IACS Unified Interpretation SC 246 for SOLAS II-1/Regulation 29 is applied to ships contracted for construction on or after 1 July 2012. According to the unified interpretation, when trials are conducted with the vessel not at the deepest seagoing draught, the loading condition may be accepted on either one of the following conditions unless any specific instruction is provided by the flag administration (*).

(a) Trial is conducted on the condition that the rudder is fully submerged (at zero speed waterline) and the vessel is in an acceptable trim condition.
(b) Trial is conducted at its as deep draft condition as practicable, provided that the rudder load and torque at the trial loading condition have been reliably predicted and extrapolated to the full load condition.

In order to confirm that "the rudder load and torque at the trial loading condition have been reliably predicted and extrapolated to the full load condition." mentioned in the above (b), please send the following information to ClassNK service site. The surveyor will confirm it from the trial draft condition, measured hydraulic oil pressure and speed during the trial as well as the information in the drawing of steering gear and the drawing of rudder.

i) Planned trial draft condition
ii) Rudder immersion area on the planned draft condition
iii) Prospected trial speed

A project team of IACS Machinery Panel has been launched and a unified method that "the rudder load and torque at the trial loading condition is reliably predicted and extrapolated to the full load condition." is under development. The unified method, if it is decided, will be informed.

(*) So far we had an instruction from Republic of the Marshall Islands. When trials are conducted with the vessel flying Republic of the Marshall Islands' flag not at the deepest seagoing draught, a document to predict the steering capability at the full load condition shall be submitted for the attending surveyor to confirm the document and send it to Republic of the Marshall Islands. The way to predict the steering capability is not specifically instructed by the Administration.

(To be continued)