FES M100 motor

After evaluating available electric motors on the market, it was clear that there was no suitable electric motor which would fulfil all our requirements. We decided to design our own electric motor. After two years of work, many tests and a few development versions, we have created a state of the art brushless DC electric motor. Our BLDC motor offers several advantages over brushed DC motors including higher efficiency and reliability, reduced noise, longer lifetime (no brush erosion), elimination of ionizing sparks from the commutation, more power, and an overall reduction of electromagnetic interference.

Complete weight of front assembly (motor, spinner, propeller...) is bellow 10kg. Weight of the batteries behind the wings perfectly compensate front assembly weight and so centre of gravitiy of FES equipped gliders is in most cases the same as at pure glider.

Basic data of our standard FES electric motor:

  • Out runner BLDC brushless synchronous permanent magnet motor with electronically controlled commutation system 3 phase
  • Max power 22kW
  • 20kW continuous power
  • Diameter 180mm
  • Length 100mm
  • Weight of motor is only 7,3-8kg
  • Efficiency up to 95%.
  • Rotor position by hall sensors

BLDC motors need special Controllers for their operation. Controller is mounted on top of main wheel box.

FES FCU Instrument

FES Control Unit instrument (FCU) is designed for simple FES system operation. It fits into standard 57mm diameter hole. It is equipped with sunlight readable, high resolution, colour display. The screen is really bright, so it is readable in the strongest of sunshine! It indicates important parameters like, RPM, Power, Voltage, Current, Battery capacity, Remaining time and Temperatures. In case that one of the parameters is out of limit, alarm is activated together acustic signal. FCU also counts total engine running time, and some other parameters. All FES parameters are logged to internal SD card every second.

Above the screen there is ON/OFF switch. FCU instrument should be always switched ON during flight. Bellow the screen there is knob with rotary encoder which acts as throttle and also as propeller brake. Knob, acts also as a button with additional functions like message confirmation, message recal etc.

To use external potentiometer as a throttle is also possible, however in most gliders there is no suitable space available.

FCU instrument was specifically developed for FES system in cooperation with leading manufacturer of gliding instruments LXNAV company.

On suitable location in the cockpit is located so called "Power switch" (as a key switch or as toggle switch under red safety cap) which powers up the motor controller electronic and main contactor, which connect battery to motor controller.

FES foldable propeller

We developed a special very light carbon fibre foldable propeller. The propeller opens quickly using centrifugal force when rotation starts. It has 1m in diameter. Each propeller blade weighs only 260 grams. The blades are slightly bent to take the shape of the front surface of the fuselage. Each glider type we have different shape of propeller blades and soinner. During propeller folding, pitch of blades is reduced when they rotate closer to the fuselage. Drag of the folded propeller blades is minimal as proved on numerous gliding competitions and also by accurate Idaflieg flight performance measurements.

After propeller is stopped by electronic braking, it is automatically positioned to horizontal position. The composite spinner has recesses for the middle section of propeller blades and a central hole for cockpit ventilation and for air cooling of the electric motor. The ventilation can be closed during soaring flight and must be opened when motor is running.

Pitot measurement point is on top of vertical stabilizer, and works fine also during powered flight.

Nose cone in your trailer needs to be slightly modified, so that is not pressing to the propeller blades.

FES Battery packs

The traction Battery packs of the FES consists of 28 high quality Superior Lithium Polymer cells produced by world leading LiPo battery producer Kokam. We are using special high power cells SLPB100216216H with capacity of 40 Ah each. We pack cells into special composite boxes by our self. Cells are wired in serial and operates at a voltage range of 90-116V. There is a total of 4,2kWh of energy available in the two Battery packs, and each weight 15,7kg. They are located in reinforced fuselage area behind the wings. The batteries fully compensate the weight of motor and propeller in front.

Our latest GEN2 Battery packs have integrated BMS (Battery Management System) and RADSOK high power quick connectors!

FES batteries are also used to supply power for all instrumentation on board through a DC/DC converter.  No other battery onboard is required anymore.

Power consumption of all instrumentation is very small (5W to max about 30W) compared to the motor consumption at full power. So you will finally have enough power for your radio, flight computer, PDA and transponder.

If batteries are discharged during flight using the motor, they still have plenty of power for instrumentation. It is easy to take them out of the fuselage, for charging.

For transportation and storage should be used FES stanless steel boxes which offer good protection to the batteries.


Charging of FES Battery packs


With each FES system are provided two 600W programmable Li-Po chargers, as standard. Available are also optional 1200W or 2000W chargers. Inside of each FES GEN2 battery pack is integrated advanced BMS (Battery Management System) electronic circuit board. BMS monitors the voltage levels of each cells, and their condition by calculating internal resistance of each cell in the pack. At end of charge cells voltage levels are equalized in precision of 2mV, using advanced balancing algorithms. BMS communicate with charger and controls charging start, charging current and when charging should stop.

Charging time for both battery packs with two standard 600W chargers is about 5-6h when batteries are fully discharged. If they are only 50% discharged, than charging time is shorter. LiPo cells do not have memory effect like NiCd cells, so it is better to charge them before they are fully discharged! Charging process can be monitored on PC using dedicated FES BMS control software, or with FES LCD display.

With quicks 2000W chargers optionaly available - for club operations. Charging time of one pack is about 1h.

Unlike lead acid batteries, Li-Po batteries can be stored for months without significantly losing charge. Self discharge rate is less then 1% per month at room temperature!

Cell manufacturer claims that at discharging rate of 1C (horizontal flight) life expectancy of batteries could be up to 4000 cycles. After that the battery will still have 80% of the original capacity.