Section 5 Guidelines on conducting ship verification trials

5.1.1 These guidelines provide information on performing the verification trials in accordance with these Rules.

5.1.2 A detailed trials agenda is to be agreed before the commencement of any verification trials. This agenda should include:

• Agreement on the trials site.
• Notification of the possible restrictions that may be imposed by environmental conditions.
• A procedure to calibrate the data logging and measurement system.
• A procedure for data recording.
• The sequence in which the manoeuvring trials are to be conducted.
• The procedure for conducting each manoeuvre, including agreement on the starting and finishing points, the approach speeds and engine setting.

5.1.3 Environmental conditions can have a pronounced influence on the manoeuvring performance of a ship, therefore the verification trials are to be conducted within the environmental restrictions imposed by these Rules.

5.1.4 The following points are to be noted when determining the trials agenda:

• The ship’s dynamic stability is required to be assessed in accordance with Vol 3, Pt 1, Ch 4, 4.5 Representative manoeuvres (LMA notation) 4.5.2. It is recommended that the pull-out manoeuvre is performed at the end of the turning circle manoeuvres, see Vol 3, Pt 1, Ch 4, 5.5 Pull-out manoeuvring trials.
• The initial turning ability of the ship, required by Vol 3, Pt 1, Ch 4, 2.3 Manoeuvres to be assessed 2.3.1.(d), can be measured during the 10º/10º zig-zag manoeuvring trial, see Vol 3, Pt 1, Ch 4, 5.7 Zig-zag manoeuvring trials.

5.2.1 Before commencing the verification trials, the data logging and measurement system is to be calibrated. The allowable measurement tolerances and the frequency of each measurement are given in Table 4.5.1 Data measurement and accuracy requirements.

5.2.2 The measurement system’s time and the ship’s time are to be synchronised with a recognised time signal. The time and date, relative to Universal Time Constant (UTC), are to be recorded.

5.2.3 The position of the ship is to be determined by all available means and calibrated with range and/or bearing fixes from three prominent landmarks, including radar responding beacons (racons). Where the ship’s position is to be measured using land-based transponders, the installation, set-up and calibration of such measurement equipment are to be carried out to the manufacturer’s instructions.

5.2.4 The ship’s speed over the ground is to be calibrated with range and/or bearing fixes from three prominent landmarks (including racons), whilst held on a steady course with no alteration in engine setting.

5.2.5 The gyro repeaters are to be adjusted until they are synchronized with the master gyro compass reading.

5.2.6 The steering gear is to be tested to calibrate the rudder angle indicator(s), over the full range of movement against the actual rudder angle reading given on the rudder stock.

5.2.7 The rate of turn indicator can be calibrated against the actual change in heading per second during a turn.

5.2.8 Where an automatic data logging and measurement system is to be used, the installation, set-up and calibration of such measurement equipment are to be carried out to the manufacturer’s instructions.

5.2.9 The equipment used to measure prime mover/ propeller shaft revolutions and shaft power (torsion meters) is to be calibrated before trials.

5.3.1 The data describing manoeuvring performance is to be measured and recorded in accordance with the requirements of Table 4.5.1 Data measurement and accuracy requirements. This data is to be measured and recorded from the start of the approach run and terminated at the end of the manoeuvring trial. The start of the manoeuvring trial is to be defined by a specific engine order or helm change noted on the recorded measurements.

5.3.2 An automatic data logging and measurement system is the preferred option. However, where the manoeuvring data is to be recorded manually, it is necessary to have suitable indicators and repeaters available to allow a sufficient number of persons to record the required parameters. Sufficient personnel are to be present to ensure that each person is recording no more than three parameters in each trial.

5.3.3 All recordings are to be synchronized to a common time datum.

5.3.4 The following data is to be clearly recorded for each trial manoeuvre:

1. Date.

2. Time.

3. Ship’s loading condition (draught and trim).

4. Initial approach speed and heading.

5. Water depth.

6. Environmental conditions, including:

   current speed and direction;

   wind speed;

   wind direction relative to the ship’s head;

   sea state.

7. Position (latitude and longitude) (The use of calibrated GPS systems is acceptable.)

8. Ship’s heading.

9. Rate of turn.

10. Speed.

11. Rudder angle.

12. Propeller revolutions.

13. Propeller pitch, where applicable.

5.3.5 The steady approach conditions for each trial are to be recorded for at least two minutes before the initiation of the manoeuvring trial.

5.4.1 These trials measure the effectiveness of the rudder(s) in initiating a turn and the ship’s steady state turning characteristics.

5.4.2 The turning circle manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the relative approach condition defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions is satisfied and the ship is running head to wind; and

   2. the rudder is ordered hard over to port or starboard.

2. It must continue without any alteration to the engine control settings.

3. It is to be terminated when the ship has completed a 540º turn.

5.4.3 The following information is to be derived from the trials data, see Figure 4.5.1 Presentation of turning circle manoeuvring trial results:

1. Time taken to reach each 90º change of heading.

2. Advance at each 90º change of heading.

3. Transfer at each 90º change of heading.

4. Tactical diameter.

5. Steady turning diameter.

6. Loss in forward speed during the turn.

7. Rate of turn during the turn, r, see Vol 3, Pt 1, Ch 4, 5.9 Spiral manoeuvring trials 5.9.5.(c)

Figure 4.5.1 Presentation of turning circle manoeuvring trial results

5.5.1 The pull-out manoeuvre is a simple trial which has been developed to give a quick indication of the ship’s dynamic stability and course keeping ability. The pull-out manoeuvre is to be performed at the end of each turning circle manoeuvring trial. The results of these manoeuvres will indicate whether a spiral manoeuvre trial is required to be conducted, see Vol 3, Pt 1, Ch 4, 5.9 Spiral manoeuvring trials.

5.5.2 The pull-out manoeuvre is to be conducted as follows:

1. The ship is to be in a steady state turn (constant rate of turn) with the rudder hard over. This manoeuvre is normally conducted on the termination of the turning circle manoeuvring trial.

2. This manoeuvre is initiated when the rudder is ordered amidships.

3. With the rudder held amidships, the rate of turn will decrease.

4. If the ship possesses ‘dynamic stability’, the rate of turn will reduce towards zero with equal residual rates of turn for both port and starboard turns with the rudder held amidships. If there is an unequal residual rate of turn with the rudder held amidships, then the ship is to be considered ‘dynamically unstable’, see Figure 4.5.2 Presentation of pull-out manoeuvring trial results.

5.5.3 The following information is to be derived from the trials data, and presented as shown in Figure 4.5.2 Presentation of pull-out manoeuvring trial results:

A plot of the time histories of the ship’s head, rate of turn and ship’s speed.

Figure 4.5.2 Presentation of pull-out manoeuvring trial results

5.6.1 A ship’s stopping performance is normally represented by the crash stop manoeuvre, which determines the stopping ability of the ship from the time an order of full astern is given until the ship stops dead in the water for a given approach speed. In addition to the crash stop manoeuvre, a coasting stop manoeuvre is required to be conducted with the engines delivering no power to the propeller.

5.6.2 The stopping manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the relative approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions are satisfied and the ship is running with the wind astern, and

   2. the demand for full astern power or stop is given from the engine control position on the bridge.

2. The rudder is to be used to a minimal extent and only to keep the ship on course for as long as possible.

3. It is to be terminated when the ship has stopped dead in the water.

5.6.3 The following information is to be derived from the trials data, see Figure 4.5.3 Presentation of both stopping trials' results:

1. Minimum speed at which course can be maintained.

2. Head and track reach.

3. Lateral deviation and final heading.

4. Time to stop dead in the water.

5.7.1 These trials measure the effectiveness of the rudder(s) to initiate and check changes in heading. This manoeuvre is normally defined as a θ₁/θ₂ zig-zag manoeuvre (e.g. 20º/20º) where:

1. θ₁ is the required rudder angle, in degrees, to be applied during the trial, and

2. θ₂ is the deviation, in degrees, of the ship’s head, from the original course, before application of θ₁ to check changes in heading.

5.7.2 The zig-zag manoeuvre involves the cyclic movement of the ship about an initial base course. The zig-zag manoeuvre is conducted as follows:

1. It is to be initiated when:

   1. the approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions have been satisfied and the ship is running head to wind; and

   2. the rudder is ordered to θ₂ degrees to starboard (or port).

2. It must continue without any alteration to the engine control settings.

3. When the heading has changed by θ₂ degrees from the original course, the rudder is to be ordered to the opposite angle θ₁ degrees to port (or starboard).

4. When the heading has changed by θ₁ degrees from the original course, the rudder is to be ordered to the opposite angle θ₂ degrees to starboard (or port).

5. This manoeuvre is to be terminated when the ship’s head has crossed the base course at least three times.

Figure 4.5.3 Presentation of both stopping trials' results

5.7.3 The following information is to be derived from the trials data, see Figure 4.5.4 Presentation of zig-zag manoeuvring trial results:

1. A plot of the time histories of the rudder angles and corresponding ship’s heading.

2. First overshoot angle.

3. Second overshoot angle.

4. Time to check yaw (rate of change of heading equals zero) at each rudder reversal.

5. Initial turning time.

Figure 4.5.4 Presentation of zig-zag manoeuvring trial results

5.8.1 The initial turning manoeuvring trial measures the transient effectiveness of the rudder(s). To ascertain the ship’s initial turning ability, in accordance with Vol 3, Pt 1, Ch 4, 4.4 Approach conditions, the following data is to be recorded from the 10º/10º zig-zag manoeuvring trials:

When the ship’s head has moved 10º off the base course, after the initial rudder command, the number of ship lengths travelled is to be recorded.

5.9.1 This trial measures the ship’s steady state rate of turn as a function of the applied rudder angle, providing a qualitative measure of the ship’s dynamic stability.

5.9.2 There are two possible variations of the manoeuvring trials that can be used to assess the ship’s dynamic stability, namely:

The direct, or Dieudonne, spiral manoeuvre.

The reverse, or Bech, spiral manoeuvre.

5.9.3 The direct spiral manoeuvre will yield more information about the degree of instability. However, this manoeuvre is very time-consuming, requires good weather conditions and, for larger ships, needs considerable sea room. The reverse spiral manoeuvre provides a procedure for defining the instability loop more rapidly than the direct spiral manoeuvre. However, this trial requires accurate rudder angle and rate of turn indicators. Where the ship is to be steered manually, the helmsman is to be able to read the rate of turn indicator.

5.9.4 The direct spiral manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions have been satisfied, and

   2. the rudder is ordered to 25º to starboard.

2. It must continue without any alteration to the engine control settings.

3. The rudder is to be held until the indicated rate of turn is assumed constant.

4. The rudder angle is then to be decreased by 5º and held until the rate of turn is assumed constant.

5. The manoeuvre is to be terminated when the rudder has moved through the range of 25º to starboard to 25º to port and then back to 25º to starboard in incremental rudder angles of 5º.

6. For dynamically unstable ships, the incremental rudder angle in the range of 10º to starboard through to 10º to port is to be 2º.

5.9.5 The reverse spiral manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions have been satisfied; and

   2. the first constant rate of change of heading is achieved.

2. It must continue without any alteration to the engine control settings.

3. The recommended constant rates of turn are defined as percentages of the steady state rate of turn, r, derived from the turning circle, as shown in Table 4.5.2 Recommended constant rate of change of heading. For the LNMA notation specific constant rates of turn may be specified.

4. The points P1 to P8 represent positions on the spiral curve, see Figure 4.5.5 Presentation of spiral manoeuvring trial results for a dynamically unstable ship.

5. The first and last points on the spiral curves (P1 and P8) can be derived from the turning circle manoeuvres.

6. The ship is to be steered at a constant rate of turn and the mean rudder angle to achieve the desired rate of turn is to be noted. The rudder angle deviations are not to be greater than ± 2º.

7. The manoeuvre is to be terminated when all points have been determined.

Table 4.5.2 Recommended constant rate of change of heading

Points	Rate of change of heading
P1 and P8	1,0 r
P2 and P7	0,6 r
P3 and P6	0,3 r
P4 and P5	0,1 r
where r = change of heading per second =

5.9.6 The following information is to be derived from the trials data, see Figure 4.5.5 Presentation of spiral manoeuvring trial results for a dynamically unstable ship:

1. A time history of the rudder angle and corresponding rate of turn.

2. A plot of the constant rate of turn as an ordinate against the applied rudder angle.

Figure 4.5.5 Presentation of spiral manoeuvring trial results for a dynamically unstable ship

5.10.1 The man overboard manoeuvre provides the Master with important information on the time taken and the deviation from course necessary to retrieve a person or object from the sea. The elliptical and Williamson turns are two well-known man overboard manoeuvres. These manoeuvres will, in the absence of wind and current, bring the ship back to the position where the man overboard incident occurred.

5.10.2 The elliptical turning manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions have been satisfied, and

   2. the rudder is ordered hard over.

2. It must continue without any alteration to the engine control settings.

3. The rudder is to remain hard over until the ship has altered course by 180º. The ship is to be steadied on the reciprocal heading until the approach speed has been regained.

4. The rudder is once again placed hard over and the ship is steadied on the original course.

5. This manoeuvre is to be terminated when the ship has returned to the position, or nearest position, where the manoeuvre was initiated.

5.10.3 The Williamson turning manoeuvre is considered quicker than the elliptical turning manoeuvre in returning the ship to the original man overboard position. This manoeuvre is to be conducted as follows:

1. It is to be initiated when:

   1. the approach conditions defined in Vol 3, Pt 1, Ch 4, 4.4 Approach conditions have been satisfied, and

   2. the rudder is ordered hard over.

2. It must continue without any alteration to the engine control settings.

3. The rudder is to remain hard over until the ship has altered course by 70º. The rudder is then ordered hard over to the opposite side, until the ship is on a course which is the reciprocal of the original approach course.

4. It is terminated when the ship has returned to the position, or nearest position, where the manoeuvre was initiated.

5.10.4 The following information is to be derived from the trials data, see Figure 4.5.6 Presentation of the Williamson turn, man overboard, manoeuvring trial results:

1. A plot of the ship’s track.

2. The time taken to return to the point, or nearest position to that point, at which the manoeuvre was initiated.

3. The lateral deviation from the initial course at the point, or nearest position to that point, at which the manoeuvre was initiated.

Figure 4.5.6 Presentation of the Williamson turn, man overboard, manoeuvring trial results

5.11.1 Where a ship is fitted with auxiliary thrusters, such as bow thrusters, a turning circle manoeuvre is required to be performed to determine the effectiveness of those thrusters in turning the ship through 180º. This trial is to be carried out with the wind initially from the stern and the ship turning into the wind.

5.11.2 The auxiliary thrusters’ turning circle is to be conducted as follows:

1. All primary thrusters stopped and the ship dead in the water.

2. The ship is to be completely stopped in the water with head to wind.

3. The auxiliary thrusters are to be set to maximum power to turn the ship.

4. The manoeuvring trial is to be completed when the ship has turned through 180º.

5.11.3 The following information is to be derived from the trials data:

1. The time taken to reach a 90º change of heading.

2. The time taken to reach a 180º change of heading.

3. The transfer at a 90º change of heading, see Figure 4.5.1 Presentation of turning circle manoeuvring trial results.

4. The transfer at a 180º change of heading, see Figure 4.5.1 Presentation of turning circle manoeuvring trial results.

5. The steady state rate of change of heading.

5.11.4 If required by Vol 3, Pt 1, Ch 4, 3.2 Verification requirements 3.2.6 (LNMA notation only) a self berthing manoeuvre is to be carried out:

1. The ship is to be positioned bow or stern to the wind.

2. All primary thrusters stopped and the ship dead in the water.

3. The auxiliary thrusters are to be set to maximum power for transverse motion.

4. The manoeuvre may be terminated when the ship has recorded a steady transverse speed with zero rate of rotation.

5.11.5 The following information is to be derived from the trials data:

1. The time taken to reach a steady transverse velocity.

2. The maximum transverse velocity attained.

3. The heading of the vessel at least every two seconds during the manoeuvre.

5.12.1 The acceleration trials information on the distance and time to achieve a speed defined by 80–100 per cent MCR set speeds from a dead stop.

5.12.2 The following trial procedure is to be followed as illustrated in Figure 4.5.7 Acceleration trial:

1. Establish a steady ship speed in accordance with the trial agenda and adjust the ship’s heading to a steady course. At a position roughly one ship length before the point where the engine order is initiated, start the acquisition system.

2. Execute the prescribed engine order.

3. The rudder is to be used to a minimal extent and only to keep the ship on course.

4. When the ship attains the steady terminal speed stated in the trial agenda, the test is complete.

5.12.3 The following information is to be derived from the trials data:

1. The time taken to reach the terminal speed specified in the trials agenda.

2. The distance covered from the time the engine order is initiated until the ship reaches the terminal speed specified in the trials agenda.

3. Lateral deviation and final heading.

Figure 4.5.7 Acceleration trial

5.13.1 The turning from rest manoeuvre is to be conducted as follows:

1. All primary and auxiliary thrusters are stopped and the ship dead in the water;

2. the rudder is ordered hard over;

3. the demand for full ahead power is given from the engine control position on the bridge;

4. the ship must continue without any alteration to the engine control settings;

5. the rudder is to remain hard over until the ship has altered course by 90°;

6. this manoeuvre is to be terminated when the ship has altered course by 90°.

5.13.2 The time taken from the full ahead order until the ship has altered course by 90° is to be recorded.