US Navy's first San Antonio Flight II amphibious warship USS Harrisburg completes sea trials with over 200 design changes.

HII’s Ingalls Shipbuilding completed builder’s sea trials for the future USS Harrisburg (LPD 30) in the Gulf of Mexico on October 31, 2026, testing propulsion, steering, communications, and combat systems. As the lead vessel of the San Antonio-class Flight II variant, the 25,300-tonne amphibious transport dock incorporates over 200 modifications, including the AN/SPY-6(V)2 radar, LCAC-100 compatibility, and CH-53K support, to replace legacy Whidbey Island and Harpers Ferry-class dock landing ships. The milestone advances LPD 30 toward Navy acceptance trials ahead of target delivery.

HII’s Ingalls Shipbuilding successfully completed builder's sea trials for the future USS Harrisburg (LPD 30) off the Mississippi coast, marking the initial operational sea test for the U.S. Navy's San Antonio-class Flight II amphibious transport dock program. (Picture source: HII)

Key tactical insights

• Trial Scope: Multi-day sea testing evaluated propulsion, steering, communications, mission systems, and combat system integration prior to returning to the shipyard in Pascagoula.

• Design Modifications: The Flight II standard incorporates over 200 modifications compared to Flight I hulls, including the Raytheon AN/SPY-6(V)2 Enterprise Air Surveillance Radar (EASR), conventional steel masts, and compatibility with LCAC-100 Ship-to-Shore Connectors and CH-53K heavy-lift helicopters.

• Capacity & Specifications: The 25,300-tonne vessel measures 208.5 meters in length and accommodates 631 embarked Marines alongside a primary crew of 383.

• Program Status: Harrisburg now prepares for official U.S. Navy acceptance trials ahead of targeted delivery by late 2026 and planned commissioning in 2027. Flight II ships are built to replace aging Whidbey Island and Harpers Ferry-class dock landing ships.

On October 31, 2026, HII's Ingalls Shipbuilding completed the builder's sea trials of the USS Harrisburg (LPD 30), the first San Antonio-class Flight II amphibious transport dock of the US Navy, following multi-day testing of propulsion, steering, ship control equipment, communications, mission systems, and combat system integration. Announced on November 3, the milestone advances the 14th San Antonio-class vessel toward acceptance trials and anticipated delivery before the end of 2026, with commissioning projected for summer 2027. The Flight II also incorporates more than 200 modifications compared with the lead ship of the class, the USS San Antonio (LPD-17). These include the AN/SPY-6(V)2 radar, conventional steel mast, updated electronic warfare equipment, common-rail diesel injection, and compatibility with CH-53K helicopters and LCAC-100 landing craft.

Nevertheless, the 25,300-tonne ship retains the original class's hull dimensions, propulsion output, and two-LCAC well deck, but reduces accommodation from 699 to 631 Marines. Developed to replace Whidbey Island-class and Harpers Ferry-class dock landing ships, the Flight II standard now combines the functions of these LSDs with the larger aviation, personnel, and vehicle facilities of the San Antonio design. The USS Harrisburg (LPD 30) was ordered on March 26, 2019, under a $1.47 billion fixed-price incentive contract, following a $165.5 million long-lead materials award in August 2018. Its keel was authenticated on January 28, 2022, launching followed on October 5, 2024, and christening took place on January 11, 2025, producing a 57-month keel-to-builder's-trials interval, including 25 months after launching.

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HII also confirmed that the vessel had returned to its Pascagoula shipyard in Mississippi after meeting the principal trial objectives. The ship measures 208.5 m in length, 32 m in beam, 7 m in full-load draft, and displaces 24,900 long tons (25,300 metric tonnes). Four sequentially turbocharged Colt-Pielstick diesel engines produce 41,600 shp (31 MW) through two shafts, enabling speeds exceeding 22 knots. Electronically controlled common-rail injection, first delivered aboard the transitional Flight I USS Richard M. McCool Jr. (LPD 29), replaces mechanical fuel metering to improve combustion control, fuel efficiency, emissions, and maintenance without changing installed propulsion power. The planned complement now comprises 383 sailors, three Marines assigned to the ship's company, and accommodation for 631 embarked Marines, giving a total of 1,017 personnel.

However, the USS Harrisburg, like many new vessels of the U.S. Navy, was already 15 months behind its earlier schedule in September 2024, which illustrates the amount of outfitting, equipment integration, harbor testing, and correction work needed on a modern warship like the San Antonio-class. The original San Antonio design consolidated several amphibious capabilities previously distributed among Austin-class LPDs, including the Cleveland and Trenton sub-classes, Newport-class LSTs, Anchorage-class LSDs, and Charleston-class LKAs. Compared with the Austin-class, San Antonio ships increased length from 173 to 208.5 m (+20.5%) and full-load displacement from 16,900 to 25,300 tonnes (+49.7%), while providing roughly twice the vehicle stowage area despite reducing troop capacity from roughly 900 to 699 Marines.

Newport-class LSTs, measuring 159 m and displacing 8,450 tonnes, could discharge vehicles directly onto beaches through a 34 m bow ramp; the San Antonio-class instead transfers them through LCACs or LCUs, allowing the ship to remain offshore but making delivery dependent on connector availability and turnaround times. Anchorage-class LSDs, measuring 169 m and displacing 14,000 tonnes, accommodated three LCACs after modernization, compared with San Antonio's two, but lacked equivalent permanent aviation maintenance and troop facilities. Charleston-class LKAs, measuring 176 m and displacing 18,500 tonnes, relied on cargo holds, cranes, and landing craft, whereas the San Antonio integrated vehicle decks, a floodable well deck, aviation facilities, and internal cargo movement.

The newer class also introduced RAM missiles, 30 mm guns, the Ship Self-Defense System, improved shock protection, reduced-radar-signature structures, and integrated command networks. Consolidation therefore increased the range of transport functions available within one hull but sacrificed direct beach access, one LCAC position compared with Anchorage, and specialized cargo-handling capacity. The Flight II redesign originated in the LX(R) program, which selected a derivative of the San Antonio hull to replace the Whidbey Island-class LSDs, capable of carrying four legacy LCACs, and the Harpers Ferry-class LSDs, which exchanged two LCAC positions for additional cargo storage. Flight II consequently retains two LCAC positions but combines them with the San Antonio-class's permanent aviation hangar, larger troop accommodation, and integrated vehicle facilities.

Among the Flight II's approximately 200 modifications, the original Advanced Enclosed Mast/Sensor structures, whose composite enclosures reached 28.3 m in height and 10.7 m in diameter, are replaced by conventional steel masts, reducing specialized composite manufacturing and antenna maintenance requirements, but at the cost of some passive radar-signature reduction and environmental protection. This change began with the transitional Flight I USS Fort Lauderdale (LPD 28), while the USS Richard M. McCool Jr. introduced the AN/SPY-6(V)2 radar and common-rail fuel injection. Revised electrical distribution also supports newer sensors and electronics. Moreover, early LX(R) proposals considered reducing troop capacity to 500, eliminating the hangar, replacing the 30 mm guns with 25 mm weapons, and reducing medical facilities; the final design instead retains 631 Marine berths, the hangar, and two Mk 46 30 mm mounts.

Nevertheless, the USS Harrisburg's principal sensor upgrade is the AN/SPY-6(V)2 Enterprise Air Surveillance Radar (EASR), a rotating S-band AESA manufactured by Raytheon, that uses nine radar modular assemblies, each containing 144 transmit-and-receive modules, for a total of 1,296. Unlike the four fixed 37-assembly faces of the AN/SPY-6(V)1 aboard Flight III Arleigh Burke-class destroyers, the EASR uses one rotating face for 360-degree air surveillance. The retained X-band AN/SPQ-9B radar complements it by tracking small surface contacts and low-altitude threats, while the modernized AN/SLQ-32(V)6 SEWIP system supports electronic surveillance and threat classification. Defensive weapons now comprise two 21-cell Mk 49 launchers carrying up to 42 RAM Block 2 missiles and two Mk 46 Mod 2 mounts armed with 30 mm Mk 44 Bushmaster II cannons. The RAM Block 2 improves propulsion, guidance, and maneuverability against anti-ship missiles, while the guns provide close-range defense against small craft.

Without a standard Mk 41 vertical launching system or Standard Missiles, the USS Harrisburg logically remains dependent on escorting combatants for area air defense, particularly against simultaneous missile attacks exceeding its point-defense engagement capacity. The Flight II San Antonio-class accommodates 631 embarked Marines, compared with 699 on original Flight I ships and 650 on LPD 28 and LPD 29, which represents reductions of 9.7% and 2.9%, respectively. Its floodable well deck retains enough capacity for two LCACs or one LCU, while vehicle spaces accommodate up to 14 amphibious assault vehicles. The Flight II also incorporates well-deck and control-system modifications for the LCAC-100 Ship-to-Shore Connector, which increases rated payload per craft from 60 to 74 short tons (54.4 to 67.1 tonnes), a 23.3% improvement, giving two connectors a combined nominal payload of 148 short tons per loaded movement.

However, this does not increase the number of simultaneous landing craft departures, and actual delivery rates remain dependent on loading time, transit distance, sea conditions, and connector availability. The flight deck supports simultaneous operation of two MV-22 Ospreys, while the retained hangar provides aircraft maintenance and storage facilities. Several changes to aviation facilities and supporting equipment allow the Flight II to be compatible with the CH-53K King Stallion, the Marine Corps' newer heavy-lift helicopter designed to carry up to 27,000 lb (12,247 kg) externally over a 110-nautical-mile mission radius in hot-and-high conditions. These changes preserve the ship's surface and vertical transport functions while reducing its troop accommodation, shifting the balance toward equipment movement rather than increasing the size of the embarked landing force.

The USS Harrisburg also incorporates the U.S. Navy’s primary tactical network program of record, called the Consolidated Afloat Networks and Enterprise Services (CANES), first introduced into the class aboard LPD 28. This system replaces multiple separate computing environments with a single, secure, virtualized, standardized shipboard network for communications, information processing, cybersecurity, and software maintenance. For instance, the CANES replaces or merges older systems like ISNS, SCI Net, CENTRIXS-M, GCCS-M, and NTCSS across surface ships (such as aircraft carriers and destroyers) and submarines, while the Ship Self-Defense System coordinates sensor information and defensive engagements. The Flight II acquisition configuration also includes the Cooperative Engagement Capability (CEC), although the USS Harrisburg's specific installation and performance were not detailed during builder's trials.

Furthermore, the CANES facilitates information exchange between dispersed amphibious ships and Marine units. Flight II consequently reflects reduced requirements for extensive amphibious headquarters facilities compared with the original LPD design, because its primary mission is replacing LSDs rather than duplicating every command function of larger amphibious assault ships. Aegis and Mk 41 vertical-launch options were also examined separately and are not standard Flight II equipment. Ingalls delivered 13 San Antonio-class vessels between May 13, 2005, and April 11, 2024, and is constructing the USS Harrisburg, USS Pittsburgh (LPD 31), and USS Philadelphia (LPD 32), whose keels were laid on January 28, 2022, June 2, 2023, and March 3, 2026, respectively.

On September 24, 2024, the U.S. Navy also awarded $5.79 billion for USS Travis Manion (LPD 33) through LPD 35, averaging $1.93 billion per ship, alongside $3.8 billion for the USS Helmand Province (LHA 10). The combined $9.6 billion contract package was calculated to save $901 million, or 8.6%, compared with separate acquisitions, including government-furnished equipment; its total value reaches $11.5 billion. Eastern Shipbuilding Group is manufacturing six structural modules for the USS Philadelphia, scheduled for delivery during the second half of 2027, transferring selected fabrication work beyond Pascagoula while Ingalls retains final assembly.

This arrangement increases parallel production opportunities but introduces several dependencies involving module tolerances, transport, and integration schedules. Harrisburg's previously identified 15-month delay illustrates the continuing effects of workforce shortages, limited shipyard capacity, and overlapping construction programs. With six Flight II ships contracted, the principal industrial challenge is therefore to convert procurement commitments into deliveries quickly enough to replace retiring LSDs without further reducing the amphibious fleet's capacity.

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Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, South Korea, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.