FES - Front Electric Sustainer or Self-Launcher

A magnificent piece of engineering!
The FES is designed and manufactured specifically for use in sailplanes by LZ Design. It is aerodynamically clean, effectively maintenance free, and operationally very uncomplicated compared to a retractable power plant. While initially designed as a sustainer for use in conventional gliders, the FES also serves as a Self-Launcher in lightweight airframes (such as the SILENT 2 Electro).

The FES is comprised of several key components:

Two purpose built battery packs..
Two purpose built battery packs - each comprised of 14 Lithium Polymer cells of the very highest quality deliver a total of 4.2kWh. The packs themselves are built by LZ Design to very exacting standards and incorporate a sophisticated Battery Management System (BMS) to ensure optimum performance and safety during both charge and discharge cycles. The cells are automatically balanced to within 2 mV and  voltage, current and temperature are continuously monitored. 

Each pack weighs 15.5kg and is very easily removed for re-charging.

A brushless DC motor..

Designed and manufactured entirely by LZ Design, this DC brushless out-runner motor is designed and manufactured in meticulous detail and exudes quality in every aspect.

All the the components are produced in-house from highest quality materials and to extremely exacting mechanical and electrical standards using a combination of the latest in Electric Wire Discharge Machining and modern CNC techniques.

The bearings are sealed and the motor is essentially maintenance free.

Weighing just under 8 kg, the motor is capable of delivering 20kW continuous power (23kW peak) and is up to 95% efficient. The coils are hand wired and rotor position is precisely controlled via Hall effect sensors. The entire system, including motor, propeller and spinner is dynamically balanced.

Its like no other!

FES Control Unit ..

This standard 57mm instrument is produced jointly by LZ Design and LX Nav. The FES Control Unit (FCU) provides the all important interface between man and machine.

All key system parameters are displayed  including, Propeller RPM, Battery Capacity, Time Remaining (at current power setting), Voltage/Current, and Temperatures.

Power is virtually instantaneous and variable, from zero to maximum (23 kW), simply at the twist of a knob. Stopping the motor in flight is as simple as reducing the power to zero, whereupon automatic electric brake parks the propeller neatly along the fuselage sides. Nothing could be simpler!

Folding propeller..

Produced entirely by LZ Design, the lightweight Carbon fibre propeller and associated spinner is designed to offer minimal drag while folded against the fuselage sides but is deployed is seconds to deliver very respectable climb rates of up to 3m/sec at full power (4,500 RPM).

Manufactured to the highest standards in precise moulds, the propeller has a diameter of 1m and each blade weighs just 240 grams.

Performance, Simplicity & Safety..
The system provides a powerful and very highly reliable source of clean aerodynamic thrust at the twist of a knob. Straight and level flight is typically achieved at a power setting of about 4kW, which provides endurance of about 1 hour. However climb rates of 2-3 m/sec are possible, depending on the weight and type of sailplane in which the FES is installed. Self launching at full power (20-23 kW) is allowed only in the case of light sailplanes, in which case ground runs of the order of 80-100m can be expected. 

The benefits compared to a combustion engine on a retractable pylon are numerous:

  • No forward moment on take-off.
  • Virtually instantaneous start & stop.
  • Operationally very simple.
  • Aerodynamically clean.
  • Consistent motor performance regardless of altitude.
  • No aerodynamic change when deployed.
  • No smelly or flammable fluids on-board.
  • Virtually maintenance free.
  • Relatively quiet and vibration free.
  • Provides more than adequate battery capacity for even the most complex panel!
UK Support..
As a keen advocate of the FES from the start, we have followed the development closely and have considerable personal experience of the system.

Having been factory trained at LZ Design, we are very pleased to offer advice or assistance on any aspect of operation and maintenance to FES users in the UK.

Allan Arthurs


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