Avenger (MCM 1)
These 14 relatively large Mine Counter-measures (MCM) ships locate and destroy mines that cannot be countered by conventional minesweeping techniques or minesweeping helicopters. The basic MCM design is similar to previous MSO (Ocean Minesweeper) classes. The long-forecastle hull has a low magnetic signature, being constructed of fiberglass-sheathed wood (laminated oak framing, Douglas fir planking, and deck sheathing with reinforced fiberglass covering). A degaussing system further reduces the signature.
One or two Honeywell AN/SLQ-48 Mine Neutralization System (MNS) vehicles are carried in addition to conventional sweep gear.
The ships are fitted with Magnavox AN/SSN-2(V) Precise Integrated Navigation System (PINS). The MCMs were initially fitted with the AN/SQQ.-30 variable-depth sonar. This equipment was succeeded in later ships by the AN/SQQ-32. Influence mines are swept by the AN/ SLQ-37(V)2 magnetic/acoustic sweep equipment; the mechanical sweep is the Oropesa Type 0 Size 1.
All ships have four very-low-magnetic diesel engines for propulsion; the original engine design had several defects. Electrical power for minesweeping gear is provided by gas turbines.
DEVELOPMENT •
When laid down in 1983, the Avenger-was the first large minesweeper under construction for the US Navy since the Assurance (MSO 521) was completed 25 years earlier; she entered service in 1987. Peterson of Sturgeon Bay, Wisconsin, built all but three of the class; Marinette constructed the Defender, Champion, and Patriot. The program suffered delays (especially due to engine problems) and the last of 14 wasn ‘t due to commission until 1995.
COMBAT EXPERIENCE •
The Avenger cleared traffic lanes near the Kuwaiti coast for combatants during Operations Desert Shield/Desert Storm, especially the battleships Missouri and Wisconsin. After the cease-fire, she and a large international minesweeping flotilla cleared more than 1,200 mines. She was relieved in June 1991 by the Guardian, which remained in the Persian Gulf until February 1992.
SPECIFICATIONS •
DISPLACEMENT 1,312 tons full load
DIMENSIONS
length 224 ft 4 in (68.4 m)
overall beam 39ft (11.9m)
draft 11 ft 6 in (3.5 m)
MACHINERY 4 diesels, Waukesha L-1616 2,600 blip (first 2 ships), Isotta-Fraschini ID36 SSA6V AM 2,720 blip (remaining ships), 2 shafts with controllable-pitch propellers=13.5 kts, (max minehunting speed is 5 kts), low-speed maneuvering by 2 220-hp electric motors turning propellers, 1 350-hp bow thruster, electric power 1,125 kW
CREW 72 SENSORS
SPS-55 surface-search radar
SQQ-30 mine-detecting sonar in first 9
SQQ-32 mine-detecting sonar in last 5
Osprey (MHC 51)
These 12 coastal minehunters are based on the Italian-designed Lena-class coastal minehunter design. After the expensive failure of the Cardinal (MSH 1) surface-effect minehunter in the mid-1980s, these ships were procured virtually as a Non-developmental Item (NDI) to shore up the Navy’s weak mine warfare capability.
Ospreys have a Glass-Reinforced Plastic (GRP) monohull single-skin structure and operate the remotely operated underwater vehicle known as the AN/ SLQ-48 Mine Neutralizing System (MNS). Mechanical and influence min-esweeping systems are being developed independently. The ships are capable of coastal mine clearance operations of up to five days without replenishment. In the translation of the Italian design to US requirements, full-load displacement climbed to almost 900 tons.
DEVELOPMENT •
The contract for adapting the Lerici design was awarded in August 1986 to Interrnarine USA (established by Interrnarine Sarzana of Italy, builders of the original Lerici design), which was chosen in May 1987 to construct the lead ship of this class. The first ship was laid down in May 1988 and was scheduled for delivery in April 1991. Almost immediately (and inevitably) delays crept into the schedule and none of the original target dates was met. Inter-marine contracted for eight of the 12 craft, and Avondale of Westwego, Louisiana, received contracts for the other four.
SPECIFICATIONS •
DISPLACEMENT 895 tons full load
DIMENSIONS
length 187 ft 10 in (57.25 m)
overall
beam 35 ft 11 in (10.95m)
draft 9 ft 6 in (2.9 m)
MACHINERY 2 Isotta-Fraschini ID 36 SS 6V-AM diesels, 1,160 bhp driving 2 Voith-Schneider vertical cycloidal propellers = 12 kts, range 2,500 nm at 12 kts (2 180-bhp hydraulic motors for minehunting, 1 180-hp bow thruster), electric power 600 kW
CREW 51 WEAPONS
1 30-mm or 40-rnm gun
SENSORS
SPS-64(V)9 surface-search radar SQQ-32 mine-detection sonar SLQ-48 (V) MNS
