{{Short description|Propulsion system}} [[File:Glider (sailplane) with front-end electric sustainer (FES).jpg|thumb|Glider showing propeller of FES electric sustainer]] '''Front electric sustainer (FES)''' is a propulsion system for [[glider (sailplane)|gliders]] that uses an electric motor powered by batteries and a foldable propeller. It is produced by LZ Design d.o.o. in [[Logatec]], [[Slovenia]].<ref>{{cite web|url=http://www.lzdesign.si/|accessdate=6 September 2020|title=LZ Design web-site}}</ref>
The system uses a 22 kW compact [[outrunner]] [[brushless DC electric motor]] located in the nose of the sailplane. Power is provided by two [[lithium-ion battery]] packs. Lighter gliders are able to self-launch with FES. Heavier gliders can use it as a sustainer system, i.e. climb and cruise sufficiently high and far to avoid an out-landing. Although gliders with FES have a shorter range (70–100 km)<ref name="highlights">{{cite web|url=http://www.front-electric-sustainer.com/highlights.php|title=LZ Design web-site }}</ref> under power than gliders with two-stroke gasoline sustainer engines (10 litres at 8.5 L/h at 100 km/h = 120 km)<ref>{{cite web|url=https://www.schempp-hirth.com/en/individual/engine-options/turbo-sustainer-engine|accessdate=6 September 2020|title=Schempp-Hirth web-site}}</ref> or jet sustaining engines (150–200 km),<ref>{{cite web|url=http://hphuk.co.uk/hph-products/shark-sj-ms/|title=HPH web-site|accessdate=6 September 2020}}</ref> the electric motor can be expected to start reliably provided there is sufficient energy in the batteries.<ref name="highlights"/>
The one-metre diameter propeller is made of [[carbon fibre]] and folds across the nose. It opens using centrifugal force when rotation starts. Each propeller blade weighs 260 grams. They are slightly bent to take the shape of the front surface of the fuselage of each type of glider to which they are fitted.<ref>{{cite web|url=http://www.front-electric-sustainer.com/technology.php|title=LZ Design web-site }}</ref>
Unlike some electric gliders such as the [[Lange Antares]] and [[Schleicher AS 34Me]], the batteries can be removed from the glider for charging off-site. No power supply is needed near the glider itself. The two battery packs each contain 28 Kokam [[LiPo|lithium polymer cells]]. The cells are wired in serial and operate at a voltage range of 90–116V. The two packs contain a total of 4.2 kW⋅h of energy. Each pack weighs 15.7 kg and are mounted in a reinforced area in the fuselage behind the wings. This configuration balances the weight of the motor and propeller. Reinforced carrying cases are used to transport the battery packs to a location where they can be charged.<ref>{{cite web|url=http://www.front-electric-sustainer.com/PDF%20Articles/Dear%20fellow%20glider%20pilots,%20FES%20owners%20and%20electric%20flight%20enthusiasts.pdf|title=LZ Design web-site }}</ref>
More than 240 gliders of eleven different types, from seven manufacturers, are already equipped with this system.
* [[Schempp-Hirth Ventus 3]] and its predecessor [[Schempp-Hirth Ventus 2]]<ref name="Schempp-Hirth web-site">{{cite web|url=https://www.schempp-hirth.com/en/individual/engine-options/fes-front-electric-sustainer|accessdate=6 September 2020|title=Schempp-Hirth web-site}}</ref> * [[Schempp-Hirth Discus 2]]<ref name="Schempp-Hirth web-site"/> * [[Schempp-Hirth Duo Discus]]<ref>{{cite web|url=https://www.schempp-hirth.com/en/company/latest-updates/latest-updates-details/duo-discus-fes-fliegt|accessdate=30 April 2021|title=Schempp-Hirth web site}}</ref> * [[DG Flugzeugbau DG-1000]]<ref>{{cite web|url=https://www.dg-flugzeugbau.de/dg-flugzeugbau-news/erstflug-dg-e/60443|accessdate=6 September 2020|title=DG web-site}}</ref> * [[Rolladen-Schneider LS8]]<ref>{{cite web|url=https://www.dg-flugzeugbau.de/dg-flugzeugbau-news/ls8-piloten-umruestung/60373|accessdate=6 September 2020|title=DG web-site}}</ref> * [[LAK-17]] and Mini-LAK<ref>{{cite web|url=http://lak.lt/?option=com_content&task=view&id=22&Itemid=135|accessdate=6 September 2020|title=LAK web-site}}</ref> * [[HPH 304]]<ref>{{cite web|url= http://www.hph.cz/products/hph-304s-shark/|accessdate=6 September 2020|title=HPH web-site}}</ref> * [[Diana Sailplanes Diana]]<ref>{{cite web|url=https://www.diana2sailplane.co.uk/|accessdate=6 September 2020|title=Diana web-site}}</ref> * [[Alisport Silent 2]]<ref>{{cite web|url=http://www.alisport.com/?page_id=657|accessdate=6 September 2020|title=Alisport site}}</ref> * [[Albastar AS]]<ref>{{cite web|url=https://www.gliders-albastar.com/|accessdate=6 September 2020|title=Albastar web-site}}</ref>
==References== {{reflist}}
==External links== *[http://www.front-electric-sustainer.com/sailplanes.php LZ Design web-site]
[[Category:Electric motors]] [[Category:Slovenian brands]] [[Category:Electric aircraft]]