Harrier aircraft flight simulation. Supercomputer image of a Harrier aircraft hovering over a runway in a virtual wind tunnel. The lines beneath the aircraft show the air flow from the aircrafts engine. The lines colours show the airs tempera ture gradient, from red (highest), through orange, yellow, green, and blue, to purple (lowest). The Harrier is a Vertical TakeOff and Landing (VTOL) fighter aircraft which directs air from its Rolls Royce Pegasus engine through 4 swivelling nozzles along the side of its fuselage. The nozzles point downwards for takeoff, before rotating backwards to accelerate the aircraft into wingborne flight.