Why FES (Front Electric Selflaunch/Sustainer)?
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.
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.
|LZ design d.o.o., Obrtniska 6G, 1370 Logatec, Slovenia, Europe, tel: +386 41 449 194, email: email@example.com|