Motor glider
A motor glider is a fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

 that can be flown with or without engine power. The FAI Gliding Commission
FAI Gliding Commission
The International Gliding Commission is a leading international governing body for the sport of gliding.It is one of several Air Sport Commissions of the Fédération Aéronautique Internationale , or "World Air Sports Federation"...

 Sporting Code definition is: A fixed wing aerodyne equipped with a means of propulsion (MoP),
capable of sustained soaring
Lift (soaring)
Gliding flight is heavier-than-air flight without the use of thrust. It is employed by gliding animals and by aircraft such as gliders. The most common human application of gliding flight is in sport and recreation using aircraft designed for this purpose...

 flight without thrust from the means of propulsion.


In 1935, an occasional or auxiliary motor that could be retracted was suggested by Sir John Carden.


Most motor gliders are equipped with a propeller
Propeller (aircraft)
Aircraft propellers or airscrews convert rotary motion from piston engines or turboprops to provide propulsive force. They may be fixed or variable pitch. Early aircraft propellers were carved by hand from solid or laminated wood with later propellers being constructed from metal...

, which may be fixed, feathering, or retractable. However jet engines are now available from some manufacturers.

Touring motor gliders

Motor with fixed or full feathering propellers are generally classified as Touring Motor Gliders (TMGs). TMGs can take off and cruise like an airplane or soar with power off, like a glider
Glider aircraft
Glider aircraft are heavier-than-air craft that are supported in flight by the dynamic reaction of the air against their lifting surfaces, and whose free flight does not depend on an engine. Mostly these types of aircraft are intended for routine operation without engines, though engine failure can...


They are fitted with front-mounted engines, similar to a small airplane. The large wingspan
The wingspan of an airplane or a bird, is the distance from one wingtip to the other wingtip. For example, the Boeing 777 has a wingspan of about ; and a Wandering Albatross caught in 1965 had a wingspan of , the official record for a living bird.The term wingspan, more technically extent, is...

s of TMGs provide a moderate gliding
Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word soaring is also used for the sport.Gliding as a sport began in the 1920s...

 performance, though worse than that of unpowered gliders
Glider aircraft
Glider aircraft are heavier-than-air craft that are supported in flight by the dynamic reaction of the air against their lifting surfaces, and whose free flight does not depend on an engine. Mostly these types of aircraft are intended for routine operation without engines, though engine failure can...

. However TMGs are more efficient than conventional light aircraft
General aviation
General aviation is one of the two categories of civil aviation. It refers to all flights other than military and scheduled airline and regular cargo flights, both private and commercial. General aviation flights range from gliders and powered parachutes to large, non-scheduled cargo jet flights...


Most TMGs are designed with engines of 80 to 100 hp and typically cruise (under power) at 85 - 100 knots (196 km/h). Most have fuel tanks capable of holding 50 and up to 100 liters (13 to 26 US gallons) of fuel, giving a range under power of up to 450 US nautical miles (approximately 830 kilometers).

Some TMGs are equipped with folding wings to allow them to fit in standard small airplane T-hangar
A hangar is a closed structure to hold aircraft or spacecraft in protective storage. Most hangars are built of metal, but other materials such as wood and concrete are also sometimes used...

s. Tow hooks are unnecessary, since aircraft with self-launch ability do not require access to winch or tow plane for launching like a conventional glider.

Some TMGs, like the Europa
Europa Aircraft
Europa Aircraft is a British kitplane manufacturer that produces the Europa XS.The company was established to produce a small kit-built low-wing aircraft for personal use within Europe, with these design goals: high speed, low cost, able to be built and stored at home, easily transportable, using...

, can also be supplied with interchangeable wings so that they can be flown as a standard touring aircraft as well as a TMG.

The landing gear
Landing Gear
Landing Gear is Devin the Dude's fifth studio album. It was released on October 7, 2008. It was his first studio album since signing with the label Razor & Tie. It features a high-profile guest appearance from Snoop Dogg. As of October 30, 2008, the album has sold 18,906 copies.-Track...

 configuration on TMGs usually incorporates two fixed main wheels, allowing it to be taxied
Taxiing refers to the movement of an aircraft on the ground, under its own power, in contrast to towing or push-back where the aircraft is moved by a tug...

 on the ground without a wing walker. While some TMGs have only one main wheel, with auxiliary trolley wheels on the wings for taxiing, it is becoming more common to find them being manufactured with tricycle and conventional (two fixed main wheels - i.e. a "tail-dragger") landing gear configurations.

Since the additional drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 of the stopped propeller and landing gear reduces their gliding performance, TMGs are seldom used in competition.

Retractable propeller

The retractable propeller is usually mounted on a mast that rotates up and forward out of the fuselage
The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

, aft of the 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.

Sustainer motor gliders must be launched like an unpowered glider, but can climb slowly to extend a flight once the engine is deployed and started. They generally do not have an alternator
An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...

 or starter motor, so the engine is started by "wind-milling" the propeller in flight. The propeller may be a rigid 2-blade design, or may have more than two blades that fold at the hub when the engine is retracted. The propeller hub is usually attached directly to the crankshaft, but there is at least one example of a sustainer with a belt reduction drive, the DG-1000T.

The smaller sustainer engines are usually not equipped with a throttle, but instead have a cable to open decompression valves in each cylinder to allow the engine to turn freely for starting. Sustainer engines are typically two-stroke two-cylinder air-cooled engine
Air-cooled engine
Air-cooled engines rely on the circulation of air directly over hot parts of the engine to cool them.-Introduction:Most modern internal combustion engines are cooled by a closed circuit carrying liquid coolant through channels in the engine block and cylinder head, where the coolant absorbs heat,...

s in the range of 18–30 hp (14–22 kW). They are lighter in weight, and simpler to operate than self-launching powerplants.

Self-launching retractable propeller motor gliders have sufficient thrust and initial climb rate to take off without assistance, or they may be launched as with a conventional glider. The engines also have a starter motor and a large battery to allow the engine to be started on the ground, and an alternator to recharge the battery. A two-blade propeller is typically coupled to the engine via a belt reduction drive
Reduction drive
A reduction drive is a mechanical device to shift rotational speed. A planetary reduction drive is a small-scale version using ball bearings in an epicyclic arrangement instead of toothed gears....

. In older designs, the propeller alignment must be checked by the pilot using a mirror, before it is retracted into the fuselage; however in current production gliders, propeller alignment is fully automatic.

Another solution is the single-blade propeller
Single-blade propeller
A single-blade propeller may be used on aircraft to generate thrust. Normally propellers are multiblades but the simplicity of a single-blade propeller fits well on motorized gliders, because it permits the design of a smaller aperture of the glider fuselage for retraction of the powerplant...

 that offers the advantage of a smaller opening in the fuselage to retract the engine.

Internal combustion engines can benefit from mounting in the fuselage, rather than on the propeller mast. This allows them to be connected to a larger muffler for reduced noise when operating, something which is mostly relevant to European operation. It also allows the belt tension to be relieved when the engine is retracted to extend the life of the belt and bearings. The drawback of this arrangement is that engines fixed low in fuselages are more difficult to pre-flight and service, and highly stressed power transmission belts should not be bent or twisted.

Self-launching engines are equipped with a throttle that allows the engine power to be adjusted for ground operations. Self-launching engines are typically in the range of 50–60 hp (38–45 kW). The higher engine output power requires liquid cooling with a separate radiator mounted on the propeller mast. Engines commonly used are two-stroke piston engines, or Wankel rotary engines
Wankel engine
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...



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 taxiied 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 and a turbocharger
A turbocharger, or turbo , from the Greek "τύρβη" is a centrifugal compressor powered by a turbine that is driven by an engine's exhaust gases. Its benefit lies with the compressor increasing the mass of air entering the engine , thereby resulting in greater performance...

 on the engine, which allows the aircraft to cruise at altitudes up to 30,000 feet (9,000 m).

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


Although most motor gliders have gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...

-fueled internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

s, recently electric-powered self-launchers have been developed mainly for environmental reasons such as the Lange Antares 20E, Lange Antares 23E, Taurus Electro G2
Pipistrel Taurus
|-See also:...

, Silent 2 Targa LE
Alisport Silent 2 Targa
*Cockpit width 0.63 m * Cockpit height 0.91 m *Wing profile IMD 050 *Wing loading 34 kg/m² *Stall speed 64 km/h...

 (Lithium Electric), and the closely related Air Energy AE1 Silent, Yuneec Apis 2, Yuneec EViva, Alpaero Exel, Aériane Swift
Aériane Swift
The Aériane SWIFT is an unusual family of aircraft. Originally conceived as a rigid hang glider with sailplane-like performance, it was designed by Bright Star Gliders in collaboration with engineers at Stanford University as a boomerang-shaped wing with fins at its tips...

 and Alatus AL12. Other examples are available with sustaining engines including the Schempp-Hirth Arcus
Schempp-Hirth Arcus

 and DG Flugzeugbau DG-1000. An electric sustainer is also offered on the ESAG LAK-17B which is notable in that the airflow keeps the propeller folded against the nose of the glider when it is not in operation.


The first production self-launching motor glider fitted with a jet engine
Jet engine
A jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...

 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
Jonker JS-1 Revelation
The JS-1 Revelation is a 18 metre class glider built of glass-fibre, carbon fibre and Kevlar.The manufacturer is Jonker Sailplanes of Potchefstroom South Africa, founded in 2004 by two brothers, Attie and Uys Jonker. The designer is Attie Jonker, while the airfoil was developed by Johan Bosman in...

 and the HPH 304S, all featuring sustainer jet engines.

Other self-launching types include the experimental LET L-13TJ Blaník, a version of the Alisport Silent Club
Alisport Silent Club
|-References:*Silent Club Flight Manual***Soaring March 2005...

 and a version of the TeST TST-14 Bonus
TeST TST-14 Bonus
|-See also:-External links:**...


Use of engines in self-launching sailplanes

The engine cannot always be relied upon to start in flight, so the pilot must allow for this possibility. The generally accepted practice is to get in position for landing at a suitable airport, or off-airport out-landing field, before extending the propeller and attempting an engine start. This allows for a safe landing in the event that the engine cannot be started in time.

In soaring competitions, starting the engine is usually scored the same as an out-landing in an unpowered glider. To detect the use of the engine, GNSS Flight Recorders used in motor gliders must have a noise sensor that allows recording the sound level along with position and altitude. In many competitions, the rules require that the pilot start the engine at the beginning of the flight, before starting the task, to ensure an engine start later in the flight will be detected.

Gliders without an engine are lighter and, as they do not need a safety margin for an engine-start, they can safely thermal at lower altitudes in weaker conditions. So, pilots in unpowered gliders may complete competition flights when some powered competitors cannot. Conversely, motor glider pilots can start the engine to extend a flight if conditions will no longer support soaring, while unpowered gliders will have to land out, away from the home airfield, requiring retrieval by road using the glider's trailer.

The presence of an engine can increase the safety of gliding, as a powerplant increases the ability of the pilot to avoid storms and off-airport landings. An opposing view is that motor gliders are against the spirit of the sport, and, more importantly, that they sometimes give pilots a false sense of security.

Touring motor gliders are seldom used in competition, but they can be useful in training for cross-country flights. After take-off, the engine is switched off, and the trainee flies the aircraft as a glider. Landings in unfamiliar fields can be practiced while the motor idles. If the trainee chooses an inappropriate field, or misjudges the approach, the instructor can apply power and climb away safely.

Licenses or certificates

In Europe, powered gliders are categorized into gliders with retractable propellers/engines, which can be flown with an ordinary glider pilot license
Glider pilot license
In most countries one is required to obtain a glider pilot license or certificate before acting as pilot of a glider. The requirements vary from country to country....

 (GPL), and touring motor gliders (TMG), which require a license extension to the standard GPL. In the United Kingdom, where gliding is regulated by the British Gliding Association
British Gliding Association
The British Gliding Association is the governing body for gliding in the United Kingdom. Gliding in the United Kingdom operates through 85 gliding clubs which have 2,310 gliders and 9,462 full flying members , though a further 17,000 people have gliding air-experience flights each year.-History:A...

, pilots of self-sustaining gliders, like those of pure gliders, do not have to be licensed with the United Kingdom Civil Aviation Authority
United Kingdom Civil Aviation Authority
The Civil Aviation Authority is the public corporation which oversees and regulates all aspects of aviation in the United Kingdom. The CAA head office is located in the CAA House on Kingsway in Holborn, London Borough of Camden...


In South Africa, Touring Motor Glider (TMG) is an independent National Pilots License category under Recreation Aviation, Part 62, subpart 17.

In the United States, a private glider pilot certificate allows the pilot to fly unpowered gliders, self-launching motor gliders (including touring motor gliders and gliders with retractable engines or propellers), and sustainer motor gliders. An instructor must provide instruction and sign the logbook of the pilot to authorize the launch method, which may be by airplane towing, ground launch (winches, bungee, auto tow), or, in the case of a suitable motor glider, by self-launching. In the US, motor gliders are classified as gliders, and may be operated by a glider pilot without the medical certificate required to operate an airplane.

In Canada, a glider pilot license allows the pilot to fly unpowered gliders, self-launching motor gliders (including motor gliders and gliders with retractable engines or propellers), and sustainer motor gliders. An instructor must provide instruction and sign the logbook of the pilot to authorize the pilot to carry passengers. In Canada, motor gliders are classified as gliders, and may be operated by a glider pilot without the medical certificate required to operate an airplane.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.