What is the purpose of Thrust Vectoring ?

Thrust vectoring is the ability of an aircraft or other vehicle to direct the thrust from its main engine(s) in a direction other than parallel to the vehicle's longitudinal axis. The technique was originally envisaged to provide upward vertical thrust as a means to give aircraft vertical (VTOL) or short (STOL) takeoff and landing ability. Subsequently, it was realized that using vectored thrust in combat situations enabled aircraft to perform various maneuvers not available to conventional-engined planes. To perform turns, aircraft that use no thrust vectoring must rely on only aerodynamic control surfaces, such as ailerons or flaps; craft with vectoring must still use control surfaces, but to a lesser extent.

Most currently operational vectored thrust aircraft use turbofans with rotating nozzles or vanes to deflect the exhaust stream. This method can successfully deflect thrust through as much as 90 degrees, relative to the aircraft centerline. However, the engine must be sized for vertical lift, rather than normal flight, which results in a weight penalty. Afterburning (or Plenum Chamber Burning, PCB, in the bypass stream) is difficult to incorporate and is impractical for take-off and landing thrust vectoring, because the very hot exhaust can damage runway surfaces. Without afterburning it is hard to reach supersonic flight speeds. A PCB engine, the Bristol Siddeley BS100, was cancelled in 1965.

Tiltrotor aircraft vector thrust via rotating turboprop engine nacelles. The mechanical complexities of this design are quite troublesome, including twisting flexible internal components and driveshaft power transfer between engines.

Most current tiltrotor designs feature 2 rotors in a side-by-side configuration. If such a craft is flown in a way where it enters a vortex ring state, one of the rotors will always enter slightly before the other, causing the aircraft to perform a drastic and unplanned roll.

Thrust vectoring is also used as a control mechanism for airships, particularly modern non-rigid airships. In this use, most of the load is usually supported by buoyancy and vectored thrust is used to control the motion of the aircraft. But, designs have recently been proposed, especially for Project WALRUS, where a significant portion of the weight of the craft is supported by vectored thrust. The first airship that used a control system based on pressurized air was the Forlanini's Omnia Dir in 1930s.

Thurst vectoring is one of the best feature in Sukhoi SU-30 MKI. The Thurst vectoring nozzle works in such a way that we can direct the engine thrust in a desired direction.it enhances the maneuverability, and it is this reason due to which Su-30 can perform cobra maneuvers and which is quite beneficial during dogfight. India is the second country after Russia to have an aircraft in service with such thrust vectoring capability.