4.1 Stability instruments ^footnote

  4.1.1.1 The scope of stability calculation software should be in accordance with the approved stability booklet and should at least include all information and perform all calculations or checks as necessary to ensure compliance with the applicable stability requirements.

  4.1.1.2 An approved stability instrument is not a substitute for the approved stability booklet, and is used as a supplement to the approved stability booklet to facilitate stability calculations.

  4.1.1.3 The input/output information should be easily comparable with the approved stability booklet so as to avoid confusion and possible misinterpretation by the operator.

  4.1.1.4 An operation manual should be provided for the stability instrument.

  4.1.1.5 The language in which the stability calculation results are displayed and printed out as well as the operation manual is written should be the same as used in the ships approved stability booklet. A translation into a language considered appropriate may be required.

  4.1.1.6 The stability instrument is ship specific equipment and the results of the calculations are only applicable to the ship for which it has been approved.

  4.1.1.7 In case of modifications of the ship which cause alterations in the stability booklet, the specific approval of any original stability calculation software is no longer valid. The software should be modified accordingly and re-approved.

  4.1.1.8 Any change in software version related to the stability calculation should be reported to and be approved by the Administration.

  4.1.2.1 A passive system requires manual data entry.

  4.1.2.2 An active system replaces partly the manual entry with sensors reading and entering the contents of tanks, etc.

  4.1.2.3 Any integrated system which controls or initiates actions based on the sensor-supplied inputs is not within the scope of this Code except the part calculating the stability.

 Three types of calculations performed by stability software are acceptable depending upon a vessel's stability requirements:

• Type 1
  Software calculating intact stability only (for vessels not required to meet a damage stability criterion).

• Type 2
  Software calculating intact stability and checking damage stability on basis of a limit curve (e.g., for vessels applicable to SOLAS part B-1 damage stability calculations, etc.) or previously approved loading conditions.

• Type 3
  Software calculating intact stability and damage stability by direct application of pre-programmed damage cases for each loading condition (for some tankers, etc.). The results of the direct calculations performed by the stability instrument could be accepted by the Administration even if they differ from the required minimum GM or maximum VCG stated in the approved stability booklet.

 Such deviations could be accepted under the condition that all relevant stability requirements will be complied with by the results of the direct calculations.

  4.1.4.1 The stability instrument should present relevant parameters of each loading condition in order to assist the master in his judgement on whether the ship is loaded within the approved limits. The following parameters should be presented for a given loading condition:

• .1 detailed deadweight data items including centre of gravity and free surfaces, if applicable;

• .2 trim, list;

• .3 draught at the draught marks and perpendiculars;

• .4 summary of loading condition displacement, VCG, LCG, TCG, VCB, LCB, TCB, LCF, GM and GM_L;

• .5 table showing the righting lever versus heeling angle including trim and draught;

• .6 down-flooding angle and corresponding down-flooding opening; and

• .7 compliance with stability criteria: Listings of all calculated stability criteria, the limit values, the obtained values and the conclusions (criteria fulfilled or not fulfilled).

  4.1.4.2 For ships engaged in anchor handling operations planning tools should be provided in compliance with operational manual requirements. Information such as ballasting and consumables sequences, permissible tension, working sectors, heeling angles and use of roll-reduction devices should be stated.

  4.1.4.3 If direct damage stability calculations are performed, the relevant damage cases according to the applicable rules should be pre-defined for automatic check of a given loading condition.

  4.1.4.4 A clear warning should be given on screen and in hard copy printout if any of the limitations are not complied with.

  4.1.4.5 The data should be presented on screen and in hard copy printout in a clear unambiguous manner.

  4.1.4.6 The date and time of a saved calculation should be part of the screen display and hard copy printout.

  4.1.4.7 Each hard copy printout should contain identification of the calculation program including version number.

  4.1.4.8 Units of measurement should be clearly identified and used consistently within a loading calculation.

 Depending on the type and scope of programs, the acceptable tolerances should be determined differently, according to 4.1.5.1 or 4.1.5.2. Deviation from these tolerances should not be accepted unless the Administration considers that there is a satisfactory explanation for the difference and that there will be no adverse effect on the safety of the ship.

 The accuracy of the results should be determined using an independent program or the approved stability booklet with identical input.

  4.1.5.1 Programs which use only pre-programmed data from the approved stability booklet as the basis for stability calculations should have zero tolerances for the printouts of input data.

 Output data tolerances should be close to zero, however, small differences associated with calculation rounding or abridged input data are acceptable. Additionally differences associated with the use of hydrostatic and stability data for trims and the method calculating free surface moments that differ from those in the approved stability booklet are acceptable subject to review by the Administration.

  4.1.5.2 Programs which use hull form models as their basis for stability calculations should have tolerances for the printouts of basic calculated data established against either data from the approved stability booklet or data obtained using the Administration's approval model.

  4.1.6.1 Conditions of approval of the stability instrument

 The software approval includes:

• .1 verification of type approval, if any;

• .2 verification that the data used is consistent with the current condition of the ship (refer to 4.1.6.2);

• .3 verification and approval of the test conditions; and

• .4 verification that the software is appropriate for the type of ship and stability calculations required.

 The satisfactory operation of the stability instrument is to be verified by testing upon installation (refer to 4.1.8). A copy of the approved test conditions and the operation manual for the stability instrument are to be available on board.

  4.1.6.2 Specific approval

  4.1.6.2.1 The accuracy of the computational results and actual ship data used by the calculation program for the particular ship on which the program will be installed should be to the satisfaction of the Administration.

  4.1.6.2.2 Upon application for data verification, minimum of four loading conditions should be taken from the ship's approved stability booklet, which should be used as the test conditions. For ships carrying liquids in bulk, at least one of the conditions should include partially filled tanks. For ships carrying grain in bulk, one of the grain loading conditions should include a partially filled grain compartment. Within the test conditions each compartment should be loaded at least once. The test conditions normally should cover the range of load draughts from the deepest envisaged loaded condition to the light ballast condition and should include at least one departure and one arrival condition.

  4.1.6.2.3 The following data, submitted by the applicant, should be consistent with arrangements and most recently approved lightship characteristics of the ship according to current plans and documentation on file, subject to possible further verification on board:

• .1 identification of the calculation program including version number. Main dimensions, hydrostatic particulars and, if applicable, the ship's profile;

• .2 the position of the forward and aft perpendiculars, and if appropriate, the calculation method to derive the forward and aft draughts at the actual position of the ship's draught marks;

• .3 ship's lightweight and centre of gravity derived from the most recently approved inclining experiment or light weight survey;

• .4 lines plan, offset tables or other suitable presentation of hull form data including all relevant appendages, if necessary to model the ship;

• .5 compartment definitions, including frame spacing, and centres of volume, together with capacity tables (sounding/ullage tables), free surface corrections, if appropriate; and

• .6 cargo and consumables distribution for each loading condition.

 Verification by the Administration does not absolve the shipowner of responsibility for ensuring that the information programmed into the stability instrument is consistent with the current condition of the ship and approved stability booklet.

 A simple and straightforward user manual written in the same language as the stability booklet should be provided, containing descriptions and instructions, as appropriate, for at least the following:

• .1 installation;

• .2 function keys;

• .3 menu displays;

• .4 input and output data;

• .5 required minimum hardware to operate the software;

• .6 use of the test loading conditions;

• .7 computer-guided dialogue steps; and

• .8 list of warnings.

 A user manual in electronic format may be provided in addition to the written manual.

  4.1.8.1 To ensure correct working of the stability instrument after the final or updated software has been installed, it is the responsibility of the ship's master to have test calculations carried out according to the following pattern in the presence of an Administration's surveyor. From the approved test conditions at least one load case (other than light ship) should be calculated.

  Note: Actual loading condition results are not suitable for checking the correct working of the stability instrument.

  4.1.8.2 Normally, the test conditions are permanently stored in the stability instrument. Steps to be performed:

• .1 retrieve the test load case and start a calculation run; compare the stability results with those in the documentation;

• .2 change several items of deadweight (tank weights and the cargo weight) sufficiently to change the draught or displacement by at least 10%. The results should be reviewed to ensure that they differ in a logical way from those of the approved test condition;

• .3 revise the above modified load condition to restore the initial test condition and compare the results. The relevant input and output data of the approved test condition should be replicated; and

• .4 alternatively, one or more test conditions should be selected and the test calculations performed by entering all deadweight data for each selected test condition into the program as if it were a proposed loading. The results should be verified as identical to the results in the approved copy of the test conditions.

  4.1.9.1 It is the responsibility of the ship's master to check the accuracy of the stability instrument at each annual survey by applying at least one approved test condition. If an Administration's representative is not present for the stability instrument check, a copy of the test condition results obtained by this check should be retained on board as documentation of satisfactory testing for the Administration's representative's verification.

  4.1.9.2 At each renewal survey this checking for all approved test loading conditions should be done in the presence of the Administration's representative.

  4.1.9.3 The testing procedure should be carried out in accordance with paragraph 4.1.8.

  4.1.10.1 Protection against unintentional or unauthorized modification of programs and data should be provided.

  4.1.10.2 The program should monitor operation and activate an alarm when the program is incorrectly or abnormally used.

  4.1.10.3 The program and any data stored in the system should be protected from corruption by loss of power.

  4.1.10.4 Error messages with regard to limitations such as filling a compartment beyond capacity or more than once, or exceeding the assigned load line, etc., should be included.

  4.1.10.5 If any software related to stability measures such as sea keeping abilities of the vessel, evaluation of in-service inclining experiments and processing the results for further calculation, as well as the evaluation of roll period measurements is installed on board, such software should be reported to the Administration for consideration.

  4.1.10.6 Program functionalities should include mass and moment calculations with numerical and graphical presentation of the results, such as initial stability values, righting lever curve, areas under the righting lever curve and range of stability.

  4.1.10.7 All input data from automatically measuring sensors, such as gauging devices or draught reading systems should be presented to the user for verification. The user should have the possibility to override faulty readings manually.