The early Essex-class carriers had been built with a hangar-level catapult. It was called the HIVA catapult and shot planes out of the starboard forward hangar deck. The Essex's were designed to have 3 catapults (two on the flight deck bow and one in the hangar bay). The hangar catapult was for launching scout planes (pre-radar) without disturbing the deck park. It was deemed so important that when it became known that it threw off the weight distribution, the port side bow deck catapult was left off. Due to delays, only six ships were actually fitted with this catapult and by then radar was in use and the need for scout planes was eliminated. Begininning with Ticonderoga the hangar cat was omitted and both bow cats installed. Eventually all Essex's lost the hangar cat and regained the port side cat. The only carrier to keep the hangar catapult through the end of the war was USS Hornet (CV 12). See below some photos of hangar deck catapult operations:
http://aviacaoemfloripa.blogspot.com.br/2011/02/decolagens-do-hangar.html
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