According to SOLAS Convention every passenger ship regardless of size and every cargo ship having a length L of 24m and upwards, must be provided with such information (given in a simple and understandable form) as is necessary to enable the master to obtain accurate guidance as to the stability of the ship under various conditions of service.
MSC/Cir.920 dated 15th June 1999 defines the scope of onboard stability documentation, named Loading and Stability Manual . Despite that, onboard stability documentation can have very different scope and form. Very often various names are used: Intact Stability Information, Stability Booklet, etc. These terms are not sufficient to describe properly and fully the actual content of onboard stability documentation that takes into account requirements of damage stability and contains strength calculations.
Mass of empty ship and locations of its centre of gravity are parameters necessary for any stability calculations. Therefore any stability documentation must be prepared in two steps.
At the technical design stage it is necessary to prepare a preliminary documentation in order to submit it for class approval. It is carried out for estimated values of the lightship mass and location of the centre of gravity.
The true value of lightship mass and the true location of the ship centre of gravity can be determined only on the base of the inclining test carried out upon the completion of the vessel. Only then the final stability documentation can be prepared and approved.
Very often the scope of the preliminary documentation is limited just to calculations necessary to show the stability of the vessel meet the criteria in all standard loading cases. Such practice is the main reason of delays and low quality of the final documentation. Both documentations should have a very similar scope and form. With the preliminary documentation being approved, the preparation of the final documentation could be just a revision of calculations for ship’s actualized data.
Further reading: “Ship Stability in Practice”