Thrust vectoring

Thrust vectoring broadly describes the diversion of engine down wash into a preferred direction. This can be used in order to steer an aircraft, and it can be used to lift an aircraft off the ground vertically.

The key to successful VTOL via thrust vectoring is that the engine thrust, i.e. how much the engines are able to push, must be larger than the weight of the aircraft. Typically only fighter jets, which in effect are jet engines with seats, have sufficient thrust for this. They are in effect able to fly straight up, which no commercial/civil aircraft can do.

Because of the very small effective disc area and hence very high effective disc loading, the hover efficiency of VTOL via thrust vectoring is typically terrible. While a similarly heavy helicopter may need 3,000 hp in order to lift off using its large rotor, a jet has to run its engines at close to full power, generating 20,000 or more horse powers in order to hover and take off vertically.

Because of this, mission control and pilots will typically attempt to limit themselves to short take offs during which the wing already carries some weight, e.g. from an aircraft carrier or a forward airfield, landing vertically only when much lighter at the end of a mission when ordnance has been dispatched and fuel burned.