Research aircraft

Even after the development of powered aircraft, gliders have been built for research. The NASA Parasev Rogallo flexible wing is an example that was built to investigate alternative methods of recovering spacecraft. Although this application was abandoned, publicity inspired hobbyists to adapt the flexible wing airfoil for modern hang gliders.

Unpowered flying wings are another type of aircraft that have been built for aerodynamic research. Examples are the Horten flying wings, Armstrong Whitworth A.W.52G and the Baynes Bat.

In contrast to the flying wings, lifting bodies have been also developed using unpowered prototypes. Although the idea can be dated to Vincent Justus Burnelli in 1921, interest increased as an alternative for returning spacecraft. Traditional space capsules have very little control over where they land, whereas a steerable craft using wings would have more options. The lifting bodies use the fuselage itself to generate lift without employing the usual thin and flat wing. The objective of the lifting body is to minimize the drag and structure of a wing for very high supersonic or hypersonic flight as might be experienced during the re-entry of a spacecraft. This can be compared with a flying wing that seeks to minimise drag at subsonic speeds by eliminating non-lifting surfaces. Examples of type are the Northrop HL-10 and Martin-Marietta X-24.

Military gliders were

Military gliders were used mainly during the Second World War for carrying troops and heavy equipment (see Glider infantry) to a combat zone. These aircraft were towed into the air and most of the way to their target by military transport planes, eg C-47 Dakota, or by bombers that had been relegated to secondary activities, eg Short Stirling. Once released from the tow near the target, they landed on as close to target as possible. The advantage over paratroopers were that heavy equipment could be landed and that the troops were quickly assembled rather than being dispersed over a drop zone. The gliders were treated as disposable leading to construction from common and inexpensive materials such as wood, though a few were retrieved and re-used. By the time of the Korean War, transport aircraft had also become larger so that that even light tanks could be dropped by parachute, and so gliders were not used.

Glider aircraft are

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.^[1] Mostly these types of aircraft are intended for routine operation without engines, though engine failure can force other types of aircraft to glide.

There are a wide variety of types differing in the construction of their wings, aerodynamic efficiency, location of the pilot and controls. Some may have power-plants to take off and/or extend flight. Some are designed simply to descend, but the most common varieties exploit meteorological phenomena to maintain or even gain height. These types are principally used for the air sports of gliding, hang gliding and paragliding. Perhaps the most familiar type is the paper aeroplane.