The propulsion system was developed especially for self launch capable high performance gliders.
This results in a high climb rate, a very high attainable climb altitude and very low noise emission.
Great performance is only one aspect of this electrical propulsion system, amongst the others one finds impressive motor parameters, high system reliability, and intuitive, blind controllable and highly responsive motor controls.
The propulsion system has been flying in the Antares 20E since 2003, has in this period collected more than 10 000 flight hours, impressivly proving its performance and reliability.
The motor
Named EM42, the motor is currently the only EASA certified electric aircraft motor in existence. It is an brushless fixed-shaft electric motor running on DC-DC current. Running at 190 - 288 Volt, and pulling up to 160 Ampere, the motor can deliver up to 42kW. With a total efficiency of 90% and a maximum torque of 216 Nm, the motor is exceptional not only within aviation.
By using relatively few high quality components, risk of failure is minimized. The propulsion system causes very little vibration. This avoids vibration related problems, thereby increasing total system reliability.
Furthermore, all electrical components are attached to the non-moving part of the motor. The motor itself contains only 4 parts (2 ball bearings and 2 sealing rings) which are subject to wear. As a result, the TBO for the motor is an incredible 900 hrs. The simple mechanics of the motor results in simple and low cost maintenance with very long maintenance intervals.
Viability and performance of the electrical propulsion system was first tested in the LF20 flying testbed.
The first flight of the LF20 took place 05.07.1999 in Zweibrücken. As a result, testing of the propulsion system started 4 years before the first flight of the Antares 20E, which ensured a high system reliability from the start of the series production.
The two large optimized propeller blades (diameter: 2m / 6,56 ft) are attached directly to the rotating outer cylinder of the motor.
The large propeller diameter results in high propeller efficiency and low noise. The electrical motor is unaffected by air density, and leaves the propeller as the only part of the propulsion system affected by altitude. At 3000 m (9840 ft), the propeller has a maximum efficiency loss of 4% compared to sea-level. This makes the propulsion system very well suited for operating at high altitude airfields and for flying in mountains.
The noise emissions from the propulsion system were officially measured according to chapter X as a part of the certification of the Antares 20E. The measurements recorded an emission level below 48dB(A).
This is the lowest chapter X emission level ever recorded. For the Arcus E a slightly higher value can be expected because of the higher takeoff weight of the aircraft. However, the aircraft will still belong to the "stealth" category.
As is the case with the Antares 20E, it can be expected that the Arcus E will be allowed to operate unrestrictedly from airfields which have noise regulations (no self launches around noon, no self launches from various airfields in the Alps etc.).
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 “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.
The Arcus E 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 mode, 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.
Secondary propulsion interface
A dual propulsion interface has been developed for the Arcus E. This interface makes it possible to control the propulsion system also from the rear seat. This secondary interface is available as an option.
Automated switching
As with most self launching sailplanes, the Total Energy Compensated probe is situated behind the propeller. Therefore, the Arcus E automatically switches between Total Energy Compensated pressure and static pressure when switching between gliding and propulsion modes.
Charger
Running at approximately 1.7 kW, the charger requires only 9 hrs to fully charge the battery of the Arcus E. Partial recharging is also possible, since the battery possesses no memory effect. The charger can be adjusted to run on 230 or 110V AC dependent on custumer requirement.
Special cables in the trailer make it possible to charge the Arcus E also when it is stored in the trailer. Both world leading sailplane trailer producers, Spindelberger (Cobra) and Anschau, have experience with outfitting trailers for trailer charge.
The integrated charger is located in the fuselage, this charger makes it easy to recharge the batteries when roaming from airfield to airfield.
Integrated GSM Modem
The propulsion system comes standard equipped with a GSM modem connected to its main computer. This makes it possible, by using SMS or computer, to read aircraft status, download logs and control battery-charging without being in the vicinity of the aircraft. This also makes it possible for Lange Aviation technicians to provide system monitoring, software maintenance and error finding diagnostics without having to dispatch service personnel first.