JET ENGINES ARE USED BY MOST MILITARY and heavy aircraft, and by many Helicopters.The simplest type of jet engine or gas turbine is the turbojet.It work by continuous burning a mixture of fuel and air in a combustion chamber to produce a jet of hot exhaust gas, that is expelled through a nozzle to produce a thrust.The hot gas also spins the turbine blades,which ,in turn spin, the blades of an air compressor,the compressor forces air into the combustion chamber.Many of th e fastest aircraft use turbojet with additional booster units called afterburners ,but their use is restricted by their noise emission ,Most jetliners use turbofan jet engines ,which are quieter .An enormous fan ,driven by a low -pressure turbine,feed some air into the compressor but feeds most of it through bypass ducts to join the exhaust jet st