In April 1956, the finalised production drawings were formally issued. The fully navalised production Sea Vixen featured a number of improvements over earlier development models. These included the addition of a powered folding wing system, reinforcement of the landing gear to withstand the additional stresses of carrier landings, a steerable nose wheel, a revised tail unit, and the redesigning of the fuselage to carry armament. On 20 March 1957, the first true Sea Vixen, designated as the "Sea Vixen FAW.20" (fighter all-weather, later redesignated "FAW.1"), performed its first flight. This aircraft was promptly used for clearance trials, in particular for addressing handling problems; the second production aircraft was used for engineering trials and the third aircraft for conducting radar trials. On 2 July 1959, the first Sea Vixen-equipped squadron was formed.