USS Able (T-AGOS-20) Swath-S (Small) Ocean Surveillance Ship

Victorious class ocean surveillance ships are built on a Small Waterplane Twin Hull, or SWATH, design for greater stability at slow speeds in high latitudes under adverse weather conditions. The SWATH design provides greater stability at slow speeds in high latitudes under adverse weather conditions.

When operating with tactical forces, military detachments are embarked for onboard analysis and direct reporting to fleet units. A SURTASS mission consists of 60 days on station while towing an array of hydrophones that collect acoustic data.

When operating independently as in a deep ocean surveillance mission, acoustic data is transmitted to shore via satellite for analysis and reporting.

The Small Waterplane Twin Hull (SWATH) T-AGOS is the second generation class of T-AGOS ships. There are currently four ships in this class. The key feature of the SWATH design is the pair of large submerged hulls. These provide good stability and sea-keeping capability, a more stable tow point, and a more hospitable platform for extended missions.

Comparisons of characteristics show the first SWATHs of the T-AGOS 19 class to be slightly longer than the monohulls, but with much larger effective beams. The "box" atop the hull struts has a breadth of 80 ft compared to a beam of 43 ft for the monohulls. Displacement is greater but transit speed (sustained speed) at 9.6 knots is comparable to the monohulls (11 kts). The draft at 24 ft 9 inches is considerably deeper than the monohulls.

Other features of the SWATH include a "stinger" projection from the fantail for a towpoint, and the location of the aft winch/ship control station. The winch house is mounted over the water, aft of the backdeck work area. This location as well as the towpoint stinger are required because of the position of the twin propellers at the ends of the submerged hulls and well aft of the fantail. This arrangement requires a great deal of care in deployment and retrieval to avoid fouling of the propellers and damage to the array or tow cable.

T-AGOS 20 has conducted trials with a Reduced Diameter Array (RDA) with an enhanced signal processor. The Low Frequency Active component is producing both mono and bistatic performance against submerged diesel submarines in shallow water. Short thin-line twin arrays are also being developed.