Wednesday, January 17, 2007

Types of Airplane

Gliders

Gliders or sailplanes are aircraft designed for unpowered flight. Most gliders are intended for use in the sport of gliding and have high aerodynamic efficiency: lift-to-drag ratios may exceed 70 to 1. The energy for sustained gliding flight must be obtained through the skillful exploitation of naturally occurring air movements in the atmosphere. Glider flights of thousands of kilometres at average speeds over two-hundred kilometres per hour have been achieved.

Military gliders have been used in war for delivery of assault troops, and specialized gliders have been used in atmospheric and aerodynamic research. Motor gliders equipped with engines (often retractable), some capable of self-launching, are becoming increasingly common.

Propeller aircraft

Smaller and older propeller aircraft make use of reciprocating internal combustion engines that turns a propeller to create thrust. They are quieter than jet aircraft, but they fly at lower speeds, and have lower load capacity compared to similar sized jet powered aircraft. However, they are significantly cheaper and much more economical than jets, and are generally the best option for people who need to transport a few passengers and/or small amounts of cargo. They are also the aircraft of choice for pilots who wish to own an aircraft.

Turboprop aircraft are a halfway point between propeller and jet: they use a turbine engine similar to a jet to turn propellers. These aircraft are popular with commuter and regional airlines, as they tend to be more economical on shorter journeys.

Jet aircraft

Jet aircraft make use of turbines for the creation of thrust. These engines are much more powerful than a reciprocating engine. As a consequence, they have greater weight capacity and fly faster than propeller driven aircraft. One drawback, however, is that they are noisy; this makes jet aircraft a source of noise pollution. However, turbofan jet engines are quieter, and they have seen widespread usage partly for that reason.

The jet aircraft was developed in England and Germany in 1931. The first jet was the Heinkel He 178, which was tested at Germany's Marienehe Airfield in 1939. In 1943 the Messerschmitt Me 262, the first jet fighter aircraft, went into service in the German Luftwaffe. In the early 1950s, only a few years after the first jet was produced in large numbers, the De Havilland Comet became the world's first jet airliner, but was removed from service due to structural inadequacies discovered after numerous pressurization and depressurization cycles.

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