For over a year, the US Navy and its shipbuilders have been anxious to get the new aircraft carrier Gerald R. Ford (CVN 78) to sea and begin engineering trials of the first-of-class design. A number of publicly-announced target dates have come and gone, but the ship is still firmly moored at Newport News Shipbuilding in Virginia.
Now, however, a key factor in preventing the ship from casting off lines and getting underway is coming into view. A serious voltage regulator problem on the carrier’s four main turbine generators (MTGs) has prevented engineers from running the motors up to full power, and only now has the problem been identified and a fix decided upon.
The MTGs are a significant element in the ship’s power generation system – an all-new layout supporting a plant developing at least three times the electrical power of previous carriers.
The problem manifested itself June 12 when a small electrical explosion took place on the No. 2 MTG during testing. Navy sources disagree whether the term “explosion” is appropriate, but two sources familiar with the situation used the reference, one noting that “it was enough of an explosion that debris got into the turbine.” Smoke from the event reportedly was drawn into other spaces, one source reported.
According to Capt. Thurraya Kent, spokesperson for the Navy’s acquisition directorate, “personnel detected a burning smell.” There was no fire, Kent insisted, and “no fire-extinguishing actions were taken.” No one was injured and there was no evacuation of personnel, she added.
In a statement responding to a Defense News query, Naval Sea Systems Command (NAVSEA) said the issues “were not associated with the nuclear reactor plant and had no impact on safe operation of the nuclear reactor.”
On the record, NAVSEA declined to provide further details, other than to acknowledge that two MTG issues have been experienced.
But, according to sources, the June 12 event severely damaged the No. 2 MTG, and the accident slowed further MTG testing until the problem could be identified. Then in July, a similar, less-dramatic event took place on the No. 1 MTG, according to a Pentagon source.
Eventually the root cause was found to be faulty voltage regulators, the Pentagon source said. It is not clear if the voltage regulators are part of the generators, which are made by Northrop Grumman Marine Systems, or are a sub-component from another supplier.
Engineers were also debating how to repair the generators, and for a time it was feared the entire 12-ton No. 2 MTG would have to be lifted out and replaced – a complex, time-consuming and expensive operation that would involve disrupting numerous ship systems and making major cuts in several decks.
But subsequent investigation showed the No. 2 MTG’s rotors could be removed and replaced without the major disruption of a complete replacement, and No. 1 MTG could be repaired in place. Several repair options were developed, including whether or not to completely repair the MTGs before sea trials and delivery – causing further delays -- or wait until a post-commissioning shipyard period to finish the work.
On Sept. 14, the Pentagon source confirmed, Navy officials decided on a partial fix now and a permanent fix later. The No. 2 MTG rotors will be removed while repairs are made to No. 1, and full repairs to No. 2 will wait for the post-shakedown availability (PSA) overhaul sometime after the ship is commissioned.
Repairs are estimated to cost about $37 million, the Pentagon official said, and while delivery is likely delayed until about March 2017, Navy officials said enough cost offsets have been identified that the work can be completed under congressionally-imposed cost caps – currently set at $12.9 billion.
Even with the delivery delays, officials said, the planned initial deployment in 2021 is not affected, nor are full-scale shock trials now scheduled for 2019. The Pentagon source noted that if the shock trials are put off until subsequent ships – as was done with the previous carrier class – the first deployment could come sooner.
Navy Secretary Ray Mabus, in an Aug. 31 memo on the carrier’s technical issues to Pentagon acquisition chief Frank Kendall, reported the MTG issue was “likely due to a manufacturing defect,” and that “analysis of this issue revealed design vulnerabilities that must be addressed prior to ship’s delivery.”
Mabus noted that “the nation’s leading experts on shipboard power generation systems are working resolution of these issues with a priority on safe, reliable system performance while balancing cost and schedule considerations.”
In the Aug. 31 memo, a copy of which was obtained by Defense News, Mabus also ticked off the status of several other issues highlighted by Kendall in an Aug. 23 memo directing a new, 60-day independent review team to look at issues with the CVN 78 class. The power generation issue was included in the memo, but none of the other issues seem to directly prevent the ship from getting under way to conduct hull, maintenance and engineering trials.
The Electromagnetic Aircraft Launching System (EMALS), Mabus reported, “has completed all shipboard testing pending the commencement of shipboard aircraft operations” during extensive post-delivery testing and trials, adding that “the Navy is confident that EMALS is on track to support CVN 78 system performance requirements and we look forward to demonstrating continued reliability growth of this system.”
The ship’s Advanced Arresting Gear (AAG) is more problematic, and “has had significant delays in completing its land-based test program due to the technical challenges encountered in transitioning from design” through final testing, Mabus reported. Other Navy sources report dozens of roll-through tests have been conducted with the AAG at the Navy’s test facility in Lakehurst, New Jersey, but to date no true arrested landings have been accomplished.
Mabus noted that the Navy is reviewing whether to continue with AAG installation on the Enterprise (CVN 80), third ship in the class, or return to the standard Mark 7 aircraft recovery system operating on all current carriers. Installation of AAG on the second ship, John F. Kennedy (CVN 79), is continuing for now, Mabus noted, because design and construction work has progressed to the point where a replacement would have a significantly negative impact on costs and schedule.
The Ford’s dual band radar (DBR) installation is still completing its shipboard test program, Mabus reported, but full system testing won’t be carried out until the ship’s power system is lit off in conjunction with the shipboard test program. “We are confident in our ability to successfully demonstrate the functionality required for successful sea trials and, subsequently, for operation testing in post-delivery,” Mabus wrote.
Testing of the ship’s 11 advanced weapons elevators continues, Mabus said, acknowledging that “these new-design weapons elevators have experienced delays in late-stage integrated shipboard testing mainly due to correction of software discrepancies.”
While indicating he doesn’t expect all 11 elevators to be properly operating at the time of sea trials, Mabus declared that “the Navy is confident we will get through these first-of-class issues and ensure that lessons learned on CVN 78 are directly applied to CVN 79.”
