Luka is the original developer of the FES, together with his father
who is the Lak agent for Slovenia. The Lak factory has adopted the
design and you can order new gliders from the factory with FES
installed. They have a comparison with another glider suggesting that
the drag of the folded propeller is negligible. I certainly can’t
tell any difference with mine – being able to use the best lines of
energy is far more important, and saving retrieves is a huge
convenience.

As well as Lak 17s, Luka has modified a Silent which had a non-
circular nose. He had to develop a new shape, which was more cut back
and redesigned/remade along the fuselage to arrive at a circular cross
section at the point that the spinner/nose cone joined on.

(I have a Lak 17a which Luka converted to FES – it was the 6th, AIUI,
and he has done a few more since. The Silent was in his workshop with
work commenced when I took mine there in late 2010.)

He developed the FES sustainer first on his own glider, then modified
it before doing the Silent and mine, and meanwhile developed the more
powerful motor and larger battery version for self launching, with
which he won an award – see his website.

There is about 2 ½ inch clearance from propeller to level ground on
the basic Lak 17 with a 1 meter (39 inch) diameter propeller. I would
not risk running the FES while moving on the ground except on smooth
tarmac. In emergency, if it failed to stop running before landing, I
would expect damage. I don’t know if a modified undercarriage is
planned for self launch with more clearance.

I understand that Luka will consider retrofits to other gliders if
they have suitable fuselages, but I would have thought that each
different type is a major development effort, and the economics might
be difficult for a one-off. If interested, you could always write and
ask him.

(I am not an agent for Luka, just a satisfied customer via the UK
agents, Baltic Sailplanes, but I have written a couple of articles for
the BGA magazine, Sailplane and Gliding, about the FES – why I went
for it, and how I have found it – to sum up, very pleasing.)

Chris N.