Helicopters are extremely useful naval aircraft, because of their versatility, size & perhaps most of all, their VTOL capability. Many modern ships can carry at least one helicopter, usually for ASW or defence purposes. The naval helicopter has changed a lot since it was introduced in the late 40s & early 50s. It performs a wide range of roles, including assault transport, ASM delivery, ASW, SAR & AEW. The Fleet Air Arm has a wide range of helicopters which operate from Frigates, Destroyers, Assault Transports, the ‘Invincible’ class aircraft carriers & the Royal Navy’s new helicopter support ship, HMS Ocean.