Artikel 28

(1) The following minimum stability criteria shall be met unless the Administration is satisfied that operating experience justifies departures therefrom: (a) the area under the righting lever curve (GZ curve) shall not be less than 0.055 metre-radians up to 30 degrees angle of heel and not less than 0.090 metre-radians up to 40 degrees or the angle of flooding θf if this angle is less than 40 degrees. Additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30 degrees and 40 degrees or between 30 degrees and θf, if this angle is less than 40 degrees shall not be less than 0.030 metre-radians. θf is the angle of heel at which openings in the hull, superstructure or deckhouse which cannot rapidly be closed watertight commence to immerse. In applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open;
(b) the righting lever GZ shall be at least 200 millimetres at an angle of heel equal to or greater than 30 degrees;
(c) the maximum righting lever GZmax shall occur at an angle of heel preferably exceeding 30 degrees but not less than 25 degrees;
(d) the initial metacentric height GM shall not be less than 350 millimetres for single deck vessels. In vessels with complete superstructure or vessels of 70 metres in length and over the metacentric height may be reduced to the satisfaction of the Administration but in no case shall be less than 150 millimetres.
(a) the area under the righting lever curve (GZ curve) shall not be less than 0.055 metre-radians up to 30 degrees angle of heel and not less than 0.090 metre-radians up to 40 degrees or the angle of flooding θf if this angle is less than 40 degrees. Additionally, the area under the righting lever curve (GZ curve) between the angles of heel of 30 degrees and 40 degrees or between 30 degrees and θf, if this angle is less than 40 degrees shall not be less than 0.030 metre-radians. θf is the angle of heel at which openings in the hull, superstructure or deckhouse which cannot rapidly be closed watertight commence to immerse. In applying this criterion, small openings through which progressive flooding cannot take place need not be considered as open;
(b) the righting lever GZ shall be at least 200 millimetres at an angle of heel equal to or greater than 30 degrees;
(c) the maximum righting lever GZmax shall occur at an angle of heel preferably exceeding 30 degrees but not less than 25 degrees;
(d) the initial metacentric height GM shall not be less than 350 millimetres for single deck vessels. In vessels with complete superstructure or vessels of 70 metres in length and over the metacentric height may be reduced to the satisfaction of the Administration but in no case shall be less than 150 millimetres.
(2) Where arrangements other than bilge keels are provided to limit the angles of roll, the Administration shall be satisfied that the stability criteria given in paragraph (1) are maintained in all operating conditions.
(3) Where ballast is provided to ensure compliance with paragraph (1), its nature and arrangement shall be to the satisfaction of the Administration.