Hawker Siddeley Harrier single lever added in the cockpit. For horizontal flight, the nozzles are directed rearwards by shifting the lever to the forward position; for short or vertical takeoffs and landings, the lever is pulled back to point the nozzles downwards. The Harrier has two control elements not found in conventional fixed-wing aircraft: the thrust vector and the reaction control system. The thrust vector refers to the slant of the four engine nozzles and can be set between 0° (horizontal, pointing directly backwards) and 98° (pointing down and slightly forwards). The 90° vector is normally deployed for VTOL manoeuvring. The reaction control
Hawker Siddeley Harrier the P.1154 was cancelled, as the Royal Navy had already begun procurement of the McDonnell Douglas Phantom II and the RAF placed a greater importance on the BAC TSR-2's ongoing development. Work continued on elements of the project, such as a supersonic PCB-equipped Pegasus engine, with the intention of developing a future Harrier variant for the decades following cancellation. Following the collapse of the P.1154's development the RAF began considering a simple upgrade of the existing subsonic Kestrel and issued Requirement ASR 384 for a V/STOL ground attack jet. Hawker Siddeley received an order for six pre-production aircraft in 1965,