Gliders or sailplanes are aircraft designed for unpowered flight. Most gliders are intended for use in the sport of gliding and so have high aerodynamic efficiency. Lift-to-drag ratios may exceed 70 to 1. After launch, the energy for sustained gliding flight is obtained through the skillful exploitation rising air in the atmosphere. Glider flights of thousands of kilometres at average speeds over 200 km/h have been achieved. The glider is most commonly launched by a tow-plane or by a winch. Some gliders, called motor gliders, are equipped with engines (often retractable) and some are capable of self-launching. Gliding is often considered to be one the cheapest and most satisfying types of aviation. Military gliders have been used in war to deliver assault troops, and specialized gliders have been used in atmospheric and aerodynamic research.
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.
