Editing Motor glider (section)

==Motor configurations==

===Retractable propeller===
[[File:Schleicher ASH 26E sailplane 1.jpg|thumb|left|[[Schleicher ASH 26]]e self-launching motor glider, with the engine mast extended. A Stemme S10 is in the background with the nose cone extended.]]
The retractable propeller is usually mounted on a mast that rotates up and forward out of the [[fuselage]], aft of the [[Cockpit (aviation)|cockpit]] and wing carry-through structure. The fuselage has engine bay doors that open and close automatically, similar to landing gear doors. The engine may be near the top or bottom of the mast, and newer designs have the engine fixed in the fuselage to reduce noise and drag.

Unlike TMGs, most gliders with retractable propellers are also fitted with a tow-hook for aero-towing or ground launch. They have a single-axle retractable main wheel on the fuselage like most unpowered gliders, so they do require assistance during ground operations. The two-stroke engines commonly used are not efficient at reduced power for level cruising flight, and instead must use a "saw-tooth" flight profile where the glider climbs at full power, then glides with the propeller retracted.

===Cross-over===
On the [[Stemme S10]], the propeller folds into the nose cone, and is connected to the rear-mounted engine with a drive shaft. It also has two retractable main wheels, allowing it to be taxied without assistance, and to soar with low drag. These features make it a cross-over between the touring and retractable propeller motor gliders. It does not have a tow-hook, so it must self-launch. The S10-VT variant has a two-position [[Variable-pitch propeller (aeronautics)|variable-pitch propeller]] and a [[turbocharger]] on the engine, which allows the aircraft to cruise at altitudes up to 30,000 feet (9,000&nbsp;m).<ref>{{cite web|url=http://www.stemmewest.com/pages/s10vt.htm|archive-url=https://archive.today/20120917101335/http://www.stemmewest.com/pages/s10vt.htm|url-status=dead|archive-date=17 September 2012|title=Stemme AG, S10-VT Information|access-date=24 November 2006}}</ref>

On the [[AMS Carat]], the propeller folds forward, pointing straight ahead like a spear.

===Electric===
Although most motor gliders have [[gasoline]]-fueled [[internal combustion engine]]s, a number of electric-powered self-launchers have been developed including the [[Lange Antares 20E]] and [[Lange Antares 23E|23E]], [[Schempp-Hirth Arcus|Schempp-Hirth Arcus E]], [[Schleicher AS 34Me]], [[Pipistrel Taurus| Pipistrel Taurus Electro G2]], [[Alisport Silent 2 Targa|Silent 2 Targa LE]] (Lithium Electric), and the closely related [[Air Energy AE1 Silent]], [[Yuneec Apis 2]], [[Yuneec EViva]], [[Alpaero Exel]], [[Aériane Swift]], [[Electravia]] and [[Alatus AL12]].<ref>{{cite web| url= http://www.lange-flugzeugbau.com/htm/english/products/antares_20e/antares_20E.html| title= Lange Flugzeugbau GmbH, Antares 20E Information| access-date= 24 November 2006| url-status= dead| archive-url= https://web.archive.org/web/20061015141501/http://www.lange-flugzeugbau.com/htm/english/products/antares_20e/antares_20E.html| archive-date= 15 October 2006| df= dmy-all}}</ref><ref>{{Citation | url = http://www.schempp-hirth.com/index.php?id=126&L=1&tx_ttnews%5Btt_news%5D=373&tx_ttnews%5BbackPid%5D=87&cHash=8a5d51d766 | publisher = Schempp-Hirth Flugzeugbau | title = Arcus-E | url-status = dead | archive-url = https://web.archive.org/web/20150706124145/http://www.schempp-hirth.com/index.php?id=126&L=1&tx_ttnews%5Btt_news%5D=373&tx_ttnews%5BbackPid%5D=87&cHash=8a5d51d766 | archive-date = 6 July 2015 | df = dmy-all }}.</ref><ref>{{Citation | title = World Directory of Leisure Aviation | year = 2011}}.</ref><ref>{{cite web|url=http://blog.cafefoundation.org/?p=5043 | work = Café foundation|title=Going Vintage Electrically}}</ref> Some types use a pylon behind the cockpit to extend a propeller. 11 different types, from 7 manufacturers, such as the [[Alisport Silent 2 Electro]], use the [[front electric sustainer]] (FES) system with a folding propeller in the nose.<ref name="FES">{{cite web|url=http://www.front-electric-sustainer.com/|title=LZ Design web-site|access-date=14 November 2018}}</ref>

Advantages of electric power over gasoline include:
* Faster and more reliable transition from gliding to powered flight, as the time and risk required to start and warm up an internal combustion engine is eliminated.<ref name="FES1">{{cite web
|url=http://www.front-electric-sustainer.com/why.php
|title=LZ Design web-site
|access-date=14 November 2018
}}</ref> For example, the Antares 20E transitions from gliding to powered flight in under 12 seconds.{{Citation needed|date=January 2012}}  With a FES system maximum power can be available in 1–2 seconds.<ref name="FES"/>
* For types that use a pylon, lower drag and sink rate are achieved with the pylon extended and the motor not running, as there is no radiator as required to cool a gasoline engine. For FES systems, the drag from the folded propeller in the nose is negligible if the engine does not start. For safe operation, the "Engine out and not running" performance is used to plan in-air restarts in the event of a problem (even for electrics). The reduced sink-rate of electric-powered motor-gliders "engine out and not running" allows a lower altitude for a safe in-air restart.<ref name="FES1"/>
* For types that use a pylon, belt reduction drive and associated reliability issues are eliminated. As an electric motor can turn at a lower RPM than typical gasoline engines, it can be mounted at the top of the mast without a reduction system, eliminating belt-drive issues.{{Citation needed|date=January 2012}}
* Greatly reduced noise, allowing take-off from locations where other powered aircraft are not permitted.<ref name="FES1"/>
Disadvantages of current electric powered motor-gliders as compared to gasoline include:
* Reduced range or climb altitude, as the energy stored per unit weight for available batteries is less than gasoline.{{Citation needed|date=January 2012}}
* Gliders with pylon-mounted electric motors are slightly heavier than those with gasoline engines due to the batteries. An FES system weighs about the same as a two-stroke engine.<ref name="FES1"/>
* Increased cost. While electric motors are comparably inexpensive, low-weight batteries suitable for motor-gliders are a little more expensive than gasoline engines.{{Citation needed|date=January 2012}}{{when|date=August 2022}}

Electric sustainer systems (with power to sustain flight but not self-launch) are optional for the [[Schempp-Hirth Ventus-3]], [[HPH 304|HPH Shark]] and [[ESAG LAK-17B]]. These three all use the FES as used for self-launching lighter gliders, such as the Alisport Silent 2.<ref name="FES"/>

===Jet===
[[File:Jet sailplane.jpg|thumb|left|Bob Carlton's jet-powered glider.]]
The first production self-launching motor glider fitted with a [[jet engine]] was the [[Caproni Vizzola Calif]]. The jet engine was mounted inside the fuselage behind the wing, with fixed intake and exhaust ducts coupled to the outside air stream for engine operation. Since then a new generation of jets have been offered for the [[Schempp-Hirth Ventus 2]], [[Jonker JS-1 Revelation]] and the [[HpH 304]], all featuring sustainer jet engines.

Other self-launching types include the experimental [[LET L-13 Blaník#Variants|LET L-13TJ Blaník]],<ref>{{cite web|url=http://www.pbsvb.cz/dlt_motor_tj100.php?lang=en|title=Turbojet engine TJ 100, PBS Velká Bíteš, a.s.|access-date=4 December 2009}}</ref> a version of the [[Alisport Silent Club]] and a version of the [[TeST TST-14 Bonus]].