Thrust vectoring
Thrust vectoring is the use of a jet aircraft's main engine(s) to provide a variable amount of thrust in a direction other than parallel to the aircraft's length.
Rotating nozzles or vanes are used to deflect the exhaust stream from the engine to achieve this. The technique was originally envisaged to provide upward vertical thrust as a means to give aircraft VTOL or STOL capability. Subsequently it was realised that the use of vectored thrust in combat situations enabled an aircraft to perform various evasive maneuvers not available to conventional-engined planes.
A fluidic nozzle diverts the thrust via fluid effects. Tests have shown that air forced into the exhaust stream can effect deflected thrust of up to 15 degrees. Currently in the experimental stage, fluidic nozzles are desirable for their lower weight, mechanical simplicity (no moving surfaces) and lower radar cross section and will likely be featured on many 6th generation fighter aircraft.
Tilt-rotor aircraft achieve thrust vectoring by rotation of turboprop engine nacelles. The mechanical complexities of this solution are quite troublesome, including the twisting of flexible internal components and driveshaft power transfer between engines. Some believe this type of rotor thrust is significantly more susceptible to vortex ring conditions than traditional helicopter propulsion.
The pioneer and best known example of thrust vectoring is the Hawker Siddeley Harrier (with variants built by McDonnell Douglas). The technique has also been used in various experimental and development planes, some with vectored thrust in directions other than upwards.
List of vectored thrust aircraft
