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
Hawker Siddeley Harrier function had originally been added following the input of US Air Force Colonel Bill Chapman, who worked for the Mutual Weapons Development Team. Water injection was necessary in order to generate maximum thrust, if only for a limited time, and was typically used during landing, especially in high ambient temperatures. The aircraft was initially powered by the Pegasus 6 engine which was replaced by the more powerful Pegasus 11 during the Harrier GR.1 to GR.3 upgrade process. The primary focus throughout the engine's development was on achieving high performance with as little weight as possible, tempered by the amount of