Question 69 ONC01 - Master/Chief Mate Unlimited Tonnage

The Correct Answer is D. ### Why Option D is Correct **D) Underway with the wind 30° on the bow** is the standard and safest procedure for preparing a vessel for a helicopter lift (HI-LINE operation). 1. **Apparent Wind:** Helicopters require a specific amount of apparent wind (typically 15 to 30 knots) flowing across the deck to provide lift stability and minimize turbulence near the vessel's superstructure. 2. **True Wind vs. Apparent Wind:** By motoring ahead (underway), the vessel adds its own speed to the true wind speed. If the true wind is light, the vessel's speed creates the necessary apparent wind velocity. 3. **Course and Heading:** Setting the true wind 30 degrees off the bow (port or starboard) ensures that the apparent wind flows down the length of the deck, clearing the helicopter operating area (usually the stern or mid-ship) of major turbulence caused by the superstructure. This direction also gives the pilot a stable, long approach lane parallel to the ship's heading. 4. **Speed:** The combined speed (vessel speed plus true wind speed) should aim for the desired apparent wind speed over the deck, typically resulting in a vessel speed of 5 to 10 knots. ### Why the Other Options Are Incorrect **A) Underway on a course to provide no apparent wind:** * **Incorrect:** If the vessel creates no apparent wind, the helicopter operation becomes highly dangerous due to insufficient lift stability and potentially severe turbulence around the superstructure, especially in zero true wind conditions. Helicopters need significant apparent wind over the deck. **B) Stopped with the wind dead ahead:** * **Incorrect:** While putting the true wind dead ahead (0 degrees) minimizes ship-induced turbulence, stopping the vessel only utilizes the true wind speed. If the true wind is less than 15-20 knots (which is common), the apparent wind required for safe helicopter operations will be insufficient. **C) Stopped with the wind on the beam:** * **Incorrect:** This is the most dangerous scenario. Stopping the vessel reduces apparent wind if the true wind is light, and having the wind directly on the beam (90 degrees) causes maximum turbulence and complex vortex generation along the vessel's entire windward side and over the deck, making stable hovering impossible.