Sounds similar to this project at DG:
http://www.dg-flugzeugbau.de/?id=1070


On 4/17/2014 1:09 PM, Ian wrote:
On 04/16/2014 11:01 PM, wrote:

Actually when you switch ON power switch, and get green LED, and
"Controller ready" message on the screen, pilot can be 99% sure that
motor will start. There is no engine which would be 100% reliable,
but I think FES is close to that. Before each flight pilot needs to
perform a short test run, in order to be sure that all is OK. If
there is any problem in the system, is then showed already.

Have you ever considered building a pylon mounted electric sustainer,
and/or battery packs that are located in the wing? As elegant as the FES
is, the reliability of the electric solution would apply equally to a
pylon configuration electric sustainer. And if there is enough battery
power to operate the motor there must be more than enough to operate the
extraction mechanism.

Obviously it will not be quite a quick to start as FES, and there is a
possibility of a failure of the pylon mechanism which would prevent the
motor from starting, but this technology has been developed for petrol
sustainers/self launchers and should be reliable by now.

The advantage to a pylon installation is:

- No mods on the nose of the glider where tow release, pitot and/or air
vent are often mounted. This would save costs and may allow for an
easier certification process, ultimately making the technology available
on a wider selection of glider models.

- No aerodynamic drag penalty when the motor is retracted.

- Propeller protected from accidental damage on the ground.

- Many modern sailplanes are designed to accommodate a sustainer. These
should have the space and the strength to accommodate a pylon mounted
electric sustainer. Certification on these gliders should be easier.

Fitting batteries in the wing may become essential as the volume FES
currently uses to accommodate batteries would be occupied by the pylon
and motor. Batteries would need to be mounted in a container that can be
inserted/removed through the root rib. The challenges for this a

- Batteries would have to be charged in place. This has safety
implications and may require more elaborate safety circuits. (I
understand FES recommend removing batteries for charging).

- Batteries would replace some or all of the water ballast capacity.
This would require modification to, or removal of, the water ballast
system.

- Rigging would be heavier and rigging aids would be recommended.


The advantage of having the batteries in the wings is that it would
circumvent the "maximum weight of non-lifting components" limitation,
allowing installation in a wider selection of gliders. It may also
facilitate increased battery capacity thus increased range. The average
battery discharge on each use will be less which should result in
improved battery life.


But once you have got a pylon electric sustainer system sorted out, I
might even be able to fit one in my LS3a!


Ian