Glider (sailplane)

A glider is a designed for gliding aircraft. The motorless flying means alternately climbing and sliding on the upswing with little loss of altitude. In Germany gliders are air legally counted as a separate aircraft class and may weigh up to 850 kg.

The glider is in Germany, the air vehicle class with the most entries ( 7834, Booth 2011). Thereafter, single-engine airplanes follow under 2 t ( 6744, Booth 2011) and motor gliders ( 3122, Booth 2011).

Demarcation

When climbing the up the glider gains potential energy, which is converted in the subsequent gliding in forward velocity (kinetic energy). If one considers only the glide phase, in principle, any aircraft can be used as a glider. For example, put an Airbus A330 in the Air Transat Flight 236, a distance of 120 km glide back. Another example is the ditching of an Airbus on the Hudson River in 2009.

In powered aircraft, the glider usually limited to a stable gliding. Exceptions are motor glider that can take advantage of the possibility of pure gliding through their special design. The space shuttle landed as a glider. The private spacecraft SpaceShipOne was even officially recognized as "non- self-launching sailplane with auxiliary drive " admitted.

In a narrow sense refers only such aircraft as gliders, which are able to gain height in the normally occurring in the atmosphere thermals. These should both be less than the speed of rising air masses, the minimum rate of descent; On the other hand, the minimum circling diameter must be smaller than the diameter of the climb.

Properties

High glide

Gliders shall always be able to reach the next thermal. This requires a good relationship between gliding consumed height and distance traveled ( glide ratio ).

Modern gliders have a glide ratio between 1:30 and 1:60, so they can fly 30 to 60 km at 1 km altitude loss in still air. ETA, which is currently (2009) powerful glider has with its span of 30,90 m even a glide ratio of about 1:70.

Low flow resistance

In order to provide good gliding properties, a glider must be built very little resistance. A small air resistance is necessary, as otherwise too much energy is lost by friction.

• To ensure the required lift at the lowest possible resistance, have the wings of gliders compared to powered aircraft a high aspect ratio (large wingspan and low tread depth).
• In modern gliders, a retractable landing gear is standard equipment.
• The surface quality must be high to ensure the longest possible distance run by the laminar air flowing around.
• For longer distances, often Bugwipers be used, the rescue the wing leading edge during the flight from the remains of dead insects ( see picture).

To the resistance created by an airfoil, a part of the induced drag. It arises caused by the pressure balance between top ( vacuum) and bottom (gauge), the wake vortices. In order to reduce the induced drag, increasing bent- wing ends are used, so-called winglets. This can also be seen in commercial aircraft.

Weight

A low weight is only a secondary feature: While ( the quotient of mass and wing area ) allows a low wing loading and a low sink rate and thus a better climb in thermals, but the airspeed of the optimal sliding reduced by the lower potential energy. This means that a light glider in the high speed range (from about 130 km / h) faster than an identical pattern loses height, which is heavier. High wing loading results in faster straight flight - with good thermals. For this, the sink rate is slightly larger. However, the associated disadvantage of the poor rising in circling flight is negligible with good thermals.

Gliders from Standard Class up feature for increasing the weight nowadays usually over water tanks ( typical capacity is 160 liters, but realized up to 300 liters in the Nimbus 4 ) to increase the mass of the airplane. The best glide speed can significantly increase water ballast. The water is filled to before the flight and can be released in case of decreasing thermal evening. However, it must be drained before landing, on the one hand the landing is "short" (large mass means large inertia during deceleration ) and secondly the aircraft structure at touchdown and the brakes when slowing down to avoid unnecessary burdens.

Maneuverability

High maneuverability is necessary because the thermals can be very limited (especially when circling below 400 m above ground and strong turbulence ). The smaller the diameter, the more effectively the thermal be used. Modern gliders are designed so that they fly stable and secure in a speed range of about 80 to 280 km / h. Gliders in mixed construction ( vintage ) with low wing loading are sometimes even superior, every modern high-performance gliders, as they can revolve much more closely by the low airspeed curve. A Ka 8 can with 75 km / h revolve safe, while a ASH 25 with water ballast to the 110 km / h needed to still clean to circle. Thus, a diameter of 75 m results compared to almost 200 m.

Strength

Since high speed with good glide angle with relatively high wing loading is possible, care is taken in gliders on stable structure and waives extremely lightweight. But not only because of the high load during flight, gliders must be of robust construction; also an outside landing, about in fields and ungeerntetem grain must endure the plane while the pilots provide the best protection.

For reasons of strength and surface quality of both the wings and fuselage and tail of modern gliders made ​​of fiber -reinforced plastics are built.

Decomposability

Since it is not possible in case of a landing outside to start the plane again, it is on the spot " disarmed " and housed in a trailer at an airfield. These gliders are usually designed so that they are in a few minutes in a few transportable parts ( mostly wings, fuselage and tailplane ) can be split.

Start species

When aircraft towing the glider by a tow-plane is drawn into the air ( this can be a light motor plane, a microlight aircraft or motor gliders to be). The tow rope is usually clipped in on the nose hook or, in rare cases also to the CG hook on the underside of the glider. The height at which unlatches the glider is usually between 500 m and 1500 m. After release the tow plane pulls the tow rope either on an in- hull reel or throws it off before landing on the start site.

Winch launch a long steel or plastic rope controlled ( by the winch operator ) speed is retracted while the pilot controls the climb angle. At a certain height, the tow rope reaches a constructively predetermined angle to the longitudinal aircraft axis, which is falling out of the tow hook, without the pilot must manually disengage. For lengths of towing distance of 800 m to 3000 m Ausklinkhöhen of 300 m to 1300 m are reached ( inter alia dependent on wind and aircraft type). Modern, light plastic ropes allow significantly greater Ausklinkhöhen with long trailing lines.

A self launching motor glider is possible, mostly alone can start with your engine. There are also motor glider equipped with a weaker engine (called Turbo Engine, among glider pilots also called doldrums slide ) with which it can not start itself, but is only used to fly through areas with too low thermals without loss of height can to avoid off-field landing. These drives are designed with modern gliders usually as a retractable engine, in which a propeller tower from the fuselage folds out behind the wings. The engine is then attached to the tower either, or it remains in the body. In this case the propeller is then driven by a toothed belt with a corresponding reduction.

The rubber rope launch was the first opportunity to launch a glider. It can only be done in very light and usually old gliders such as the SG38 and on a slope. Here, a rubber rope is front mounted and stretched while it is held at the rear of the aircraft. In a command, the aircraft is released and flung into the air.

At the car towing the aircraft is pulled by a moving car into the air. It may be achieved any great heights.

Competitive Classes

Gliders are divided into different classes of international competition:

• FAI standard class ( rigid airfoil, 15 m span, variable surface load, max. 525 kg take-off mass )
• FAI -15 - m- class, also called racing class (15 m span, Profile by flaps changeable, variable surface load, max. 525 kg take-off mass or 50 kg/m2)
• FAI -18- m- class ( 18 m span, Profile by flaps changeable, variable surface load, max. 600 kg take-off mass )
• Open class ( max. 850 kg take-off mass, otherwise no restrictions)
• Seater Class ( two seats, a maximum of 20 m span )
• World Class ( unit aircraft PZL PW -5)
• Club Class ( older aircraft, regardless of type, up to a performance index of 107, constant wing loading )

When gliding, there are national and international competitions in the disciplines of cross country flying and glider aerobatics.

In addition to these so-called " central competitions " (all participants start from the same airfield ), the " decentralized competitions " always popular. The most important competition in Europe is the online Contest (OLC ), in which participants submit their standardized GPS logger files and be counted in a single and a club championship.

In the central events the distance flown and the achieved thereby cutting speed in the ranking is taken into account, while in the decentralized competitions, only the total distance flown counts. A particular bonus is obtained for the previous announcement of the flown distance and a route that resembles an equilateral triangle. In order to make the different types of aircraft within the competitive classes comparable to a glider - index has been introduced.