Jet airplane

A jet aircraft (or simply jet) is an aircraft (nearly always a fixed-wing aircraft) propelled by jet engines.After the first instance of powered flight, a large number of jet powerplants were suggested. René Lorin, Morize, Harris proposed systems for creating a jet efflux. In 1910 the Romanian inventor Henri Coandă filed a patent on a jet propulsion system which used piston-engine exhaust gases to add heat to an otherwise pure air stream compressed by rotating fan blades in a duct. It was installed in his Coandă-1910 but this craft probably never flew.Most people use the term 'jet aircraft' to denote gas turbine based airbreathing jet engines, but rockets and scramjets are both also propelled by jet propulsion.Because of the way they work, the typical exhaust speed of jet engines is transonic or faster, therefore most jet aircraft need to fly at high speeds, either supersonic or speeds just below the speed of sound ('transonic') so as to achieve efficient flight. Aerodynamics is therefore an important consideration.Jet engines come in several main types:Jet aircraft fly considerably differently to propeller aircraft.In aircraft overall propulsive efficiency η {displaystyle eta }   is the efficiency, in percent, with which the energy contained in a vehicle's propellant is converted into useful energy, to replace losses due to air drag, gravity, and acceleration. It can also be stated as the proportion of the mechanical energy actually used to propel the aircraft. It is always less than 100% because of kinetic energy loss to the exhaust, and less-than-ideal efficiency of the propulsive mechanism, whether a propeller, a jet exhaust, or a fan. In addition, propulsive efficiency is greatly dependent on air density and airspeed.For a long range jet operating in the stratosphere, the speed of sound is constant, hence flying at fixed angle of attack and constant Mach number causes the aircraft to climb, without changing the value of the local speed of sound. In this case: