LAK-17B is new version of LAK17A. Regarding A version, B has new wings with modified geometry and new wing profile, which allow even higher wing loadings than competitors. Fuselage and tail section is identical like A version.

The creators of Front Electric Sustainer ( FES ) are Luka Znidarsic and Matija Znidarsic, both experienced sailplane pilots and mechanical engineers in Slovenia.

Front refers to the motor’s location, right in the nose of the sailplane. A 1 meter carbon fibre propeller automatically extends when the outrunner is operating. When not in use, the propeller blades fold against the nose of the sailplane thus reducing drag. Each blade weighs just 240 g.

The Znidarsic's developed their own brushless DC synchronous permanent magnet electric motor and controller for the application which is light, small and mounted on top of main whell box. The motor is 7.3 kg (16.1 pounds), and puts out 22 kW (30 horsepower) at 116 Volts. Total weight for the power package is 45-50 kg (99-110 pounds), with Kokam lithium-ion batteries in two packs ( each behind the rear spar, balancing the weight of the motor and propeller in the nose ).

If batteries are discharged during flight using the motor, they are easily accessible from the top of the fuselage so that you can take them out for charging. Unlike lead acid batteries, Li-Po batteries can be stored for 3 or 5 months without significantly losing charge. Charging time of batteries is about 6 hours (2 hours with quick charger) .

For more information about FES please visit

You can also read first customer impressions about FES installed on LAK-17B from WGC 2010 in Szeged, Hungary in our NEWS section.

Sailplane LAK-17B LAK-17B FES
Wing span, m 15 18 15 18
Wing area, m2 9,18 10,32 9,18 10,32
Wing aspect ratio 24,51 31,39 24,51 31,39
Fuselage length, m 6,53 6,53 6,53 6,53
Fuselage height, m 1,322 1,322 1,322 1,322
Empty mass approx. kg 250 260 285 295
Max TOW, kg 550 600 550 600
Water ballast (wings), kg 160 200 130 170
Water ballast (fuse-option), kg 30 30 batteries batteries
Batteries weight, kg     31kg (15,5kg each pack) 31kg (15,5kg each pack)
VNE, km/h 270 270 270 270
Min. wing loading 34,85 31,97 39 35,8
Max. wing loading 59,91 58,13 59,91 58,13