SCB-125 was the United States Navy designation for a series of upgrades to the Essex class of aircraft carriers planned by the Ship Characteristics Board and conducted between 1954 and 1959. These upgrades included the addition of an angled flight deck and other enhancements (such as with catapults and elevators) aimed at improving flight operations and seakeeping .
21-565: The SCB-125 modifications included The SCB-125 upgrade program was first applied to the final three Essex -class carriers to undergo the SCB-27C modernization while they were still in the midst of their original refit. Ultimately every SCB-27 ship would undergo the SCB-125 modification with the exception of Lake Champlain . Despite the drastic alteration of the carriers' appearance, the SCB-125 refit involved relatively little modification of
42-498: 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 Hancock and 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,
63-489: Is a gun fire-control system made up of AN/SPG-35 radar tracker and the Mark 42 ballistic computer . The directional board is maneuverable, equipped with an X-band radar Mk.35 (later renamed AN/SPG-35 based on the naming convention for military electronic equipment) and an optical sight, and is manned with two operators on board. Target tracking by the operator's optical sight is also possible, but fully automated tracking
84-462: Is the basic operation, and blindfire is also possible for the first time in the US Navy. First, the target is captured by a spiral scan that slowly scans the space by swinging the beam at an angle of 6 degrees, and then a conical scan that quickly measures and distances by narrowing the beam swing angle to 0.5 degrees. Track the target by scanning. The speed of the tracking target is obtained by
105-454: 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
126-689: 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. Portions of this entry were drawn from the Naval Historical Center SCB-27 information and photos Archived 20 June 2012 at the Wayback Machine Mark 56 Gun Fire Control System Mark 56 Gun Fire Control System ( Mk.56 GFCS )
147-521: The gyroscope of the directional board and the tachometer generator of the distance tracking servo system . Ballistic calculation was performed by the Mk.42 ballistic computer housed in the ship, and it was possible to aim two types of guns at the same target by adding a ballistic calculation housing. During the war, there were many cases where radar tracking could not catch up with the attacking aircraft incoming at high speed. The first model of this model
168-413: The 27C ships as part of SBC-125. The first three 27C ships ( Hancock, Intrepid and Ticonderoga ) had had their No 3 elevators moved from the centerline to the starboard deck edge, in a position relatively far aft. The next three ( Shangri-La, Lexington and Bon Homme Richard ), which underwent 27C and 125 concurrently, had the elevator relocated to a deck-edge position farther forward, and this location
189-631: The SBC-27C carriers were equipped with jet blast deflectors , deck cooling, fuel blending facilities, emergency recovery barrier and storage and handling for nuclear weapons , 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
210-552: 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
231-434: 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. New Mark 56 fire-control systems were also added to the ships. The island was completely redesigned, made taller, but shorter in overall length with
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#1732798093170252-416: 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 rooms 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
273-447: The ships' existing structure compared to SCB-27, and took around six to nine months as against the approximately two years of the earlier program. The original SCB-27A vessels, which were fitted with a pair of H 8 hydraulic catapults , were not upgraded with the C 11 steam catapults fitted to their SCB-27C sister ships due to machinery space limitations. The SBC-27As also did not receive the enlarged No. 1 (forward) elevator installed in
294-616: 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 but one of the SCB-27 modernized Essex carriers, the USS ; Lake Champlain , were further modified under
315-579: Was commissioned in 1946 and 1958. The Type 904 radar tracker was also developed as a derivative of the GWS.22 Seacat air defense missile system . In addition, the Mk.64 GUNAR, which changed the shooting command radar to the gun side equipment (initially the same AN/SPG-34 as the Mk.63 , later AN/SPG-48 ), was also developed, and this was mainly used by the Royal Canadian Navy . This later evolved into
336-507: Was delivered in August 1945, and has been in operation since the 1950s. Performance improvements continued after the war, and it became possible to start shooting in 2 seconds from the start of tracking for subsonic aircraft . Mk.68 GFCS was the standard for the Mark 42 5"/54 cal gun , but this machine was also used as a secondary directional board. Well known electric engineer Ivan A. Getting
357-563: Was increased to 300,000 US gallons (1,135,624 L) (a 50% increase) and its pumping capacity enhanced to 50 US gallons (189.3 L) 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
378-753: Was involved in the creation of AN/SPG-35. The Japan Maritime Self-Defense Force requested the equipment of this model with the Harukaze-class destroyer , which was the first domestic escort ship after the war, but it was not approved by the US side, and the actual equipment was in the Second Defense Build-up Plan. In the United Kingdom , the MRS-3 (Medium Range System) was developed based on this model. The Type 903 radar tracker
399-550: Was referred to as a SCB-125A vessel. These changes also made Oriskany the only SCB-27A vessel to receive steam catapults. Source: www.history.navy.mil Lexington was redesignated CVA upon completion of SCB-27C/125 SCB-27 SCB-27 (also known as "Two Seven-Alpha" or "Two Seven-Charlie") was the United States Navy designation for a series of upgrades to the Essex -class aircraft carriers (both
420-400: Was removed and blisters were fitted to the hull sides to compensate, widening waterline beam by 8 to 10 feet (2.4 to 3.0 m). The ships also sat lower in the water, and maximum speed was slightly reduced, to 31 knots (57 km/h; 36 mph). The two sub-types of SCB-27 modifications were primarily a result of changes in catapult technology in the early-1950s. SCB-27A vessels used
441-400: Was used for the 27A ships as they in turn underwent SCB-125. Oriskany , the prototype for the SCB-27 conversion, was the final Essex to undergo SCB-125 conversion and as such, received further enhancements. As a result of the addition of aluminum flight-deck cladding, Mk 7-1 arresting gear and more-powerful C 11-1 steam catapults to the standard SCB-125 modifications, Oriskany alone
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