Hawker Siddeley Harrier as VTOL and STOL manoeuvres (where the traditional lift and control surfaces are useless) requiring skills and technical knowledge usually associated with helicopters. Most services demand great aptitude and extensive training for Harrier pilots, as well as experience in piloting both types of aircraft. Trainee pilots are often drawn from highly experienced and skilled helicopter pilots. In addition to normal flight controls, the Harrier has a lever for controlling the direction of the four vectoring nozzles. It is viewed by senior RAF officers as a significant design success, that to enable and control the aircraft's vertical flight required only a
Invincible-class aircraft carrier to evolve. The order for the first ship was given to Vickers (Shipbuilding) on 17 April 1973. By now, the design was for a 19,000 ton "CAH" (helicopter carrying heavy cruiser, styled after the US Navy hull classification symbols) with up to fourteen aircraft and a Sea Dart missile launcher on the bows. The government decided that the carrier needed fixed-wing aircraft to defend against Soviet reconnaissance aircraft. In May 1975, it authorised the maritime version of the Hawker Siddeley Harrier, which was successfully developed into the Sea Harrier. This meant that the design was reworked again to include a