Although the nacelle engines were capable of producing adequate thrust as to allow the aircraft to steadily hover on dry thrust alone, concerns over the smoothness of transition from dry thrust to reheat led to a requirement being approved for the aircraft to have the ability of taking off vertically under reheat. Accordingly, this required a very short reheat pipe to be adopted in order to provide the necessary ground clearance. The reheated engines featured a relatively simple two-position nozzle, which could switch between reheat and non-reheat; the inlet duct was also capable of being moved forward when the aircraft was moving at slow speeds or during a hover, which opened an auxiliary air intake.