TRANSFER OF PERSONNEL FROM A VESSEL UNDER ADVERSE WEATHER CONDITIONS

In this brief article, we will discuss how to safely disembark from or board a vessel while it is underway under adverse weather conditions.

While addressing the topic, we will focus on minimizing the interactions created by adverse weather conditions such as wind, heavy seas, and dead seas between the vessel and the transfer vessel, which make the transfer risky.

Another critical element of the topic is the equipment used for the transfer, such as the strop, combination ladder, etc.

This aspect has already been covered in many valuable articles.

Figure-1 Making a lee under normal conditions

When we refer to adverse weather conditions related to personnel transfer from a vessel, the first thing that comes to mind is the waves created by the prevailing wind in the area. As the vessel approaches the transfer point, it reduces the interaction between the vessel and the transfer vessel by leaving the prevailing waves on the opposite side of the strop. This maneuver is referred to as making a lee. The angle between the direction of the prevailing waves and the vessel's bow can vary between 30 and 90 degrees, depending on the size and intensity of the waves. When the vessel reaches the transfer position, it generally adjusts its speed to between 5 and 10 knots, depending on the characteristics of the transfer vessel.

An important point to keep in mind is this: When adverse weather conditions increase, vessels under 150 meters in length cannot create a full lee effect, even if they take the prevailing waves at a close angle to the side. Moreover, if the vessel is not loaded, the lee effect diminishes even further.

Let’s explain another method that can be applied under such conditions through Figure-2:

Figure-2 Making a lee under worsening weather conditions

As shown in the drawing, the weather conditions have relatively worsened, and the wave heights have increased accordingly. If the vessel were to make a lee as in the first example, the transfer vessel approaching from the starboard side would still be somewhat affected by the waves due to the vessel not being fully loaded or its tonnage and length. Consequently, the vessel would continue to move up and down, albeit to a lesser extent, at the vessel's side. This situation creates a dangerous and unsafe condition for the pilot or another personnel attempting to disembark from or board the vessel.

In this case, as shown in the example, while the vessel has taken the seas on the port shoulder, it adjusts its speed and, shortly before the personnel disembarks or boards, makes a starboard turn to significantly flatten the area on the starboard side where the transfer will take place.

Since the pivot point, or axis of rotation, of a vessel moving forward is located near the bow, the stern moves more during the turn, thereby temporarily flattening the waves significantly, much like an iron smoothing out a wrinkled pair of pants.

It would not be incorrect to refer to this maneuver as sweeping a lee, as this maneuver is also called sweeping a lee in maritime English.

To ensure a safe transfer, it is essential to confirm that a safe marine area is available and that the parties are aware of each other's maneuvers in advance through means such as radio communication.

If the adverse conditions worsen further, and a storm-like wind begins to dominate the area, leading to increasing wave heights, let’s examine another method that can be applied through Figure-3:

In the example, there is a prevailing wind of 25 knots and waves approximately 2 meters high coming from the same direction. If the safe navigation area and traffic conditions are suitable, the vessel continues its course in a manner that will meet the waves close to the bow. The transfer vessel requires the vessel's speed to be between 7-8 knots at the time of transfer. If it is a high-speed vessel, when it reaches the point shown in the figure, it adjusts its speed to be between 10-12 knots according to its tonnage. The vessel turns toward a course perpendicular to the wave direction and sails at maximum speed until it reaches point 4, allowing its speed to drop to 10 knots at that point.

The aim here is to create waves from the vessel in a direction exactly opposite to the prevailing wave direction. Thus, even if the vessel cannot completely eliminate the prevailing waves, it significantly reduces their effect.

When the vessel reaches point 4, its speed has dropped to approximately 10 knots, and while executing a starboard turn, it proceeds toward point 5. The effect of the starboard turn on the rudder tends to decrease speed, and the engine throttle is adjusted accordingly to reduce the speed to 7-8 knots for the transfer. A safe transfer is achieved by sweeping a lee with both the vessel's wave-preventing effect and the starboard turn.

Figure-3 Making a lee under storm-force weather conditions

Between points 1 and 4, the vessel can navigate at a higher speed depending on its tonnage, draft, and other characteristics. However, when the vessel reaches point 4, its speed must not exceed 10 knots. Throughout this process, the parties must remain in constant communication and inform each other of their maneuvers in advance.

While executing these maneuvers, it is necessary to ensure that a safe marine area exists and to plan in such a way that it does not create a situation that would obstruct or pose a danger to surrounding vessel traffic.

Different approaches and solutions are certainly possible along similar principles, but regardless of the circumstances, when weather conditions become extremely adverse, it is safer to avoid creating a dangerous situation by pushing the limits and to wait for more favorable conditions.

Source: SeaNews Türkiye