Question 39 LB01 - Lifeboat Operator

The Correct Answer is C ### Explanation for Option C (Gravity davits) **Gravity davits** are the most common type of davit found on modern ships, especially for launching enclosed lifeboats. They rely on gravity for the initial outboard movement of the lifeboat. Because of their sophisticated mechanical and often hydraulic systems, and the need to control the speed and travel limits of the launching mechanism (especially the falls and the movement of the davit arms), they require **limit switches** for the following critical safety functions: 1. **Upper Limit Stop:** To automatically stop the winch when the lifeboat is fully hoisted and stowed in the "chocks-in" position, preventing the lifeboat from being pulled too far and damaging the davit structure or the falls (over-hoisting). 2. **Lower Limit Stop (Anti-two-block):** To ensure that the hook assembly or block cannot be pulled up so high that it jams into the davit arm sheaves, which is a dangerous condition (often called 'two-blocking'). ### Why the Other Options are Incorrect **A) Quadrantal davits:** Quadrantal davits (a type of pivot/slewing davit, often with a luffing action) are older designs. While they use mechanical winches, their outboard movement (slewing) is usually controlled by manually releasing a locking pin and rotating the structure. The focus is on mechanical locks and brakes, not the sophisticated electrical controls and automatic limit switches required for the free-fall nature of modern gravity systems. **B) Sheath-screw davits:** Sheath-screw davits (often referred to as mechanical luffing davits) use a screw mechanism to turn a luffing arm, moving the lifeboat outboard. While the winch itself will have controls, the movement of the davit arm relies on the physical limits of the screw mechanism or manual stops, not typically on electrical limit switches controlling the *stowing* limits of the falls or the *launching* path itself in the same way modern gravity systems do. They are an older, less automated design. **D) Radial davits:** Radial davits (or "pivot davits") are the oldest and simplest type. They consist of fixed or pivotable arms that are swung out manually or by simple mechanical means. They have no complex gravity-assisted mechanism or electrically controlled movement, thus they do not utilize limit switches for automated control of their travel or hoisting limits. Their operation is entirely manual and relies on brakes and locking pins.