Why FES?

Why Front?

Powered sailplanes are usually equipped with a retractable propeller. Because the front part of a fuselage is not a suitable location for a big and heavy combustion engine this approach is not used in high performance sailplanes.

However there is enough space for powerful electric motor.

With front engine there is no additional drag of a propeller mast and that mean less power is needed for equal performance. In our case, less power means less still of expensive batteries and smaller motor, resulting in less additional weight and costs and the potential for the best sustainer system for sailplanes.

In my youth I mounted a small Cox combustion engine above the fuselage of a light 2m wingspan RC sailplane. The first flight tests were very disappointing as the model barely flew horizontally under full power. After I installing the same engine in the front part of fuselage, the difference was unbelievable as the model climbed very well.

Why Electric?

  • Powerful electric motor can be smaller and lighter than combustion engine.
  • Virtually silent propulsion without loud exhaust noise, no ear plugs needed!
  • Very clean - no smell of gas in cockpit, no oil film from exhaust on the tail and no 2-stroke oil to mix.
  • Very reliable - no fuel pumps, no filters, no spark plugs, and no carburetor icing.
  • Instant restarts - no warm-up needed.
  • Virtually vibration free!
  • The only movable parts are the propeller and the motor's bearing and rotor.
  • Almost no maintenance of motor, no lubrication issues, no moving parts to wear out
  • Full torque from zero to max rpm (BLDC).
  • No loss of motor performance at higher altitude, equal performance day to day.
  • Easy to operate - just flip a switch and open the "throttle".
  • Lower carbon footprint, especially with solar charging (might be on top of your trailer).

Why Sustainer and not Self-launcher (SLS)?

  • It is less expensive.
  • It is safer.
  • It is lighter.
  • A better handling of sailplane.
  • The possibility to upgrade older sailplanes.
LZ design d.o.o., Trzna 3, 1000 Ljubljana, Slovenia, Europe, tel:+386 41 449 194, email: lukaznidarsic@lzdesign.si