What is General intact stability criteria for all ships?

The following   criteria are recommended   for  passenger and cargo  ships.

  • The area under the righting lever  curve   (GZ curve)   should not be less than 0.055  metre-radian  up to e = 30° angle of heel and not  less than 0.09  metre-radian  up to 9 = 40°  or the angle of flooding θf if this angle is less than 40°.   Additionally,   the area under  the righting  lever  curve   (GZ curve)   between  the angles of heel of 30°  and 40°  or between  30°  and θf ,   if this angle  is less than 40°,  should  not  be less than 0.03 metre-radian.
  • The righting  lever   GZ  should  be at least 0.20  m at an angle of heel equal  to or greater  than 30°.
  • The maximum  righting  arm should  occur  at an angle of heel preferably  exceeding  30° but not less than  25°.
  • The initial  metacentric   height  GMo    should  not  be less than 0.15 
  • In addition, for passenger ships, the angle of heel on account  of crowding  of passengers to one side as defined   should  not exceed  10 degree.
  • Where anti-rolling  devices  are installed  in a ship,  the Administration    should  be  satisfied  that  the above  criteria  can be maintained  when  the devices   are in operation.
  • In addition,   for  passenger ships, the  angle  of  heel on  account  of turning  should  not  exceed  10 degree when  calculated  using the following.


For timber deck cargo ship

For ships loaded  with  timber  deck  cargoes  and  provided   that  the cargo  extends  longitudinally   between  superstructures   (where  there  is no  limiting  superstructure   at the after  end,  the timber  deck  cargo  should extend  at least to the after end of the aftermost  hatchway)  transversely for the full beam of ship after due allowance   for  a  rounded   gunwale   not  exceeding   4%  of  the  breadth   of  the  ship  and/or   securing  the supporting  uprights  and which  remains securely fixed at large angles of heel, the Administration   may apply the following   criteria .