Question 61 ONC03 - Master LT 500-1600 GRT

The Correct Answer is C ### Why Option C is Correct: **C) The backwash of the propeller reaches amidships** When a vessel is stopping its forward motion (or "making way") by putting the engines astern (reverse), the propeller generates a powerful flow of water (backwash) moving forward along the hull. When the vessel is still moving ahead, the ship is essentially running away from this backwash. As the vessel slows down, the backwash eventually catches up to the hull. The moment the vessel's forward motion stops (zero speed over the water), the backwash is observed hitting the hull near the midship section. This physical observation is a highly reliable and immediate visual cue used by navigators and pilots to confirm that the vessel has achieved zero headway or sternway *relative to the water*, which is the required condition for safely dropping anchor. ### Why Options A, B, and D are Incorrect: **A) The ship's Doppler log reads zero** The ship's Doppler log measures speed, but its reliability in this specific situation (coming to a complete stop over the water using propeller wash) is often questioned for precise maneuvering. Furthermore, logs can measure speed *over ground* or *over water*. While speed over water is desired, the log's reading can be influenced by currents and its mounting location. Most importantly, the physical, immediate visual cue (C) is the primary method taught and used, as it provides instant, non-instrument-dependent verification right as the momentum is killed. Relying solely on a log reading (an instrument) is less preferred than direct visual confirmation of the water flow. **B) An azimuth bearing on the beam remains steady** Taking an azimuth bearing (a compass bearing) on an object abeam (on the side) and observing if it remains steady is a method used to determine if the vessel is swinging or drifting (side-to-side movement) relative to the ground. However, observing a steady bearing only confirms the vessel is not moving sideways or swinging at the moment the bearing is taken; it **does not reliably confirm that the vessel has stopped making headway or sternway** (forward or backward motion over the water). The standard technique for confirming longitudinal motion stoppage relies on observing the propeller wash (C). **D) All of the above** Since options A and B are either unreliable or measure different types of movement (swing/drift) rather than zero headway, "All of the above" cannot be the correct answer. Option C is the definitive and standard method for confirming zero headway in this anchoring scenario.