47-foot Motor Lifeboat

A USCG MLB in the surf zone off the coast of Morro Bay
Class overview
Name47′ MLB
BuildersTextron Marine
Operators United States Coast Guard,Maritime Search and Rescue (Mexico)
Preceded by44-foot motor lifeboat
Cost$1,214,300[1]
In service1997–present
Plannedc. 227[2]
Completed227[2]
Active227
General characteristics
Displacement18 t (20 short tons)[3]
Length14.6 m (47 ft 11 in)[3]
Beam4.27 m (14 ft 0 in)[3]
Draft1.37 m (4 ft 6 in)[3]
Propulsion
  • 2 × Detroit Diesel 6V92TA DDEC-IV engines, 435 hp (324 kW) each[3]
  • 1,500 liter (373 usable imperial gallons) fuel capacity [3]
Speed
  • 25 knots (29 mph; 46 km/h) maximum
  • 22 knots (25 mph; 41 km/h) cruising[3]
Range200 nmi (370 km) cruising[3]
Complement34 persons, 4 crew, 30 passengers[3][4]
Armament1 × M240B machine gun (optional)[4]
An MLB ready for deployment at Motor Lifeboat Station Morro Bay, California

The 47-foot MLB is the standard lifeboat of the United States Coast Guard (USCG). The 47′ MLB is the successor to the 44′ MLB.[5]

At Station Chatham where the new 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. [6] (Note that the 42-foot near shore lifeboat were decommissioned in 2021 and replaced with a pair of 45-foot RB-M craft[7])

The 47′ MLB is designed to weather hurricane force winds and heavy seas, capable of surviving winds up to 60 knots (110 km/h), breaking surf up to 6 m (20 ft) and impacts up to three G's.[3] If the boat should capsize, it self-rights in less than ten seconds with all equipment fully functional.[3]

The boat's hull and superstructure are constructed entirely from 5456 marine grade aluminum.[3] Designed with a hard chined deep "V" planing hull,[8] 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.[8]

Employing "fly-by-wire" control systems,[9] the boat can be operated from four different locations: two from the enclosed bridge, and two amidships from an open bridge.[3] Because of the fly-by-wire system, the boat is controlled by joysticks instead of wheels.

Situated less than 1 ft (30 cm) above the water line are recessed retrieval wells,[9] allowing for easier recovery of persons and jetsam, and easier boardings.[3] A watertight survivor's compartment is equipped for comprehensive first aid.[9] It is situated at the combined center of rotation of the ship.[9] If needed, a light machine gun can be fitted at the front of the vessel.

  1. ^ 47-foot Motor Lifeboat (MLB)
  2. ^ a b USCG: About Us – Aircraft & Cutters
  3. ^ a b c d e f g h i j k l m n USCG: International Affairs: FMS Archived 2011-12-30 at the Wayback Machine
  4. ^ a b COMDTINST M16114.25B 47FT MOTOR LIFEBOAT OPERATOR'S HANDBOOK
  5. ^ Coast Guard bids adieu to 44-foot boat – Local News Updates – The Boston Globe
  6. ^ COAST GUARD COMPASS OFFICIAL BLOG OF THE U.S. COAST GUARD
  7. ^ Fraser, Doug. "Chatham rescue boats to be retired — replacement vessels are not rated for breaking surf". Cape Cod Times. Retrieved 2024-10-30.
  8. ^ a b Operational Logistics Support Plan (OLSP) for the 47′ Motor Lifeboat (MLB)
  9. ^ a b c d Textron Marine MLB datasheet[permanent dead link]