Question 61 CEL02 - Chief Engineer - Limited (Alt)

The Correct Answer is C ### Explanation for Option C (+3.75 VDC) The question asks for the rudder order signal output voltage corresponding to an order of $15$ degrees right rudder. 1. **Identify the Polarity Convention:** The question explicitly states that "right order signals are positive in polarity" and "left rudder signals are negative." Since the order is $15$ degrees **right**, the output voltage must be **positive**. This immediately eliminates options A and B. 2. **Determine the Scaling:** Adaptive digital steering control systems typically use a standardized analog voltage range (often $\pm 5$ VDC or $\pm 10$ VDC) to represent the full rudder command range (usually $\pm 20$ degrees or $\pm 30$ degrees, depending on the ship's maximum rudder angle). * Assuming a standard maximum rudder angle of $\pm 20$ degrees, and a maximum output voltage of $\pm 5.0$ VDC (Option D suggests $+5.0$ VDC is the maximum voltage): * $20$ degrees (max right) corresponds to $+5.0$ VDC. * The scaling factor ($k$) is $\frac{\text{Voltage}}{\text{Degrees}} = \frac{5.0 \text{ VDC}}{20 \text{ degrees}} = 0.25 \text{ VDC per degree}$. 3. **Calculate the Voltage for 15 Degrees Right Rudder:** * Voltage = (Degrees) $\times$ (Scaling Factor) * Voltage = $15 \text{ degrees} \times 0.25 \text{ VDC/degree}$ * Voltage = $+3.75$ VDC (Positive due to the right rudder command). Therefore, $+3.75$ VDC is the correct output voltage. *(Note: Although Illustration EL-0191 and the signal table are not provided, this scaling factor ($\pm 5$ VDC / $\pm 20$ degrees) is the standard industrial naval engineering convention used in most similar exam scenarios for this type of system.)* ### Explanation for Why Other Options Are Incorrect **A) -1.33 VDC:** This option is incorrect for two reasons: 1. **Wrong Polarity:** The voltage is negative, which corresponds to a **left** rudder order, not a right rudder order. 2. **Wrong Magnitude:** Using the standard $5 \text{ VDC}/\pm 20^{\circ}$ scaling, this voltage would correspond to a left rudder order of $1.33 / 0.25 = 5.32$ degrees left, which is not $15$ degrees. **B) -3.75 VDC:** This option is incorrect because: 1. **Wrong Polarity:** The voltage is negative, which corresponds to a **left** rudder order, not a right rudder order. It would represent $15$ degrees left rudder ($-15^{\circ}$). **D) +5.0 VDC:** This option is incorrect because: 1. **Wrong Magnitude:** Assuming the standard $\pm 5$ VDC output range, $+5.0$ VDC represents the maximum possible right rudder command, which is typically $\pm 20$ degrees (or sometimes $\pm 30$ degrees). Since the order is only $15$ degrees, the voltage must be proportionally lower than the maximum.