CVN-68 Nimitz-class Modernization
Aircraft carriers are generally estimated to have useful operating lives of 50 years. The Navy plans 33-month nuclear refueling Refueling Complex Overhauls [RCOH] for its Nimitz-class carriers beginning with the USS Nimitz in fiscal year 1998. Other Nimitz-class carriers will follow so that a carrier will be in a shipyard undergoing a nuclear refueling overhaul for about the next 30 years, with the exception of about 4 years during this period.
On 01 May 1998 Newport News Shipbuilding was awarded a contract by the US Navy to perform refueling and overhaul work on the USS Nimitz (CVN 68). The contract, valued at approximately $1.2 billion, was signed by Navy and Newport News Shipbuilding officials on April 30, 1998. Nimitz, the lead ship of the class, was also the first of its class to undergo this major life-cycle milestone. The ship arrived in late May 1998 and the work performance period was scheduled to last approximately 33 months. In addition to the refueling of both of the ship's reactors, significant modernization work included a major upgrade of the island house that involved the shipyard removing the top two levels of the island house and replacing them. This action was driven by the installation of a new antenna mast that runs down along the island and will provide for better radar capabilities. The shipyard also integrated a new radar tower aboard Nimitz. The Navy elected to overhaul the Nimitz without adding cooperative engagement, integrated ship self defense, the advanced combat direction system, the rolling airframe missile, the AN/SPQ-9 navigation radar, a common high-band data link, the battlegroup passive horizon extension system, an outboard weapons elevator, conversion of nuclear magazines, emergency ordnance handling, and improved propellers. More than 3,200 Newport News Shipbuilding employees worked aboard Nimitz during peak periods of the overhaul and refueling project.
The second overhaul was scheduled for fiscal year 2001, and the third was initially projected to begin about fiscal year 2005. The overhaul of the Dwight D. Eisenhower (CVN 69), scheduled for 2000, was the ship's first and only refueling during a service-life expected to span approximately 50 years. On 12 February 1999 Newport News Shipbuilding was awarded a $169,790,050 modification to previously awarded contract for the FY 99 advance planning of the refueling and complex overhaul of Eisenhower and her reactor plants. Eisenhower arrived at Newport News in late 2000 and remained for approximately three years.
Newport News redelivered the nuclear-powered aircraft carrier USS Dwight D. Eisenhower (CVN 69) to the U.S. Navy on 25 March 2005 after completing its one and only refueling and complex overhaul (RCOH) in a 50-year life span. The ship was redelivered after four days of sea trials, an aggressive series of operational tests to demonstrate that Eisenhower's two nuclear propulsion plants are fully mission capable. Eisenhower is the second ship of the Nimitz class to undergo the major life-cycle milestone. The work took more than three years to complete and included the refueling of both of the ship's reactors as well as extensive modernization work to more than 2,300 compartments, including the ship's mess decks and medical, dental, laundry and berthing spaces. Maintenance and repair work was performed below the ship's waterline and included the application of new paint. In addition, nearly 3,000 valves were replaced and another 600 were overhauled in various ship systems. Major upgrades were made to the flight deck, catapults, combat systems and the island. The top two levels of the island were removed and replaced to install a new antenna mast which provides better radar capabilities. Newport News also installed a new radar tower aboard the ship.
USS Carl Vinson began RCOH in November of 2005. May of 2006 marked six months since the aircraft carrier USS Carl Vinson (CVN 70) moved from pier 14 of Naval Station Norfolk to dry dock 11 of Northrop Grumman Newport News (NGNN) shipyard to begin its refueling complex overhaul (RCOH). The RCOH is an extensive yard period that all Nimitz-class aircraft carriers go through approximately halfway through their 50-year life cycle. During RCOH, Carl Vinson's nuclear fuel is being replenished and the ship's services and infrastructure are being upgraded to make her the most state-of-the-art aircraft carrier in service and prepare her for another 25 years or more of service. With nearly one-third of the dry docking portion of the RCOH complete, the "Gold Eagle," in partnership with NGNN, is well on her way to adding that 25 years or more of service to Carl Vinson.
Carrier upgrades and modifications continue to increase the operational effectiveness, technical efficiency, and maintainability of our carrier force. In the area of command and control, USS Dwight D. Eisenhower (CVN 69) received the CEC system in conjunction with the Advanced Combat Direction System Block 1. Permanent Extremely High Frequency (EHF), Super High Frequency (SHF) including Commercial "C" Band Challenge Athena III, and upgraded Ultra High Frequency (UHF) satellite communication suites provide vastly improved access to information databases worldwide. Link 16/JTIDS, being installed in all carriers, provides a new dimension in tactical information exchange. Numerous processing and display system upgrades will ensure that joint planners, decision makers, and warfighters in carriers have near real time access to the latest data available.
Radar upgrades continue to increase the reliability of current systems and improve their maintainability and performance in littoral operating areas. Plans were in place to upgrade the aircraft carrier's self-defense weapons mix. AN/SPS-48E radars were installed on USS Abraham Lincoln (CVN 72) and USS George Washington (CVN 73). The AN/SPQ-9B horizon search radar replaced the initially installed Target Acquisition System. The Evolved Sea Sparrow Missile was the successor to the RIM-7P Sea Sparrow ship self-defense missile system.
In 1994, the self-defense configuration for Nimitz class carriers included the SPS-49 two-dimensional radar, the SPS-48E three-dimensional radar, MK-23 target acquisition system, and the SLQ-32 electronic warfare system. The SWY-1 integrator performed the control function by interfacing the MK-23 target acquisition radar with the NATO Sea Sparrow Surface Missile. Engagement systems consisted of the NATO Sea Sparrow Surface Missile and the Phalanx Block 1.
Since 1994, ship self-defense capability improvements have consisted of the installation of Advanced Combat Direction System (ACDS). This system integrates with the SWY-1 in performing the control function. In 1998, the Navy had assessed the ship self-defense capability of this class as being low against the near-, mid-, and far-term threat requirements. The Navy's representation of the ship self-defense capability is based on the assumption that the ships in the class had been equipped with the ACDS Block 1. As of September 30, 1999, only one of the eight ships had ACDS Block 1, six ships had Block 0, and one ship was being overhauled. When the overhaul of this ship is complete, it will have both SSDS MK II and ACDS Block 1.
According to its 1999 plans, the Navy expected to upgrade the detect systems to include the SPQ-9B and the Cooperative Engagement Capability, the control system to include the SSDS MK II, and the weapon systems to include the RAM Block 1 and the Rearchitectured NATO Sea Sparrow Surface Missile System. By adding these systems, the Navy believed that the ship self-defense capability of these carriers will be moderate to high in meeting the near- and mid-term threat requirements and low to moderate in meeting the far-term threat requirement.
In the area of aircraft launch and recovery systems, the Improved Carrier Optical Landing System, which includes the Improved Fresnel Lens Optical Landing System and the Long-Range Line-up System provide optical displays so that the pilot can make early corrective actions to prevent landing accidents and improve aircraft boarding rates.
Other upgrades of carrier systems are more prosaic, but are also critical to the performance of carriers and their crews. For instance, during a recent complex overhaul, Eisenhower received an additional air conditioning plant as well as upgrades to the chilled water distributive system. These same modifications have also been performed in Lincoln, and for USS Carl Vinson (CVN 70) and USS Enterprise (CVN 65) during their availabilities.
Aircraft carriers are also being modified to make them more environmentally "friendly." As part of the Navy's Pollution Control Program, R12 refrigerant conversions began in FY 1996 on Lincoln; this upgrade will be incorporated on all carriers by the year 2000. R114 refrigerant conversions will take place from FY 2000 through FY 2005. Planning is also underway for the installation of oily water separators and plastic waste processors in all carriers.
USS George Washington (CVN 73) (GW) Sailors completed a key milestone 21 June 2007 during its Planned Incremental Availability plus Docking [PIA+D] at Norfolk Naval Shipyard (NNSY) when contractors returned ownership of the ship's main mast to the crew. Replacing the mast fulfilled a major objective in the maintenance schedule for the Nimitz-class carrier, keeping the crew on schedule to complete the availability in Summer 2007. The former mast was removed 10 November 2006. The new mast, which stands 15 feet taller, was installed Jan. 13, 2007 after contractors completed continuity checks and cable banding, along with painting and closing all access covers leading to the interior of the mast. The new mast features a variety of upgrades. One of the major upgrades with the installation of the new mast, all cables and cooling system pipes are housed inside the mast itself rather than mounted to the outside. This will reduce wear and tear from environmental elements and increase the reliability of the equipment. Another new upgrade for the ship is the new SAF-T-LOK system, which will make aloft evolutions far safer and will make equipment more accessible to Sailors performing maintenance to systems on the main mast. GW was undergoing a $300 million shipyard availability at NNSY as she prepared to relieve USS Kitty Hawk (CV 63) as the Navy's forward-deployed aircraft carrier in Japan in 2008.
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