Propulsion

 

The patented propulsion system was developed especially for the Antares 20E and is the heart of the concept.

PropulsionLightweight environmentally friendly batteries with high performance, a brushless 42 kW external rotor electric motor, new power electronics and a large slowly rotating propeller were developed into one system and tailored especially for the Antares 20E into an optimized configuration. For the first time, a complete propulsion system has been developed exclusively for one motorglider.

The results are convincing: The Antares 20E combines a high climb rate (approx. 4.4 m/s / 866 ft/min during takeoff) with a very high attainable climb altitude (approximately 3000 m / 9850 ft in calm air) and very low noise emission.

Great performance is only one aspect of this new propulsion system, amongst the others one finds impressive motor parameters, high system reliability, and intuitive, blind controllable and highly responsive motor controls.

 

The motor

Named EM42, the motor of the Antares 20E has been developed especially for Lange Aviation, and it 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 - 288V, and pulling up to 160A, the 42kW motor can deliver maximum torque over a wide RPM range. With a total efficiency of 90% and a maximum torque of 216 Nm, the motor is exceptional not only within aviation.

torque vs engine speed
 

EngineBy using relatively few high quality components, risk of failure is minimized. The Antares 20E 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. The TBO for the motor is 900 hrs. The simple mechanics of the motor results in simple and low cost maintenance with very long maintenance intervals. Maintenance consists of exchanging the two sealing rings, and it must be performed every 200 hours of motor time or every 10 years, whichever happens first.

 
PropulsionViability and performance of the electrical propulsion system was first tested in the LF20 flying testbed. The first flight of the LF20 took place 07.05.1999 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 propeller

Attached directly to the rotating outer tube of the motor are two large propeller blades (diameter: 2m / 6,56 ft), which have been especially designed and optimized for the Antares.

propeller efficiency



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. 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

InterfaceAll 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

InterfaceThe Antares 20E 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.

InterfaceIn 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:

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.


Antares 20E: Advanced simplicity