CAN-Bus systems. The CAN-Bus system was originally developed by Bosch for the utilisation in ABS brake systems. A distinguishing feature of the CAN-Bus system is that it through its data transfer protocoll does not allow erronous datatransfers to take place. This has led to more and more (large) aircraft manufacturers introducing CAN-Bus systems in their products.

Battery system

The Antares 23E is equipped with a battery-system utilizing Li-Ion cells of the type SAFT VL41M. Lange Aviation was worldwide the first company to utilize these cells, but meanwhile an impressive array of other users have recognized the advantages of this cell, and its field of application is constantly broadening.

Why Lithium Ion cells?

Lithium is the lightest of all metals, and has the highest negative standard potential. The low weight and high voltage level of the system result in a high specific energy density. Compared to other currently available Lithium based cells (Li-Po / Li-Su), SAFT VL41M exhibits very high current capability and very good cycleability. This qualifies SAFT VL41M Li-Ion cells for application as aircraft energy storage before all other available cells. 

Battery life

The life expectancy of the Antares 23E E drive battery is determined by two factors:

  • the number of charge/discharge cycles
  • the natural chemical aging

Charge / discharge cycles

The capacity of a battery diminishes with the number of charge-discharge cycles it undergoes. According to the latest knowledge, the battery will withstand more than 4500 SAE cycles. One SAE cycle consists of a full charge, and a discharge down to 20% of battery capacity. A partial charge and discharge equals a partial full cycle. After 3000 SAE cycles, the cells will retain at least 80% of their original capacity. For the pilot, this means that the drive battery will yield approximately 10.800.000 climb altitude before it should be replaced.

Natural aging

More relevant to the practical application is the natural chemical aging of the battery. If the battery is stored at an average temperature of 20°C (68°F), then it is advised to change the battery after 20 years. At this point the battery will have a remaining capacity of 80% of the original capacity. 

Availability

As a user of SAFT VL41M cells, Lange Aviation is in good company. SAFT VL41M are also used in most new European satellites, the RQ-4B Global Hawk UAV, the F35 Joint Strike Fighter, the Airbus A380 and in many other high-tech applications. Next to being a great vote of confidence to SAFT VL41M cells, the military implementations mean that the cells which are now being built into the Antares 23E will be available at least until 2031.