Glider Design

A glider has the same basic shape as a powered airplane, but its wings are longer and very narrow. Narrow wings produce less drag than wide wings. The longer the wings, the more wing area the glider has to generate lift. A competition sailplane may have wings that are 70 feet (21 meters) long but less than 3 feet (1 meter) wide. Just like a powered air­plane, gliders’ wings have ailerons-and sometimes flaps as well-for control in flight. Many gliders carry water as bal­last in the wings. The ballast, which pro­vides additional weight for extra control in fast rising air currents, is jettisoned (dropped) before the glider lands.

The fuselage (or body) of a glider is slim, again to reduce drag. It is often so

slim that the pilot has to lie almost prone in the cockpit. Trainer gliders, designed for two people-an experienced pilot and a student-have slightly wider bodies and cockpits in which the passen­gers can sit upright.

Gliders are made of lightweight materials, usually aluminum, fiberglass, metal, and wood. The outer skin is smoothed and polished to reduce air resistance. Landing gear on a glider usu­ally consists of one landing wheel that folds away after the glider is airborne.

Launching

Most gliders are launched by a towing airplane. A towrope or wire, usually 150-200 feet (46-61 meters) long, is fastened from a hook on the towing

GLIDER CLASSIFICATION

The French Federation Aeronautique Internationale (FAI) is recognized as the world’s air sports association. It classes gliders for competition in various ways.

The classes include:

• Standard class: no flaps, wingspan 49.21 feet (15 meters).

• 15-meter (49.21-feet) class:

flaps allowed.

• 18-meter (59.06-feet) class:

flaps allowed.

• Open class: no restrictions.

• Two-seater class: maximum wingspan 65.62 feet (20 meters).

• Club class: open to a range of types, including older gliders.

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airplane to another hook on the nose of the glider. As the towing airplane takes off, it pulls the glider after it, and the two airplanes gain height. Once a glider has gained sufficient altitude-usually between 2,000 and 3,000 feet (610 and 915 meters)-the glider pilot frees the glider from the towrope by using a con­trol in the cockpit.

Gliders also can be launched by cat­apulting them off hillsides or by towing them behind a vehicle, but the most usual alternative to tow launching is to use a winch. This process is similar to launching a kite. A power-operated winch is set at one end of the takeoff

О The Duo Discus is a high-performance glider used in fast cross-country flying. Built in the Czech Republic, the two-seater used for high-level training and often is seen in competitions.

Powerful air currents, known as mountain waves, are found on the lee (sheltered) side of steep, high mountains. Flying a glider in mountain waves is sometimes called ridge running. A glider also will soar when it flies into a shear line, or convergence zone, where a mass of cool air has forced a block of lighter, warm air to rise. Experienced glider pilots learn to take full advantage of these air currents and other favorable flying conditions.

New records are frequently set by gliders for height, distance, and speed. Gliders have climbed to heights of over

49,0 feet (14,940 meters) and have made straight-line flights of more than 1,240 miles (1,995 kilometers).

A glider pilot has four basic flying instruments: an airspeed indicator, an altimeter (to show altitude), a compass, and a vario/altimeter that indicates the rate at which the plane is rising or falling. The vario/altimeter helps the pilot determine the glider’s position in relation to nearby rising air currents. The pilot also can use computers and GPS systems to keep track of the air­craft’s position and course.

Using airbrakes to slow its descent, a glider can land on almost any flat field, often miles from its launch. Most are designed to be taken apart so they can be loaded on a trailer for the trip home.

Regulations for glider pilots are simi­lar to those for other airplane pilots. In the United States, the Federal Aviation Administration is responsible for regu­lating pilots and gliders.

SEE ALSO:

• Aerodynamics • Aeronautics

• Cayley, George • Lift and Drag

• Lilienthal, Otto • Wright, Orville

and Wilbur

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