HMS Invincible was the lead ship of a class of British light aircraft carriers built between 1973 and 1985, originally designed as "through-deck cruisers" (TDC). This set them apart from conventional helicopter-carrying ships of the time, which typically featured a flight deck in the aft section of the vessel. Invincible -class carriers were the world's largest warships powered by gas turbines and featured a modular design which allowed replacement and upgrades of various elements of the propulsion system and equipment without the need for any structural modifications of the hull.A characteristic feature of the Invincible class was a "ski-jump" ramp at the end of the flight deck designed for VSTOL Sea Harriers, which at that time were state-of-the-art combat platforms.As designed, the ship was to carry five Sea Harriers and nine Sea King helicopters (six ASW variants and three transports).