SCB-27

SCB-27, or "Two Seven-Alpha"/"Two Seven-Charlie," was the United States Navy designation for a series of upgrades to the Essex-class aircraft carriers (both the short-hull and long-hull (Ticonderoga) versions), conducted between 1947 and 1955. These upgrades were intended to allow the World War II-era carriers to operate jet aircraft.

USS Oriskany, laid up incomplete at the conclusion of World War II, served as the prototype and was re-ordered to the SCB-27 standard. All of the SCB-27 modernized Essex carriers, save USS Lake Champlain, were further modified under the SCB-125 modernization program.

Officially, Ship Characteristics Board Program 27 proper referred to the completion of Oriskany, left unfinished at war's end, to a heavily revised design; reconstructions of earlier ships were programs SCB-27A and 27C. The SCB-27 modernization was very extensive, requiring some two years for each carrier. To handle the much heavier, faster aircraft of the early jet-era, the flight deck structure was significantly reinforced, able to support aircraft weighing up to 52,000 pounds (23,587 kg), namely the North American AJ Savage. Stronger and larger elevators, much more powerful catapults, and new Mk 5 arresting gear were installed. The original four twin 5-inch/38 gun mounts were removed, clearing the flight deck of guns. The new five-inch gun battery consisted of eight weapons, two on each quarter beside the flight deck. Twin 3-inch/50 gun mounts replaced the 40 mm guns, offering much greater effectiveness through the use of proximity fuzed ammunition. The reconstruction eliminated the difference between "short-hull" and "long-hull" ships; all now had similar clipper bows.

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