The Federal Aviation Administration (FAA) defines a glider as a heavier-than-air aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend principally on an engine. [Figure 1-5] The term “glider” is used to designate the rating that can be placed on a pilot certificate once a person successfully completes required glider knowledge and practical tests.
Another widely accepted term used in the industry is sailplane. A sailplane is a glider (heavier-than-air fixed-wing aircraft) designed to fly efficiently and gain altitude solely from natural forces, such as thermals and ridge waves. [Figure 1-6] Older gliders and those used by the military were not generally designed to gain altitude in lifting conditions, whereas modern day sailplanes are designed to gain altitude in various conditions of lift. Some sailplanes are equipped with sustaining engines to enable level flight even in light sink, or areas of descending air flow. More sophisticated sailplanes may have engines powerful enough to allow takeoffs and climbs to soaring altitudes. In both cases, the powerplants and propellers are designed to be stopped in flight and retracted into the body of the sailplane to retain the high efficiency necessary for nonpowered flight.
Gliding, that is flying a glider or sailplane, is relatively easy to learn, but soaring, which is gaining altitude and traveling without power, is much more difficult and immensely satisfying when accomplished. Soaring refers to the sport of flying sailplanes, which usually includes traveling long distances and remaining aloft for extended periods of time. Gliders were designed and built to provide short flights off a hill down to a landing area. Since their wings provided relatively low lift and high drag, these simple gliders were generally unsuitable for sustained flight using atmospheric lifting forces. Both terms are acceptable and are synonymous. Early gliders were easy and inexpensive to build, and they played an important role in flight training. The most well-known example today of a glider is the space shuttle, which literally glides back to earth. The space shuttle, like gliders that remain closer to the earth, cannot sustain flight for long periods of time.
Self-launching gliders are equipped with engines; with the engine shut down, they display the same flight characteristics as nonpowered gliders. [Figure 1-7] The engine allows them to be launched under their own power. Once aloft, pilots of self-launching gliders can shut down the engine and fly with the power off. The additional training and procedures required to earn a self-launch endorsement are covered later in this section.