While this discussion (which I continue below) is an interesting one, it
mostly side-steps the RAS response to the announcement that Lange will
offer an 18 M glider with a gas engine sustainer:

Disappointment.

Nobody seemed excited at the idea that yet another 18 M gas engine
sustainer was going into production, probably because you can already
get one from Schleicher, Schempp-Hirth, LAK, and DG. Lange made a
marketing decision, not a technical one, to compete in this (undoubtedly
larger) market with it's many vendors. They could have chosen to offer
an 18 M electric sustainer for what I'm sure is a smaller market, and be
the only vendor, as they did with the Antares.

Andor Holtsmark wrote:

-Self launching is a task. An aircraft is a system
optimized for one or more tasks.Self launching is
a way to get airborne and reach thermaling altitude
easily and with a minimum of hazzle. The 20E performs
this task beautifully.

The Antares is a very desirable glider, and I would be very happy with
it. I love the idea, and that is why the Lange 18 M with a gas engine is
such a disappointment.

How often do you need 3000 m
climb altitude to enter your first thermal?

Perhaps twice a year, but not always to a thermal, but sometimes to
enter a wave.

In my experience,
500-800 m should be enough. This should in most cases
leave you with quite a bit of energy to get home with,
or at least to the nearest airfield..

Almost always, in my experience.

or if you really
have messed things up, to a landable area. It should
here be noted that if you happen to be high, then an
electrical propulsion system is superior to an internal
combustion based one, since the engine is unaffected
by altitude, and the propeller only is minimally affected.


Now.. If you plan to regularily turn on the engine
and shake for 2-3 hours, then you should buy a Cessna.

Or perhaps a Stemme? Or a Carat? My point is "self-launching" does not
set the requirements, but the intended customer. Lange may be correct
that it would not be profitable to market an 18 M electric sustainer. I
hope they are wrong.

The self sustainer concept (in general) was meant as
a way to get home that one day in the year when the
thermals end and you have only flown 800 out of the
planned 1000 km. It was not meant for regular use.

I think this is a very narrow view of what a sustainer can do and how
they are really used. Don't many European pilots often take a winch
launch, then use the sustainer to get to lift 20 or 30 miles away? I
know some pilots (USA and elsewhere) count on the sustainer to get them
home in areas where sea breezes and other effects routinely kill the
soaring near home late in the day. Our club has this problem, and a
sustainer that provided 3000 feet of climb would be plenty to overcome it.

Apis and Silent both offer self-launching electrics with about 1500
meter climb capability. After a typical launch, they would have even
less climb left than the 1000 meters I suggest would be adequate for an
electric sustainer. So, there are designers who seem to think that many
pilots could be happy with much less than 3000 meters to get home!

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"