Question 69

The Correct Answer is C. ### Explanation of Why Option C ("Both I and II") is Correct The steering gear system (commonly the electro-hydraulic type) is designed to translate the small movement of the steering wheel (helm) into a controlled, large-force movement of the rudder. The core mechanism involves a control system that regulates the flow of hydraulic fluid by adjusting a variable delivery pump, such as a Hele-Shaw pump or a swashplate pump. **Statement I (rate of steering gear ram movement will be proportional to amount of helm angle input):** This statement is generally true in modern steering gear systems, especially when considering the rate of displacement (speed) during the initial steering action. * The helm angle input dictates the desired rudder position. * The farther the helm is moved (e.g., 10 degrees to 30 degrees), the larger the initial signal sent to the control system. * A larger input signal typically results in a greater adjustment of the pump's output (larger swashplate/tilting plate angle), leading to a higher flow rate of hydraulic fluid. * A higher flow rate means the steering gear ram (connected to the rudder stock) will move faster, i.e., the rate of movement is proportional to the magnitude of the desired change. This speed allows the rudder to reach the commanded position quickly. **Statement II (degree of tilting plate (box) angle will be proportional to the amount of helm angle input):** This statement is also correct and represents the direct control mechanism. * The variable delivery pump (e.g., Hele-Shaw or swashplate pump) controls the flow direction and rate of the hydraulic fluid. * The output flow rate (and therefore the speed of the ram/rudder movement) is directly determined by the angle of the tilting plate (or swashplate/tilting box). * When the helm is moved, the hunting gear (or equivalent electronic control system) adjusts the position of the tilting plate. The further the helm is moved, the greater the required flow, and thus the larger the angle the tilting plate must adopt to achieve that flow. * Therefore, the adjustment in the tilting plate angle is directly proportional to the magnitude of the helm angle change commanded by the helmsman. Since both I (ram speed being proportional to input) and II (tilting plate angle being proportional to input) accurately describe the function and control mechanism of the hydraulic steering gear when the helm angle is changed, C is the correct answer. ### Why the Other Options Are Incorrect * **A) I only:** Incorrect because Statement II (the proportional control of the tilting plate) is the fundamental mechanical/hydraulic means by which Statement I (proportional ram speed) is achieved. Both must be true. * **B) II only:** Incorrect because Statement I describes the necessary consequence of the tilting plate adjustment (Statement II). If the tilting plate angle changes proportionally, the ram speed must change proportionally to move the rudder to the desired position. * **D) Neither I nor II:** Incorrect because both statements accurately describe key operational events in a modern electro-hydraulic steering gear system.