February 8, 2012: The U.S. Navy has upgraded the sonars on its Avenger class mine hunter ships. The new AN/SQQ-32(V)4 mine hunting sonar improves the ability of the sonar to spot mines on sea bottoms cluttered with other stuff (natural or manmade). In many parts of the world shallow coastal waters are used as a dumping ground for junk that won’t float ashore. This has been found to help hide bottom mines.
The upgrade is also part of an attempt to deal with delays in the new LCS class ships or at least the ones equipped for mine hunting. So for the last six years the navy has been hustling to refurbish its existing Avenger class minesweepers. The Avengers got new engines, new sonars, improved hydraulics, and new mine destruction systems.
The 3,000 ton LCS ships are designed for minesweeping (and a lot of other jobs) but the 1,400 ton Avengers specialize in minesweeping. Built mostly of wood and very little iron the fourteen Avengers entered the fleet between 1987 and 1994 and all are still in service. The upgrades will enable the Avengers to remain in service at least until 2016 and probably until the end of the decade.
These 72.3 meter (224 foot) long ships draw only 4.8 meters (15 feet) of water, enabling them to operate close to shore. They are armed with two .50 cal. (12.7mm) machine guns, two 7.62mm machine guns, two 40mm grenade launchers, and have a crew of 84. The four original diesel engines in each Avenger have never been very reliable. With the new engines the Avengers can still move at up to 27 kilometers an hour. Normally, however, the Avengers move much more slowly (3-4 kilometers an hour) when searching for mines.
Four Avengers operate out of Bahrain, in the Persian Gulf, and four out of Sasebo, Japan. The rest are based at San Diego, California. Five years ago, most of the Avengers were based at Ingleside, Texas. The Texas Congressional delegation thought they had scored a coup when they forced the navy to base its mine hunting ships at this Texas base. But this was the last place the navy wanted it's mine hunting ships. That's because the most likely places mine hunters would be needed in wartime are at the major ports on the east and west coasts, not in the Gulf of Mexico. But the Texas Congressional delegation made keeping the minesweepers, (and all the local jobs and business for Texas firms) right where it is, a major issue. Eventually, however, logic and military necessity prevailed and all the Avengers were shifted to Pacific and Persian Gulf bases.
The navy also had a dozen smaller Osprey class coastal mine hunters (900 tons displacement, crew of 51), but these were all given away to foreign navies and replaced by the LCS (which has been delayed) and new minesweeping helicopters (which are on schedule).