Why FES (Front Electric Selflaunch/Sustainer)?

Why Front?

Powered sailplanes are usually equipped with a retractable propeller as in front part of a fuselage is not enough space available for a combustion engine. So up to now front motors were not used in high performance sailplanes.

However there is just enough space for specially developed, small but very powerful electric motor.

With front engine arrangement 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 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 carburettor 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).
  • Futher advantages:

  • With FES equipped glider is possible to safely transit to a preplanned ridge soaring area after launch on zero thermal days.
  • Transit to return to base at the end of the day arriving safely at circuit height for landing after such flights.

Sustainer or Selflauncher?

"S" letter of FES means in most cases "Sustainer" but for some light sailplanes means "Selflaunch."

FES is aerodynamically very clean so 23kW is more than enough power for lighter sailplanes to perform safe selflaunch with good climb rate! However for decent climbing of heavier sailplanes more power is necessary. Most of modern sailplanes have also a problem with propeller clearance to the ground. So for heavy sailplanes our system is available only as sustainer.