Regulations 5.4 and 5.5
SOLAS regulations II-1/5.4 and II-1/5.5 read:
"Regulation 5
Intact stability
…
4 Where any alterations are made to a ship so as to materially affect the stability
information supplied to the master, amended stability information shall be provided. If
necessary, the ship shall be re-inclined. The ship shall be re-inclined if anticipated
deviations exceed one of the values specified in paragraph 5.
5 At periodical intervals not exceeding five years, a lightweight survey shall be
carried out on all passenger ships to verify any changes in lightship displacement and
longitudinal centre of gravity. The ship shall be re-inclined whenever, in comparison
with the approved stability information, a deviation from the lightship displacement
exceeding 2% or a deviation of the longitudinal centre of gravity exceeding 1% of L is
found or anticipated."
Revised Explanatory Notes to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1
and Rev.2) read:
"Regulation 5.4
1 When alterations are made to a ship in service that result in calculable differences
in the lightship properties, a detailed weights and centres of gravity calculation to
adjust the lightship properties should be carried out. If the adjusted lightship
displacement or longitudinal centre of gravity, when compared to the approved values,
exceeds one of the deviation limits specified in regulation 5.5, the ship should be
re-inclined. In addition, if the adjusted lightship vertical centre of gravity, when
compared to the approved value, exceeds 1%, the ship should be re-inclined. The
lightship transverse centre of gravity is not subject to a deviation limit.
2 When a ship does not exceed the deviation limits specified in explanatory note 1
above, amended stability information should be provided to the master using the new
calculated lightship properties if any of the following deviations from the approved
values are exceeded:
-
.1 1% of the lightship displacement; or
-
.2 0.5% of L for the longitudinal centre of gravity; or
-
.3 0.5% of the vertical centre of gravity.
However, in cases when these deviation limits are not exceeded, it is not necessary to
amend the stability information supplied to the master.
3 When multiple alterations are made to a ship in service over a period of time and each
alteration is within the deviation limits specified above, the cumulative total changes
to the lightship properties from the most recent inclining also should not exceed the
deviation limits specified above or the ship should be re-inclined."
Interpretation
Definition of lightweight calculation
For the purposes of this interpretation, the term "lightweight calculation" means a
detailed calculation of weights on and weights off a ship, resulting from all
alterations to the ship since the date of the last approved inclining test, to determine
the adjusted lightship properties. Lightship properties include weights and the centre
of gravity. The documented weights and their centres of gravity should be verified on
board/on-site by the attending class surveyor.
When weights are added, removed or relocated, the final cumulative change is to be
compared to the last approved inclining test.
"Lightweight survey" is defined in the International Code on Intact Stability
2008, paragraph 2.24.
Definition of stability information
"Stability information" includes any document (whether on paper or electronic) or
electronic means of calculation of stability which includes lightship properties. This
could include, but is not limited to, the approved stability book, computer software for
onboard calculation of stability, the approved strength book and the loading instrument.
Amendment of stability information in conjunction with alterations of lightship
properties
1 If the lightweight calculation, regardless of keel laying date, shows a deviation in
lightweight mass, or the longitudinal or vertical position of the centre of gravity:
-
.1 beyond any of the tolerance limits specified in explanatory note 1 to SOLAS
regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and
Rev.2), then the ship should be re-inclined and the stability information, as
defined above, should be updated to reflect the lightship properties derived from
the inclining test and should be approved;
-
.2 within the tolerance limits specified in the explanatory note 1 and exceeding
any of the deviations specified in explanatory note 2 to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and
Rev.2), then the stability information should be updated to reflect the lightship
properties derived from the lightweight calculation and should be approved; or
-
.3 within the tolerance limits specified in explanatory note 2 to SOLAS regulation II-1/5.4 (resolutions MSC.429(98)/Rev.1 and
Rev.2), then a copy of the endorsed lightweight calculation report should be
provided on board for future reference with no further amendments required to the
stability information. However, even if addition, removal or relocation of any
weight results in lightship particulars being within tolerable limits, that weight
should still be noted and the "constant" adjusted for lightweight calculation in
the stability information for all future references and calculations.
2 A summary of paragraph 1 of this interpretation is provided in the following table.
Where stability information is to be updated, it should be approved and provided to the
master with the instruction that it should now be used for all stability
calculations.
| Scenario, as calculated by lightweight
calculation
|
Requirement for Inclining Test
|
Update of Stability Information
|
| Lightweight change > 2%
|
Yes
|
Yes, using new incline result
|
| LCG change > 1% of L (either forward or aft)
|
Yes
|
Yes, using new incline result
|
| VCG change > 1%
|
Yes
|
Yes, using new incline result
|
|
|
|
|
| 1% < Lightweight change ≤ 2%
|
No
|
Yes, using lightweight calculation
|
| 0.5% of L < LCG change ≤ 1% of L (either forward or aft)
|
No
|
Yes, using lightweight calculation
|
| 0.5% < VCG change ≤ 1%
|
No
|
Yes, using lightweight calculation
|
|
|
|
|
| Lightweight change ≤ 1%
|
No
|
No
|
| LCG change ≤ 0.5% of L (either forward or aft)
|
No
|
No
|
| VCG change ≤ 0.5%
|
No
|
No
|
3 Lightship properties should be consistent in all documents which use them, e.g.
loading manual, stability manual and computer data.
4 A change in lightweight will result in a change in deadweight unless there is an
associated change in freeboard. The consequences of the change could have an impact on
compliance with other regulations, e.g. MARPOL Annex VI.