47-foot Motor Lifeboat
The 47-foot MLB is the standard lifeboat of the United States Coast Guard. The 47′ MLB is the successor to the 44′ MLB, which were in service from 1963 until 2009.
Design
The 47′ MLB is designed to weather hurricane force winds and heavy seas, capable of surviving winds up to, breaking surf up to and impacts up to three G's. If the boat should capsize, it self-rights in less than ten seconds with all equipment fully functional.The boat's hull and superstructure are constructed entirely from 5456 marine grade aluminum. Designed with a hard chined deep "V" planing hull, the 47′ MLB exceeds its hull speed. The frame is composed of 17 vertical bulkhead frames, each of which is welded to the deck and hull, and five of which are watertight.
For the international version, Textron have modified the design slightly to use Caterpillar C12 diesel engines with Tier I emissions.
Employing "fly-by-wire" control systems, the boat can be operated from four different locations: two from the enclosed bridge, and two amidships from an open bridge. Because of the fly-by-wire system, the boat is controlled by joysticks instead of wheels.
Situated less than above the water line are recessed retrieval wells, allowing for easier recovery of persons and jetsam, and easier boardings. A watertight survivor's compartment is equipped for comprehensive first aid. It is situated at the combined center of rotation of the ship. If needed, a light machine gun can be fitted at the front of the vessel.
Operating history
Textron Marine & Land Systems was awarded the prototype construction contract in 1988 and the first prototype was assigned hull number CG-47200, entering service in 1990, followed by the pre-production boats, which were delivered in 1993 and 1994. After Textron was awarded the production contract in 1995, the first production MLB, CG-47206, was delivered in 1997. By 2003, Textron had delivered 117 47' MLBs to the USCG.Textron also has been awarded international contracts for the 47' MLB from Egypt and Mexico.
At Station Chatham where the 47-foot boat would draw too much to get over the bar, the 42-foot Near Shore Lifeboat was designed to replace the 44' MLB. The 42-foot near shore lifeboat were decommissioned in 2021 and replaced with a pair of 45-foot RB-M craft.
A service life extension program for the 47' MLB will extend their useful life by 20 years to 2047; the first boats to undergo the SLEP were returned in June 2023, and, 107 47' MLBs are planned to complete SLEP by 2030. The SLEP contract, which was awarded to Birdon Group in 2019, is being implemented at its facilities in Bellingham, Washington and Portland, Connecticut.