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 carrier s ( 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 . Modifications . Officially , Ship Characteristics Board Program 27 proper referred to the completion of USS " Oriskany " ( CV - 34 ) , 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 , 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 " / 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 " / 50 gun mounts replaced the 40mm guns , offering much greater effectiveness through the use of proximity fuze d ammunition . The reconstruction eliminated the difference between " short - hull " and " long - hull " ships ; all now had similar clipper bows . The island was completely redesigned , made taller , but shorter in overall length with the removal of its gun mounts . In addition , the boiler uptakes were rebuilt and angled aft to accommodate a single radar and communications mast atop the island . To better protect aircrews , ready room s were moved from the gallery deck to below the armored hangar deck , with a large escalator on the starboard side amidships to move flight crews up to the flight deck . Internally , aviation fuel capacity was increased to ( a 50 % increase ) and its pumping capacity enhanced to per minute . Fire fighting capabilities were enhanced through the addition of two emergency fire and splinter bulkheads to the hangar deck , a fog / foam firefighting system , improved water curtains and a cupronickel fire main . Also improved were electrical generating power , and weapons stowage and handling facilities . All this added considerable weight : displacement increased by some twenty percent . The armor belt was removed and blisters were fitted to the hull sides to compensate , widening waterline beam by eight to ten feet . The ships also sat lower in the water , and maximum speed was slightly reduced , to 31 knots . Modification sub - types . The two sub - types of SCB - 27 modifications were primarily a result of changes in catapult technology in the early - 1950s . SCB - 27A vessels utilized a pair of H 8 slotted - tube hydraulic catapults , while the later SCB - 27C vessels were fitted with a pair of C 11 steam catapults , a British innovation ( in fact the first four installed , on USS " Hancock " and USS " Ticonderoga " , were British - built ) . To accommodate the catapult machinery , the SCB - 27C vessels were slightly heavier ( 43 , 060 vice 40 , 600 tons ) and after bulging wider abeam ( 103 vice 101 feet ) than their SCB - 27A sisters . Additionally , the SBC - 27C carriers were equipped with jet blast deflector s , deck cooling , fuel blending facilities , emergency recovery barrier and storage and handling for nuclear weapon s , which was not included in all of the SCB - 27A carriers . Under SCB - 27C the No . 3 ( after ) elevator was moved to the starboard deck edge ; this elevator was located further aft on the first three SCB - 27C ships than it was on the ships which received it concomitantly with an angled flight deck under the SCB - 125 program . The greater capacity of steam catapults meant that the 27C ships were able to serve as attack carriers through the Vietnam era while their hydraulic - equipped 27A sisters were relegated to antisubmarine duties . Program history . USS " Oriskany " ( CV - 34 ) , 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 " ( CV - 39 ) , were further modified under the SCB - 125 modernization program . Modified vessels . " Source : www . history . navy . mil " References . Portions of this entry were drawn from : Naval Historical Center SCB - 27 information and photos